Seismic Sources Identification and Characterization for Myanmar: Towards Updating the Probabilistic Seismic Hazard Maps (2012)

Abstract:

Myanmar, lying in the Alpide earthquake belt, is quite earthquake-prone. There have been at least 16 major earthquakes (M 7.0 – 7.9) and a great earthquake (M 8.0, 1912) in the past 175 years, some of which were quite destructive, for example, 1839 Ava (Innwa) earthquake. With an objective of reducing earthquake risk in Myanmar, seismic zone maps have been constructed since 1959. The first-generation maps were mainly the intensity zoning maps using Modified Mercalli Intensity (MMI) Scales (Gorshkov, 1959; Maung Thein, 1985; Maung Thein, 2001). The second-generation maps were partly historical, and partly deterministic (Maung Thein et al., 2003; Maung Thein et al., 2005). In 2012, the third-generation maps, the probabilistic seismic hazard assessment (PSHA) maps were constructed for the whole country. Seismic hazards in these maps are represented by means of peak ground acceleration (PGA), peak ground velocity (PGV), and spectral acceleration (SA) in the periods of 0.2 s, 0.3 s and 1.0 s. The seismic hazards are calculated in 0.1° x 0.1° interval, assuming the firm rock site condition and all of the PSHA were carried out for 2% and 10% probability of exceedance in 50 years.

Now, the seismic hazard maps of Myanmar,2012 are planned to update by remodeling the seismic sources. As the first step in updating the previous probabilistic seismic hazard maps developed in 2012 we re-identify the seismogenic sources for Indo-Burma Arc, Eastern Himalaya Arc and Andaman Rift Zone as the areal seismic sources. The major active faults which are seismically very hazardous for Myanmar: Sagaing fault, Kyaukkyan fault, Nan Pon fault, Kabaw fault, Myauk-U fault, Dawei fault, Gwegyo Thrust, major thrusts in north-west Myanmar, and the left-lateral strike-slip faults in the Eastern Highland are identified as the fault sources. The seismic source parameters for each source; the b-value, maximum earthquake potential, and annual rate of exceedance for the specific magnitude earthquake; are estimated by Gutenberg-Richter Law and maximum likelihood method of Kijko (2004) with the complements of geologic and paleoseismic data.

Keywords: probabilistic seismic hazard assessment, PSHA maps, PGA, PGV, SA, major active faults, areal seismic sources, Indo-Burma Arc, Eastern Himalaya Arc, Sagaing Fault