Abstract

The subsurface site structure of the Swabian Jura, southwest Germany, seismic network has been modeled from the inversion of locally recorded SH wave microearthquake seismograms. The observed records have been deconvolved from the effects of apparent source pulse broadening due to the combined influence of frequency bandlimited source signals, absorption, peg leg multiple reflections, and the recording system following the procedure of Scherbaum and Stoll (1985). Corresponding pseudo-reflection seismograms were calculated based on the Kunetz-Claerbout relation for SH waves and inverted using a Levison recursion algorithm. The final structural models have been optimized in terms of numbers of layers and depth resolution using Ferber's (1985) noise stabilization technique.

The resulting impedance models for the Swabian Jura, southwest Germany, seismic network show some strongly correlated reflectors in the uppermost layers, which are well understood in terms of the local stratigraphy. The comparison of the inverted impedance model HSN with the P-wave velocity log from a nearby exploration drilling (Trochtelfingen, BEB) shows a high degree of similarity of the dominating reflectors down to a depth of several hundred meters.

As a consequence, the coda-generating process for the early part of the coda of the observed Swabian Jura microearthquake seismograms (Wood-Anderson magnitude MWA < 3.0) can be completely interpreted as an effect of the local subsurface structure.

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