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首页> 外文期刊>Journal of Asian earth sciences >Subsurface imaging, TAIGER experiments and tectonic models of Taiwan
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Subsurface imaging, TAIGER experiments and tectonic models of Taiwan

机译：台湾的地下成像，TAIGER实验和构造模型

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The seismicity, deformation rates and associated erosion in the Taiwan region clearly demonstrate that plate tectonic and orogenic activities are at a high level. Major geologic units can be neatly placed in the plate tectonic context, albeit critical mapping in specific areas is still needed, but the key processes involved in the building of the island remain under discussion. Of the two plates in the vicinity of Taiwan, the Philippine Sea Plate (PSP) is oceanic in its origin while the Eurasian Plate (EUP) is comprised partly of the Asian continental lithosphere and partly of the transitional lithosphere of the South China Sea basin. It is unanimously agreed that the collision of PSP and EU is the cause of the Taiwan orogeny, but several models of the underlying geological processes have been proposed, each with its own evolutionary history and implied subsurface tectonics. TAIGER (TAiwan Integrated GEodynamics Research) crustal- and mantle-imaging experiments recently made possible a new round of testing and elucidation. The new seismic tomography resolved structures under and offshore of Taiwan to a depth of about 200 km. In the upper mantle, the steeply east-dipping high velocity anomalies from southern to central Taiwan are clear, but only the extreme southern part is associated with seismicity; toward the north the seismicity disappears. The crustal root under the Central Range is strongly asymmetrical; using 7.5 km/s as a guide, the steep west-dipping face on the east stands in sharp contrast to a gradual east-dipping face on the west. A smaller root exists under the Coastal Range or slightly to the east of it. Between these two roots lies a well delineated high velocity rise spanning the length from Hualien to Taitung. The 3-D variations in crustal and mantle structures parallel to the trend of the island are closely correlated with the plate tectonic framework of Taiwan. The crust is thickest in the central Taiwan collision zone, and although it thins toward the south, the crust is over 30 km thick over the subduction in the south; in northern Taiwan, the northward subducting PSP collides with Taiwan and the crust thins under northern Taiwan where the subducting indenter reaches 50 km in depth. The low Vp/Vs ratio of around 1.6 at a mid-crustal depth of 25 km in the Central Range indicates that current temperatures could exceed 700 ℃ The remarkable thickening of the crust under the Central Range, its rapid uplift without significant seismicity, its deep exhumation and its thermal state contribute to make it the core of orogenic activities on Taiwan Island. The expanded network during the TAIGER deployment captured broadband seismic data yielding enhanced S-splitting results with mainly SKS/SKKS data. The polarization directions of the fast S-waves follow very closely the structural trends of the island, supporting the concept of a vertically coherent Taiwan orogeny in the outer few hundred kilometers of the Earth.
机译：台湾地区的地震活动性，变形率和相关的侵蚀清楚地表明，板块构造和造山活动处于较高水平。尽管仍需要在特定区域进行关键测绘，但主要地质单元仍可以整齐地放置在板块构造背景下，但仍在讨论该岛建设所涉及的关键过程。在台湾附近的两个板块中，菲律宾海板块（PSP）的起源是海洋，而欧亚板块（EUP）的一部分由亚洲大陆岩石圈组成，一部分由南海盆地的过渡岩石圈组成。 PSP和EU的碰撞是台湾造山运动的成因，但已达成一致意见，但已提出了几种潜在的地质过程模型，每个模型都有其自身的演化历史和隐含的地下构造。台虎（台湾综合地球动力学研究）的地壳和地幔成像实验最近使新一轮的测试和阐明成为可能。新的地震层析成像技术可将台湾下方和近海的结构分解到约200公里的深度。在上地幔中，从台湾南部到中部陡峭的东倾高速异常是明显的，但只有南部极端与地震活动有关。向北的地震活动消失了。中央山脉下的地壳根极不对称；以7.5 km / s为指导，东部的陡峭西倾面与西部的逐渐东倾面形成鲜明的对比。较小的根存在于沿海山脉的下方或略微向东。在这两个根部之间有一个轮廓分明的高速上升，横跨从花莲到台东的长度。地壳和地幔结构的3-D变化与该岛的趋势平行，与台湾的板块构造框架密切相关。在台湾中部碰撞带，地壳最厚，尽管向南变薄，但在俯冲带南部，地壳却超过30公里。在台湾北部，向北俯冲的PSP与台湾相撞，而台湾北部下方的地壳变薄，俯冲压头深度达到50 km。在中央山脉中部地壳深25 km处，低Vp / Vs比约为1.6，这表明当前温度可能超过700℃中央山脉下地壳的明显增厚，其快速隆升而没有明显的地震活动，其深度较深。发掘及其热态使其成为台湾岛造山活动的核心。在TAIGER部署过程中扩展的网络捕获了宽带地震数据，其中主要是SKS / SKKS数据产生了增强的S分裂结果。快速S波的极化方向非常紧密地遵循了该岛的结构趋势，支持了地球几百公里外垂直相干台湾造山运动的概念。

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