Analysis of the Seismicity Pattern Change for Probabilistic Seismic Hazard Analysis (PSHA) and Mitigation: Mapping the Probability Difference Before Large Earthquake and Its implementation for PSHA & Mitigation around southern off the coast of Sumatra - West Java

Abstract

The implementation of the Seismic Quiescence Index (SQI) into seismic hazard study and analysis mapped around the off southern coast of Sumatra - West Java. The 15 years of Region Time Length (RTL) were used in this study. To construct the SQI, first of all, we divided the period of the declustered shallow earthquake catalog of observation into two parts, i.e., a period of 1978 to 1992 and 1993 to June 2006. Two rate models were then developed to estimate the probability of a given magnitude and a specified time window. The result was then used to determine the probability difference between the two periods of observation and SQI estimation. The SQI then used better to understand the pattern of seismicity changes for PSHA. To construct the model for SHA is done by developing the seismicity rate model of the period 1978 to June 2006 and then weighted by the SQI index. Furthermore, the median Peak Ground Acceleration (PGA) of 10% probability exceedance level for 50 years is estimated and mapped. By incorporating an amplification factor, the PGA value on the surface can be determined. The amplification factor is calculated using the Horizontal-Vertical Spectral Ratio (HVSR) method. This result might be useful for better understand the future PSHA and mitigation before a large earthquake.