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• +  John Douglas
• +  Louis Geli
• +  Nurcan Meral Özel 1
• +  Nurcan Meral Özel 2
• +  Paolo Favali

Video: Nurcan Meral Ozel, John Douglas, Louis Geli, Paolo Favali explain MARsite.

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MARSite has 11 Work Packages dealing with Management, Research and Develeopment, Data Integration and Dissemination acivities.

The main objective of WP1 is to ensure the successful completion of the project goals on time within the limits defined by the budgetary framework and quality standards imposed by the EU. WP1 is also responsible for the Consortium Management, assessment of progress and results addressed in them.

The aim of WP2 is the collection and integration of seismological, geochemical, and geodetic data to detect and model the interactions between fluids, crustal deformation and ruptures of the active tectonic structures of the Marmara area and, thereby, to contribute to its seismic hazard assessment.

In WP3, long-term continuous monitoring of the crustal deformation will be investigated by exploiting the existing land and space based geodetic crustal deformation monitoring systems.

A multi-parameter borehole system and surface array as closest as to the main Marmara Fault (MMF) in the western Marmara Sea will be installed in WP4 to measure continuously the evolution of the state of stress of the fault zone surrounding the MMF and to detect any anomaly or change which may occur before earthquakes by making use of the data from the arrays already running in the eastern part of the Marmara Sea.

WP5 will concentrate on real- and quasi-real-time Earthquake &Tsunami Hazard Monitoring, where an integrated approach by harmonizing geodetic and seismic data to be used in early warning applications will be implemented, so that in addition a quick determination of the rupture characteristics could also assist the identification of the tsunamigenic potential of an earthquake in combination with a tectonic origin tsunami scenario database.

The aim of WP6   is to improve the preparedness of those seismically induced landslide geohazards, through the using and the improvement of monitoring and observing systems in hydrogeotechnical and seismically well-constrained areas within the supersite.

Re-evaluation of the seismo-tectonics of the Marmara Region will be conducted in WP7 and Monitoring seismicity and fluid activity near the fault using existing cabled and autonomous multiparameter seafloor instrumentation will be performed in WP8. WP9 will focus on Early Warning and Development of the Real-time shake and loss information for the supersite.

Integration of data management practices and coordination with ongoing research infrastructures are the responsibilities of WP10, through which the data and the results will be exploited.

Analysis of the target users and production of a communication plan for the dissemination and public outreach strategy of MARsite , together with the dissemination activities will be the responsibility of WP11.

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Work package title: Coordination and Project Management

WP Leader:  KOERI

Objectives

The main objective of this WP is to ensure the successful completion of the project goals on time within the limits defined by the budgetary framework and quality standards imposed by the EU. This work package will oversee the administrative and financial management and it will ensure financial and scientific/technical coordination, project planning and evaluation of the project progress, while emphasizing quality assurance. The objectives are the following:

• Administration and co-ordination of the project resources, including budget spent and efforts utilized;
• Monitoring and control of the workplan and preparation of detailed workplans;
• Coordination and monitoring of the work among the WP Leaders;
• Compilation and issuing of periodic reports;
• Arrangement of the project level meetings and issuing the minutes;
• Structuring a consortium communication, including deliverables, reviews, etc.; and

A clear and swift communication between the Project and the EC officers.

Description of work

According to the Consortium Agreement drafted with reference to the simplified FP7 Model Consortium Agreement (DESCA 3.0), the Consortium General Assembly (CGA) will be the ultimate decision-making body of the Consortium. The Project Coordinator (PC) will be the legal entity acting as the intermediary between the Parties and the European Commission and will also be responsible for the execution of the Project. The PC will also report to and be accountable to the General Assembly. The Project Manager (PM) is in charge of all operational and management aspects of the project and will report directly. PC and PM will be supported by the MARsite Project Office (PO), which will execute the daily management tasks like the financial and contractual issues, the management of budget and time, the monitoring and execution of quality checks, the reporting to the EC and the PC, the communication and flow of information within the project and the necessary input to the project web portal. PO will be located at KOERI and will provide administrative and financial assistance to the PC and PM. Moreover, Project Coordinator will be assisted by a Project Coordinator Assistant who will also support the Project Manager in quality checks, the reporting to the EC and the PC, the communication and flow of information within the project and the necessary input to the project web portal. An External Expert Advisory Board (EEAB) will be appointed and steered by the PC and the CGA. A project web-portal will be created and maintained. The MARsite web-portal will be an essential element of the internal and external project communication. The portal will provide project overviews and highlights, up-to-date information on project results, including public and periodic reports where appropriate. Additional information project events including meetings, conferences and workshops as well as contact details will be available.

The activities of this work package are divided into three interrelated tasks:

Task 1. Project Management and Communication

The purpose of this task is to ensure effective implementation of the project management procedures through the following activities:

• Establishment and maintenance of a management structure and governance through the preparation and implementation of the Consortium Agreement;
• Coordination with the WP Leaders to plan project-related activities at the project, sub-project and WP levels;
• Elaboration and submission of periodic progress reports and cost statements;
• Cost and time management by maintaining the project budget, and managing the allocation of human and financial resources and related accounting;
• Preparation of annual review reports and review presentations;
• Preparation of annual workplans in coordination with the WP Leaders and revise when necessary;
• Establishment of a communication mechanism through e-mail, phone, video-conferencing, web-based conferencing, fax or face-to-face meetings;
• Organization of a kick-off and regular consortium meetings, prepare agendas, chair the meetings and elaborate minutes;
• Overall coordination and reporting to the EC representatives, including the submission of all project documentation and deliverables; and
• Creation and maintenance of a project web-portal.

Task 2. External Expert Advisory Board

The purpose of this task is the foundation and maintenance of the External Expert Advisory Board. The EEAB will assist and facilitate the decisions made by the General Assembly of MARsite. The Project Coordinator will be responsible for writing the minutes of the EEAB meetings and prepare the implementation of the EEAB’s suggestions. While the work package is organized and maintained by the project coordinator, all partners in the consortium will be contributing to the periodic delivery scheme foreseen.

 Task 3. Quality Assurance and risk management

For quality management the following performance indicators will be identified: input, output, outcome and impact indicators. A consistent set of working guidelines will be implemented throughout the whole project. Process management will involve management of documents, which will be undertaken by the PM, whereas management of the quality of the input data will be the joint responsibility of the WP Leaders and the Project Coordinator. This task will include systematic activities to provide confidence that the project will satisfy relevant quality standards and will be performed throughout the project. The main potential risk in MARsite is the large number of participants, which may lead to inadequate communication, difficulty in overall management, insufficient participation and integration. These will be dealt with by the effective coordination among the WP leaders, PC, PM and PO supported by a clear CA and clear description of responsibilities in working plans, which will be dealt with in Task 1. Other risk areas may include deliverables being not on time or lacking quality, which will be addressed by the close monitoring of the project processes by the WP leaders, PC and PM.

The following activities will be carried out:

• Audit and review project plans to ensure the defined processes are followed;
• Audit and review project deliverables to ensure the work performed is according to the project plan;

Assess the process improvements.

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Work package title: Land-based long-term multi-disciplinary monitoring

WP Leader: INGV

Objective:

The aim of WP2 is the collection and integration of seismological, geochemical, and geodetic data to detect and model the interactions between fluids, crustal deformation and ruptures of the active tectonic structures of the Marmara area and, thereby, to contribute to its seismic hazard assessment. We aim to continue the monitoring of pre-earthquake transients by data recorded from the already established stations and networks. We will carry out in-situ measurements of fluid expulsions and their composition to recover information on changes in the fluid conduits and fluids chemistry, possibly related to pre-earthquake crustal deformation. Since some of the pre-earthquake transients might develop due to small nearby earthquakes, we aim to integrate existing seismological networks belonging to TUBITAK, KOERI and Kocaeli University (KOU). Additionally, we propose to develop multi-parameter data analyses and set-up of physical models that will enable us to correlate seismic and deformation activity with changes in near surface fluid (gas and water) emanation.

