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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS014 Poster presentation 2271 Moho and Crustal Structures of the South China sea from satellite gravity anomaly Mr. Trung Nguyen Nhu Department of Geomagentic and Geoelectricity Institute for Marine Geology and Geophysics, VAST IAG Satellite gravity is a superb tool for marine tectonic study. It provides a firsthand glimpse into seafloor morphology and tectonic elements such as spreading ridge, offset, continental-ocean boundary, faults, basins, volcanoes in the ocean. Interpretation of the gravity data constrained by the seismic data is most useful tools for investigating the crustal structure. In this paper, we present interpretation results of the satellite gravity data constrained by the deep seismic for predicting the Moho depth, fault systems and volcano/magma in the East Sea. The Moho surface was investigated by three different compute methods (i.e. isostatic model method, correlation regression method and 3D direct inversion) has shown that the given Moho depth has high accurate and reliable. Comparing to the seismic Moho depth, Comparing with the deep seismic data in the region (i.e. Sonobouy, OBS and ESP) reveals that the correlation regression and 3D gravity inversion solution give the RMS errors of 5, 7-5, 6 %, and RMS errors of the isostatic model is 9, 4%. The Moho depth in the East Sea changes in a wide range of 8-32 km. They are 10-14 km in the ocean Central Basin, 31-28 km along the coast of the margins and 28-18 km in the Hoangsa and Truongsa archipelagos. The crust of the East Sea consists of oceanic and continental crust. The crustal thickness is 4-10 km in the oceanic crust in which the northern side of the spreading ridge is thicker than that in the southern side. The crustal thickness is 31-12 km in the continental crust. The crust in the northern margin is thicker than that in the southern margin. The average crustal thickness is about 12-16 km in the southern margin and 16-20 km in the northern margin. The Red River, Phukhanh, Namconson, Tuchinh-Vungmay basins and Palawan trough lie on the thin continental crust (10-12 Km). Beibuwan, Pearl River Mouth and Cuulong basins lie on the thicker continental crust (20-24 Km). The results also determine the deep fault systems and volcano/magma that develop mainly in the NE-SW, NW-SE and NS directions and in the thin crust area. The volcano/magma activities in the southern side are stronger than that in the northern side of the East Sea. Keywords: satellite gravity, south china sea, moho

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS014 Poster presentation 2272 Seismotectonic models of the three recent devastating SCR earthquakes in India Prof. Jnana Kayal Department of Applied Geophysics Indian School of Mines IASPEI During the last decade (1993-2003), three devastating earthquakes, Killari 1993, Jabalpur 1997 and Bhuj 2001, M 6.0 7.7, occurred in the Stable Continental Region (SCR) of India. These three earthquake sequences are well studied by deploying temporary microearthquake networks. The 1993 Killari earthquake (mb 6.3) is a typical shallow (0-10 km) SCR event. The 1997 Jabalpur earthquake (mb 6.0) and the 2001 Bhuj earthquake (MW 7.7) are, on the other hand, deeper (25-35 km) paleo-rift zone earthquakes within the continental region. The September 30, 1993 Killari earthquake (mb 6.3) occurred in the Deccan province of central India. The Killari earthquake and its 150 well located aftershocks were confined to a shallower depth (0-15 km), a common type of SCR seismicity. The main shock occurred by reverse faulting at a depth of 6 km; the deeper (6-15 km) aftershocks also occurred by reverse faulting. The shallower aftershocks, (0-

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