Asperity along the North Anatolian Fault imaged by magnetotellurics at Duzce, Turkey

The magnetotelluric (MT) method has been applied to show resistivity variations in the vicinity of the epicenter of the 1999 Duzce earthquake (M(w) = 7.2) where a large rupture velocity difference was seen between the western and eastern parts of the epicenter. MT data for frequencies ranging between 320 and 0.0005 Hz were acquired along two parallel profiles to the west and the east of Duzce earthquake's epicenter. Both profiles crossed the Duzce basin and the Duzce fault in the north and the North Anatolian Fault (NAF) in the south. MT data analysis shows almost two-dimensionality in the region, at the depth starting from 2-3 km beneath the surface. According to two-dimensional MT modeling, a higher resistive layer extends beneath the eastern side of Duzce earthquake epicenter, compared with the western side. This resistivity structure correlates well with the aftershock distribution of the Duzce earthquake.