Crustal seismic velocity structure in the epicentral region of the Latur 
Earthquake (Sept. 29, 1993), Southern India: inferences from modeling of the 
aftershock seismograms

Krishna, V. G.; Rao, C. V. R. K.; Gupta, S. K.; Sarkar, D.; Baumbach, M.; 2.1 Physics of Earthquakes and Volcanoes, 2.0 Physics of the Earth, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum

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Crustal seismic velocity structure in the epicentral region of the Latur Earthquake (Sept. 29, 1993), Southern India: inferences from modeling of the aftershock seismograms

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Krishna, V. G.
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Rao, C. V. R. K.
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Gupta, S. K.
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Sarkar, D.
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Baumbach, M.
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Krishna, V. G., Rao, C. V. R. K., Gupta, S. K., Sarkar, D., Baumbach, M. (1999): Crustal seismic velocity structure in the epicentral region of the Latur Earthquake (Sept. 29, 1993), Southern India: inferences from modeling of the aftershock seismograms. - Tectonophysics, 304, 241-255.

https://gfzpublic.gfz-potsdam.de/pubman/item/item_226173

Abstract

Abstract: We present 1-D models of crustal P and S wave velocity structure in the epicentral region of the devastating 1993 Latur earthquake in southern India. Travel time and relative amplitude modeling of a seismogram section of well located aftershocks out to 80 km offset, by reflectivity synthetic seismograms, reveal alternating low-velocity layers (LVLs) for P and S waves in the upper crust at depths of 6.5-9.0 km and 12.3-14.5 km with about 7% velocity reduction. A lower crustal LVL at 24-26 km depth is also inferred by modeling. The seismic activity in the Latur region is essentially confined to shallow upper crustal depths of less than 6 km, above the LVLs. The upper crustal velocity models further reveal a relatively low Vp/Vs ratio of 1.65, while synthetic seismogram models consistent with the upper crustal P wave reflection phases reveal a Qp/Qs ratio certainly less than 1. A high-conductivity zone at a shallow depth of 6-10 km brought out by broad band MT soundings in this region, is found to be coincident with the upper crustal LVLs. These coincident anomalous properties of the upper crust suggest the presence of fluids (probably in a partially- or slightly under-saturated state) below the hypo-central region of the Latur earthquake and its aftershocks.