Kilauea slow slip events: Identification, source inversions, and relation to seismicity
Kilauea slow slip events: Identification, source inversions, and relation to seismicity
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基拉韦厄慢滑事件：识别、震源反演以及与地震活动的关系
DOI：
10.1029/2008jb006074
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发表时间：
2009
影响因子：
--
通讯作者：
A. Miklius
中科院分区：
文献类型：
--
作者：
E. Montgomery‐Brown;P. Segall;A. Miklius
[1]根据GPS每日定位的瞬时位移，推断了几个位于夏威夷基拉韦厄火山南翼下的慢滑动事件。为了寻找可能接近GPS时间序列中噪声水平的较小事件，我们将基拉韦厄南侧的位移场与先前确定的慢滑事件中的位移模式进行比较。匹配的位移模式发现了几个新的候选事件，虽然位移比以前确定的事件小得多。2000年5月29日的一个候选事件与一个微地震群重合，就像所有以前确定的慢滑事件一样。微震发生在缓慢滑动之后，这意味着它们是由滑动过程中的应力变化触发的。新的慢滑事件使1997年至2007年期间基拉韦厄的事件总数达到8起，最小的MW = 5.3，最大的MW = 6.0。4起最大事件之间的复发时间为2.11 ± 0.01年，所有8起事件的重复时间为0.9 ± 0.6年。我们反演断层的几何形状和分布的滑动在缓慢的滑动事件。假设弹性半空间中的均匀滑移位错，5公里的最佳震源深度比伴随的震群地震（6.5-8.5公里）要浅得多，这将使地震位于库仑应力降低的区域。反演包括地形和层状弹性结构的影响，在正演模型中有利于与微震深度相当的深度，这样地震就位于库仑应力增加的区域。我们还直接从30秒的GPS相位观测值反演随时间变化的断层滑动，将源约束到最佳均匀滑动几何。根据这些反转，较大的事件持续1.5-2.2天。这些数据无法解决滑动沿着断层的迁移问题。伴随的微震的时间模式是一致的断层滑动历史假设的地震活动率理论的基础上速率和状态摩擦，使群震同震和余震的慢滑事件。
[1] Several slow slip events beneath the south flank ofKilauea Volcano, Hawaii, have been inferred from transient displacements in daily GPS positions. To search for smaller events that may be close to the noise level in the GPS time series, we compare displacement fields on Kilauea's south flank with displacement patterns in previously identified slow slip events. Matching displacement patterns are found for several new candidate events, although displacements are much smaller than previously identified events. One of the candidates, 29 May 2000, is coincident with a microearthquake swarm, as are all of the previously identified slow slip events. The microearthquakes follow the onset of slow slip, implying that they are triggered by stress changes during slip. The new slow slip event brings the total number of events on Kilauea, between 1997 and 2007, to eight, the smallest having M w = 5.3, and the largest having M w = 6.0. While the recurrence time between the four largest events is 2.11 ± 0.01 years, the repeat time for all eight events is 0.9 ± 0.6 years. We invert for the fault geometry and distribution of slip during the slow slip events. The optimal source depths of 5 km, assuming uniform slip dislocations in an elastic half-space, are considerably shallower than the accompanying swarm earthquakes (6.5-8.5 km), which would place the earthquakes in a zone of decreased Coulomb stress. Inversions including the effects of topography and layered elastic structure in the forward models favor depths comparable to microearthquake depths, such that the earthquakes are located in a region of increased Coulomb stress. We also invert for time-dependent fault slip directly from the 30 s GPS phase observations, constraining the source to the optimal uniform slip geometry. On the basis of these inversions, the larger events last between 1.5-2.2 days. The data are unable to resolve migration of slip along the fault. The temporal pattern of accompanying microearthquakes is consistent with the fault slip history assuming a seismicity rate theory based on rate and state-friction, making the swarm earthquakes coshocks and aftershocks of the slow slip events.