Fast report: strong-motion characteristics of 2025 ML 6.4 Dapu earthquake, Taiwan

Abstract

Abstract We used near-field strong-motion data to investigate the characteristics and underlying causes of the intensified ground motion in the mountain region of southwestern Taiwan during the 2025 Dapu earthquake. Using the empirical Green’s function method by considering the broadband waveforms (0.2 ~ 10 Hz), the result revealed that the 2025 Dapu earthquake exhibited southward rupture directivity with a strong motion generation area (SMGA) of 4.0 km × 3.0 km and high stress drops of 25.4 MPa. Buried faults would strengthen strong ground shaking and reinforce the focusing effect for the hanging-wall sites. For this investigated region, we should pay attention to the low-rise buildings due to amplification in frequency band of 2–5 Hz. Understanding the source properties and site effects is important and should be considered to the application of seismic hazard mitigation, especially for the buried earthquakes.

Keywords

• Rupture directivity
• Strong motion generation area
• Site response