HR: 0800h
AN: T51C-0692    [Abstracts]
TI: Magnetotelluric Imaging Across the North Anatolian Fault, Erzincan Basin, Turkey
AU: AVSAR, U
EM: avsaru@itu.edu.tr
AF: Department of Geophysical Engineering, Istanbul Technical University Faculty of Mines, Istanbul, 34390, Turkey
AU: Turkoglu, E
EM: eturk@phys.ualberta.ca
AF: Department of Physics, University of Alberta, Edmonton, AB T6G 2G7, Canada
AU: * Unsworth, M
EM: unsworth@phys.ualberta.ca
AF: Department of Physics, University of Alberta, Edmonton, AB T6G 2G7, Canada
AU: Caglar, I
EM: caglari@itu.edu.tr
AF: Department of Geophysical Engineering, Istanbul Technical University Faculty of Mines, Istanbul, 34390, Turkey
AB: The Erzincan pull-apart basin is located on the North Anatolian Fault (NAF) which is one of the most active faults in the world. In the last century, two destructive earthquakes have occurred in this basin which have surface wave magnitudes of Ms=8.2 in 1939 and Ms=6.8 in 1992. Recent geodynamic models have shown that fluids may play an important role in the earthquake-cycle. Specifically, it has been suggested that fluids in a fault zone can raise the pore pressure, lowering the shear stress needed for rupture. These fluids, if interconnected in a fault zone will significantly decrease the resistivity of the subsurface and be detected with magnetotellurics (MT). Thus, MT can be used as an effective tool for determining the fluid content in an active fault. MT is a passive electromagnetic technique which images subsurface resistivity by recording naturally varying EM fields at the surface of the Earth. For this purpose, broad-band magnetotelluric data were acquired in the Erzincan Basin in 2005. Data were recorded at 24 stations on two parallel profiles that crossed the basin with a spacing 1-2 km. The time-series data were processed using statistically robust algorithms and remotely referenced to remove incoherent magnetic noise. All data were processed using tensor decomposition, which showed a geoelectric strike direction of N70°W. This is parallel to the strike of the NAF as expected. Two-dimensional regularized inversion models were then created and these models imaged the conductive sedimentary rocks in the Erzincan Basin to a depth of 5km. This depth is consistent with that inferred from seismic tomography. The models also contain a strong near surface conductor which underlies the surface trace of the NAF. This is similar to features observed in resistivity models of the San Andreas Fault at Parkfield where a near surface conductor in the fault zone was attributed to the presence of fluids in the fault gauge.
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8107 Continental neotectonics (8002)
DE: 8111 Continental tectonics: strike-slip and transform
SC: Tectonophysics [T]
MN: 2007 Fall Meeting