Description of work

The objective of this WP is to collect, manage, and integrate all kinds of useful data for monitoring of the Marmara region. As modifications of the fluid geochemistry are normally related to changes in the mixing ratios of fluids from different sources, the genesis of the circulating fluids (including both gases and waters) and their behaviour in time may allow us to discriminate modifications due to the development of the seismogenesis (crustal deformation) or to episodes of faulting activity (ruptures, seismic shocks). A geochemical survey carried out at regular time intervals (monthly rate) over the time span of the entire project (3 years) integrated with high-frequency data from the existing continuous multidisciplinary monitoring networks will allow us to collect enough data providing the necessary information to discriminate seismogenic-related changes from seasonal and anthropic-induced modifications. The temporal changes of geochemical, geodetic and seismic data will be integrated and modelled to gain a step-forward for a deeper knowledge of the development of the seismogenic processes induced by the NAFZ activity thus contributing to a better assessment of the seismic hazard of the area. Several observations have already suggested (Caracausi et al., 2005; Heinicke et al., 2009; Italiano et al., 2004, 2009a, b) that fluids are intimately linked to a variety of faulting processes. Over the Marmara sea area, fluids generated by deep crustal processes seem to be released by the recent faulting activity (e.g. Geli et al., 2008, Gasperini et al., 2012) supporting the necessity to take a look at the seismic hazard assessment by a multilateral view integrating information coming from seismic activity, fluids geochemistry and crustal deformation.

In this WP coordinated by INGV, 6 different institutions contribute: INGV with geochemical field work for sample collection and natural degassing, laboratory analyses, geochemical data validation and contribution to continuous monitoring and data integration and modelling. TUBITAK, KOERI, KOU, and GFZ with data from existing seismic networks. TUBITAK also with geochemical sample collection and laboratory analyses and contribution on natural degassing measurements, data validation, data sharing, data integration and modelling; GFZ with task 2 coordination, management of continuous monitoring geochemical stations (together with TUBITAK), development of existing network with new stations (together with INGV). Ifremer will promote the consideration in WP2 of the submarine, multi-parameter data collected within WP8. After the multi-parameter data integration, all partners will contribute, to data analyses and modelling.

Task 1. Land-based geochemical and geophysical monitoring

The aim of the geochemical investigations is the assessment of the chemical and isotopic features of the discharged fluids to be used in an interpretative geochemical model aimed to constrain the fluids/faults relationships. The geochemical features will allow us to identify the following topics: 1) Chemical and isotopic characterization aimed to constrain the origin of the fluids 2) the main End-Members involved in the studied system (crustal, mantle-derived, radiogenic, etc.); 3) type and degree of water-rock and gas-water interaction processes, 4) Mixing proportions among the End-Members and their temporal changes. As such, the goal of task 1 is to build up a wide geochemical data set regarding fluids circulation, origin and interactions with the faults over the Marmara area. The data will be also combined with those from “Marmara poly-project” (1997). The geochemical survey will include the monthly collection of:

• gas samples for chemical analysis, isotopic analysis of carbon of both CO2 and CH4, isotopic analysis of the noble gases (³He/⁴He, ³⁶Ar/⁴⁰Ar);
• water samples to make chemical analysis of major, minor and trace elements, isotopic composition of oxygen and deuterium; and
• samples for dissolved gas analysis to make both chemical and isotopic analyses.

The analytical work can be done by both INGV and TUBITAK that share the samples, perform the analyses validation, and merge the collected data before moving them to the task 3 and 4 activities.

A general survey for natural degassing measurements of CO2, Rn, CH4 will be also carried out at the earlier stage of the project. Since the discharge of any fluid at the surface is an indication of ground discontinuities, the preliminary results, proposed on GIS-generated maps, will allow us to recognize possible hidden fault traces even in the absence of other surface evidences. This aspect might become a very relevant feature of a faulted area to indicate high-risk of future superficial ruptures in coincidence of seismic events.

Task 2. In-situ measurement of fluid expulsions using existing/improved systems

The existing in-land continuous fluid monitoring network is composed of automatic stations equipped with different probes as a function of the specific features of the selected site (e.g. radon soil degassing equipment, temperature and conductivity of thermal springs within the TUBITAK network covering the whole Marmara region; fluid pressure and water level within the local ARNET operated by GFZ). ARNET is located on the Armutlu peninsula SW of Istanbul centred on the western end of the rupture of the 1999 Izmit earthquake. The automatic stations can also perform real-time data transmission and/or in situ data storage. Based on the results of the fluid mapping (task 1) and a critical evaluation of the existing time-series of continuous measurements, we will choose key sites to install and test new fluid monitoring equipment (e.g. instruments to measure the content of dissolved gases developed at INGV) to be integrated with the existing TUBITAK network for radon and springs measurements and the fluid pressure sites of ARNET.

Task 3. Integration of real-time networks data for Marmara area

Around the Marmara Sea, KOERI, TUBITAK, KOU and GFZ independently run different networks (see WP4). In this task, the main goal is to integrate real time data which comes from different networks. The starting point for this task is the collection of existing data from the continuous seismic, geochemical (spring waters and soil radon) and geodetic networks. For example, TUBITAK networks include more than 40 seismological, 35 geochemical and 21 GPS sites. The ARNET (Armutlu Network) includes 23 broadband and short period seismic stations plus 6 accelerometers and 5 hydrothermal stations. All collected data will be organized in a joint database. The existing GPS data will be evaluated, after a daily data cleaning and pre-analysis (to remove the atmospheric noise) and will be ready to serve for the MARsite project. This integration helps in understanding the anomalies in the time series, detect the false anomalies, and will be a powerful tool to interpret data sets together. Briefly, the main output will be a combined data catalogue of the multi-disciplinary observations ready to be processed in Task 4.

Task 4. Multi-parameter data analysis, physical models for correlating geochemical, geodetic and seismic activity

Data from the land based seismological, geochemical (spring waters and soil radon) and geodetic (microgravity, tilt, GPS) measurements already integrated in a database (task 3) will be analysed by different statistical approaches to remove periodical changes (e.g. earth-tide effects) thus discriminating changes and behaviours closely related to possible speed-up of seismogenic process. Marine data from the fault zone collected within WP8 will also be considered in the present task. Possible pre-earthquake „short-term‟ anomalies can be recognized and interpreted. Multi-parameter interpretative models can be proposed to contribute to the hazard assessment of the Marmara region.

The post WP2- Land Based long-term multi-disciplinary monitoring appeared first on MARsite.

Work package title: Long-term Continuous Geodetic Monitoring of Crustal Deformation

WP Leader: TUBITAK

Objectives

In this WP, long-term continuous monitoring of the crustal deformation will be investigated by exploiting the existing geodetic crustal deformation monitoring systems (Marmara Continuous GPS Network, with the complementary GPS surveys) (Task 1). Additionally, we propose to process SAR data, made available through the Supersites Initiatives archives, acquired by the old and new generation radar sensors, to compute the time series of the occurred and on-going surface displacements (Task 2). To this aim, two different advanced InSAR techniques, the SBAS and PSI ones, will be applied to C-, X- and L- band SAR data. Hence, the integration of the GPS, SBAS and PSI measurements (Task 3), with the contribution of seismological data, will allow us to map the dense spatial-temporal evolution of the present-day crustal deformation phenomena affecting the MARsite area. After the separation of the regional and local deformation processes, we will develop analytical and numerical modelling to define the seismic cycle and map the deformations on the secondary branches of the NAFZ (Task 4). While studying the ERS1/2 and ENVISAT radar data sets, we will update the algorithms and software tools for the future ESA GMES Sentinel-1 A and B satellites (Task 5) and we will be ready for the future. To increase the quality of advanced InSAR analysis, we will develop new approaches to reduce the atmospheric in-homogeneities at the time of acquisition of the different SAR images (Task 6). All efforts will be combined to better determine the 4D deformations in order to understand earthquake cycle processes, to develop probabilistic earthquake forecasting models and to constrain the seismic hazard models in the Marmara region.

Description of work

Task 1. Land-based continuous monitoring of crustal deformation

Interpretation of the data, from existing geodetic crustal deformation monitoring systems (Marmara Continuous GPS Network of TUBITAK-MAGNET, with the complementary TUBITAK GPS surveys) show that the Marmara region is subject to faulting, compaction induced subsidence, inflation and landslides, each of which process is posing a hazard to population and infrastructure. This is a crucial task to measure the tectonic strain accumulation across the Istanbul metropolitan area and western section of the 1999 Izmit rupture by combining the InSAR and GPS data. During the project, this task will supply the key geodetic ground control data to other task, based on the short- and long-term deformations in order to produce the hazard maps. MAGNET daily data flows to TUBITAK’s archive and merges with historical data, automatically. Using the daily updated archive, the GPS time series will be analysed to catch the short time deformation analysis, continuously. In addition, continuous time-series will be merged with survey data and the velocity maps will be obtained in semi-annual periods, in order to define long-term secular motions in detail.

 Task 2. Exploitation of the SBAS and PSI algorithms for surface deformation analysis

 2.1 IREA intends to apply the advanced version of the SBAS technique to X-band SAR data acquired by the new generation radar sensors, made available through the Supersites Initiatives archives. This will allow monitoring the temporal evolution of crustal deformation occurring in selected areas of the NAFZ via the generation of displacement velocity maps and deformation time-series.

