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Origin and Properties of Hydrothermal Tremor at Lone Star Geyser, Yellowstone National Park, USA
Journal of Geophysical Research: Solid Earth ( IF 3.9 ) Pub Date : 2020-11-20 , DOI: 10.1029/2020jb019711
Avinash Nayak 1, 2 , Michael Manga 1 , Shaul Hurwitz 3 , Atsuko Namiki 4 , Phillip B. Dawson 3
Affiliation  

Geysers are rare geologic features that intermittently discharge liquid water and steam driven by heating and decompression boiling. The cause of variability in eruptive styles and the associated seismic signals are not well understood. Data collected from five broadband seismometers at Lone Star Geyser, Yellowstone National Park are used to determine the properties, location, and temporal patterns of hydrothermal tremor. The tremor is harmonic at some stages of the eruption cycle and is caused by near‐periodic repetition of discrete seismic events. Using the polarization of ground motion, we identify the location of tremor sources throughout several eruption cycles. During preplay episodes (smaller eruptions preceding the more vigorous major eruption), tremor occurs at depths of 7–10 m and is laterally offset from the geyser's cone by ~5 m. At the onset of the main eruption, tremor sources migrate laterally and become shallower. As the eruption progresses, tremor sources migrate along the same path but in the opposite direction, ending where preplay tremor originates. The upward and then downward migration of tremor sources during eruptions are consistent with warming of the conduit followed by evacuation of water during the main eruption. We identify systematic relations among the two types of preplays, discharge, and the main eruption. A point‐source moment tensor fit to low‐frequency waveforms of an individual tremor event using half‐space velocity models indicates average VS  0.8 km/s, source depths ~4–20 m, and moment tensors with primarily positive isotropic and compensated linear vector dipole moments.

中文翻译:

美国黄石国家公园孤星间歇泉热液震颤的起源与性质

间歇泉是罕见的地质特征,间歇性地通过加热和减压沸腾来驱散液态水和蒸汽。火山喷发形式和相关地震信号变化的原因尚不十分清楚。从黄石国家公园孤星间歇泉的五个宽带地震仪收集的数据用于确定热液震颤的性质,位置和时间模式。地震在喷发周期的某些阶段是谐波,是由离散地震事件的近周期性重复引起的。利用地震动的极化,我们确定了整个喷发周期中震源的位置。在赛前发作期间(剧烈爆发前较小的喷发),震颤发生在7-10 m的深度处,并从间歇泉的圆锥体横向偏移〜5 m。在主要爆发时,震颤源向侧面移动并变浅。随着喷发的进行,震颤源沿着相同的路径但向相反的方向迁移,从而结束了玩前震颤的起源。爆发过程中,震源的向上和向下迁移与导管变暖,然后在主要爆发过程中排空水相一致。我们确定了两种类型的预演,放电和主要喷发之间的系统关系。使用半空间速度模型拟合单个震颤事件的低频波形的点源矩张量表示平均值 在赛前震颤起源的地方结束。爆发过程中,震源的向上和向下迁移与导管变暖,然后在主要爆发过程中排空水相一致。我们确定了两种类型的预演,放电和主要喷发之间的系统关系。使用半空间速度模型拟合单个震颤事件的低频波形的点源矩张量表示平均值 在赛前震颤起源的地方结束。爆发过程中,震源的向上和向下迁移与导管变暖,然后在主要爆发过程中排空水相一致。我们确定了两种类型的预演,放电和主要喷发之间的系统关系。使用半空间速度模型拟合单个震颤事件的低频波形的点源矩张量表示平均值V小号   0.8公里/ S,源深度〜4-20米,和矩张量与主要正各向同性和补偿线性载体的偶极矩。
更新日期:2020-12-26
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