Eurasian Surface Wave Phenomenology and Inversion for Crustal and Upper Mantle Structures.

Abstract

Abstract : Earthquake seismograms recorded by several global and regional networks between 1988 and late 1995 were used to measure the group velocity dispersion of fundamental Rayleigh and Love waves crossing Eurasia. More than 9,000 three component long period seismograms following more than 600 events with Ms greater than 4.5 were processed. This data set was reduced by clustering observations along similar paths into measurements along the unique path, and rejecting outliers. The resulting curves were used to construct group velocity maps from 20s period to 200s period for Rayleigh waves and up to 150s period for Love waves. These maps have better resolution and are more reliable than globally estimated dispersion maps or such maps computed from current global models of the crust and mantle. In particular, they contain new information about large sedimentary features, lower crustal and upper mantle structures, Moho topography. These maps guide the identification and extraction of surface waveforms which emanate from small seismic events. They should be added to the Knowledge Base used to monitor clandestine nuclear tests. More accurate and detailed crustal and upper mantle models derived from these maps are very important for improvement of location/depth estimation in the strategic areas of Eurasia characterized by complex geology.