ESTIMATION OF VS30 BASED ON SOIL INVESTIGATION BY USING MICROTREMOR OBSERVATION IN PADANG, INDONESIA

Abstract

Several powerful earthquakes have struck Padang during recent years, one of the largest of
which was an M 7.6 event that occurred on September 30, 2009 and caused more than 1000 casualties.
Following the event, we performed single observations of microtremors at 110 sites in Padang. The results
enabled us to estimate the site-dependent amplification characteristics of earthquake ground-motion. We also
conducted a 12-site microtremor array investigation to gain a representative determination of the soil condition
of subsurface structures in Padang. From the dispersion curve of array observations, the central business district
of Padang corresponds to relatively soft soil condition with Vs30 less than 400 m/s, the predominant periods
due to horizontal vertical ratios (HVSRs) are in the range of 2.0 to 4.0 s.