Young fault movements along the Southern Segment of Sri Sawat Fault, Amphoe Sri Sawat, Changwat Kanchanaburi; and their Tl-dating results

Abstract

The purpose of this research is to clarify the paleoearthquakes along the southern segment of the Sri Sawat Fault (SSF), to determine the age of fault movements, to estimate their slip-rates and the magnitudes of paleoearthquakes, and to indicate whether this fault is still active. By means of remote-sensing interpretation, the appearance of sharp lineaments are well observed together with morphotectonic features. These indicate the right-lateral displacement of SSF in the southern segment. Young deposition of sediments are found in field locations nearby SSF. In addition, the offset of top-soil and pediments observed from the recent road-cut exposures strongly indicate the local reverse fault movement of the SSF. Therefore, the fault is consequently regarded as the oblique slip fault. Seven representative samples of colluvial sediments related to the SSF were collected from the Kaeng Khaep excavated trench and ten from Pha Tawan I and II trenches forthrmoluminescence (TL) dating using particularly quartz concentrates extracted. However, the results indicate four faulting events, i.e., the prior 80.4 ka, the 36.7 to 49.3 ka, the 29.5 to 30.0 ka and 5.8 to 9.2 ka events. The slip-rates of movements of SSF, based on the method of McCalpin (1996), is about 0.672 mm/year and its magnitude using surface rupture length (SRL), based on method described by Wells and Coppersmith (1994), is about 6.3 MW. The dating result shows the activeness of SSF within Holocene Epoch.