HR: 09:00h
AN: S11E-05    [Abstracts]
TI: 3-D Local Earthquake Tomography Within The Marmara Sea Region
AU: * Gok, R
EM: gok1@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave L-206, Livermore, CA 94550
AU: Husen, S
EM: husen@sed.ethz.ch
AF: Swiss Seismological Service, ETH Hoenggerberg, Zurich, 8093 Switzerland
AU: Hutchings, L
EM: hutchings2@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave L-206, Livermore, CA 94550
AB: High resolution P velocity structure of the Marmara Sea Region has been imaged using selected subsets of the 3700 Izmit and Duzce, Turkey aftershocks recorded by 77 seismic stations. We performed a step by step increase in complexity of inversion to equalize the path coverage and earthquake distribution. First, we used 440 homogenously distributed events to develop a minimum 1-D model for the entire region. This model was used as an initial model to the 3-D inversion. The 3-D inversion is a non-linear iterative algorithm and simultaneously solves the coupled hypocenter-velocity problem. We used the same 440 events to develop a smooth 3-D model with a coarse grid of 30 km. The station and event distribution is very dense in eastern Marmara. So, we performed an inversion with a finer grid and selected earthquakes which had a minimum of 8 P readings and maximum 180\deg azimuthal gap. We performed checkerboard test and tests with synthetic velocity models that represent the observed structure. In addition to synthetic tests we used all the other available information, such as resolution estimates, diagonal element of the resolution matrix and spread function to assess the solution quality of our model. Preliminary results show significant heterogeneities in the upper crust. We observe concentrations of seismicity of the relocated earthquakes in several distinct zones of the North Anatolian Fault.
DE: 7218 Lithosphere and upper mantle
DE: 7230 Seismicity and seismotectonics
DE: 8123 Dynamics, seismotectonics
DE: 7205 Continental crust (1242)
SC: Seismology [S]
MN: 2004 AGU Fall Meeting