Paleoearthquake Investigations of the Mae Hong Son Fault, Mae Hong Son Region, Northern Thailand

Abstract

We applied remote sensing and aerial photographic techniques to a study of the Mae Hong Son Fault (MHSF), located in the Mae Hong Son region, northern Thailand. Several fault lines are recognized in the region, trending mainly NE–SW, NW–SE, and N–S. The main morphotectonic landforms associated with the MHSF are fault scarps, offset streams, linear valleys, triangular facets, offset ridge crests, hot springs, and linear mountain fronts. A trench, a quarry, and a road cut in Caenozoic strata were used to analyze fault geometries in the area. We identified eight paleoearthquake events from trenching, quarry, and road-cut data, and from optically stimulated luminescence (OSL) and thermoluminescence (TL) dating. The OSL and TL ages of the events are: (1) 78,000 yr BP; (2) 68,000 yr BP; (3) 58,000 yr BP; (4) 48,000 yr BP; (5) 38,000 yr BP; (6) 28,000 yr BP; (7) 18,000 yr BP; and (8) 8,000 yr BP. The recurrence interval of seismic events on the MHSF appears to be ca. 10,000 years, and the slip rate was estimated as ca. 0.03–0.13 mm/yr. There is a low possibility of a large earthquake on the MHSF in the near future.