Seismicity trends and detachment fault structure at 13°N, Mid-Atlantic Ridge
Seismicity trends and detachment fault structure at 13°N, Mid-Atlantic Ridge
复制标题
大西洋中脊北纬13°地震活动趋势和滑脱断层结构
作者：
Parnell-Turner, R.;Sohn, R.A.;Peirce, C.;Reston, T.J.;MacLeod, C.J.;Searle, R.C.;Simão, N.M.
在缓慢扩张的海脊，板块分离通常部分由长期存在的拆离断层上的滑动所适应，暴露出海底的上地幔和下地壳岩石。然而，这一过程的机制，地下结构，以及这些断层的相互作用在很大程度上仍然未知。我们报告了2016年在大西洋中脊13 N附近部署的56个海底地震仪（OBS）网络的结果，该网络提供了两个相邻的剥离断层和中间脊轴的密集空间覆盖。虽然这两个determines表现出高水平的地震活动性，他们被一个108公里宽的地震带，这表明他们是机械解耦。地震活动的线性带，可能表明岩浆活动，横切13 - 30′ N的圆顶状拆离面，证实了以前的断层废弃证据。再往南，2016年OBS网络与2014年进行的类似调查在空间上重叠，观察到这些调查之间的地震活动模式发生了显着变化。这些变化表明，大洋台经历了以前未观察到的应力积累和释放的周期，板块扩张是适应。
At slow-spreading ridges, plate separation is commonly partly accommodated by slip on long-lived detachment faults, exposing upper mantle and lower crustal rocks on the seafloor. However, the mechanics of this process, the subsurface structure, and the interaction of these faults remain largely unknown. We report the results of a network of 56 ocean-bottom seismographs (OBSs), deployed in 2016 at the Mid-Atlantic Ridge near 13 N, that provided dense spatial coverage of two adjacent detachment faults and the intervening ridge axis. Although both detachments exhibited high levels of seismicity, they are separated by an∼ 8-km-wide aseismic zone, indicating that they are mechanically decoupled. A linear band of seismic activity, possibly indicating magmatism, crosscuts the 13 30′ N domed detachment surface, confirming previous evidence for fault abandonment. Farther south, where the 2016 OBS network spatially overlapped with a similar survey done in 2014, significant changes in the patterns of seismicity between these surveys are observed. These changes suggest that oceanic detachments undergo previously unobserved cycles of stress accumulation and release as plate spreading is accommodated.