5:15 PM - 7:15 PM
[SGD01-P02] Geodetic measurements on the April 2024 Hualien earthquakes, in eastern Taiwan
Keywords:co-seismic displacement, post-seismic displacement, CORS, Central Range Fault
The April 3rd ML 7.2 earthquake struck Hualien, eastern Taiwan, where located in the transition from subduction to collision and characterized by complex fault systems. To estimate the coseismic and postseismic displacements, we analyzed the spatial pattern of ground deformation using data from Continuous Operating Reference Stations in 2012-2024, Single-frequency CORS stations in 2018-2024, as well as two precise leveling routes measured 13 and 18 days after the mainshock.
For the ML 7.2 mainshock, high-rate CORS data reveal coseismic horizontal displacements exceeding 24 cm in the Hualien area, with the largest deformation observed near the coast. The CORSs from the west of the Central range show primary southeastern displacements, while GNSS horizontal displacements exhibit divergent patterns, with movements changing from northeastern to southeastern north and south of Hualien. Precise leveling indicate a maximum vertical displacement of 48 cm in the Coastal Range. Two precise leveling routes spanning from the Longitudinal Valley to the Coastal Range show significant continuous uplift but no notable gap across the Lunding fault. Two prominent aftershocks with magnitudes of ML 6.1 and 6.2 on April, 23, 2024, caused offsets of about 18 cm and 7 cm, respectively.
We utilized 3 different geodetic measurements and an elastic half-space model to invert coseismic slip distributions. Testing both west-dipping and east-dipping fault yields reasonable fits to the geodetic data. For the west-dipping fault (30°), maximum slip of approximately 3 m occurred at depths of 15-25 km, while for the east-dipping fault (70°), maximum slip of about 3 m occurred at depths of 30-40 km. The inferred coseismic geodetic moment corresponds to a Mw 7.3 earthquake, consistent with the USGS solution.
For the ML 7.2 mainshock, high-rate CORS data reveal coseismic horizontal displacements exceeding 24 cm in the Hualien area, with the largest deformation observed near the coast. The CORSs from the west of the Central range show primary southeastern displacements, while GNSS horizontal displacements exhibit divergent patterns, with movements changing from northeastern to southeastern north and south of Hualien. Precise leveling indicate a maximum vertical displacement of 48 cm in the Coastal Range. Two precise leveling routes spanning from the Longitudinal Valley to the Coastal Range show significant continuous uplift but no notable gap across the Lunding fault. Two prominent aftershocks with magnitudes of ML 6.1 and 6.2 on April, 23, 2024, caused offsets of about 18 cm and 7 cm, respectively.
We utilized 3 different geodetic measurements and an elastic half-space model to invert coseismic slip distributions. Testing both west-dipping and east-dipping fault yields reasonable fits to the geodetic data. For the west-dipping fault (30°), maximum slip of approximately 3 m occurred at depths of 15-25 km, while for the east-dipping fault (70°), maximum slip of about 3 m occurred at depths of 30-40 km. The inferred coseismic geodetic moment corresponds to a Mw 7.3 earthquake, consistent with the USGS solution.