Regional Attenuation at GSETT-3 Stations and the Transportability of the Lg/P Discriminant.
Scientific rept. no. 1,
SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA
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Recent studies have shown that the high-frequency LgP ratio can be an effective discriminant at regional distances. However, this ratio must be recalibrated for each new source region. We are developing regional wave attenuation models for up to 10 subnetworks of the International Data center IDC primary network, and will use them to evaluate the transportability of the LgP discriminant to uncalibrated regions. We are measuring amplitudes of regional phases in the time and frequency domain, and using our new software program, AmpInv, to invert for source and attenuation models. During the first year of this two-year project we developed all software needed for this study, investigated alternative amplitude measures, and compiled a data set for an Australian subnetwork. During the second year we will compile the data sets for the other IDC subnetworks, estimate regional wave attenuation using AmpInv, and evaluate the accuracy and transportability of the LgP discriminant. We will also obtain ground-truth identification for as many of the events as possible, and we will use knowledge of the local natural and industrial seismicity when this information is not available.