| dc.description.abstract | Chihshang Fault is one of the most active segments of Longitudinal Valley Fault in eastern Taiwan. The Chihshang Fault is the active fault with the significant uplift rate is up to 22 mm/yr during the inter-seismic period. The previous study stated that the trace of the Chihshang Fault corresponded with the major escarpment that struck from Fuli to Wanan. Many observations had been conducted along this major escarpment to study the Chihshang Fault. One of these locations is the Tapo ES area. Pieces of evidence of surface deformation, such as the fractured concrete wall and the tilted slide platform, can be observed along the major escarpment in this area. Two boreholes were penetrated on the hanging wall and footwall of the major escarpment, respectively. However, these boreholes observation showed the continuity of the sub-horizontal layer with less evidence of significant uplift rate in between. We suspect that the upper tip of the Chihshang Fault in this area does not correspond with the the major escarpment; yet the relation between the major scarp and the Chihshang Fault will be interesting to study. Thus, to understand this phenomenon, the aim of this research is to probe the characteristic of Chihshang Fault and the relation between the Chihshang Fault with the surface deformation at Tapo ES area. We utilized 7 boreholes cores, radiocarbon (C-14) dating, Electric Resistivity Tomography (ERT), and inclinometer monitoring to support this research. In Chinyuan, 2 km to the south from Tapo ES, the Chihshang Fault has several branch faults. In this research, to differentiate the Chihshang main fault from the Chihshang branch fault, we define the Chihshang main fault as the fault with the most slip movement, which we expect to see the evidences through the structure of the rock and the inclinometer monitoring result. From the rock core, we observe the Holocene deposits that intercalate into the Lichi mélange near the boundary of these two materials. This feature is consistently observed in three boreholes. From the inclinometer, the active displacement is observed on the boundary between the Holocene deposits and the Lichi mélange. We infer that the Chihshang main fault, in Tapo ES area, separates the Lichi mélange and the Holocene deposits layer with a dip angle of 77o which the upper tip of this main fault does not correspond with the major escarpment mentioned above. Furthermore, from the insight study of the rock cores, we observe the presence of the reworked mélange near the surface with non-sheared irregular structure which indicates the result of the slumping mechanism. Thus, we infer that the recent deformation on the escarpment is affected by two mechanisms, faulting and slumping. | en_US |