DETERMINATION OF THE SUBSURFACE STRUCTURE OF PADANG CITY, INDONESIA USING MICROTREMOR EXPLORATION

Abstract

Microtremor observations were carried out to determine the subsurface structures of the Padang City, Indonesia. Serious damages occurred by the strong ground motions during the 2009 Southern Sumatra earthquake in the area. The S-wave velocity structure models at the 12 sites were determined from array observation records. The predominant period at 60 sites were obtained from 3-componet observation records. The S-wave velocities of alluvial layers were 80-300m/s. The predominant period was 1.5-3.0 period that H/V spectral ratio has clear single peak models along the coast line area. It was found that soft alluvial layer was distributed whole area from S-wave velocity structure. Depth to bedrock (S-wave velocity is 500m/s layer) was about 100m maximum in the area.