colluvium and alluvial fan deposits, low hills and rolling land appear in the
central region. The land with gentle slope and flat land overlaid by alluvium, flood plain and deltaic deposits along the
eastern part of the study area in the lower central plain. In
terms of geology, the area is composed of wide-ranging rock
types; sedimentary, igneous, and metamorphic rocks, which
range in age from inferred Pre-Cambrian to Quaternary. However, Paleozoic rocks are predominant, in particular, Ordovician, Silurian-Devonian and Permian clastic and carbonate
rocks and Permo-Carboniferous glacio-marine facies of the
Kang Krachan Formation or former Phuket Series. Structurally, the rock units show a preferred strike orientation in a
northwest-southeast direction, parallel or sub-parallel to the
SSF, along parts of the Kwae Yai River in the northern and
the TPF along the Kwae Noi River in the southern part of the
area (Figure 2). An updated active fault map of Thailand was
prepared by the Active Fault Research Section of the Environmental Geology Division and published by the Department of Mineral Resources in 2007. There on the map no
TPF extends to the Cenozoic Basin of Central Thailand