Temporal and spatial history of the 1999–2000 Endeavour Segment seismic series, Juan de Fuca Ridge
Temporal and spatial history of the 1999–2000 Endeavour Segment seismic series, Juan de Fuca Ridge
复制标题
1999-2000年奋进段地震系列的时空历史，胡安德富卡海岭
DOI：
10.1029/2004gc000735
复制
发表时间：
2004
期刊：
影响因子：
3.7
通讯作者：
M. Fowler
中科院分区：
文献类型：
--
作者：
D. Bohnenstiehl;R. Dziak;M. Tolstoy;C. Fox;M. Fowler
1999年6月和2000年1月发生的两大地震活动群主导了胡安·德富卡海岭奋进段沿着的近期地震活动。1999年6月的序列对水文系统的影响，其中包括在主奋进排气口领域内的排气口温度和化学的变化，已被很好地记录在以前。地震和水声数据的分析表明，这两个序列表现出一个群状的行为，其特点是没有一个主导的主震事件。两个震群的震中位置在空间上重叠，震中位置分别位于北纬47°49′和47°46′附近。在1999年6月的群，最初的活动跨越沿着-轴区域，其中一个浅轴向岩浆房反射体后来成像。然后，震中以0.3 m/s的速度向南迁移12 km，与侧向岩墙传播一致。在科布段重叠部分的勘测者火山附近也发生了一系列不同的事件。考虑到它与主群的距离，这种活动可能代表了对动态震动的触发反应。相对于1999年6月的震群，2000年1月的震群具有更有限的沿着轴范围，没有横向迁移的迹象。这种活动大部分集中在一个地区，预计已经历了扩展，由于在1999年堤防传播。虽然它包含较少的总事件和较短的持续时间，相对于1999年6月的群，2000年1月的活动表现出更高的地震活动的峰值率和更大的平均事件震级。由于2000年1月没有进行现场温度监测，直到2000年6月才对喷口流体进行取样，因此不知道这一群对热液系统的影响。奋进段的最南端也被发现是一个重复的蜂群活动的区域。虽然形态学证据表明科布段最近一直在向北传播，但这种地震活动表明奋进-科布重叠带的西翼仍然活跃。
Two large clusters of earthquake activity in June of 1999 and January of 2000 have dominated recent seismicity along the Endeavour Segment of the Juan de Fuca Ridge. The impacts of the June 1999 sequence on the hydrologic system, which include changes in vent temperature and chemistry within the Main Endeavour Vent Field, have been well documented previously. Analysis of seismic and hydroacoustic data indicates that both sequences exhibit a swarm‐like behavior, characterized by the absence of a dominant main shock event. The epicentral locations of events within the two swarms overlap spatially, with centroid positions near 47°49′ and 47°46′N latitude. During the June 1999 swarm, the initial activity spans the along‐axis region where a shallow axial magma chamber reflector was later imaged. The epicenters then migrate ∼12 km to the south at a rate of 0.3 m/s, consistent with lateral dike propagation. A distinct subcluster of events also occurred in the vicinity of Surveyor Volcano on the overlapping portion of the Cobb Segment. Given its distance from the main swarm, this activity may represent a triggered response to dynamic shaking. The January 2000 swarm has a more limited along‐axis extent, relative to the June 1999 swarm, with no indication of lateral migration. Much of this activity is concentrated in a region predicted to have undergone extension due to dike propagation in 1999. Although it contains fewer total events and is of shorter duration, relative to the June 1999 swarm, the January 2000 activity exhibits a higher peak rate of seismicity and greater mean event magnitude. As in situ temperature monitoring was not in place during January 2000 and vent fluids were not sampled until June 2000, the impacts of this swarm on the hydrothermal system are unknown. The southernmost tip of the Endeavour Segment also is found to be a region of repeating swarm activity. Although morphologic evidence indicates the Cobb Segment has been propagating northward recently, this seismic activity suggests that the western limb of the Endeavour‐Cobb overlap zone remains active.