Local Seismicity of the Rainbow Massif on the Mid-Atlantic Ridge
Local Seismicity of the Rainbow Massif on the Mid-Atlantic Ridge
复制标题
大西洋中脊彩虹地块的局部地震活动
DOI：
10.1002/2017jb015288
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Dunn, R. A.
中科院分区：
文献类型：
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作者：
Horning, G.;Sohn, R. A.;Canales, J. P.;Dunn, R. A.
彩虹地块是一个位于大西洋中脊(36°N)上非转换界面上的大洋核心杂岩，以承载通过超镁铁质岩石的高温热液而闻名。在这里，我们报告了一项为期9个月的微地震调查结果，该调查使用部署在彩虹地块及其周围的13个海底地震仪组成的网络，作为2013-2014年水手实验的一部分。在地块下方检测到了高速率(约300次/天)的低震级(平均ML~0.5级)微震。震源不沿深穿透断裂面聚集，也不显示主震/余震序列，支持与地块折返有关的断裂活动目前不活跃的假说。取而代之的是，震源在地块下方相对较浅(~3千米)处划定了连续、低震级变形的扩散带，夹在海底和地震反射器之间，地震反射器被解释为驱动热液对流的岩浆岩床。大多数地震活动位于地震折射数据显示蛇纹状超镁铁质寄主岩石的地区，尽管我们部署的地震台网无法约束大多数事件的震源机制，但我们的分析表明，蛇纹岩作用可能在彩虹地块的微震发生中发挥重要作用。
The Rainbow massif, an oceanic core complex located in a nontransform discontinuity on the Mid‐Atlantic Ridge (36°N), is notable for hosting high‐temperature hydrothermal discharge through ultramafic rocks. Here we report results from a 9 month microearthquake survey conducted with a network of 13 ocean bottom seismometers deployed on and around the Rainbow massif as part of the MARINER experiment in 2013–2014. High rates (~300 per day) of low‐magnitude (averageML~ 0.5) microearthquakes were detected beneath the massif. The hypocenters do not cluster along deeply penetrating fault surfaces and do not exhibit mainshock/aftershock sequences, supporting the hypothesis that the faulting associated with the exhumation of the massif is currently inactive. Instead, the hypocenters demarcate a diffuse zone of continuous, low‐magnitude deformation at relatively shallow (< ~3 km) depths beneath the massif, sandwiched in between the seafloor and seismic reflectors interpreted to be magmatic sills driving hydrothermal convection. Most of the seismicity is located in regions where seismic refraction data indicate serpentinized ultramafic host rock, and although the seismic network we deployed was not capable of constraining the focal mechanism of most events, our analysis suggests that serpentinization may play an important role in microearthquake generation at the Rainbow massif.