Seismicity of Southern Thailand and Peninsular Malaysia

Abstract

Prior to the occurrence of the 2004 Sumatra-Andaman earthquake, Southern Thailand and Peninsular Malaysia experienced relatively little earthquake activities and considered as low seismicity regions. However, after the devastating 2004 earthquake, the seismicity in both regions increases with the occurrence of plenty of local intraplate earthquakes. The objectives of this study are: firstly, to analyze the seismicity of Southern Thailand and Peninsular Malaysia focusing on the temporal-spatial distribution and magnitude variation of local earthquakes, and their relationship with local fault zones; secondly, to investigate characteristics of earthquake sequences happened in Phuket Island (Southern Thailand) in 2012 and in Bukit Tinggi (Peninsular Malaysia) in 2007-2009; and thirdly, to evaluate the impacts of several regional earthquakes on the local seismicity and crustal deformation in both regions in terms of geodynamic implications. This study created earthquake catalogs from 227 earthquakes in Southern Thailand covering a period 1970 – 2020 and 58 earthquakes in Peninsular Malaysia during a period 1922 – 2020 which was compiled from observations of local, regional/national, and global networks. Available digital seismograms from both regions were processed and interpreted by using SEISAN software. This study reveals that epicenters of local earthquakes are predominantly distributed in the vicinity of fault zones in Southern Thailand and Peninsular Malaysia, indicating that they are the main contributors to the local seismicity. This study categorizes the 2012 Phuket and 2007-2009 Bukit Tinggi earthquakes as the earthquake swarms and complimented by mini swarms. This study also reveals that several large regional earthquakes in Sumatra region had considerable geodynamic implications on local seismicity and deformation. Therefore, this study is essential for providing considerations on the seismic hazards in both regions.