© 2019, Seismological Society of America. All rights reserved.Site characterization is one of the most important components in seismic hazard analysis because it accounts for the important effects of near-surface geology on ground motion. It is usually quantified based on the time-averaged S-wave velocity (VS) for the top 30 m of the profile (VS30). In this study, we estimate the site class in Jakarta based on VS structure estimated using microtremor array observations. The results show that microtremor-derived VS profiles agree well with standard penetration test-derived profiles at nine sites. The site-class estimates in the Jakarta area can be divided into two National Earthquake Hazards Reduction Program classes: (a) site class E (soft soil) located in alluvium, beach ridge, and alluvial fan deposits in northern and western Jakarta, and (b) site class D (stiff soil) found mainly in alluvial fan deposits in southeastern Jakarta. The variation of VS30 in Jakarta leads to different soil amplification factors that will impact the seismic hazard at the surface. We show that the seismic hazard resulting from selected ground-motion models (GMMs) illustrates a clear influence of site effects at long periods (>1 s). However, the effect on peak ground acceleration and response spectra for short periods (0.2 s) appear to be less pronounced, due to the GMMs’ treatment of basin effects and nonlinear soil behavior. Available GMMs may not accurately account for such effects in the Jakarta basin, and GMMs specific to Indonesia should be developed to accurately assess seismic hazard there.

Ground motion model,Near-surface geology,Nonlinear soil behavior,Peak ground acceleration,Seismic hazard analysis,Seismic hazard assessment,Site characterization,Standard penetration test

[{‘$’: ‘The authors gratefully acknowledge the Research Institute for Housing and Human Settlement (RIHHS), Ministry of Public Works and Housing, the Republic of Indonesia, the seismic microzonation study team and the Research Centre for Disaster Mitigation (PPMB), Institut Teknologi Bandung (ITB), for supporting data and assistance during this study. The authors thank I. G. Wong and two anonymous reviewers for their constructive comments that improved the article significantly. The authors also thank A. Cipta for providing his model for the depth to bedrock in Jakarta. This research is part of the microzonation study for Jakarta supported by RIHHS and the Indonesian Ministry of Research, Technology and Higher Education through the Penelitian Dasar Unggulan Perguruan Tinggi (PDUPT) Research Grant 2017–2019 awarded to Sri Widiyantoro.’}, {‘$’: ‘The authors gratefully acknowledge the Research Institute for Housing and Human Settlement (RIHHS), Ministry of Public Works and Housing, the Republic of Indonesia, the seismic microzonation study team and the Research Centre for Disaster Mitigation (PPMB), Institut Teknologi Bandung (ITB), for supporting data and assistance during this study. The authors thank I. G. Wong and two anonymous reviewers for their constructive comments that improved the article significantly. The authors also thank A. Cipta for providing his model for the depth to bedrock in Jakarta. This research is part of the microzonation study for Jakarta supported by RIHHS and the Indonesian Ministry of Research, Technology and Higher Education through the Penelitian Dasar Unggulan Perguruan Tinggi (PDUPT) Research Grant 2017?2019 awarded to Sri Widiyantoro.’}]

https://doi.org/10.1785/0120190040