The Determination of the Slip Rates of Main Fault Zones Driving Turkey's Neotectonics and the Formationof Block Deformation Models Through Geodetic Methods

Project Manager: Prof. Dr. Haluk Özener

Abstract:
Turkish Active Fault Map published in 1992 by General Directorate of Mineral Research and Exploration provided a template for various research studies. However, a comprehensive revision study was initiated in view of the developments in earth sciences in the last 20 years and it was completed in 2012. The revised active fault map involves twice as many active faults as the previous active fault map. The revised fault map shows that there are about 500 active faults in Turkey. The seismotectonic map of Turkey is needed to use the active fault map which was revised through aerial photography, satellite imagery and geological field studies in earthquake hazard prediction and assessment. In this respect, it is necessary to analyze the active faults through seismological and geodetic data and to determine the fault zones which accumulated high strain energy. Therefore, it is required to determine the fault slip rates of main active faults in Turkey through geodetic methods. The most common method for this purpose is to use GPS observations. In parallel to his concept, the directorate of Disaster and Disaster Management initiated National Earthquake Strategy and Action Plan-2023 which involves Action A.1.1.4 (Monitoring and modeling of interseismic, coseismic and postseismic crustal deformation with national geodetic networks), Action A.2.1.2 (Determination of fault slip rates to obtain some of the parameters of active faults) and Action A.2.1.1 (The preparation of 1/250000 scale active fault maps and seismotectonic maps and visualization of some of fault parameters through GIS capabilities). Similarly, the preparation of the seismotectonic map of Turkey is also included in the strategy and action plan. While various local studies exist, the slip rates of many active faults in Turkey are not available. The slip rates are the most common input to produce the seismotectonic maps.The block modeling is also a very common method to determine the fault slip rate through geodetic observations. GPS velocity filed required for block modeling will be compiled from the literature, will be computed from the raw observations obtained from the organizations and will be combined. Various stochastic models will be analyzed to produce a homogeneous and optimal velocity field. GPS velocity fields are combined globally to produce Global Strain Map which involves strain analysis of sparse data sets.In this study, a similar attempt is made for Turkey but with a more comprehensive and detailed analysis. For instance, this study involves the computation of fault slip rates as opposed to strain analysis in Global Strain Map Project. Moreover, an advanced variance component analysis is also planned to optimally combine the GPS velocity fields. In this project; the data from Turkish National Permanent GPS Stations, the data from Turkish National Permanent GPS Stations–Active and Turkish National Fundamental GPS Network will be obtained, episodic GPS measurements will be done at selected points, the GPS data available in the literature will be compiled, new stochastic models will be developed and a homogenous combined velocity field will be produced. This combined velocity will be used to infer the fault slip rates through block modeling. The output of the project will the fault slip rate map of main active faults of Turkey and will be one of the most important inputs of Turkish Seismotectonic Map.

The multidisciplinary investigation of the creep, along the Hazar-Palu section of the DAF

Project Manager: Prof. Dr. Semih Ergintav

Abstract:
Surrounding the eastern Mediterranean region, in particular in our region, the general kinematics has been studied during the last 20 years. (Oral, 1992, Oral, 1995; McClusky et al., 2000; Reilinger et al., 2006; Özener et al., 2010; Aktuğ et al., 2009; Aktuğ et al., 2013). In the recent years, the basic results of these studies has pioneered the increasing number of new studies focusing on present-day velocities along the major faults in Turkey, the North Anatolian (NAF) and the East Anatolian faults (EAF), detailed mapping of strain accumulation along the faults as well as creeping zones and monitoring the earthquake related deformations as a function of time (e.g. Tatar et al., 2011; Cakir et al. , 2005; Cakir et al. , 2012; Tiryakioğlu et al., 2013; Ergintav et al., 2009, 2013). Using geodetic methods, e.g. GPS (Global Positioning System) and InSAR (Synthetic Aperture Radar Interferometry), the properties of the faults that they were exposed to long- and short-term stress fields, were questioned and earthquake hazards were analyzed. However, most of the studies have been carried out for the NAF. Studies, along EAF, have been limited to only a few of studies focusing on the region around the triple junction between the Dead Sea Fault and the EAF using GPS (Mahmoud et al., 2012; Nocquet, 2012) and overall deformation along the EAF using InSAR (Cavalier and Jonsson, 2014).

Cavalier and Jonsson (2014) suggested a shallow locking depth along the EAF, target area in the proposal, and supported their results with an observation of very low seismicity during the recent centuries (Ambraseys, 1989; Ambraseys and Jackson, 1998; Ambraseys and Melville, 1995; Burton et al., 1984; Bulut et al., 2012) and magnetotelluric studies in the region (Türkoğlu, 2009). Therefore, they proposed a creeping mechanism for the upper crust section of the EAF. Based on the fact that there is not a published study relating the surface deformations with the creep, they assumed that creep does not reach to the surface and it remains within the crust. Similar to the creep observations along the Ismetpasa segment of the NAF (Çakır and diğ., 2005; Özener and diğ., 2013), investigation of creeping sections along the EAF is crucial to improve existing earthquake hazard models, which are related to the long term behavior of EAF (Nalbant and diğ., 2002; Çetin and diğ., 2003; Koçyiğit and diğ., 2003; Reilienger and diğ., 2006; Aksoy, 2007; Çetin, 2008; Çolak and diğ, 2011; Duman and Emre, 2013).

Using the permanent scatters approach of the InSAR method (PsInSAR) and the data of ENVISAT satellites, ESA (European Space Agency), the creep zones surrounding Hazar-Palu section have been preliminarily investigated resulting in a promising evidence for a local creep. Our results indicate that creep velocity reaches up to 10 mm/yr. Based on the GPS data resulting an average velocity of 10 mm/yr on EAF (Reilinger et al., 2006), our results claim that the creep reaches to the lower crust. As a result of the creep in upper crust, the strain accumulation will never occur and therefore creeping sections of the EAF will not produce a major earthquake. However, the stress and the earthquake potential will be increased at the tips of the creep zone. Obviously, locating the boundaries of the creeping zone along the fault is very important to elaborate on earthquake hazard assessment.

In this multidisciplinary proposal, our primary focus is to monitor potential variations of the creep velocity between Hazar-Palu, and to locate boundaries of the creeping zone in order to model mechanical behavior of the EAF. For this purpose, in order to control the creep as a result of InSAR analysis, in-situ observations will be realized by 4 fault perpendicular GPS profiles, which include 6 GPS sites to observe the creep in right position, with 5 surveys, during the proposed project. Turkey's National Permanent GPS Network-ACTIVE (TUSAGA-ACTIVE) data will be integrated to our database in order to