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Earthquake-triggered landslides have an increasing disastrous impact in seismic regions due to the fast growing urbanization and infrastructures. Just considering disasters from the last fifteen years, among which the 1999 ChiChi earthquake, the 2008 Wenchuan earthquake, and the 2011 Tohoku earthquake, these events generated tens of thousands of coseismic landslides. Those resulted in amazing death toll and considerable damages, affecting the regional landscape including its hydrological main features. Despite a strong impetus in research during past decades, knowledge on those geohazards is still fragmentary, while databases of high quality observational data are lacking. These phenomena call for further collaborative researches aiming eventually to enhance preparedness and crisis management. The MARSITE project gathers research groups in a comprehensive monitoring activity developed in the Sea of Marmara Region, one of the most densely populated parts of Europe and rated at high seismic risk level since the 1999 Izmit and Duzce devastating earthquakes. Besides the seismic threat, landslides in Turkey and in this region constitute an important source of loss. The 6th Work Package of MARSITE project gathers 9 research groups to study earthquake-induced landslides focusing on two sub-regional areas of high interest among which the Cekmece-Avcilar peninsula, located westwards of Istanbul, as a highly urbanized concentrated landslide prone area, showing high susceptibility to both rainfalls while affected by very significant seismic site effects. A multidisciplinary research program based on pre-existing studies has been designed with objectives and tasks linked to constrain and tackle progressively some challenging issues related to data integration, modeling, monitoring and mapping technologies. Since the start of the project, progress has been marked on several important points as follows. The photogeological interpretation and analysis of ENVISAT-ERS DInSAR temporal series has been undertaken, providing global but accurate Identification and characterization of gravitational phenomena covering the aera. Evaluation of the resolution and identification of landslide hazard-related features using space multispectral/hyperspectral image data has been realized. Profit has been gained from a vast drilling and geological - geotechnical survey program undertaken by the Istanbul Metropolitan Area, to get important data to complete the geological model of the landslide as well as one deep borehole to set up permanent instrumentation on a quite large slow landslide, fully encircled by a dense building environment. The selected landslide was instrumented in 2014 with a real-time observational system including GPS, rainfall, piezometer and seismic monitoring. Objective of this permanent monitoring system is three folds: first to detect and quantify interaction between seismic motion, rainfall and mass movement, building a database opened to the scientific community in the future, second to help to calibrate dynamic numerical geomechanical simulations intending to study the sensitivity to seismic loading, and last but not least. Last but not least important geophysical field work has been conducted to assess seismic site effects already noticed during the 1999 earthquake .Data, metadata and main results are from now progressively compiled and formatted for appropriate integration in the cloud monitoring infrastructure for data sharing.

International audience; Earthquake-triggered landslides have an increasing disastrous impact in seismic regions due to the fast growing urbanization and infrastructures. Just considering disasters from the last fifteen years, among which the 1999 Chi-Chi earthquake, the 2008 Wenchuan earthquake, and the 2011 Tohoku earthquake, these events generated tens of thousands of coseismic landslides. Those resulted in amazing death toll and considerable damages, affecting the regional landscape including its hydrological main features. Despite a strong impetus in research during past decades, knowledge on those geohazards is still fragmentary, while databases of high quality observational data are lacking. These phenomena call for further collaborative researches aiming eventually to enhance preparedness and crisis management. As one of the three SUPERSITE concept FP7 projects dealing with long term high level monitoring of major natural hazards at the European level, the MARSITE project gathers research groups in a comprehensive monitoring activity developed in the Sea of Marmara Region, one of the most densely populated parts of Europe and rated at high seismic risk level since the 1999 Izmit and Duzce devastating earthquakes. Besides the seismic threat, landslides in Turkey and in this region constitute an important source of loss. The 1999 Earthquake caused extensive landslides while tsunami effects were observed during the post-event surveys in several places along the coasts of the Izmit bay. The 6th Work Package of MARSITE project gathers 9 research groups to study earthquake-induced landslides focusing on two sub-regional areas of high interest. First, the Cekmece-Avcilar peninsula, located