Basic understanding on seismic hazard zone in Malaysia

This article provides a basic understanding of seismic hazard zones and earthquake measurement metrics in Malaysia, prompted by a magnitude 4.1 (M4.1) earthquake that occurred near Segamat, Johor, on 24 August 2025. The seismic event, caused by activity within the Mersing Fault Zone at a shallow depth of 10 km, was felt across multiple states in Peninsular Malaysia and followed by several aftershocks ranging from M2.7 to M3.4. While no casualties or severe structural damages were reported, minor non-structural damages such as wall cracks and plaster failures were observed. The paper highlights key concepts in seismic engineering, explaining the technical distinction between earthquake magnitude measured on the Richter scale—which quantifies energy release using logarithmic wave amplitudes—and Peak Ground Acceleration (PGA), which measures maximum ground acceleration to evaluate ground shaking intensity, structural damage risk, and inform emergency response strategies.