IMPROVING LOCATIONS OF EARTHQUAKES BY NATIONAL EARTHQUAKE DATA CENTER OF MYANMAR
Supervisor: Nobuo HURUKAWA
By comparing hypocenter locations of earthquakes which occurred in 2014 by National Earthquake Data Center (NEDC) of Myanmar with those of the same earthquakes by European-Mediterranean Seismological Centre (EMSC), we found that NEDC locations scattered larger than EMSC ones. Therefore, we tried to improve the locations of NEDC by adding EMSC data. We used the Modified Joint Hypocenter Determination (MJHD) method for relocation in integration with the local stations arrival times of P and S phases reported by NEDC and global stations P phases reported by EMSC.
Dividing the study area into five sub-regions; from A to E, we applied the MJHD method to each sub-region. The total number of the well-relocated earthquakes was 150 among 184 events which occurred in and around Myanmar in 2014. In comparison with NEDC and EMSC hypocenters, the MJHD method gave more accurate locations and plausible focal depths in each region. We found a sub-crustal earthquake with P-axis oriented east-west in the western subduction zone which adopted the seismogenic layer of the Burma Plate above the subducting India Plate, startings from ~93.0°E to the east and toward the Sagaing Fault. Therefore, by adding EMSC data to NEDC data, we will be able to improve locations of earthquakes in Myanmar.
Furthermore, we relocated three mainshocks with Mw ≥ 5.9 and their related aftershocks which occurred within a week of the mainshocks. After the relocations, we identified the fault planes, rupture directions and fault lengths of the mainshocks by getting clearer distributions of the aftershocks. Using these results, we also obtained the relationship between moment magnitude (Mw) and length of the fault plane (L, km) estimated by the aftershock area in eastern Myanmar. The equation is Log L = 0.72 Mw – 3.16. This equation will be useful to quickly estimate damage areas by large earthquakes.