Microseismicity of the Mid-Atlantic Ridge at 7°S-8°15′S and at the Logatchev Massif oceanic core complex at 14°40'N-14°50'N
Microseismicity of the Mid-Atlantic Ridge at 7°S-8°15′S and at the Logatchev Massif oceanic core complex at 14°40'N-14°50'N
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DOI：
10.1002/ggge.20197
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发表时间：
2013-09-01
影响因子：
3.5
通讯作者：
Moeller, Stefan
中科院分区：
文献类型：
--
作者：
Grevemeyer, Ingo;Reston, Timothy J.;Moeller, Stefan
在缓慢扩张速率下的岩石圈形成是异质的，具有多种形式，有利于岩浆作用占主导地位的对称扩张或构造作用占主导地位的核杂岩和内角高形成。我们报告的微震从三个部署在大西洋中脊（MAR）的地震网络。两个网络调查了Ascension转换断层附近南纬7度附近的MAR。三个内角高设置进行了研究。然而，它们在地震活动上基本上保持不活跃，主要的地震活动发生在沿着中央山谷的中心。相比之下，在洛加切夫地块核心复杂的14度45 N的地震活动是稀疏的中央山谷的中心，但集中沿着东部裂谷山脉的蛇纹石托管洛加切夫热液喷口领域的西部。然而，在洛加切夫的北部和南部，地震活动沿着山脊轴发生，强调了洛加切夫段地震活动的不对称性。震源机制表明，大量的逆断层事件发生在附近的喷口领域在3-5公里的深度，我们解释，以反映体积膨胀伴随着蛇纹岩化。在较浅的深度为2-4公里，在喷口区附近的一些地震表现出正常的断层行为，这表明正断层促进热液循环喂养喷口区。此外，还出现了第二组横切断层，表明油田的地表位置受局部断层系统控制。
Lithospheric formation at slow spreading rates is heterogeneous with multiple modalities, favoring symmetric spreading where magmatism dominates or core complex and inside corner high formation where tectonics dominate. We report microseismicity from three deployments of seismic networks at the Mid-Atlantic Ridge (MAR). Two networks surveyed the MAR near 7 degrees S in the vicinity of the Ascension transform fault. Three inside corner high settings were investigated. However, they remained seismically largely inactive and major seismic activity occurred along the center of the median valley. In contrast, at the Logatchev Massif core complex at 14 degrees 45N seismicity was sparse within the center of the median valley but concentrated along the eastern rift mountains just west of the serpentine hosted Logatchev hydrothermal vent field. To the north and south of the massif, however, seismic activity occurred along the ridge axis, emphasizing the asymmetry of seismicity at the Logatchev segment. Focal mechanisms indicated a large number of reverse faulting events occurring in the vicinity of the vent field at 3-5 km depth, which we interpret to reflect volume expansion accompanying serpentinization. At shallower depth of 2-4 km, some earthquakes in the vicinity of the vent field showed normal faulting behavior, suggesting that normal faults facilitates hydrothermal circulation feeding the vent field. Further, a second set of cross-cutting faults occurred, indicating that the surface location of the field is controlled by local fault systems.