[S-EM12] Electric, magnetic and electromagnetic survey technologies and scientific achievements

[SEM12-15] Preliminary Results achieved with the Numerical Modeling of the Magnetotellurics data collected at epicentral area of the Kahramanmaraş Earthquakes – I

*Sabri Bulent Tank¹、Yasuo Ogawa²、Ryokei Yoshimura³、Masaki Matsushima⁴、Selda Altuncu⁵、Tülay Kaya⁶、Serhun Zoroglu⁶ (1.Bogazici University, Kandilli Observatory and Earthquake Research Institute, Istanbul, Türkiye、2.Tokyo Institute of Technology, Institute of Innovative Research, Tokyo, Japan、3.Kyoto University, Disaster Prevention Research Institute, Uji, Kyoto, Japan、4.Tokyo Institute of Technology, Dept. Of Earth and Planetary Sciences, Tokyo, Japan、5.Bogazici University, Kandilli Observatory and E.R.I., RETMC, Istanbul, Türkiye、6.Bogazici University, Kandilli Observatory and E.R.I., Dept. of Geodesy, Istanbul, Türkiye)

キーワード：Magnetotellurics, Electrical Conductivity, Faults, Fluids

On February 6, 2023, two major and devastating earthquakes (with magnitudes 7.8 and 7.6) occurred in the East Anatolian Fault Zone, south-southeast Türkiye. Nine hours apart the catastrophic events took place one after the other in two close but distinct segments of the fault system. They are named Kahramanmaraş earthquake doublets. Early seismological studies claimed that the first event triggered the second one via stress transfer. In this study, we attempted to elucidate the distribution of subsurface fluids around the 1st epicenter by using magnetotellurics, a natural source electromagnetic method that is sensitive to electrical conductivity variations of the sub-surface. The survey was planned and conducted in September 2023 around the epicenter. Thirty-five wideband magnetotellurics observations were made with four- (Ex, Ey, Hx, and Hy) and two-channel (Ex and Ey) MT systems. The preliminary two- and three-dimensional numerical models achieved from 15 four-channel MT data collected around the 1^st epicenter suggested that there is a highly conductive anomaly underneath the hypocentral area that may be interpreted as a fluid-rich zone. This result agrees well with the hypothesis that is being tested and claims that the fluid contribution is a crucial component in the earthquake generation process.