- 期刊
- OpenAccess
Can Great Earthquakes Occur in the Southernmost Ryukyu Arc-Taiwan Region?
琉球島弧最南段至臺灣之間能發生大地震嗎？
並列摘要
We have compiled new free-air gravity anomaly(FAA)and magneticanomaly maps,shedding light on the tectonics in the Taiwan-Luzon region.To have a suitable datum level for both the available gravity and magneticanomaly data,the set of data from an ACT cruise,conducted during May27 to June 21,1996,was chosen as a reference.Based on the cross-overerror analysis,all the other data were adjusted accordingly.Some satellitederived, airborne or land data were also added to the compilation to obtainbetter coverage.Several major new insights into the Taiwan-Luzon region are revealedby the new maps.(1)A prominent NE-SW trending belt of gravity andmagnetic anomalies is present in the onshore and offshore areas of southwestern Taiwan.The Peikang High is located on this belt.(2)Located in theoffshore region west of Taiwan and to the north of the belt described above,the Taishi Basin,in contrast,occupies a relatively low FAA area.It couldbe regarded as a fiexural basin on account of the loading of a thrust-and-fold belt in western Taiwan.(3)A probable NW-SE trending old transformfault is well imaged off southwestern Taiwan,which separates the lithosphere (plate)of the South China Sea from a trapped piece of the PhilippineSea plate.(4)Located east of the Luzon Arc,the Huatung Basin containsseveral E-W trending magnetic reversals and two N-S trending old fracture zones.The Huatung Basin is separated from the West Philippine Basin by the”123E Fracture Zone”.Accordingly,the Gagua Ridge corresponds to a transverse ridge bounding the 123E Fracture Zone.(5)TheLuzon Arc is abnormally concave toward the Manila Trench and becomeswider toward the south.The internal deformation of the Luzon Arc in termsof several NE-SW discontinuities could be related to its collision with eastern Taiwan.(6)Three previously proposed NW-SE trending strike-slip faultsin the southern Okinawa Trough,west of 123.5°E,are well imaged on boththe FAA and magnetic anomaly maps.Post-collisional volcanism off northeastern Taiwan occurs along these NW-SE trending faults.