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

9526116梅尔策，加利福尼亚州北部的沿海地区，从北纬390度到北纬42度，代表了一个活跃的构造体制从俯冲突然转变为门多西诺三重交汇处的运动的地区。对该区域地壳和上地幔结构的了解，与板块构造历史、地质结构、地震活动以及热流入和随后的地表火山作用的时间和程度的信息相结合，限制了控制大陆生长和演化的过程。由于三重结点一直沿着北美海岸向北迁移，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，并将有助于更好地评估以卡斯卡迪亚俯冲带和圣安德烈亚斯断裂系统北部为代表的地震灾害。1993年和1994年，主要研究人员收集了一个大口径地震剖面网络，以成像加利福尼亚州北部和邻近大陆边缘之下的地壳和上地幔结构。这些数据包括大约650公里的陆上地震折射/反射数据，2000公里的海上多道地震(MCS)反射数据，以及MCS气枪震源的陆上和海上同步记录，以产生大口径数据。来自12个以上机构的科学家参与了数据采集，由来自俄勒冈州立大学、利哈伊大学、赖斯大学和斯坦福大学以及美国地质调查局的主要调查人员组成的团队领导。该奖项为大陆动力学项目提供了第四个年头的支持，使主要研究人员能够完成数据分析和演示。还支持举办研讨会，在此期间，他们将与更广泛的地球科学家社区讨论他们的地震学结果，这些科学家对与北美西部边缘地区板块相互作用有关的地质、地质动力学和自然灾害问题感兴趣。***

9526116 Meltzer The coastal region of northern California from latitude 39oN to42oN 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, ge odynamic, and natural hazard issues associated with plate interactions in along the western margin of North America. ***