Surface creep along the Longitudinal Valley fault, Taiwan from InSAR measurements

We use interferometric synthetic aperture radar (InSAR) analysis in eastern Taiwan to study reverse creep on the Longitudinal Valley fault (LVF). A stack of the three highest-quality image pairs spanning 1997–2000 shows sharp range change offsets along the eastern side of the Longitudinal Valley, suggesting 11–35 mm/yr of surface creep between 23 and 23.4°N. No shallow slip was observed along the northern or southern ends of the valley, nor on mapped fault traces on the western edge of the valley. The width of the zone of deformation varied, suggesting distributed shear in shallow sediments above the creeping fault in some places. The InSAR results support the view that although surface creep is rapid in certain locations, significant portions of the LVF are locked and thus represent a substantial seismic hazard.