THE CRUSTAL STRUCTURE OF THE EASTERN MARMARA REGION, TURKEY BY TELESEISMIC RECEIVER FUNCTIONS

Abstract

We study the crustal structure of eastern Marmara region by applying the receiver function method to the data obtained from the 11 broad-band stations that have been in operation since the 1999 İzmit earthquake. The stacked single-event receiver functions were modelled by an inversion algorithm based on a five-layered crustal velocity model to reveal the first-order shear-velocity discontinuities with a minimum degree of trade-off. We observe crustal thickening from west (29-32 km) to east (34-35 km) along the North Anatolian Fault Zone (NAFZ), but we observe no obvious crustal thickness variation from north to south while crossing the NAFZ. The crust is thinnest beneath station TER (29 km), located near the Black Sea coast in the west and thickest beneath station TAR (35 km), located inland in the southeast. The average crustal thickness and S-wave velocity for the whole regions are 31 ± 2 km and 3.64 ± 0.15 km s-1, respectively. The eastern Marmara region with its average crustal thickness, high heat flow value (101 ± 11 mW m-2) and with its remarkable extensional features seems to have a Basin and Range type characteristics, but the higher average shear velocities (~3.64 km s-1) and crustal thickening from 29 to 35 km towards the easternmost stations indicate that the crustal structure shows a transitional tectonic regime. Therefore, we conclude that the eastern Marmara region seems to be a transition zone between the Marmara Sea extensional domain and the continental Anatolian inland region. © 2006 The Authors Journal compilation © 2006 RAS.