Seismicity and Fault Structure of Oceanic Detachment Faults

海洋扩张中心的板块裂谷是通过断裂和岩浆注入的结合而发生的，两者都缓解了与全球构造力相关的累积应力。有时，断层作用会起主导作用，导致在一个平面上持续滑动一百多万年。在这种“分离断层”时期形成的海底与海底普遍存在的典型的线性火山山不同。相反，由于断层上的相对运动，最初的深层岩石没有顶，形成了圆顶状的特征，海底起伏达几公里。这项研究的目的是展示剥离断层在地震上的表现——沿着断层的深度发生小地震的地方，以及这种活动在横向上的变化。这项研究获得的新见解可能适用于其他伸展构造应力和岩浆活动发生的地区，例如美国盆地和山脉省的部分地区。本研究由美国国家科学基金会海洋地质与地球物理项目和国际科学与工程分部联合资助。在大西洋中脊13°N和26°N海底地震仪6个月部署期间记录的微地震活动数据将进行分析，以阐明年轻海洋核复体的断层活动。13°N项目是更广泛的英法美合作项目的一个组成部分；26°N地震的研究重点是在之前研究过的地震之间的中等大小的地震；新的结果将首次集中在浅于3公里的地壳上。将比较这两个地区的地震活动模式，因为这两个地区都有海洋核复合体。记录地震的分布，可能还有一些震源机制，目的是评估剥离断层在三维中的表现，以及断层强度和时空演变方面的含义。

Plate rifting at oceanic spreading centers occurs through a combination of faulting and injection of magma, both of which relieve built-up stress associated with global tectonic forces. At times faulting can dominate, leading to sustained slip along a single plane for over a million years. Seafloor formed during such periods of 'detachment faulting' differs from the typical, linear volcanic hills that are ubiquitous on the seafloor. Instead domal features, with up to a few km seafloor relief, develop as initially deep rock is unroofed by relative motion across the fault. This study aims to show how detachment faults behave seismically- where small earthquakes occur with depth along the fault and how that activity varies laterally. New insights gained in this study could be applicable to other regions where extensional tectonic stress and magmatism occur, such as parts of the U.S. Basin and Range province. This study is jointly supported by the Marine Geology and Geophysics Program and the International Science and Engineering section of NSF.Analysis of microseismicity data recorded during 6-month deployments of ocean bottom seismometers at 13°N and 26°N on the Mid-Atlantic Ridge will be conducted in order to elucidate fault activity at young oceanic core complexes. The 13°N work is one component of broader UK-French-US collaborative project; the 26°N effort focuses on earthquakes intermediate in size between events that were previously studied; new results will focus in detail on crust shallower than 3 km for the first time. The seismicity patterns of these two areas, that both host oceanic core complexes, will be compared. Documentation of the distribution of earthquakes, and possibly some focal mechanisms, aims to assess how detachment faults behave in 3-D and what the implications might be in terms of fault strength and spatial/temporal evolution.