Collaborative Research: Lithospheric Evolution in Response to Triple-Junction Migration: Seismic Images of the Mendocino Triple Junction Region

9527001 Trehu 美国北方加州的沿海地区，从北纬39度到北纬42度 代表了一个活跃的构造体制突然从俯冲转变为在门多西诺三重结（MTJ）转换运动的地区。 对这一区域地壳和上地幔结构的了解，加上板块构造史、地质结构、地震活动、热流入的时间和范围以及随之而来的地表火山活动等方面的资料，对控制大陆生长和演变的过程产生了制约。 由于三联点一直沿沿着北美海岸向北迁移，因此了解该地区的地壳结构和演化将有助于深入了解整个美国西海岸大陆边缘的地质历史，并有助于更好地评估卡斯卡迪亚俯冲带和北方圣安德烈亚斯断层系统所代表的地震危险。 1993年和1994年，主要调查人员收集了一个大孔径地震剖面网络，以便对北方加州和邻近大陆边缘的地壳和上地幔结构成像。 这些数据包括约650公里的陆上地震折射/反射数据、2 000公里的海上多道地震反射数据，以及同时在陆上和海上记录MCS气枪震源以产生大孔径数据。 来自超过12个机构的科学家参与了数据采集，由来自俄勒冈州、利哈伊、赖斯和斯坦福大学以及美国地质调查局的主要研究人员组成的团队领导。 该奖项提供了大陆动力学计划的第四年支持，以允许主要研究人员完成数据分析和演示。 还为一个讲习班提供了支助，在讲习班期间，他们将与更广泛的地球科学家社区讨论他们的地震学成果， 地质、地球物理和自然灾害问题与板块相互作用在沿着北美西部边缘。 ***

9527001 Trehu The coastal region of northern California from latitude 39oN to 42oN represents a region in which the active tectonic regime changes abruptly from subduction to transform motion at the Mendocino Triple Junction (MTJ). Knowledge of the crustal and upper-mantle structure in this region, when combined with information on the plate-tectonic history, geologic structure, seismic activity, and timing and extent of heat influx and consequent surface volcanism, places constraints on the processes that control continental growth and evolution. Because the triple junction has been migrating north along the coast of North America, an understanding of crustal structure and evolution in this region will provide insights into the geologic history of the entire U.S. west coast continental margin and will contribute to better assessments of the seismic hazards represented by the Cascadia subduction zone and northern San Andreas Fault system. In 1993 and 1994 the principal investigators collected a network of large-aperture seismic profiles to image the crustal and upper- mantle structure beneath northern California and the adjacent continental margin. The data include approximately 650 km of onshore seismic refraction/reflection data, 2000 km of offshore multichannel seismic (MCS) reflection data, and simultaneous onshore and offshore recording of the MCS airgun source to yield large-aperture data. Scientists from more than 12 institutions were involved in data acquisition, which was led by a team of principal investigators from Oregon State, Lehigh, Rice, and Stanford Universities and from the U.S. Geological Survey. This award provides a fourth year of support from the Continental Dynamics program to permit the principal investigators to complete data analysis and presentation. Support for a workshop is also provided during which they will discuss their seismological results with the broader community of earth scientists interested in geological, geod ynamic, and natural hazard issues associated with plate interactions in along the western margin of North America. ***