2.2 BRGM proposes to process SAR data made available through the Supersites Initiatives archives, acquired by the archived C-band radar sensors to retrieve time-series of surface displacement on selected areas of the NAFZ. This will allow us to map the spatial-temporal evolution of the present-day crustal deformation phenomena affecting the MARsite Area with high level of temporal/spatial details. The goal is to highlight the long-term behaviour of active faults and eventual interactions between structures. Complementarily, where possible on selected areas -nominally on secondary branches of the NAFZ- we also propose to use the archived example L-Band data to demonstrate the advantages of L-band.

2.3 INGV will define in agreement with the other teams, selected areas over which start a detailed monitoring using the X-band COSMO-SkyMed constellation, with a revisit time of 4 or 8 days in ascending and descending geometries. INGV will also process the COSMO data using the SBAS or PSI techniques, depending on the area. . The high frequency of InSAR monitoring is expected to provide new information on possible deformation transients in the pre-seismic phase, while in case of seismic event the 4D deformation maps will monitor the evolution of the post-seismic strain diffusion. Moreover, the high-resolution deformation maps provided by COSMO are needed in Task 4 to separate the regional and local deformation processes.

Task 3. Integration and harmonization of InSAR, GPS and seismic data

Task 1 of WP2, Tasks 1 and 2 of WP3 and Tasks 1 and 2 of WP5 will be the main data sources for this task. In addition, the PSI products of TERRAFIRMA project will be used. In the framework of TERRAFIRMA the European Space agency (ESA) made available the whole SAR database (ERS-1-2 and Envisat) to be used applying PSI in order to obtain surface velocity maps and time series all over the Marmara Region area. In particular, the available PSI products of TERRAFIRMA cover the time interval 1992-2009. This time interval will be extended with new TerraSAR-X and COSMO-SkyMed data sets. The results will be validated with measurements in Task 1 of WP3 and other in situ data made available in other WPs.

The short-time revisit capability of COSMO-SkyMed data is extremely important when studying the theoretically predicted precursory phenomena to earthquake preparation (dilatancy), and the various processes occurring in the post-seismic phase: dilatancy recovery, pore pressure readjustments, afterslip and visco-elastic relaxation. The integration of high resolution InSAR deformation maps with the precise CGPS measurements is the only possible way to fully appreciate the patterns of these elusive signals, whose understanding is crucial to verify (or develop) the theories describing the seismic cycle.

In conclusion, under the contribution of seismological data sets, we will focus to integration and correlation of different data sources, for different earthquake data sets in the past and future.

INGV In the framework of the European project Terrafirma the European Space agency (ESA) made available the whole SAR database (ERS-1-2 and Envisat) to be used applying PSI in order to obtain surface velocity maps and time series all over the Marmara Region area. In particular, the available PSI products of TERRAFIRMA cover the time interval 1992-2009. This time interval will be extended with new TerraSAR-X and COSMO-SkyMed data sets. The results will be validated with measurements in Task1 of WP3 and other in situ data made available in WPs, and will be used for the modelling activities and CFF estimates in Task 4.

We will carry out the joint analysis of CGPS data and DInSAR time-series, to provide more accurate and cross-validated ground velocity maps. We will use the CGPS data to constrain the deformation components at long spatial wavelengths. Using the different information content of CGPS and DInSAR data we will model the effects of possible error sources due to atmosphere, topography, orbital biases.

Task 4. Separation of the regional and local deformation processes and modelling

GPS and InSAR data commonly show various interfingered deformation processes. Separation of the regional and local deformation processes is required to further utilize data for kinematic and physical models. Using decomposition approaches such as those based on singular values, we propose to identify and separate the overlapping deformation signals. The goal is to identify dominant signatures in the data, which might be visually hidden due to their temporal and spatial scale. Furthermore, the task is to use these signals separately for quantitative analysis. This will be done by inversion methods that will be further developed to model both the original data and the decomposed signatures. The aim is to improve understanding of both local processes and regional scale processes. Local processes might be land compaction or landslides. Regional scale deformation processes might be the inter-seismic steady-state plate motion combined with co-seismic and transient deformation processes that have happened in the past, taking the full deformation time series and herewith time dependent rheological complexities into account.

In particular, modelling of the deformation processes is foreseen in the following ways; (a) elastic dislocation block-models with the aim to study microplate kinematics in the framework of major plate convergence, and active strain build-up at block-bounding faults.  Kinematically consistent elastic block-model will be used to infer the pattern of fault-coupling on the plate-boundary faults, by a constrained inversion of GPS and InSAR velocity maps. (b) Time-series deformation data (from Multitemporal InSAR and CGPS) will be modelled using both analytical and numerical modelling techniques. Based on principal component analysis the space-time evolution of slip on fault planes is to be investigated during both the interseismic and post-seismic phases (for both archived and new incoming data streams). (c) Modelling of time-series data shall allow investigation of different rheological behaviours in the body and the fault zone, such as those associated with creep, visco- and poro-elasticity and plastic deformations. (d) Modelling deformation data together with double integration of accelerometer data (see WP5), and finally (e) models shall allow to analyse the fault interaction with the Coulomb Failure Function (CFF), i.e. co-seismic and interseismic perturbations to the regional stress field.

As a final goal, the developed models shall be investigated with respect to microseismological data (see WP2 and WP4) to detect branches of the NAFZ, and to evaluate the power of such improved data handling for probabilistic earthquake forecasting.

Task 5. Extension and the transition into the new (GMES) satellite constellation and data for advanced InSAR analysis

The future ESA GMES Sentinel-1 A and B satellites will represent an unprecedented source of regular, consistent and frequent SAR data, of high interest for any application that calls for continuous monitoring of small terrain displacements. As soon as the constellation will be operational, a continuous coverage will be guaranteed, with one acquisition every 6 days with characteristics suitable for interferometric combination. This feature has been obtained by exploiting a new acquisition modality (TOPS) that, implementing a burst-mode and scanning geometry, allows covering very large areas while worsening some geometric resolution in one (azimuth) of the two directions.

The availability of Sentinel-1 data will also cover the gap after the change of orbit of the ENVISAT satellite that hindered the possibility to continue the formation of displacement time series over long-time intervals. The new Sentinel-1 acquisition modality, while very interesting, calls for a significant update of the algorithms and software tools that are exploited during advanced (PS + SBAS) InSAR analysis of long SAR data time series. The aim of this Task is first to update an existing operational processing chain for advanced InSAR analysis (the SARscape^®Interferometric Stacking module), currently based on stripmap, spotlight and/or ScanSAR acquisitions, to also support the Sentinel-1 TOPS (Interferometric Wide Swath) acquisition mode. The launch of the first Sentinel-1 platform (Sentinel-1A) is currently scheduled for May 2013; it is hence foreseen that some of the developments will be performed with simulated data, and then with not fully-calibrated data originating from the mission’s CAL/VAL campaign, when available. The updated processing chain will be then validated and exploited for processing new data obtained from the Sentinel-1 operational phase, to start building new displacement time series.

Task 6. Integrating a few independent sources for atmospheric artefacts reduction (MERIS, MODIS, OSCAR from JPL, GPS) into PSINSAR and SBAS analysis

Atmospheric in-homogeneities at the time of acquisition of the different SAR images that are combined together to perform advanced InSAR analysis are a significant source of artefacts (the so-called Atmospheric Phase Screen) and distortions, that ad-hoc filtering aims to minimize to increase the final accuracy of the displacement measurements.

The typical approach of these filtering algorithms relies on different expected temporal and spatial distribution of the APS respect to the displacement signal to be measured. In particular, it is expected that the APS is (for satellite acquisitions separated of one or more days) temporally uncorrelated (high-pass signal), while the deformation signal has a significant temporal correlation (low-pass signal). This assumption is, of course, risky, in particular in case of abrupt events like earthquakes, where discontinuities of the measured displacement are often directly to be related to real deformations and not to artefacts.

The availability of external, independent sources to characterize, estimate and as far as possible subtract APS components is hence a key issue to minimize their impact on the final measurements accuracy and not to risk to mix the atmospheric and displacement signals in what is subtracted from the original data. In this case three main types of sources can be considered: multi-spectral imagery (e.g. MERIS and MODIS sensors), weather forecast (e.g. WRF, ECMWF) models and GNSS (e.g. GPS) measurements; these systems can be exploited to estimate Zenith Path Delay layers at the time of acquisition of the SAR images and compensate for their temporal difference.

One goal of this work-package is to build a set of software bridges between the existing PS and SBAS SARscape^® processing chain and ZPD layers obtained from the different cited sources. In particular, one example of such a data source will be the OSCAR system of JPL that allows dedicated software clients to request and obtain ZPD information that is derived from combined MODIS and ECMWF data. Another source of particular interest for ENVISAT ASAR data is the MERIS instrument. This sensor can acquire multi-spectral data at the same time and on the same area of ASAR, providing as standard product a water vapour layer that can be simply converted into ZPD estimation.

