Composite Earthquake Source Mechanism for 2018 Mw 5.2–5.4 Swarm at Kīlauea Caldera: Antipodal Source Constraint
Composite Earthquake Source Mechanism for 2018 Mw 5.2–5.4 Swarm at Kīlauea Caldera: Antipodal Source Constraint
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2018 年基拉韦厄火山口 5.2–5.4 级地震群的复合地震源机制：反足源约束
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发表时间：
2019
影响因子：
3.3
通讯作者：
R. Butler
中科院分区：
文献类型：
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作者：
R. Butler
我回顾了 2018 年 5 月至 8 月期间在基拉韦厄火山口发生的 50 次不寻常的地震群，震级为 5.2-5.4 次。考虑到已发表的由质心矩张量 (CMT) 方法得出的震源机制的高度相似性，我将全球分布的台站从本地距离到对映距离的 P 波进行了叠加。复合源机制与正常平面断层一致，走向 335° NNW，倾角 78° W，倾角接近 -90°。复合震源和波形衍生震源之间的差异部分归因于震源深度、地震速度和基拉韦厄山峰下方刚性的选择。震源底部的反足 PKIKP 观测结果来自南部非洲约 175°Δ 处的三个全球地震网络 (GSN) 台站的叠加数据。堆积的 PKIKP 位移数据显示膨胀的第一运动，显然与在加拉帕戈斯群岛、三宅岛和冰岛观察到的类似群的火山地震活动的活塞模型不一致。正如这些先前的研究所认识到的，垂直 P 补偿线性矢量偶极子 (CLVD) 矩张量解可能是由弓形断层产生的，这些断层共同限制了火山口。群体序列的事件间隔时间不是随机的；相反，每次地震事件之间的时间间隔会增加 ∼1=2 小时。电子增刊：来自美国地质调查局 (USGS) 目录的地震震源机制图、显示基拉韦厄对映位置的南部非洲地图，以及相对于 50 个事件的高频（USGS 目录）起源时间的长周期 P 波时间选取。
I review the unusual swarm of 50 earthquakes, Mw 5.2–5.4, which occurred at Kīlauea caldera between May and August 2018. Given the strong similarity in published source mechanisms derived by centroid moment tensor (CMT) methods, I stacked the P waves from a global distribution of stations from local to antipodal distances. The composite source mechanism is consistent with a normal planar fault striking 335° NNW, dipping 78° W, with a rake nearly −90°. The differences between the composite source and waveform-derived sources are due in part to the choice of source depth, seismic velocity, and rigidity beneath Kīlauea summit. Antipodal PKIKP observations of the bottom of the source are derived from stacked data from three Global Seismographic Network (GSN) stations at ∼175°Δ in southern Africa. The stacked PKIKP displacement data show dilatational first motions, apparently inconsistent with proposed piston models of the volcano– earthquake activity for comparable swarms observed in the Galapagos, Miyakejima, and Iceland. As recognized in these prior studies, the vertical-P compensated linear vector dipole (CLVD) moment tensor solutions likely result from arcuate faults, which collectively circumscribe the caldera. The interevent times of the swarm sequence are not random; rather, the time interval between events increases by ∼1=2 hr for each earthquake. Electronic Supplement: Figures of earthquake source mechanisms from U.S. Geological Survey (USGS) catalog, map of southern Africa showing the locations antipodal to Kīlauea, and long-period P-wave time picks relative to the high-frequency (USGS catalog) origin time of the 50 events.