Details of the abstract

Title of paper 3D lithospheric structure beneath the Marmara Sea by Magnetotellurics
List of authors T. Kaya-Eken, Y. Ogawa, Y. Usui, T. Kasaya, M. K. Tunçer, Y. Honkura, N. Oshiman, M. Matsushima, W. Siripunvaraporn
Affiliation(s) Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan,
Volcanic Fluid Research Center, Tokyo Institute of Technology, Tokyo, Japan,
Department of Geodesy, Boğaziçi University, Istanbul, Turkey, tulay.kaya@boun.edu.tr,
Earthquake Research Institute, The University of Tokyo, Tokyo, Japan,
Japan Agency for Marine–Earth Science and Technology, Yokosuka, Japan,
Department of Geophysics Engineering, Istanbul University-Cerrahpaşa, Istanbul, Turkey,
Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan,
Department of Physics, Mahidol University, Bangkok, Thailand
Summary The North Anatolian Fault (NAF), a 1500 km long transform boundary between the Eurasian and Anatolian plates, is a seismically active zone in Turkey. During the 20th century, destructive earthquakes with magnitude Mw>7 took place on this fault zone increasing the seismic hazard in the Marmara Sea. Several studies have implied that segments in the Marmara Sea, not ruptured since 1766, are highly prone to generate a destructive earthquake (>Mw7.2) in the near future. Therefore, a proper understanding of lithospheric structure of the NAF Zone beneath the Marmara Sea is of utmost importance to the seismic hazard assessment studies. The energy released after an earthquake depends on the accumulated stress along fault zones and shear fracture strength that is controlled by the amount of pore fluid. The distribution of deep crustal fluids and connectivity of fluid-filled pores affect the electrical resistivity variation in the subsurface. Thus, electromagnetic methods, sensitive to the electrical resistivity, are powerful tools for imaging subsurface fluids in the deep crust. We present a study revealing the resistivity variation that reflects the rheological configuration of the lithosphere in relation to the fluid dynamics in the crust and mantle structure of the study region. We have collected magnetotelluric data at 25 sites in and around the Marmara Sea to elucidate 3D electrical resistivity distribution across the NAF zone and to determine the brittle-ductile zones. To achieve this we performed a 3D inverse modeling on magnetotelluric data using an unstructured tetrahedral mesh with the finite element method. The main findings from this study include resistive–conductive boundaries marking the trace of the NAF; prominent shallow (down to 5 km) and deep conductors located between Çınarcık and Central Basins and beneath them, respectively; a profound resistive structure below ~15 km consistent with the known seismic gap in this region.
Session Keyword 4.0 Tectonics, Magmatism, Geodynamics
File upload 4.0_3d_lithospheric_structure_kaya eken.pdf
Back