The ZPD data will be integrated within the SARscape advanced InSAR processing chain to optimize the APS filtering stages, minimizing artefacts due to possibly wrong assumptions.

The extended processing chain will then be exploited to generate new versions of displacement time series over the test site area, allowing to analyse and to quantify the improvements that can be obtained with this combined approach.

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Work package title: Establishment of Borehole Observation System and High Resolution Seismic Studies in the Marmara Sea

WP Leader: IU

Objectives

The main objective of this WP is to install a multi-parameter borehole system and surface array as closest as to the main Marmara Fault (MMF) in the western Marmara Sea, and measure continuously the evolution of the state of stress of the fault zone surrounding the MMF and to detect any anomaly or change which may occur before earthquakes by making use of the data from the arrays already running in the eastern part of the Marmara Sea. The data from the new borehole system is also integrated to the data set to be used in the analysis.

The key objectives of this WP are the following.

• To design and build multiparameter borehole system consisting of very wide dynamic range and stable borehole (VBB) broad band seismic sensor, and incorporate 3-D strain meter, tilt meter, and temperature and local hydrostatic pressure measuring devices,
• Determination of 1-D S-wave velocity structure beneath the borehole system by array microtremor measurements,
• Combining borehole and surface network data for earthquake location improvement,
• Determination of surface and near-surface effects on seismic waves,
• Estimation of the near-surface geology effects masking the source related information.
• Monitoring rupture nucleation and propagation using borehole and surface array data,
• Closely inspection and monitoring of the last stages of the preparation stage of a major rupture,
• To measure continuously the evolution of the state of stress of the fault zone surrounding the Main Marmara Fault (MMF), and to detect any anomaly or change which may occur before earthquakes,
• To identify the presence of repeating earthquakes along the MMF,
• To better understand the existing seismically active structures and their role in local tectonic settings,
• To understand the stress transfer mechanism from east to west,
• To obtain continuous high resolution locations of micro-seismicity including development of relative location technique from cross-correlation methods (multiplet analysis) and study the space-time evolution of the activity,
• To search for low frequency events (non-volcanic tremor) from continuous recording,
•  To analyze triggering mechanisms like Coulomb transfer, aseismic slip, or fluid migration and possible declustering methods.

These activities will be performed by four well instrumented networks; one is multiparameter borehole system which will be deployed in the frame of this project, in the western part of MMF, and the other three which are already running are; 1) PIRES array having two sub arrays each consisting of five seismic stations located on the Princess Islands, very close to the MMF, 2) CINNET array located around Cinarcik Basin in the eastern part of MMF. The data from these networks will be integrated and outputted to other workpackages, especially to WP2, WP3 and WP6.

Description of work

Task 1. Deployment of surface microearthquake array and borehole seismometers and integrating of borehole and surface array data for better location of microearthquakes

Bringing face to face the seismograms of microearthquakes recorded by borehole and near-surface instruments portrays quite different contents. The shorter recording duration and nearly flat frequency spectrum up to the Nyquist frequencies of borehole records are faced with longer recording duration and rapid decay of spectral amplitudes at higher frequencies of a surface seismogram. The main causative of the observed differences are near-surface geology effects that masks most of the source related information the seismograms include, and that give rise to scattering, generating longer duration seismograms.

In view of these circumstances, studies on microearthquakes employing surface seismograms may bring on misleading results. Particularly, the works on earthquake physics and nucleation process of earthquakes requires elaborate analysis of tiny events. It is obvious from the studies on the nucleation process of the 1999 Izmit earthquake that tens of minutes before the major rupture initiate noteworthy microearthquake activity happened (Bouchon et al.,). The starting point of the 1999 rupture was a site of swarm activity noticed a few decades prior the main shock. Nowadays, analogous case is probable in western Marmara sea region, prone to a major event in near future where the seismic activity is prevailing along the impending rupture zone. Deploying a borehole seismometer e.g. in Marmara Island and/or eastern end of the Ganos fault zone may yield invaluable data to closely inspect and monitor the last stages of the preparation stage of major rupture.

The proposed Multiparameter digital Borehole seismic station will use the latest update technologies and design ideas to record “Earth tides” signals to the smallest magnitude -3 events.  As the region is seismically active, strong motion sensors will also be incorporated so as to cover the widest dynamic range ever recorded in borehole systems.  The Measurements of other parameters with the confines of a deep borehole will assist the study of seismology to give better understanding of seismic activities.  The additional parameters are:  local tilt, temperature, local hydrostatic pressure, local “3-D strain” and acoustic signals. The data collected by this system will be used in other tasks in the package, especially Task 2 and Task 3.

Task 2. Analyzing response of near-surface geology to earthquake ground motion and its effects masking the source related information through borehole data

This task will take advantage of the data from multi-parameter borehole system and surface array (Task 1). Strong motion data recorded by vertical arrays of accelerometers offer the opportunity to study the propagation of the waves in the subsoil. However, boreholes recording, that due to the lower signal-to-noise ratio and a smaller effect of the shallow layer attenuation might seems to be more appropriated to study source parameters and to determine the input ground motion, are affected by the contamination of down-going waves (Parolai et al., 2009) that have therefore to be removed before any estimation of source parameters can be carried out. On the other hand, the surface recordings might be strongly biased by the site response that has to be accounted for. Within this task, different methods for correcting the borehole seismograms, both based on the knowledge of the subsoil structure or independent from it (Bindi et al., 2010), will be tested, improved, and developed. The influence of the amplitude of ground motion recorded in the results of the different correction schemes (and therefore in turn on the source parameters, and in the estimation of the input ground motion) will be estimated. A close cooperation is envisaged with Task 1 of WP9, where recordings from data installed in nearby buildings (SOSEWIN) will also be examined.

Task 3. Monitoring the fault zone and source process in the near field

Continuous evolution of fault zone properties:

The zones surrounding major faults are highly fractured and their physical properties (density of open fractures, fluid presence and circulation, velocity of seismic waves) evolve with their state of stress. Recent advances based on seismic noise correlation techniques (Campillo and Paul, 2003), allow very fine measurements of possible changes in seismic wave velocities over time. We propose to use these techniques to monitor the evolution of seismic wave velocities in the zone surrounding the Main Marmara Fault (MMF).

We will proceed in two major stages. First, we will test the application of seismic noise correlation to the Marmara Sea environment and to the configuration of its permanent seismic stations. This will help define the stations and the paths of the seismic waves, which best sample the fault zone.

In a second stage, we will try to set-up and organize a semi-automatic system, which, from the Kandilli Observatory, will correlate the seismic signals and make a daily monitoring of the seismic wave velocities in the fault zone.

The objective of this work is to measure continuously the evolution of the state of stress of the fault zone surrounding the MMF and to detect any anomaly or change which may occur before earthquakes.

Search for repeating earthquakes on the Main Marmara Fault:

Recent advances in measuring deformation at the earth surface have changed considerably our view and understanding of how tectonic plates move relative to one another. With the discoveries of non-volcanic tremors, low-frequency earthquakes, slow slip events, and silent earthquakes over the last decade, our knowledge of the dynamics of plate motion has changed dramatically and has been greatly enriched.  We now know that plate boundaries can slip in a variety of ways between the continuous slip that takes place at depth and the catastrophic slip of the large earthquakes. Because all the slip modes of a plate interface, like the North Anatolian Fault, necessarily interact with one another, understanding where and when large earthquakes will occur requires accurate measurements of the various modes of slip of the interface. In this respect, repeating earthquakes have proven to be a powerful tool to investigate if a fault is slowly slipping (Vidale et al., 1994).  Repeating earthquakes are small seismic events, typically a few hundred meters in size, which occur repetitively from time to time at exactly the same place. Each time they rupture the same patch of the fault, which requires a continuous reloading of stress. This reloading is produced by the slow slip of the fault area surrounding the patch. Thus, the simple presence of repeating earthquakes on a fault segment implies that this segment is slowly creeping. The amplitude and timing of these repeating events gives an estimate of the amount of slow slip that is occurring.

We will try to identify the presence of repeating earthquakes along the Main Marmara Fault. In a first stage this will require the fine relocation of events that occur along the various segments of the MMF and, in a second stage, the development of a computer code able to identify recurrent seismic waveforms.  If we find these repeating events, we will model their source and study their timing to infer the presence and the rate of slow slip occurring. The observation that the Izmit earthquake began 44 minutes before the catastrophic rupture with the slow slip of the fault at depth, accelerating as the time to the earthquake was approaching (Bouchon et al., 2011), emphasizes the close connection that we think exists between slow slip and the nucleation of large earthquakes.

