The potential for a great earthquake along the southernmost Ryukyu subduction zone
Interseismic GPS data along the Hualien-Suao coast (NE Taiwan) shows a pattern of strain accumulation that is consistent with a potential future large shallow earthquake along the southernmost Ryukyu subduction zone. The measured shortening rate parallel to the Ryukyu Trench is 80 mm/yr, about twice of the shortening rate perpendicular to the Ryukyu Trench. We invert for slip-deficit rates and the geometric configuration of the plate interface. Our preferred fault model dips 10° northward and extends about 70 km from the Ryukyu Trench to a depth of 13 km. The slip deficit rate exhibits a left-lateral motion of 78 mm/yr and a normal motion of 36 mm/yr on a 290°-trending fault. The slip rate budget of the southernmost Ryukyu subduction zone is close to the plate convergence rate, suggesting the plate interface is fully locked. Assessments of seismic hazard in this region need to consider the potential threat from M_w 7.5~8.7 tsunami earthquakes generated by shallow ruptures.
Additional Information© 2012 American Geophysical Union. Received 16 June 2012; accepted 18 June 2012; published 26 July 2012. The authors thank the Editor, Andrew Newman, as well as Emma Hill and an anonymous reviewer for their constructive suggestions. The generous provision of continuous GPS data at the Ryukyu Islands from GEONET (GPS Earth Observation Network) established by the Geographical Survey Institute (GSI), Japan is appreciated. We thank the Central Weather Bureau and Ministry of the Interior, Taiwan and IGS community. GMT was used to create several figures [Wessel and Smith, 1998]. This is the contribution of the National Science Council of the Republic of China grant NSC 98-2119-M-001-033-MY3; the Institute of Earth Sciences, Academia Sinica, IESAS1716; Caltech Seismological Laboratory, Seismo 10077, and Tectonics Observatory, TO# 204.
Published - Hsu2012p19273Geophys_Res_Lett.pdf
Supplemental Material - 2012gl052764-txts01.doc