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

合作研究：岩石圈演化对三重交界处迁移的响应：门多西诺三重交界区的地震图像

• 批准号: 9219598
• 负责人: Anne Meltzer
• 金额: $ 34.12万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-06-15 至 1997-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9219598&HistoricalAwards=false
• 关键词: Collaborative; Research; Lithospheric; Evolution; Response

The coastal region of northern California from latitude of 38o to 41oN represents a region in which the present tectonic regime changes abruptly from subduction to transform motion at the Mendocino Triple Junction (MTJ). Because the triple junction is migrating north along the coast of North America, an understanding of the crust and upper mantle structure in this region will provide insights into the tectonic evolution of the entire U.S. west coast continental margin as well as other convergent margins worldwide. This project involves an integrated seismic experiment to image the structure of the crust and upper mantle immediately before and after passage of the MTJ. This study represents an important part of a long-term, multi-disciplinary effort on the part of many investigators to exploit this well defined system as an in-situ laboratory to study physical and chemical processes associated with mantle upwelling, melt segregation and migration, tectonic accretion, and crustal deformation in both transform and convergent tectonic settings, and to evaluate the implications of these processes for continental growth and evolution. The study encompasses two field seasons. One season involves acquisition of eight multichannel seismic (MCS) profiles designed to image deep crustal structure beneath: 1) Pt. Arena basin, San Andreas fault, and extinct trench south of the MTJ; 2) the Mendocino Transform fault; and 3) the Eel River basin and Cascadia subduction zone north of the MTJ. The profiles intersect wells both north and south of the MTJ to provide stratigraphic control. The MCS profiles will also be recorded on ocean-bottom hydrophones and seismographs and on REFTEK seismographs deployed onshore to provide complementary large aperture data. The other season involves acquisition of three onshore explosive-source refraction profiles, two of which extend onshore/offshore transects shot north and south of the MTF, in order to cross the fore-arc and slabless window. The third refraction profile will follow the trend of the Franciscan terrane in order to cross the southern edge of the Gorda plate, map possible along-strike variations in crustal structure and tie together the two primary onshore-offshore profiles. All three land profiles will be densely instrumented with REFTEK and SGR seismographs.

加利福尼亚州北部沿海地区从北纬 38 度到北纬 41 度之间，代表了当前构造形态从门多西诺三重交界点 (MTJ) 的俯冲运动突然转变为变换运动的区域。 由于三重交界点沿着北美海岸向北迁移，了解该地区的地壳和上地幔结构将有助于了解整个美国西海岸大陆边缘以及全球其他汇聚边缘的构造演化。 该项目涉及综合地震实验，以对 MTJ 通过前后的地壳和上地幔结构进行成像。 这项研究代表了许多研究人员长期、多学科努力的重要组成部分，他们利用这个明确的系统作为原位实验室来研究与地幔上涌、熔体分离和迁移相关的物理和化学过程，构造增生以及变换和聚合构造环境中的地壳变形，并评估这些过程对大陆生长和演化的影响。 该研究包括两个野外季节。 一个季节涉及采集八个多道地震 (MCS) 剖面，旨在对下面的深层地壳结构进行成像：1) Pt。阿雷纳盆地、圣安德烈亚斯断层和 MTJ 以南的灭绝海沟； 2）门多西诺变换断层； 3) MTJ 以北的 Eel 河流域和卡斯卡迪亚俯冲带。 这些剖面与 MTJ 北部和南部的井相交，以提供地层控制。 MCS 剖面还将记录在海底水听器和地震仪以及陆上部署的 REFTEK 地震仪上，以提供补充的大孔径数据。 另一个季节涉及采集三个陆上爆炸源折射剖面，其中两个延伸了 MTF 北部和南部的陆上/海上横断面，以便穿过前弧和无板窗口。 第三个折射剖面将遵循方济各地体的趋势，以便穿过戈尔达板块的南缘，绘制地壳结构中可能的沿走向变化图，并将两个主要的陆上和海上剖面联系在一起。 所有三个土地剖面都将配备 REFTEK 和 SGR 地震仪。