Seismogenic structure beneath the northern Longitudinal Valley revealed by the 2018–2021 Hualien earthquake sequences and 3-D velocity model

Abstract This study uses the 3D crustal velocity model and relocated earthquake hypocenters, including 2018–2021 sequences, to re-assess seismogenic structures at northern Longitudinal Valley. Earthquake focal mechanisms hypocenters from clusters suggest a gentle west-dipping fault existing under Valley Coastal Range. associated with this indicate it develops along base of high-velocity Central Range metamorphic rocks is likely branched out previously recognized Fault (CRF). Both geometry structure truncates north 23.7° N, separating northernmost LVF into shallow deep segments. The segment then plausibly evolves be transpressional system that mainly accommodates left-lateral motions. interpretation coincides geomorphological geodetic observations showing dominated by faulting, instead significant reverse component as in southern limited width also imply its seismic potential relatively limited, while underling deeper are major structure. Such development CRF-related could accommodate northwestward subduction Philippine Sea Plate reactivate part Offshore Eastern Taiwan Thrust Belt.