[S-IT20] MAGMA, FLUID TRANSPORT, AND SEISMICITY IN THE EARTH'S INTERIOR

[SIT20-P04] Completeness magnitude of earthquakes and spatial variations of b-VALUE in Myanmar

Ngun Za Iang¹, *Saeko Kita² (1.Department of Meteorology and Hydrology (DMH), Ministry of Transport and Communications, Naypyitaw, Myanmar, 2.Building Research Institute)

Keywords:b-value, Myanmar, intraslab earthquake, the Sagaing Fault, seismicity

In order to estimate completeness magnitude of earthquakes and b-value of events in Myanmar and surrounding areas, we examined 1,350 hypocenters in the NEDC (National Earthquake Data Center, Myanmar) hypocenter catalog from 2014 to 2018, which determined by a hypocenter determination code SEISAN (Havskov and Ottemoller, 2010) and 21 seismic stations. The completeness magnitude (Mc) was estimated as 2.8 with a b-value of 0.68±0.02 in the whole study area, and the b-values regionally varied from 0.52 to 1.0. The values of completeness magnitude became improved with increase of time. The tendency relation between b-value and faulting styles was found along the Sagaing Fault. The southern part with a smaller b-value indicates thrust type focal mechanism, whereas the northern part with a larger b-value shows strike-slip type focal mechanism. The b-value generally increases with the increase of depth in the whole study area. In the active fault region, the b-value decrease with the increase of depth at depths of less than 15 km. At a depth of more than 15 km, the b-value then increases with the increase of depth. In contrast, a significant decrease of b-value with depth was observed at depths of 75-85 km in the subduction zone of the study region, which could be related with the dehydration process in the subducting oceanic plate. The information of spatial variation of b-value could help to understand the seismotectonics beneath Myanmar and the methodology of this study might be fruitful for the evaluation of ability of detectivity of seismicity there.