The 2018 eruption of Sierra Negra volcano, Galápagos, Ecuador has provided new insights into the mechanisms of caldera resurgence, subsidence, and fissuring at basaltic shield volcanoes. Here, we integrate local (∼0.4 km) seismo-acoustic records and regional (∼85 km) infrasound array data to present new observations of the 2018 Sierra Negra eruption with improved time and spatial resolutions. These observations include: air-to-ground coupling ∼2 hr before the time of the eruption onset, migration of the infrasound tremor from 22:54 June 26 to 12:31 June 27 UT (all times in UT), and persistent infrasound detections during the weeks between 5 July and 18 August from an area that does not coincide with the previously documented eruptive fissures. We interpret air-to-ground coupling as infrasound tremor generated in the nearby fissures before the main eruptive phase started, although ambiguity remains in interpreting a single seismic-infrasonic sensor pair. The progressive location change of the infrasound tremor agrees with the migration of the eruption down the north flank of Sierra Negra at a rate of ∼0.15 ± 0.04 m/s. The weeks-long persistent detections coincide with a region that has thermal anomalies, co-eruptive deformation, lava fields, and geological features that could be interpreted as multiple lava tube skylights. Our observations and interpretations provide constraints on the mechanisms underlying fissure formation and magma emplacement at Sierra Negra.

中文翻译：

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2018 年加拉帕戈斯群岛 Sierra Negra 破火山口复苏和裂缝喷发的地震声学特征


2018 年厄瓜多尔加拉帕戈斯群岛 Sierra Negra 火山喷发为玄武岩盾状火山破火山口复苏、沉降和裂缝的机制提供了新的见解。在这里，我们整合了本地 （∼0.4 km） 地震声学记录和区域 （∼85 km） 次声阵列数据，以改进的时间和空间分辨率呈现对 2018 年 Sierra Negra 喷发的新观测结果。这些观测包括：喷发开始前 ∼ 2 小时的空对地耦合，UT 年 6 月 26 日 22：54 至 6 月 27 日 12：31 的次声震移（所有时间均为 UT），以及 7 月 5 日至 8 月 18 日期间从与先前记录的喷发裂缝不一致的区域持续进行的次声探测。我们将空对地耦合解释为在主要喷发阶段开始之前附近裂缝中产生的次声震颤，尽管在解释单个地震-次声波传感器对时仍然存在歧义。次声震的逐渐位置变化与喷发以 ∼0.15 ± 0.04 m/s 的速度向 Sierra Negra 北侧迁移一致。长达数周的持续探测与一个具有热异常、共同喷发变形、熔岩场和地质特征的区域相吻合，这些特征可以解释为多个熔岩管天窗。我们的观察和解释为 Sierra Negra 裂缝形成和岩浆放置的机制提供了限制。