Velocity Structure Beneath the Eastern Offshore Region of Southern Taiwan Based on OBS Data

Using travel time data from local earthquakes and air-gun shots recordedby the Central Weather Bureau Seismographic Network,the transitionfrom a typical subduction to a collision suture in the southeasternTaiwan area is imaged in terms of a three-dimensional Vp structure.Thesouthern prolongation of the Longitudinal Valley Fault(PLVF),which ischaracterized by a sharp contrast in velocity on either side,is the primaryfeature in the velocity structure.West of the PLVF,a high velocity volumeexists from the surface to about 9-km in depth,which can be interpreted asbeing related to the Central Range.The Central Range structure seems toend near 22.2°N beneath the Hengchun Peninsula.East of the PLVF,amajor high velocity anomaly in the middle-to lower-crust beneath the SouthernLongitudinal Trough and Huatung Ridge is observed.According to thevelocity structure and the estimated composition,the high velocity bodycould be the forearc oceanic crust,which might have been torn off andseparated from the Philippine Sea plate after the Luzon arc was formed,and has been shortened during the collision of the Eurasian and PhilippineSea plates.The other conspicuous feature of the Vp model is a clearly lateralvelocity variation across the Taitung Canyon from the surface to about25-km in depth,which might be associated with the segmentation of theLuzon arc.Using the three-dimensional Vp model,earthquake events thatoccurred from 1990 to 1997 were relocated.Most of the relocated hypocentersin the study area tend to lie on the locations where there is a greatergradient in the Vp model.

並列關鍵字

Offshore Taiwan ； OBS ； Velocity Model

國際替代計量

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