[S-EM36_30PO1] Electrical conductivity, Tectono-electromagnetism

[SEM36-P08] Electrical Resistivity Imaging at Western Turkey by Wideband Magnetotelluric Method

*Mustafa kemal TUNCER¹, Ozlem CENGIZ², Bulent TANK², Elif TOLAK-CIFTCI², Tulay KAYA³, Yasuo OGAWA⁴, Yoshimori HONKURA⁴, Masaki MATSUSHIMA⁴, Naoto OSHIMAN⁵, Cengiz CELIK² (1.Istanbul University-Turkey, 2.Bogazici University-Turkey, 3.Tokyo Institute of Technology, Japan, 4.Tokyo Institute of Technology-Japan, 5.Kyoto University-Japan)

Keywords:North Anatolian Fault, Fluids, Electrical resistivitiy, Magnetotellurics, geo-electric models

The westward migration of large magnitude earthquakes along the North Anatolian Fault Zone indicates that a major event may take place at and around the Marmara region, following the Izmit (Mw7.4) and Duzce (Mw7.2) earthquakes that took place in 1999 in northwest Turkey. For this reason many studies were conducted around Marmara sea, west of these events. These studies focused mostly on the northern part of this area because of the high damage risk near Istanbul, but the similar potential is also present for the southern Marmara. In order to investigate the upper crustal electrical resistivity structure at this location, wide-band magnetotelluric data were collected at sixteen sites forming two parallel profiles. These profiles were constructed to cross the southern branches the North Anatolian Fault. Following the application of Groom and Bailey decomposition that has been applied to remove the surplus features and to deduce the appropriate geo-electric strike direction which is an important requirement for two-dimensional interpretation, an inversion algorithm developed by Ogawa and Uchida (1996) was utilized to develop electrical resistivity models. These models pointed out a relatively complicated shallow (surface-to-5 km) structure which may be associated with the presence of crustal fluids, but below these depths the electrical resistivity is more uniform with only a deep conductor appearing beneath the northern ends of the two profiles. The known faults in the survey area correlate well with the features characterized in the final geo-electric models. A resistive-conductive boundary between Manyas - Karacabey basin and Bandirma-Karadag uplift on the western and Uluabat uplift and Mudanya uplift on the eastern profiles may be associated with the South Marmara Fault.