westwards of Istanbul, is a highly urbanized concentrated landslide prone area, showing high susceptibility to both rainfalls while affected by very significant seismic site effects. Second, the off-shore entrance of the Izmit Gulf, close to the termination of the surface rupture of the 1999 earthquake, that shows an important slump mass facing the Istanbul coastline. A multidisciplinary research program based on pre-existing studies has been designed with objectives and tasks linked to constrain and tackle progressively some challenging issues related to data integration, modeling, monitoring and mapping technologies. Concerning the on-shore area, this program includes the refined analysis of the seismic site response, the permanent multi-parameter ground monitoring of a representative unstable slope as well as the in-depth slope stability analysis based on the stress-strain dynamic numerical modelling approach. Hyperspectral and Dinsar imagery technologies are also deployed to complete inventory and observational information. The development of a dynamic GIS tool featuring capabilities to integrate and process very different types of data, and up-date susceptibility maps based on near to real-time rainfall-seismic shaking input, is currently undertaken. Moreover, the research is gaining high profit of a vast drilling program undertaken by the Istanbul Metropolitan Area, aiming to yield a detailed geological and geotechnical characterization of the slopes. Also included in the objectives is to test a landslide early warning system. As regards the selected off-shore area, high resolution geophysical marine surveys are being conducted to complete its geomorphological description to help in mapping possible incipient mass movements. This is especially expected to provide better-constrained input for both laboratory testing and numerical modeling of tsunami scenarios thank to a unique lab-scale tsunami channel.

The European Project MARsite (http://marsite.eu/), started in 2012 and leaded by the KOERI, aims to improve seismic risk evaluation and preparedness to face the next dreadful large event expected for the next three decades. MARsite is thus expected to move a “step forward” the most advanced monitoring technologies, and offering promising open databases to the worldwide scientific community in the frame of other European environmental large-scale infrastructures, such as EPOS (http://www.epos-eu.org/ ). Among the 11 work packages (WP), the main aim of the WP6 is to study seismically-induced landslide hazard, by using and improving observing and monitoring systems in geological, hydrogeotechnical and seismic onshore and offshore areas. One of the WP6 specific study area is the Avcilar Peninsula, situated between Kucukcekmece and Buyukcekmece Lakes in the north-west of the region of Marmara. There, more than 400 landslides are located. According to geological and geotechnical investigations and studies, soil movements of this area are related to underground water and pore pressure changes, seismic forces arising after earthquakes and decreasing sliding strength in fissured and heavily consolidated clays. The WP6 includes various tasks and one of these works on a methodology to develop a dynamic system to create combined earthquake and rainfall induced landslides hazard maps at near real time and automatically. This innovative system could be used to improve the prevention strategy as well as in disaster management and relief operations. Base on literature review a dynamic GIS platform is used to combine theoretical models, variable on-site data (rainfall, earthquake, etc), products and results obtained by other WP6 partners’ contributions. This platform is in progress, a 1D deterministic method for calculating co-seismic displacements was for the moment implemented in the GIS based on Newmark’s method for mapping shallow slides. Rigid sliding block analysis is commonly adopted to predict the potential for earthquake-induced landslides. These predictions give the expected level of displacement as a function of the characteristics of the natural slopes and the characteristics of earthquake shaking. In our case the first characteristics are the results of a precise DEM data and an existent landslide inventory. The geotechnical parameters used come from the literature and will be improved thanks to a borehole geological and geotechnical campaign in progress. The static hydrogeological model in our GIS will be replaced by transient models for hill slope hydrology and time series of intense and/or prolonged precipitation (provided by Tubitak) which will be shortly accessible. Our next aim is to introduce, when ready, site effects information issued from the next IU geophysical campaign, results from numerical simulations and automatic near real time shake maps (developed by KOERI). Moreover, in the spring 2014, an observation & Early Warning System (EWS) prototype system will be set up on an active but slow landslide (pilot site) and composed of GPS devices, seismic probes, piezometers, meteorological station and inclinometers. This will improve our scientific understanding of Avcilar landslides and enable to also improve and better calibrate our GIS platform.