Revisiting seismic hazard assessment for Peninsular Malaysia using deterministic and probabilistic approaches

Seismic hazard assessments, both deterministic and probabilistic, for Peninsular Malaysia have been carried out using peak ground acceleration (PGA) data recorded between 2004 and 2016 by the Malaysian Meteorological Department using triaxial accelerometers placed at 19 seismic stations on the peninsula. Seismicity source modelling for the deterministic seismic hazard assessment (DSHA) used historical point sources whereas in the probabilistic (PSHA) approach, line and areal sources were used. The earthquake sources comprised the Sumatran subduction zone (SSZ), Sumatran fault zone (SFZ) and local intraplate (LI) faults. Gutenberg-Richter law b value for the various zones identified within the SSZ ranged between 0.56 and 1.06 (mean = 0.82) and for the zones within the SFZ, between 0.57 and 1.03 (mean = 0.89). Suitable ground motion prediction equations (GMPEs) for Peninsular Malaysia along with other pertinent information were used for constructing a logic tree for PSHA of the region. The DSHA critical-worst scenario suggests PGAs of 0.07-0.80 ms(-2) (0.7-8.2 percent g), whilst the PSHA suggests mean PGAs of 0.11-0.55 ms(-2) (0.5-5.4 percent g) and 0.20-1.02 ms(-2) (1.9-10.1 percent g) at 10 % and 2 % probability of exceedance in 50 years, respectively. DSHA and PSHA, despite using different source models and methodologies, both conclude that the centralwestern cities of Peninsular Malaysia, located between 2 and 4 degrees N, are most susceptible to high PGAs, due to neighbouring active Sumatran sources, SFZ and SSZ. Of the two Sumatran sources, surprisingly, the relatively less active SFZ source with low magnitude seismicity appeared as the major contributor due to its proximity. However, potential hazards due to SSZ mega-earthquakes should not be dismissed. Finally, DSHA performed using the limited LI seismic data from the Bukit Tinggi fault at a reasonable moment magnitude (M-w) value of 5.0 predicted a PGA of similar to 0.40 ms(-2) at Kuala Lumpur.