Analysis of Changes in Seismicity Pattern for Probabilistic Seismic Hazard Analysis (PSHA) and Mitigation: Mapping Probability Difference before the Large Earthquake and Its Implementation in PSHA & Mitigation around Northern Sumatra

Abstract

The probability difference before the occurrence of a large earthquake is mapped in the northern part of Sumatra, taking the range of Region Time Length (RTL) before a major earthquake (December 26, 2004) around 15 years. By normalizing the absolute value of probability difference between two periods of RTL and before RTL, the Seismic Quiescence Index (SQI) is then defined. Probability difference analysis is done by dividing observations of shallow earthquake periods into two periods based on the similarity gradient of the annual earthquake production, namely 1963-1990 and 1991-November 2004. The results showed that areas with relatively high SQI were consistent with the presence of major earthquake events after November 2004 to 2016 that are sorted by a radius of 300 km with the center point being the epicenter position of the December 2004 earthquake. The implementation of the SQI was then used for probabilistic seismic hazards study and analysis based on an integratedmodel that is derived based on the estimated of seismicity rate of around the subduction zone and active fault of Sumatra Fault Zone (SFZ) sources. The map of Probabilistic Seismic Hazard Analysis (PSHA) is then constructed based onPeak Ground Acceleration (PGA) estimated for a 10% Probability Exceedance (PE) level in 50 years. The results of this study may be very useful for earthquake mitigation and modeling efforts for PSHA going forward.

A Microtremor Survey to Identify Seismic Vulnerability Around Banda Aceh Using HVSR Analysis

“…The last felt earthquake has occurred in 1964 with M 6.5 in the Seulimeum segment (Hurukawa andBiana, 2014, Rusydy et al, 2020). In other hands, Banda Aceh is also included in the high seismic hazard zone with acceleration peak of 0.3 -0.4 g in bedrock for a return period of 475 years (Omang et al, 2017;Irsyam, 2017;Triyoso et al, 2020).…”