Task 4. High Resolution Seismology in Marmara Sea with Arrays

The Çınarcık Basin (CB) is the complex transition zone between the unruptured main Marmara Fault and the recently ruptured zone of Izmit-Duzce earthquake sequence. The details of the actual deformation in the basin are poorly understood despite the fact that it is critical in understanding the stress transfer mechanism from east to west. The microseismic activity provides the most effective keys for developing a realistic model of the on-going deformation (Bohnhoff et all, 2006). The seismic events on the inferred Northern Boundary Fault on the Cinarcik Basin are rare but provide the essential clues for the prominent rupture in Marmara Sea (Örgülü & Aktar, 2002; Karabulut et al, 2002; Özalaybey et al, 2002). Since the seismogenic zone is entirely offshore and the number of permanently operating OBS is very limited, a permanent seismic array (PIRES) was installed on the Prince Islands, at few kilometres distances to the fault. The array consists of two subarrays installed on the two outermost islands (Yassiada and Sivriada) of the Princes Islands group offshore Istanbul. Each PIRES subarrays consist of five seismic stations at the surface spaced in a cross-shape layout. The use of the array data improved by an order of magnitude both the detection and the resolution capabilities of the seismic monitoring on the northern boundary of CB (Bulut et al, 2009). The network has recently been enlarged towards the other Princes Islands in order to improve the azimuthal control of the focal area. We additionally integrate data from local permanent stations; the ARNET seismic network on the Armutlu peninsula and CINNET array (Task 5). Combined data allowed obtaining a well-resolved scale for the hypocentral map to better understand the existing seismically active structures and their role in local tectonic settings.

Second order source properties of the local activity will also be monitored in view of the observations published recently by Bouchon et al. (2011) related to the precursory phenomena of Izmit Earthquake (1999). PIRES arrays were already used to reveal the fine details of time dependent spectral properties of seismic swarms in Çınarcık Basin (Bulut et al, 2011). We plan to monitor whether the well-known scaling of corner frequency and moments holds for repeating events of various order of magnitude or if an intermediate behaviour similar to the Izmit Precursors can be observed.

The PIRES arrays will also be used to study the structural properties of the fault zone. Since the Marmara Fault is entirely offshore, the PIRES arrays are the only on-land stations which are located closest the fault zone in the whole of Marmara Sea. They are therefore best positioned to monitor the properties of the fault zone at close distance. The high accuracy of array processing will allow the monitoring of any possible structural transformation likely to occur inside the fault zone. In particular, a modification of pore pressure is expected to have a signature in the S-wave propagation characteristics. A systematic application of cross-correlation to the array data from active quarries will reveal minor details of the wave propagation at the upper crustal level. A similar on-line monitoring procedure will also be applied to the receiver functions of teleseismic events for monitoring of the total crust.

Task 5. Monitoring structural characteristics on Çınarcık Fault (CINNET)

The analysis of the seismicity in the Çınarcık basin appears of central importance for addressing the question on the transition from the last Izmit, 1999, Earthquake to the next major event in the Marmara region. A fine monitoring of the seismicity in the East Marmara Sea region might help to address several important questions:  how the westward migration of large earthquakes since 1939 will enter the Marmara Sea in a complex transition zone between the Izmit fault and the Main Marmara Fault (Dewey, 1976; Stein et al., 1997). Twelve years after Izmit earthquake, are we back to a background activity and how is this background activity related to the extension deformation of the region (Karabulut et al., 2002) What is the recent evolution of seismic clusters observed in the Çınarcık basin (Karabulut et al, 2011).  What are the interaction mechanisms between the North Anatolian Fault and the regional seismic cluster? Are the seismic clusters related to the nucleation of the major strike-slip events?

The recent analysis of the seismicity history in the Çınarcık Basin (Karabulut et al, 2011) provides interesting information on two types of aftershocks activity: the first type of enhancement is on strike-slip fault segments (Izmit Fault, Princes Island section of the Main Marmara Fault, Gemlik Fault) immediately following the main shock and related to Coulomb stress transfer; the second type of enhancement is attached to extensional clusters (Yalova, Tuzla) with a few days delay in the onset of strong activation, probably related to pore pressure increase. We observe a fast decay of the activity on strike-slip segments and slower evolution of seismic clusters with extensional features. Two years after the Izmit earthquake, seismic activity returned to the pre-earthquake pattern with most of the activity occurring within extensional clusters. It appears that the influence of the last large strike-slip event on the spatial seismicity distribution in the eastern Marmara Sea is less significant than the effect of the long term regional extension.

The CINNET network was deployed in 2008 around the Çınarcık basin to obtain a fine monitoring of the activity in the region (Karabulut et al, 2011). We propose to maintain and develop this network in connection with KOERI regional network. One objective is to update the network with telemetry systems and to implement up to date software for data management (Seiscomp). Scientifically, objectives are threefold:  1) obtain continuous high resolution locations of micro-seismicity including development of relative location technique from cross-correlation methods (multiplet analysis) and study the space-time evolution of the activity (Got et al, 1994); 2) search for low frequency events (non-volcanic tremor) from continuous recording (Shelly and Hardebeck, 2010); 3) analyze triggering mechanisms like Coulomb transfer, aseismic slip, or fluid migration and possible declustering methods.

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Work package title: Real- and quasi-real-time Earthquake &Tsunami Hazard Monitoring

WP Leader: KOERI

Objectives

The main aim of this WP is to implement an integrated approach by harmonizing geodetic and seismic data to be used in early warning applications, such as fast centroid moment tensor inversion and rapid slip inversion, so that in addition a quick determination of the rupture characteristics could also assist the identification of the tsunamigenic potential of an earthquake in combination with a tectonic origin tsunami scenario database. This integrated approach will provide a unique performance compared with only seismic or geodetic networks and false alarm will be minimized for Earthquake and Tsunami warnings. Together with a finite source description and calibration of available geodetic and seismic data, a rapid and quantitative Shake map generation scheme will be provided. For this purpose, data processing techniques and computing algorithms will be investigated and designed by making full use of the monitoring system of the MARsite. Rapid source information (not only hypocenter, magnitude but also, for example, rupture directivity) is vital, particularly for damage estimation in the configuration of the Marmara region and Istanbul with respect to the NAFZ, and especially the expected large earthquake. From this point of view inversion of geodetic data immediately enhances the speed and accuracy of the preliminary damage maps.  It is intended to create high-resolution geodetic/seismic infrastructure, at a test site, to receive real-time GPS and Seismic data and is to develop and improve analysis techniques and methods to develop PGV shake maps that is obtained with automated finite-source inversion results. Taking into account the continuous geodetic (GPS) data will be a key issue. High resolution geodetic/seismic infrastructure will be installed (update of 26 GPS stations by cGPS with co-deployment of strong-motion sensors) in this area to provide real-time data necessary for the finite-source inversion (Task 1), rapid finite source inversion tools will be improved (Task 2), ground-motion simulation tools will be calibrated (Task 3), a scenario database for both for seismic and tsunami hazard evaluation will be created (Task 4), the final hazard map by taking into account uncertainties  and ground-motion variability will be improved (Task 5)  and finally long and short-term earthquake forecast maps will be developed (Task 6).

Description of work

Task 1. Establishment of appropriate infrastructure (particularly for GPS and strong motion stations in Marmara Region) to obtain real time data

Two objectives of this task are to update 16 of 26 GPS sites in order to establish real-time data transmission and installation of strong ground motion instruments.  The acquisition and harmonization of real time GPS and Strong Motion time series will provide excellent time resolution of real time earthquake monitoring and also provide to measurements of tectonic strain accumulation across the Marmara Fault zone. These measurements will also enable a quick determination of the rupture characteristics to assist the identification of the tsunamigenic potential of an earthquake. In other words, this refined and newly established infrastructure and combined GPS and Seismic real time data will contribute to develop real-time applications that allow to closely and rapid monitor earthquake processes and tsunami assessment.

The next-generation geodetic and seismic data can be used for EEW applications, fast centroid moment tensor inversion and rapid slip inversion. This infrastructure will also opportunity to research unknown fault parameters and decisive contribute to refinement of the seismic hazard map for this important region. This integrated approach will provide a unique performance compared with only seismic or geodetic networks and false alarm will be minimized for Earthquake and Tsunami warnings. Currently, the existing GPS monitoring arrays do not provide real-time data because of the absence of proper continuous power and communication infrastructure. All of the GPS sites (26) in Marmara Region will be improved upon by the installation of power source unit, (GPRS or Satellite). The output of this Task will be real time GPS and Seismic time series and will be an input of the Task 2, 3 and 4.

