Structural and Hydrological Evolution of the Central Oregon Accretionary Prism

在岩石圈俯冲过程中，由于海洋沉积物的刮离作用，深海海沟的向陆侧形成了增生棱柱。几个相互关联的因素影响了这些厚沉积物棱柱的演化，包括沉积物组成、物理性质、逆冲速率以及脱落沉积物中的流体脱水和运移。流体的运移和排出对变形带沉积物的力学行为、流体压力和岩化作用起着重要的作用。目前的续签合同将使用多通道地震技术完成对俄勒冈增生边缘结构的研究。在以前的资助下，沿着这条边界获得了2000公里的数据。数据分析方面的进展非常好。流体的来源和运移路径都可以在数据中成像。进一步的分析和解释将集中在：1)基底地形对边缘构造演化的控制作用；2)逆冲断层的性质；3)在数据初步分析中发现的斜断层；4)沉积层序孔隙度。这些数据是1992年后期在该地区进行一次大型石油开发计划署钻井巡航的基础。

Accretionary prisms form along the landward side of deep sea trenches in response to offscraping of oceanic sediments during lithospheric subduction. Several interrelated factors influence the evolution of these thick sediment prisms including sediment composition, physical properties, rate of underthrusting, and fluid de-watering and migration within the offscraped sediment. Fluid migration and expulsion play an important role in the mechanical behavior, fluid pressure and lithification of sediments in the deformation zone. The present renewal award will complete study of the structure of the Oregon accretionary margin using multichannel seismic techniques. Under previous funding, 2000 km of data was acquired along this margin. Progress in analyzing the data has been excellent. Both the sources and migration pathways of fluids can be imaged in the data. Continued analysis and interpretation will focus on: 1) the role of basement topography in controlling structural evolution of the margin; 2) the nature of the fault zone along which underthrusting occurs; 3) oblique faults which were discovered during initial analysis of the data; and 4) the porosity of the sediment sequence. These data are the basis for a major ODP drilling cruise to the area in late 1992.