Accommodating Oblique Plate Motion in the California Continental Borderland: The Interaction Between Rotating and Non-Rotating Domains

认识大陆构造和板块边界变形是地球科学中的一个重要问题。该项目是对南加州近海大陆边缘地区地壳结构和变形进行综合研究的协调努力的一部分。边界地区在其位移历史的70%中是太平洋-北美板块运动的轨迹，最近的GPS数据表明，目前高达20%的板块运动仍然发生在近海。 这种板块运动的大部分是由主要是西北走向的右滑断层进行的，这些断层终止于旋转的西部横贯山脉省的南部前缘。这种右旋运动是如何在断层末端转变为顺时针旋转的，以及这些转变处的断层和褶皱几何形状还不太清楚。 这些活跃的海上结构也代表了对许多加州沿海社区的一种很大程度上还不为人知的危险，并为活跃的埋藏结构提供了重要的类似物。（较难进入）陆上结构，可能会产生大量，在洛杉矶盆地地区的破坏性地震。该项目使用高质量的工业多通道地震反射数据网格（最初收集用于油气勘探），以研究板块边界近海部分的地壳变形和构造演化。正在制作数字断层表面和地层参考层位，以确定3D活动断层和褶皱几何形状，并帮助量化随时间变化的有限应变场。 主要目的是记录近海地壳结构如何适应板块边界平移、差异旋转、断层滑动的空间变化和断层的终止。这包括更好地了解活动断层如何相互作用，以分区斜向运动的系统相交的高，低角度的结构。我们的研究结果是补充陆地为基础的研究，并提供了一个更全面的看法，活跃的板块边界，包括如何在这样一个扩散的板块边界系统，两个不同的构造制度（旋转的西部横向山脉省和非旋转的北方大陆边界）相互作用，以吸收相同的整体板块运动。

Understanding continental structure and plate boundary deformation is an important problem in earth science. This project is part of a coordinated effort to conduct integrated studies of crustal structure and deformation in the Continental Borderland offshore of southern California. The Borderland was the locus of Pacific-North America plate motion for about 70% of its displacement history, and recent GPS data suggest that up to 20% of current plate motion is still occurring offshore. Much of this plate motion has been carried by predominantly NW-striking right-slip faults that terminate against the southern front of the rotating western Transverse Ranges province. How this dextral motion is transformed into clockwise rotation at fault terminations, and the fault and fold geometry at these transitions are little understood. These active offshore structures also represent a largely as yet unknown hazard to many California coastal communities, and provide important analogs to active buried (less-accessible) onshore structures that may produce large, damaging earthquakes in the Los Angeles basin area.This project is using grids of high-quality industry multichannel seismic reflection data (originally collected for hydrocarbon exploration) to investigate the crustal deformation and tectonic evolution of the offshore portion of the plate boundary. Digital fault surfaces and stratigraphic reference horizons are being produced to define active fault and fold geometry in 3D, and to help quantify the finite strain field with time. A prime objective is to document how the crustal architecture offshore accommodates plate boundary transpression, differential rotation, spatial variations in fault slip and the termination of faults. This includes a better understanding of how active faults interact to partition oblique motion on systems of intersecting high- and low-angle structures. Our results are complementing land-based studies and provide a more synoptic view of the active plate boundary, including how, within such a diffuse plate boundary system, two distinct tectonic regimes (the rotating western Transverse Ranges province and the non-rotating northern Continental Borderland) interact to absorb the same overall plate motion.