Recovering permanent displacements from seismic records of the June 9, 1994 Bolivia deep earthquake

Abstract

Ground displacements of the 1994 deep Bolivia earthquake are recovered from six on-scale velocity records of a temporary array located ∼600 km south of the epicenter. I first removed the instrument (STS-2) response using a time-domain deconvolution. To correct for baseline drift in the deconvolutions, I used two separate windows of the trace, one before and one after the transient motion from the earthquake, and fit them simultaneously with a 4th-order polynomial. The amount of permanent displacement is included in the post-transient signal window and is determined together with the polynomial coefficients by a least-squares inversion. The polynomial is then subtracted from the displacement to remove the drift. I found that this technique produces robust displacement waveforms, as demonstrated by similar results at all stations. The obtained vertical permanent subsidences range from 5.5 to 6.4 mm, which agree well with predictions by using normal mode summation.