HR: 1340h
AN: S23B-1393    [Abstracts]
TI: Seismic Tomography Of The Caucasus Region
AU: Javakhishvili, Z
EM: z.javakh@seismo.ge
AF: Seismic Monitoring Center, 77 Nutsubidze str., Tbilisi, 0177, Georgia
AU: * Godoladze, T
AF: Seismic Monitoring Center, 77 Nutsubidze str., Tbilisi, 0177, Georgia
AU: Gok, R
EM: gok1@llnl.gov
AF: LLNL, Earth Science Division L-206, Livermore, CA 94550, United States
AU: Elashvili, M
EM: m.elashvili@seismo.ge
AF: Seismic Monitoring Center, 77 Nutsubidze str., Tbilisi, 0177, Georgia
AB: The Caucasus is one of the most active segments of the Alpine-Himalayan collision belt. We used the catalog data of Georgian Seismic Network to calculate the reference 1-D and 3-D P-velocity model of the Caucasus region. The analog recording period in Georgia was quite long and 17,000 events reported in the catalog between 1956 and 1990. We carefully eliminated some arrivals due to ambiguities for analog type data picking and station time corrections. We choose arrivals with comparably low residuals between observed and calculated travel times (<1 sec). We also limited our data to minimum 10 P-arrivals and maximum azimuthal gap of 180 degrees. Finally,475 events were selected with magnitude greater than 1.5 recorded by 84 stations. We obtained good resolution down to 70 km. First, we used 1-D coupled inversion algorithm (VELEST) to calculate the velocity model and the relocations. The same model convergence is observed for the mid and lower crust. The upper layer (0-10km) is observed to be sensitive to the starting model. We used vertical seismic prospecting data from boreholes in Georgia to fix upper layer velocities. We relocated all events in the region using the new reference 1- D velocity model. The 3-D coupled inversion algorithm (SIMULPS14) was applied using the 1-D reference model as a starting model. We observed very large amount of shift at horizontal directions (up to 50 km). We observed clustered events where they are well correlated with query blasts from Tkibuli mining area. We applied the resolution test to estimate the spatial resolution of the tomographic images. The results of the test indicate that the initial model is well reconstructed for all depth slices, though it is badly reconstructed for the shallowest layer (with depth = 5km). The Moho geometry beneath Caucasus has been determined reliably by the previous geophysical studies. It has a relatively large depth variation in this region from 28 to 61 km depth, according to those studies and our tomography result for the uppermost mantle (50 km) reflects this depth variation of the Moho discontinuity.
DE: 6982 Tomography and imaging (7270, 8180)
DE: 8180 Tomography (6982, 7270)
SC: Seismology [S]
MN: 2007 Fall Meeting