Characteristics of the Moei-Mae Ping fault zone, Changwat Tak, Northwestern Thailand

Abstract

The Moei-Mae Ping Fault Zone (MPFZ) in Changwat Tak was selected for identifying its detailed characteristics and locating active faults. The application of remote-sensing data was conducted toward the present study. Events of earthquake faultings, paleomagnitudes, and slip-rates of these fault movements constitute the main tasks. Results from remote-sensing interpretation indicate that the MPFZ is the northwest-southeast trending, oblique-slip fault with a total length of about 230 km. the MPFZ can be traced from eastern Myanmar through the border zone of northwestern Thailand to the northern part of central Thailand. A number of ten fault segments, ranging in length from 8 to 43 km, are recognized and some of which run and pass through Cenozoic basins. Based on the reconnaissance surveys, several kinds of morphotectonic landforms along the Khao Mae Song segment (25 km, in total length) including fault scarps, triangular facets, shutter ridges, and offset streams, are clearly shown in northern part of the study area (Ban Mae Ou Su). A detailed topographic map at a scale of 1:750 covering this fault segment was conducted. The detailed map together with the results on two excavated paleoseismic trenches were performed for determining of its paleoseismic age dating. Estimation from the surface rupture length, the Khao Mae Song segment indicates that earthquake may have occurred in this 20 km rupture length with the maximum paleoearthquake of Mw 6.70. The slip rate of this fault segment is estimated as 0.17-0.73 mm/yr. Consequently, various evidences indicate that the MPFZ is still active till present. The Ban Tha Song Yang fault segment is regarded as the most active and was responsible for the 5.6 on the Richter scale, 1975 earthquake. The dextral movement along the fault controls Cenozoic fault-tip basins in the study area.