Task 2. Near real-time determination of the earthquake finite-fault source parameters and models, based on GPS and strong motion data

Information about the extended source properties are needed for performing the ground motion simulation associated to the earthquake rupture on the causative fault. The main goal of this task is the fast determination of the earthquake source, with special focus on its finite-fault characteristics.

Analyzing geodetic and seismic data together using a Kalman filter will provide precise and true broadband record of displacements across the entire frequency range, including the static component. These analyses can be done in near real time and are particularly suited for capturing near-source large earthquakes.

In order to improve rapid ground-motion simulations in case of large earthquakes in the Marmara region, a new tool for rapid reconstruction of the rupture process of large earthquakes using near-field strong-motion and high-rate GPS data will be developed. The array-seismological method will be extended by taking into account empirical or synthetic Green’s functions. Aim of such method will be providing a fast and reliable estimation of most relevant source parameters (e.g. moment magnitude, fault size, rupture duration, slip centroid) rather than achieving a high spatio-temporal resolution.

Furthermore, two finite-fault inversion programs will be developed, tested and compared. The first code implements a linear technique to invert strong motion and GPS data: it is very fast and produces a model of the earthquake rupture process in term of heterogeneous slip distribution, uniform rise time and constant rupture velocity. The second code is based on a simulated annealing technique: it is slower than the former, but it may handle very complicated rupture model with heterogeneous slip, rise time and rupture velocity, other than several kind of source time function. The performance of the above codes will be assessed in term of accuracy of the solution and quickness of the execution run through several synthetic tests, specifically designed for the Marmara Sea tectonic setting and observational network.

Task 3. Generation of a routine for simulation of strong ground motion based on integrated data

This task aims to establish the rapid PGV Shake maps through numerical simulations by integrating the various data (GPS and Strong Motion). Most of the automated Shake Map applications are primarily based on point source approximations; however finite source effects are significant for major earthquakes. First of all, in order to understand the variability of the ground motions, we intend to introduce a deterministic-stochastic finite source description (INGV). In parallel, we are going to optimize the existing numerical codes (e.g. finite difference, spectral element) in order to adjust the parameters requested from the expected PGV map resolution and rapidity (BRGM-KOERI). The numerical tools are to be available for further use. Finite source models are obtained from the geodetic and seismic data rapidly for major earthquakes (Tasks 1 & 2). Such information (hypocentre, fault dimension, rupture directivity and velocity, and some more) should be integrated in the simulations, and we examine the rapidity and the precisions of such rapid numerical PGV maps, which are useful for further earthquake and tsunami rapid information infrastructure (Tasks 4, 5 & 6). Multiple windows simulation techniques improved with site correction make it possible to simulate strong ground motion for generation of PGV ShakeMaps.  The suitability and sensitivity of the inversion and simulation scheme for producing rapid Shake Maps will be tested by well-recorded earthquakes; however there are limited numbers of medium to large earthquakes that are recorded with GPS receivers. Among them 2004 Parkfield earthquake data can be utilized as test data. This earthquake was recorded at thirteen 1-Hz GPS receivers and several strong motion instruments. Simulated models will also be compared with distribution of ground shaking intensity provided by available Earthquake Early Warning Algorithms.

Task 4. Creating a scenario database for earthquake triggered tsunamis and Testing of the routine with well-studied events

The goal of the present task is to build up a detailed scenario database for all possible earthquakes in the Marmara Sea with a tsunamigenic potential. Due to the very short travel times in Marmara Sea, a Tsunami Early Warning System (TEWS) cannot rely on real-time calculations and has to be based on a pre-computed tsunami scenario database to be queried in real-time, basing on the initial determination of earthquake hypocentre and Magnitude, but also on dislocation models calculated from real-time inversion of geodetic and seismic data (from Tasks 2 and 4), similarly to e.g. the GI-TEWS in Indonesia. Such a database could be inspired to that implemented in the Japanese TEWS, which nonetheless will be adapted to Marmara region. The Marmara region will be divided in grid areas of 0.1°x0.1° and tsunami scenarios will be created for each bin, where the bin centre will be characterized as the epicentre location. Earthquake source parameters will be defined based on a study of characteristic source parameters in the region, supported with historical and statistical studies. A decision support system for the TEWS should also be supported with offshore tsunameters and or hydrophone/pressure meters, if possible. In the presence of these tsunami data, together with seismic and geodetic data, the database might be also used as a set of Green’s functions for recovering the tsunami source via real time inversion with the aim of constraining the tsunami forecast. Moreover, these Green’s functions could be used for long-term probabilistic tsunami hazard assessment (PTHA) if earthquake recurrence times will be provided by Task 6 in this WP.

Task 5. Improvement of the probabilistic seismic hazard assessment by taking into account uncertainties and ground-motion variability

Probabilistic seismic hazard analysis (PSHA) is de­fined as evaluation of the probability or likelihood that there will be ground motion in excess of certain levels during a specific time period. The basic analytical procedure used in present-day PSHA was originally proposed by Cornell (1968). Since that time there has been significant progress in scientific understanding of the earthquake process and in the technique for evaluation of the relevant seismology, geo­logical, and geophysical data.  Several studies with various degree of sophistication are conducted for the assessment of seismic hazard in the Marmara Region (Atakan et al., 2002; Erdik et al., 2004; Kalkan et al., 2008).

The betterment of the knowledge on the seismotectonic regime of the Marmara region will pave the path for development of alternative source models for the improvement of existing probabilistic hazard maps. In this connection, the most recent findings and outputs of different work packages of the project, in terms of seismicity, fault segmentation, slip rate data and association of past earthquakes with individual segments will be utilized. Various renewal-type stochastic models and characteristic earthquake occurrence will be utilized for the earthquake rupture forecasting. For near fault quantification of hazard at long period spectral accelerations, the directivity affects will be considered in the analysis. The epistemic and aleatory uncertainties will be rigorously treated respectively, through the use of a comprehensive logic tree analysis and the consideration of inter-event and intra-event variabilities.

The assessment of the inter-event correlation of earthquake ground motion will be facilitated through use the data obtained from the dense accelerometric network in Istanbul.

Task 6. Develop short-term earthquake forecast maps

The aim of this task is to focus on the development of short-term earthquake forecast maps for the Marmara region. The long term probabilistic hazard models are currently the most crucial forecasting tool against earthquake damage, because they are used as guidelines for earthquake safety provisions of building codes, whereas the short-term forecasting of the earthquake aftershocks is used for time-dependent seismic hazards to help communities prepare for potentially destructive aftershocks.

The improvement of the existing long-term earthquake hazard assessments in the Marmara region will be carried out under WP5-Task 5. The possibility of developing models for the short-term forecasts in the Marmara region will be investigated in this task based on the analysis of aftershock sequences and seismic clustering. The short-term model of Gerstenberger et al. (2007), used in EU FP6 NERIES Project, will also be considered.  The possibility of integrating the studies with the on-going research in EU FP7 projects of REAKT and NERA as well as with the Collaboratory for the Study of Earthquake Prediction (CSEP, www.cseptesting.org) project will be explored.

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Work package title: Earthquake-Induced Landslide Hazard in Marmara

WP Leader: INERIS

Objectives

The 1999 Izmit and Duzce earthquakes in northwest Turkey have revealed the Ataköy area located westwards of Istanbul as affected by very significant local site effects (Sørensen et al., 2006). Moreover, the adjacent urbanized and geologically similar area of Cekmece has been geologically and geotechnically surveyed and characterized as a concentrated landslide prone area, showing high susceptibility to both landslide and liquefaction phenomena (Duman et al., 2005).

This fast developing area includes also critical facilities such as the Atatürk international airport and several industrial plants. Latest earthquake disasters underline how important better prediction of those geohazards is for the prevention of casualties and economic losses. Eventually, offshore landslide tsunamigenic hazard triggered by strong earthquake is clearly to be considered when reflecting about the closed situation of the Marmara sea.

The aim of this work package is to improve the preparedness of those seismically induced landslide geohazards, through the using and the improvement of monitoring and observing systems in hydrogeotechnical and seismically well-constrained areas within the supersite. Two areas,on-shore and off-shore, will be studied deeply to gain knowledge and improve the capabilities to work out guidelines for a LHS “Landslide Hazard Scale”, including earthquake triggering factor. The terrestrial western part of Istanbul and a potential submarine landslide detected at the entrance of the Izmit Gulf are the two identified targets.

As regards landslide pre-disposition, pre-existing geological, geomechanical and geomorpholocial and geophysical data, including high-resolution DInSAR data, will be selected and analysed to develop better understanding and enhance capabilities to hazard assessment and susceptibility mapping, including local site effects enabling the earthquake triggering of inactive or dormant landslide. Gain is expected as regards methodology for areas to be studied in the future (Task 1).

