| dc.description.abstract | Basal décollement and wedge strength domain the geometry of accretionary wedge based on thin-skin thrust theory. Therefore, we will research the frictional characteristic of décollement fault that to understand the geometry of accretionary wedge. Due to the sampling of décollement fault was hardly, there had not been to research representative specimen for frictional experiments in the past. We use Shuangdong fault gouge to substitute basal décollement material, because Shuangdong fault is the main branch of basal décollement in central Taiwan. To understand the gouge frictional characteristics in different depths and slip velocity, we use remolded gouge sample with different normal stress and velocity to conduct rotatory shear experiments, and in-situ water content used with all tests. And the results can evaluate basal décollement mechanical behavior. Research results indicate that, when the rotating shear velocity is less than 1 m/s of the test, it’s showed slip strengthening. While 1 m/s rotating shear test result shows slip weakening. We also find out that the steady-state friction coefficient( ) will decrease with increasing velocity(velocity weakening), when the velocity of rotating shear is within the range of 10-4~1 m/s. This result representing the basal décollement strength will be reduced as the velocity increases. change slightly in the same velocity(10-1、10-2 m/s), normal stress between 0.5~2.5 MPa. In other words, the variation thickness of the accretionary wedge impact limited frictional coefficient on the basal décollement. In addition, according to the observation of the microstructure, found that rotating shear velocity 1 m/s(closer to the velocity of coseismic) of the specimen, there are almost all extremely fine grained(<0.004 mm) develop above Y-shear(along rotational side). This area has discovered partial frictional melting phenomenon, which accompany with the displacement weakening of frictional coefficient. Therefore, the frictional behavior of basal décollement may be quit different between coseismic and interseismic condition. Microstructure comparisons R1-shear, Y-shear, and P-foliation continuities are mainly controlled by normal stress(from 0.5 MPa increased to 2.5 MPa). It implies that, the thickness of accretionary wedge is possible to control the basal décollement’s development of microstructure. Microstructure may affect the pore pressure dissipation process, so the thickness of the accretionary wedge may indirectly affect the strength of the basal décollement. | en_US |