Investigating Active Deformation in the Northern Longitudinal Valley and City of Hualien in Eastern Taiwan Using Persistent Scatterer and Small-Baseline SAR Interferometry

Abstract

Rapid convergence between the Eurasian plate and the Philippine Sea plate in the northern Longitudinal Valley near the city of Hualien in eastern Taiwan has produced prominent fault scarps and large earthquakes (M ¡_ 7). This study attempts to more thoroughly understand the surface deformation activities near the faults and their relation to earthquakes near Hualien City using a stable target, multi-temporal radar interferometry method to extract the surface deformation information in this area. Our results indicate that the extracted deformation signals were comparable with those in our leveling data and have a very high spatial density (exceeding 70 point km-2). Additionally, all faults in the northern Longitudinal Valley and Hualien City were not deformed monotonically. Rather, deformation time series are complex and frequent activities affected the general trends wherein, for example, 2005 earthquake swarm produced more than 10 mm of displacement near the Milun fault. Moreover, deformation rates in the study area generally ranged from around 10 - 20 mm yr-1 of relative displacement rates along the radar line of sight between the western part of Hualien City near the Central Range and the eastern part during the decade, while only the Mingyi fault displayed monotonic fault activities with change of displacement rates of approximately 5 - 10 mm yr-1 across the fault.

Keywords

• Persistent scatterer
• InSAR
• Longitudinal Valley
• Hualien
• Milun Fault