As regards local site effects, considering the pre-existent earthquake scenarios based on the closest NAF segment in the Marmara Sea (Pulido et al., 2004), ground motion modelling showed that highest ground motions are expected in this area, obviously due to its very close vicinity to the NAF. Ground motion data currently collected will be processed and modelled to grid and map site effects and to test them versus case studies (Task 2).

Description of work

Task 1. Investigations of local instability areas – onshore and offshore – and developing of advanced susceptibility mapping

It is well known that the shelves and slopes of the Sea of Marmara are prone to landslide/tsunamigenic hazard caused by the diffuse presence of potentially instable sedimentary bodies that could slump towards the basins centre as a consequence of major earthquakes. In fact, this has occurred during several strike-slip earthquakes, with mainly horizontal displacement, that have, however, caused local although destructive tsunamis, probably due to secondary mass movements caused by the shaking (Yalciner et al., 2002). The first step towards a mitigation of landslide-derived tsunami hazard has been the mapping of all potential gravitational sliding through the use of the dense-spaced marine geophysical database available. Thus, all previous geophysical surveys will be closely examined.

The first geophysical survey in the northern shelf was carried out to collect single-channel shallow seismic data, gravity cores and surface sediment sampling for studying Quaternary geology in the mid-1990s (Oktay et al. 2002). The second stage of data collection was after the disastrous earthquakes of 1999. A strong international effort that followed the 1999 Izmit earthquake that culminated with the MarNaut mission, where several dives were devoted to the study of gravitational deposits (Henry et al., 2008; Zitter et al., submitted). Then, although specific studies on fossil landslides have been carried out in the past (Gorur and Cagatay, 2010; Ozeren et al., 2010) a detailed study of submerged areas, that will be most likely sites of major landslides in the future, is missing.

Another offshore data set collected in 2007 by TÜBİTAK MAM, will be also used to focus on the fragment of the Western Black Sea fault (WBS). It includes high resolution bathymetry (<20m), bathymetry (20 m<H<100 m) and very dense shallow seismic lines along the shoreline (Ergintav et al., 2011). The multichannel seismic data acquisition is carried out for the first time at west of the Bosphorus in the northern shelf of the Sea of Marmara to investigate offshore structural features such as Çatalca Fault Zone and the shallow deformations as the result of possible submarine landslides to interpret the structural features offshore the Avcılar Peninsula (Ergintav et al., 2011).

By the way, ISMAR-CNR collected, during several expeditions starting from 2001, multi-beam bathymetry, high-resolution single- and multichannel seismic reflection data, as well as gravity cores on a major potential submarine landslide (4 x 2 x 0.2 km) located at the entrance of the Izmit Gulf, close to the W termination of the surface rupture of the 1999 Izmit earthquake (Gasperini et al., 2011). The dimensions and characteristics of the landslide, together with its location (close to the NAF northern strand, and facing the Istanbul coastline) are important reasons for attempting a detailed study of this major landslide, through already available geophysical data, and carrying out modelling along with ITU to predict its behaviour during the next major earthquakes that will probably affect this strand of the NAF.

Task 1.b On-shore landslides

The area of Cekmece, consisting essentially of gently rolling hills with low slopes, is covered by more than 400 landslides showing numerous scarps (Duman et al., 2005). Approximately half of all landslides are distributed between Büyükçekmece and Gürpınar area of the Avcılar Peninsula, which are important local landforms in the region.

Field investigations and analysis of this area have been published, delivering existing inventories, available GIS and existing monitoring of local block deformations with Global Positioning System (GPS). A deeper analysis will be undertaken (distribution, density and activity analysis of landslides, spatial persistence and temporal frequency of landslides) with further field survey for investigating landslides and evaluating the evolution of existing mass movements of much concern. Development of landslide hazard map and associated uncertainties will be carried out including strong ground motion along with estimated amplification site effects, dealing also with intense and/or prolonged precipitation as a potential worsening factor during seismic shaking. While carrying out geophysical investigations in relation with Task 2, an active landslide will be identified as a potential pilot site to be instrumented in the future with a specifically designed ground-based system for local continuous and multi-frequency observation to study physical interactions and early warning strategies.

Use of space multispectral/hyperspectral image data to identify geological and geophysical parameters and delineate corresponding areas will be completed to evaluate the resolution to identify landslide hazard-related features. Evaluation and fusion of the extracted features with InSAR related ones and geological/geophysical models should permit to design a suitable strategy to help defining a landslide hazard scale.

Moreover, the integration of geological and geomorphological analyses with high-resolution DInSAR data will allow the identification and characterization of activated and reactivated Deep-seated Gravitational Slope Deformations (DGSD). The modelling of the related deformations will permit to characterize from a geometrical point of view the sliding plane and to quantify the amount of slip.

Eventually, guidelines for an aggregation strategy between field surveys, ground-based and space geological and geophysical data will be produced to refine a regional landslide hazard scale to be used.

Task 2. Ground motion data, local seismic site effects and dynamic numerical modelling 

Task 2.a Off-shore landslide and Tsunami hazard

The numerical modelling and laboratory testing of landslide generated Tsunami scenarios in the Sea of Marmara will be an ITU contribution. Collaborations between ISMAR and ITU are already under way to study a sediment mass at the entrance of the Izmit Bay. Several seismic images of the mass are being studied (Postacioglu and Özeren, 2008). A 3D generation model will be assimilated into a shallow-water finite-element Tsunami propagation code being developed at ITU. However, ITU will carry out numerical simulations of tsunamis generated by a possible mobilization of this mass. Furthermore, run-up scenarios will be produced by using the outputs from the numerical models. A 15 m long and 60 cm wide and 1.5 m high tsunami channel has been constructed at ITU hydraulics lab to this end. Especially 1-D run-up scenarios will be tested in this channel (Özeren and Postacioglu, 2012).

Task 2.b On-shore landslides

The Ataköy area, also located in the same western part of Istanbul, has strongly been affected by the Mw=7.4 Izmit Earthquake although it is about 100 km away. Local site effects played obviously an important role to increase the damage together with the bad building stock. This has been confirmed from field studies and seismic data collected sometimes after the disaster.

The assessment of ground motion reference scenarios and local seismic amplification effect is possible by in-situ data acquisition and processing. Site effect studies (e.g. mapping of predominant frequencies and bedrock depth distribution, site amplification), 1D and 2D Vs structure around the north part of the NAFZ, specifically in the western part of Istanbul and its suburbs, will be studied. This will include compilation of strong motion data from the large earthquakes (Mw>5) in and around Marmara Sea, and the recent studies on strong ground motion and site effects, which have been performed in the area.

A series of geophysical surveys (determination of S-wave velocity structure at depth with active/passive array surface wave measurements) and geological investigations carried out by TÜBİTAK MAM, to obtain regional information on the macro scale bedrock properties with depth (Ergintav et al., 2011) will be      considered to plan a new and pointed local geophysical study of the area.

A new campaign of ambient microtremor recording to assess in a cheap and fast way the fundamental resonance frequency of a given site, based on Horizontal-to-Vertical Spectral Ratio (HVSR) from single-station measurements (also known as ”Nakamura method”) (Nakamura 1989, Nakamura 2000, Lermo & Chávez-García 1993). The resulting spectral ratio gives frequency dependent amplification for the site.

Previous study on local site effects give evidence that the Avcilar district of western Istanbul (Özel et al. 2002, Tezcan et al. 2002) is characterized by the presence of soft sediments in basin structures and this has caused strong amplification of earthquake ground motion during past earthquakes. The alluvium, on the other hand, represents the most critical unit in terms of site amplifications and is limited to the fluvial depositional centres. The gentle topography of the area, with shallow synclines and anticlines plunging towards the Marmara Sea in the south, represents an environment significantly different from classical alluvial valleys or closed sedimentary basins. In this respect, the expected site effects also differ significantly (Sørensen et al., 2006).

The microtremor campaign will be carried out also to identify the best locations to set up a temporary local seismic network to integrate the Marmara Seismology Network of Turdep.

A local seismological network is needed to fill the gaps of available seismological catalogues to catch any microseismological activity (Ergintav et al., 2011). Then, a complementary local seismic network, composed of a few broadband accelerographs, will be temporary installed to enable a good focus on this area. Following the Seismicity Map and Earthquake Density Map of the USGS Earthquake Hazard Program for the Ataköy area it will be highly probably to record earthquakes (from small to moderate) in the near and far field conditions during two years of seismic monitoring. Two stations could be installed inside and outside the landslide area chosen as pilot site, a station on the limestone outcrop (if possible) as reference station and the other two stations on alluvial deposits with known lateral variations.

