[S21-P] Poster

[S21-P-19] Three-Dimensional resistivity structure beneath Payao Fault zone: biggest earthquake in Thailand (5 may 2014)

^○Songkhun Boonchaisuk¹, Puwis Amatyakul², Tawat Rung-Arunwan³, Sutthipong Noisagool^2,5, Weerachai Siripunvaraporn^2,4 (1.Geoscience division, Mahidol University, Kanchanaburi campus Sai Yok/ Kanchanaburi, Thailand, 2.Department of Physics, Faculty of Science, Mahidol University, 272 Rama 6 Road, Rachatawee, Bangkok, Thailand., 3.Curl-E Geophysics Co., Ltd., 85/87 Nantawan Village, Uttayan-Aksa Road, Salaya, Phutthamonthon, Nakornpathom, Thailand. 73170, 4.ThEP Center, Commission on Higher Education, 328, Si Ayutthaya Road, Rachatawee, Bangkok, Thailand., 5.eEarthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Japan)

Payao Fault zone (PYFZ) is mostly aligned in north-south direction with the length about 90 km cover the area of Chiang Rai, Payao and northern part of Lampang province, Northern Thailand. Base on hazard map of Thailand, this area was classified as risk zone. On May 5, 2014, The biggest earthquake in Thailand with magnitude 6.5 was occurred at Mae Lao district, Chiang Rai province. There were also thousand aftershocks in PYFZ. More than 3500 buildings and a road was damaged. Most of the earthquakes were occurred in the area between two majors fault: the NE-SW-trending Mae Lao Fault Zone and N-S-trending Pan Fault Zone. The focal depth of main shock and major aftershocks were reported at varies depth. The focal mechanisms of main shock and after shock with high magnitude are also reported. However, there are no deep crustal structure in this area. The deep resistivity structure could improve the understanding fault mechanism, geology and tectonic in PYFZ. In order to reveal the PYFZ structure, Magnetotelluric (MT) data from 31 stations as well as a remote reference site at Kanchanaburi province (600 km apart) was installed during February and May 2015. Full impedance tensor with tipper were then inverted to obtain the 3D resistivity structure by using WS3DINV-MPI program. Interesting structures can be observed. Shallow resistivity structure vary from place to place and corresponds quite well with the surface geology. There are is conductor beneath Mae Lao segment (MLS) near the seismogenic zone. The conductor might play an important rule for the 5 May 2014 earthquake and its sequence. It was interpreted as high interconnected aqueous fluid content zone. The fluid in pre-exiting fault, MLS, can reduce the maximum fictional strength resulting the main shock and aftershocks.