Estimation of S-wave velocity structures by using microtremor array measurements for subsurface modeling in Jakarta

Jakarta is located on a thick sedimentary layer that potentially has a very high seismic wave amplification. however,the available information concerning the subsurface model and bedrock depth is insufficient for a seismic hazard analysis. in this study,a microtremor array method was applied to estimate the geometry and s-wave velocity of the sedimentary layer. the spatial autocorrelation (spac) method was applied to estimate the dispersion curve,while the s-wave velocity was estimated using a genetic algorithm approach. the analysis of the 1d and 2d s-wave velocity profiles shows that along a north-south line,the sedimentary layer is thicker towards the north. it has a positive correlation with a geological cross section derived from a borehole down to a depth of about 300 m. the spt data from the bmkg site were used to verify the 1d s-wave velocity profile. they show a good agreement. the microtremor analysis reached the engineering bedrock in a range from 359 to 608 m as depicted by a cross section in the north-south direction. the site class was also estimated at each site,based on the average s-wave velocity until 30 m depth. the sites ui to istn belong to class d (medium soil),while bmkg and ancl belong to class e (soft soil). © 2014 published by itb journal publisher.