Thus, the site effects will be expressed in terms of amplification describing the ratio of the ground motion at the free surface to that at bedrock level. For local variations of site effect H/V spectral ratios are calculated for recorded microtremor data.

All geological-geotechnical derived from task 1 and seismic data available (from permanent existing stations and complementary local seismic array) concerning the selected area will aim at pointing out local seismic amplification effects due to geology, topography as well as directivity and polarization of seismic waves. A preliminary geological model will be defined on the basis of the available data to conduct 1D and 2D linear numerical modelling aiming at analysing the role of topographic and stratigraphic conditions (including effect of incidence, directivity and polarization) on the surface shaking. The local in-situ measurements and the numerical results will be extrapolated to give a good estimate of the amplification in the areas where only sparse data are available nowadays.

Engineering-geological models will be mainly defined based on the already available data to depict the landslide geometries and to define the more adapt rheologies to be considered for the involved soils. This will allow performing dynamic numerical simulations in nonlinear conditions devoted to: i) back-analyze historical events and sequences of monitoring records for validating and calibrating the engineering-geological models, ii) evaluate the role of geological features on permanent deformations as well as on landslide triggering; iii) quantify the effect of different seismic inputs. Most results of Task 2 will provide input into Task 1.

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Work package title: Re-evaluation of the seismo-tectonics of the Marmara Region

WP Leader: ITU

Objectives

Objectives of the WP7 are three-fold:

• To generate a GIS database and relevant bibliography on the evolution of the North Anatolian Fault from an earlier shear zone in and around the Sea of Marmara;
• To synthesise all data to prepare an active fault map of the Sea of Marmara with appropriate explanation of nature, age, distribution of deformation and history of activity of the fault population;
• To evaluate the earthquake history of the Sea of Marmara and surrounding region that is important in both predicting future events and seismic risk assessment in Istanbul and the Marmara region

Description of work

The main task of the seismotectonics group is to establish the geography of the active fault system in the Sea of Marmara, its history of activity, both in terms of geologic time (since its origination in the medial Miocene) and historical time (past earthquake record). The past earthquake record requires collaboration with historians and we hope to have such supports from expert historians. The mapping of the fault population under the Sea of Marmara is almost complete. The only outstanding bit is the connection with the Thrace Basin and a part of it has been mapped using the Turkish Petroleum Company’s multichannel seismic data. Once that mapping is complete we shall have complete coverage of the active fault population of the Sea of Marmara. For the criterion of activity we simply take activity in the Quaternary as a sufficient condition, following the recommendation of Allen (1975). We acknowledge that faults may turn on and off within the time span represented by the Quaternary, but no fault belonging to a family as large and as active as the North Anatolian Fault becomes definitively dormant until the entire zone ceases its activity.

Parallel with the mapping of the faults, we shall evaluate the earthquake history of the Sea of Marmara and surrounding regions. The historical material available is huge and it is not possible for one person to deal with it. We shall have the cooperation of a historian team at the Marmara University, but also hope to consult the restoration department of the Faculty of Architecture of our own university. One serious problem is assessing historical seismicity is ascription of earthquakes to individual fault segments. Here we hope to be able to trench the suspected faults wherever possible on land. However, the closeness and on-going activity of major fault strands make definitive ascriptions difficult and we hope, at least, to be able to specify error margins in our ascriptions and produce a reliable epicentre map of historical earthquakes around the Sea of Marmara.

To understand the nature and distribution of activity along the North Anatolian Shear Zone during the geological past is of vital importance for this project. The previous estimates of the age and distribution of deformation were based on assumptions that did not stand the test of time. A serious problem is the distribution of the Neogene sediments within the Sea of Marmara. Previous estimates were based on assuming a basin-wide Neogene depocentre. More recent seismic profiling and studies of sedimentation rates on cores obtained during the numerous sea-borne missions showed that none of the Marmara basins can have any sediment older than top Pliocene at best. Almost all probably formed in the Pleistocene. This necessitates re-evaluation of the on-land sedimentary and geomorphological record and definition of the Neogene depocentres and areas of denudation in and around the Sea of Marmara. We believe that only after such a work one can make a true geological synthesis of the entire area from the late Cretaceous to the present.

Task 1. Re-evaluation of the seismo-tectonics and geohazards

Plate motion between Eurasia and Anatolia is known from geodesy, and models of slip partitioning between active faults in the transition from the Anatolian to the Aegean domains have been proposed (Meade, 2002; Le Pichon et al., 2003; Flerit et al., 2004; Reilinger et al., 2006; Hergert et al., 2010). However, the distribution of slip between offshore faults in the Sea of Marmara remains problematic. Although most of the plate motion may occur on the Main Marmara Fault of Le Pichon et al. (2001), geomechanical models suggest that other fault branches could accommodate part of it, and thus present earthquake and tsunami hazards (Hergert and Heidbach, 2010). This is in agreement with estimate of geological (10,000 year time-scale) slip-rate estimate carried out along the submerged North-Anatolian Fault system (Polonia et al., 2004; Gasperini et al., 2011a).To date, deformation rates inferred from stratigraphy and geomorphology (Sorlein et al., in press; Grall et al., 2012; Beck et al., 2007; Armijo et al., 2005; Seeber et al., 2006) are the main observations available to constrain models. Model outputs have been compared with results of local studies (Hergert et al., 2011; Muller and Aydin, 2005) but a more complete confrontation with data is needed, also taking into account variations with time and the effect of sediment compaction. The aim of the proposed work is to fully integrate available constraints from geology into kinematic and mechanical modelling efforts.

Another important task to model the behaviour of seismogenic faults is to carry out reliable co-seismic estimate of deformation associated with major historical earthquakes. This has been recently attempted in the Sea of Marmara by different working groups, which applied the methods of Earthquake Geology to the submarine environment (Polonia et al., 2002; Armijo et al., 2005; Pondard et al., 2007; Gasperini et al., 2011b).

The very large marine geophysical data set acquired in the Sea of Marmara combines observations over a range of scales: multibeam bathymetry and imagery, micro bathymetry from ROV and AUV surveys, THR sounder profiles, High resolution 3D seismic and 2D profiles, deep penetration multichannel seismic, wide angle seismic surveys and tomography. Most are now accessible and structural interpretations have been published. Available age models from sediment core analysis, and stratigraphic interpretations in term of eustatic cycles, constrain sedimentation rates over the last 10 to 500 ka. These data will be integrated with heat flow data in basin subsidence models. At a few locations, geomorphologic and 3D stratigraphic interpretations yield constraints on horizontal displacement, which also need to be taken into account. The re-evaluation of fault kinematic models will thus proceed in three steps: (a) synthesis of data offshore (structure, geomorphology, stratigraphy, heat flow) and onshore (b) modelling of basin subsidence, sediment compaction and heat flow, (c) critical assessment of kinematic and geomechanical models.

Task 2. Integration of faulting parameters from paleoseismic and historical data for hazard assessment

The North Anatolian Fault (NAF) splays into several branches in the Marmara Region (Barka and Kadinsky-Cade, 1988; Sengor et al. 2005). The most active northernmost branch prolongs between Düzce and Izmit as the on land section and enters into the Sea of Marmara in the Izmit Gulf. GPS data and elastic block models clearly show that the southern branch has relatively lower strain accumulation. However, this section of the NAF produces large and destructive earthquakes as well.  These branches are located very close to large cities such as Izmit, Bursa, Istanbul, which have very dense population and are centres of the industry in Turkey. It is well known that large earthquakes affected these settlements in the past and created many casualties, heavy destruction and economical loss.

Even many previous paleoseismological studies have been done along the North Anatolian Fault (NAF) in the Marmara Region, there are still lots of uncertainties for the past earthquakes (e.g.: Rockwell et al, 2001; Hitchcock et al., 2003; Klinger et al., 2003; Ferry et al., 2004; Pavlides et al., 2006; Pantosti et al., 2008; Dikbas and Akyüz, 2011). These studies and additional data from the Marmara Sea bottom (e.g.: Sari and Cagatay, 2002; McHugh et al., 2006; Beck et al., 2006; Cagatay et al., 2012) will be combined and integrated into a GIS-based database in this project. At least 2000-years earthquake history of the western NAF is aimed to be included within this database. The lack of precise paleoearthquake data for the southern branch of the NAF will be completed based on the fault segmentation models. Any lack of data for separate segments or gaps in historical records will be examined with new paleoseismological trench studies both on northern and southern branches of the NAF in the Marmara Region. It is believed that this study with its deliverables will provide important data for predicting future events and give strong background for seismic risk assessment in Istanbul and the Marmara region.

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