Abstract
Research on seismic microzonation of Semarang is still ongoing. The first seismic microzonation research for this area was performed on 2015. Seismic microzonation map was developed by implementing deterministic 1-D site response analysis at 190 boring locations. Lasem fault was considered to be the main earthquake source which taken into account for seismic microzonation research of Semarang. The second research for developing seismic microzonation map was performed on 2016. Following the research conducted by Team for Updating Seismic Hazard Maps of Indonesia 2016, Rawapening Fault, Ungaran Fault, Weleri Fault, Demak Fault and Semarang Fault are five new shallow crustal fault earthquake sources identified in this research. This paper presents the development of seismic risk microzonation map caused by Semarang fault earthquake scenarios with maximum 6.9 Mw. Deterministic 1-D site response analysis was performed at 288 boring locations for developing seismic risk microzonation map. This research was performed by implementing response spectral matching and site propagation analysis. Due to inadequate data caused by Semarang fault earthquake, response spectral matching was implemented in this research to obtain modified acceleration time histories. All acceleration time histories were developed from five different earthquakes with magnitude 6.05 – 6.9 Mw and maximum epicentre distance 15 Km.
Highlights
Research on seismic microzonation of Semarang is still ongoing
This paper presents the development of seismic risk microzonation map based on the surface spectra acceleration values (PGA, Spectra 0.2s and Spectral 1s) calculated using 1D site response analysis
Based on all surface PGA values calculated at 288 boring locations the distribution of PGA due to earthquake scenario with magnitude 6.9 Mw can be seen on Fig. 4(a)
Summary
Research on seismic microzonation of Semarang is still ongoing. The first research of seismic microzonation for this area was performed on 2015 by [1] and following the work conducted by Team for Revision of Seismic Hazard Maps of Indonesia 2010 (TRSHMI 2010). An active and closest shallow crustal fault, was considered to be the earthquake source scenario conducted for site response analysis. All surface spectra acceleration were developed due to Semarang fault (reverse fault mechanism) earthquake scenarios with maximum magnitude 6.9 Mw and maximum epicentre distance 15 Km. Surface PGA, spectral 0.2 s and spectral 1s were calculated at 288 boring locations. This research was performed by conducting five important steps: 1) geological, geophysical and soil investigations and analysis for developing soil profile and bedrock elevation 2) collecting acceleration time histories data from worldwide historical earthquake records due to reverse fault mechanism earthquakes with magnitude 6 - 7 Mw and maximum distance 15 km, 3) developing modified acceleration time histories by conducting response spectral matching analysis, 4) conducting shear wave propagation analysis using modified time histories and calculated using 1-D site response analysis for obtaining surface acceleration time histories and surface response spectra and 5) developing seismic risk microzonation maps
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