16:00 〜 16:15
[SCG50-09] The Offshore Seismogenic Structure Database in Northeast Taiwan
★Invited Papers
キーワード：Offshore seismogenic structures, Seismic hazard, Earthquake magnitude, Long-term slip rate, Earthquake recurrence interval
Taiwan is an active orogenic belt with numerous active structures and frequent earthquakes. The Taiwan Earthquake Model (TEM) project has identified 45 on-land structures, widely used by many scholars and government agencies for disaster assessment and preparedness. However, despite reports of active structures and many historical earthquakes offshore Taiwan, a comprehensive database of offshore seismogenic structures is still lacking.
This study integrates geological and geophysical data to determine the locations and subsurface geometry of offshore structures. Offshore northeastern Taiwan, we identified and mapped 17 structures and estimated their key structural parameters, including potential earthquake magnitudes, long-term slip rates, and recurrence intervals. Using three empirical equations, all structures have the potential to produce earthquakes exceeding magnitude 6.5. In subduction zones, some tectonic stress may be released through aseismic creeping due to material properties. To account for this, we applied published coupling ratio data to adjust slip rates, refining the estimates of effective strain accumulation on fault planes. Results show that rapidly slipping structures (~10–30 mm/yr) are concentrated in the hanging wall of the subduction system, whereas slower-slipping structures (~0.1–2 mm/yr) are found in the post-collision zone off northeastern Taiwan. Higher slip rates correspond to shorter earthquake recurrence intervals, such as the structures near the Ryukyu trench with recurrence intervals of only a few hundred years. Due to the limitation of seismic data quality and bathymetry resolution, these structural parameters still have large uncertainties and need to be refined. However, by establishing this offshore seismogenic structure database, we anticipate that the earthquake hazard assessments for the region between Taiwan and Ryukyu will be further improved.
This study integrates geological and geophysical data to determine the locations and subsurface geometry of offshore structures. Offshore northeastern Taiwan, we identified and mapped 17 structures and estimated their key structural parameters, including potential earthquake magnitudes, long-term slip rates, and recurrence intervals. Using three empirical equations, all structures have the potential to produce earthquakes exceeding magnitude 6.5. In subduction zones, some tectonic stress may be released through aseismic creeping due to material properties. To account for this, we applied published coupling ratio data to adjust slip rates, refining the estimates of effective strain accumulation on fault planes. Results show that rapidly slipping structures (~10–30 mm/yr) are concentrated in the hanging wall of the subduction system, whereas slower-slipping structures (~0.1–2 mm/yr) are found in the post-collision zone off northeastern Taiwan. Higher slip rates correspond to shorter earthquake recurrence intervals, such as the structures near the Ryukyu trench with recurrence intervals of only a few hundred years. Due to the limitation of seismic data quality and bathymetry resolution, these structural parameters still have large uncertainties and need to be refined. However, by establishing this offshore seismogenic structure database, we anticipate that the earthquake hazard assessments for the region between Taiwan and Ryukyu will be further improved.