Microearthquake patterns following the 1998 eruption of Axial Volcano, Juan de Fuca Ridge: Mechanical relaxation and thermal strain
Microearthquake patterns following the 1998 eruption of Axial Volcano, Juan de Fuca Ridge: Mechanical relaxation and thermal strain
复制标题
1998 年胡安德富卡山脊轴火山喷发后的微地震模式：机械松弛和热应变
DOI：
10.1029/2003jb002499
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发表时间：
2004
影响因子：
--
通讯作者：
S. Webb
中科院分区：
文献类型：
--
作者：
R. Sohn;A. Barclay;S. Webb
1998年轴向海山喷发后部署的海底地震网揭示了与地下岩浆活动和热应变有关的微地震活动演变模式。在15个月的观测中（1998年2月8日至1999年4月30日），地震活动率稳步下降，这与岩浆事件后浅层地壳的热和力学平衡趋势相一致。火山爆发后，在火山口东南角的60天内，地震活动率很高，1998年火山喷发的熔岩流就在这里被绘制出来。在火山爆发后100至150天，在火山的东南肩观察到一次小的地震活动爆发。这些事件的特征是在浅层地壳中几乎垂直的断层上滑动，从火山口东南角延伸约6公里，并覆盖在地壳中低速带上。在这次事件之后，直到观测期结束，即火山爆发后的455天，地震活动率一直保持在较低水平。在火山口东南边缘1998年熔岩流中，在热液喷口下的单个集群中观察到与热收缩和~ 2 × 10−3 m3的体积变化相一致的浅层（~ 0.7 km深度）事件。在最后70天的观测中观测到的微地震分布在中央火山口周围，很可能是在1998年火山喷发引起的熔体撤退后平衡的最后阶段，火山口断层上的少量下沉。
[1] Ocean bottom seismic networks deployed following the 1998 eruption of Axial seamount reveal an evolving pattern of microearthquake activity associated with subsurface magmatism and thermal strain. Seismicity rates decay steadily over 15 months of observation (February 8, 1998, to April 30, 1999), consistent with a trend toward thermal and mechanical equilibrium in the shallow crust after the magmatic event. Immediately after the eruption, seismicity rates were high for about 60 days in the southeast corner of the caldera where lava flows from the 1998 eruption were mapped. A small burst of seismic activity was observed on the southeast shoulder of the volcano from 100 to 150 days after the eruption. These events, which are characterized by slip on nearly vertical faults in the shallow crust, extend about 6 km from the southeast corner of the caldera and overlie a mid-crustal low-velocity zone. After this episode, seismicity rates remain low until the end of the observation period, 455 days after the eruption. Shallow (∼0.7 km depth) events, consistent with thermal contraction and volume changes of ∼2 × 10−3 m3 in ∼5 m3 sources, are observed in individual clusters beneath hydrothermal vents within the 1998 lava flow at the southeast edge of the caldera. Microearthquakes observed during the last 70 days of observation are distributed around the central caldera, most likely representing small amounts of subsidence on caldera faults during the final stages of equilibration following melt withdrawal associated with the 1998 eruption.