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Deciphering the Multi-fault System of the 2024 Mw 7.4 Hualien, Taiwan Earthquake Using Combined Seismic, Geodetic and Insar Datasets

Description: 

The April 3, 2024 Mw 7.4 Hualien earthquake was the largest earthquake in Taiwan in almost 25 years, and it has resulted in thousands of aftershocks so far. The intricate fault distribution in eastern Taiwan adds challenges to determining the fault geometry and slip distribution associated with this event. The USGS finite-fault solution indicates an overall east-dipping fault rupture, but inversions based on geodetic observations suggest a west-dipping thrust fault. To better constrain the fault geometry and slip distribution of the Hualien earthquake, we combine strong motion seismic, GPS, and InSAR datasets for joint inversions. We first use a Bayesian inversion scheme to constrain the most probable fault parameters, including source location, depth, strike, dip, rake, and slip with the coseismic GPS displacement solutions from the Nevada Geodetic Laboratory. We then use a finite fault inversion method to estimate slip distribution on this fault geometry with a 3 km sub-fault patch size. For the seismic dataset operated by the Taiwan Strong Motion Instrumentation Program network (TSMIP), we first explore the fault parameters by random search for a half-million parameter combinations. The results from individual GPS and seismic inversions prefer two main slip patches on two different fault planes, suggesting that a deeper west-dipping fault plane around 35 km depth may have triggered a shallower west-dipping fault around 20 km depth. A joint inversion with all 3 datasets and these two fault planes can yield a total variance reduction over 75%. The total seismic moment of the two faults is equivalent to Mw 7.39. This multi-fault geometry is also in good agreement with the aftershocks. Additionally, preliminary Coulomb stress change analysis indicates better consistency between Coulomb stress increase and aftershock locations. Our analysis supports a multi-fault system that caused the Mw 7.4 Hualien earthquake. It also highlights the value of leveraging dynamic seismic as well as static geodetic measurements such as GPS and InSAR for earthquake source inversions.

Session: Unusual Earthquakes and Their Implications [Poster]

Type: Poster

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Claire

Student Presenter: Yes

Invited Presentation: 

Poster Number: 15

Authors