Study of the fault segmentation in the northern Longitudinal Valley fault of eastern Taiwan by PS-InSAR with ALOS images
Date Issued
2014
Date
2014
Author(s)
Liao, Yu-Tzu
Abstract
Taiwan is located at the boundary between the Eurasian Plate and the Philippine Sea Plate. The Longitudinal Valley at the eastern Taiwan is considered as the oblique collision boundary. There are several faults in the valley and the most active one is the Longitudinal Valley Fault (LVF) which accommodates about one third of convergence rate between these two plates. LVF is also seismogenic fault zone which ruptured four segments of LVF in 1951 Hualien-Taitung earthquake sequences. Besides, precious studies have proposed that this region could occur a potential big earthquake with a magnitude 7.2, thus it is a crucial issue for the assessment of earthquake hazard in this area. Both geodetic survey and geomorphologic study highlight relationship of fault activity and segmentation of LVF. Therefore, a space-borne geodetic technique is used to detect the spatial distribution of interseismic deformation along the Longitudinal Valley to further access the segmentation of LVF. This study area is mainly focus on the northern LVF. To achieve our goal, we apply a Persistent Scatterer SAR interferometry approach (StaMPS) using L-band ALOS data in eastern Taiwan. The result shows a considerable improvement of density of measurement compared to previous studies using C-band ERS data. The high density of measurement allows us to get a continuous view of active deformation, which can indicate the fault segmentation of the LVF. In Hualien city, the LOS velocities in northeastern part are lower than the rest area. No velocity change is observed across the Milun fault. From Hualian river mouth to Nanfu, there is no clear LOS velocity offset across the LVF except for the northernmost part, which indicates activity of LVF might be low during the interseismic period. From our PSI (abbreviation of Persistent Scatterer SAR interferometry) result, the Linding fault can be further divided into three sub-segments by their distinct LOS velocity. In the central part of the Linding fault (between latitude of 23.85° to 23.73°), a local subsidence in LOS direction with the mean LOS velocities ranging from about 7 to -7 mm/yr is observed, while toward the north and south, the velocity is increased again. Our result shows that the Juisui fault is not active, too. However, a clear velocity gradient is observed near the eastern flank of the Central Range between latitude of ~23.63° to ~23.68°. It may be related to activity of the Central Range fault in this area. North or south of this region, the velocity change vanished. The velocity around the Chimei fault is generally higher than around the Juisui fault. The LOS deformation rate by using persistent scatterer approach is similar to the vertical deformation from continuous GPS and leveling data, which is suitable for monitoring of surface deformation in large area.
Subjects
縱谷斷層
持久散射體雷達干涉技術
ALOS
米崙斷層
嶺頂斷層
瑞穗斷層
奇美斷層
Type
thesis
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