Onshore/Offshore Wide-Angle Deep Seismic Profiling in Taiwan

臺灣寬角海陸深部震測剖析

葉義雄(Y. H. Yeh) ； 石瑞銓(R. C. Shih) ； 林正洪(C. H. Lin) ； 劉忠智(C. C. Liu) ； 顏宏元(H. Y. Yen) ； 黃柏壽(B. S. Huang) ； 劉家瑄(C. S. Liu) ； 陳寶仁(P. Z. Chen) ； 黃建興(C. S. Huang) ； 吳家楨(C. J. Wu) ； 吳大銘(F. T. Wu)

《Terrestrial, Atmospheric and Oceanic Sciences》 9卷3期 (1998/09) Pp. 301-316

並列摘要

Wide-angle reflection and refraction data are used to illustrate thecrustal structures in the central Taiwan area,across the Taiwan Orogenand in the westernmost part of the Ryukyu subduction system.The preliminarystructures were derived by modeling the data set collected usingonshore seismic recording instruments along the central cross-island highwayin 1995.Seismic signals were generated by the powerful airgun arraysof the R/V Ewing in the seas east of Taiwan.For the shallow structures,results from the forward modeling of the Pg phases show that strong lateralvariations of P-wave velocities in the upper crust were obtained.Velocitiesat the uppermost crust have a wide range from 3.0 km/sec to 5.2km/sec,and increase from 5.8 km/sec to 6.8 km/sec at the bottom of theupper crust.The thickness of the upper crust increases from 22 km beneaththe Western Central Range to 25 km beneath the Hsincheng Ridge,and it then dramatically decrease to only 10 km beneath the Hoping andNanao basins.For the deep crust structures,similar pattern of thicknessvariations,from 12 km to 20 km,was obtained.Velocities at the lower crustrange from 6.4-6.7 km/sec at its top to 7.2-7.3 km/sec at its bottom.Insummary,the crustal thickness beneath the island could be over 40 km,butonly about 25 km beneath the westernmost part of the Ryukyu forearc region.The thickest crust is not right beneath the highest mountains on theisland but with an offset of about 40 km toward the east.The result indicatesthat Taiwan has still not yet reached to its isostatic equilibrium yet.

並列關鍵字

Onshore/Offshore ； Wide-Angle ； Deep Crustal Structure