Anatomy of phreatic eruptions

• Published in: Earth, Planets and Space
• Main Authors: Corentin Caudron, Benoit Taisne, Jurgen Neuberg, Arthur D. Jolly, Bruce Christenson, Thomas Lecocq, Suparjan, Devy Syahbana, Gede Suantika
• Format: Article in Journal/Newspaper
• Language: English
• Published: SpringerOpen 2018
• Subjects: Volcanic monitoring; Phreatic eruption; Volcanic lake; Broadband seismology; Geography. Anthropology. Recreation; G; Geodesy; QB275-343; Geology; QE1-996.5; New Zealand; White Island; Crater Lake
• Online Access: https://doi.org/10.1186/s40623-018-0938-x; https://doaj.org/article/22d5725fd82d4bec93c85f3bd2e71ff1

Abstract This study investigates phreatic eruptions at two similar volcanoes, Kawah Ijen (Indonesia) and White Island (New Zealand). By carefully processing broadband seismic signals, we reveal seismic signatures and characteristics of these eruptions. At both volcanoes, the phreatic eruptions are initiated by a very-long-period (VLP) seismic event located at shallow depths between 700 and 900 m below the crater region, and may be triggered by excitation of gas trapped behind a ductile magma carapace. The shallow hydrothermal systems respond in different ways. At Kawah Ijen, the stress change induced by VLPs directly triggers an eigenoscillation of the hyperacidic lake. This so-called seiche is characterized by long-lasting, long-period oscillations with frequencies governed by the dimensions of the crater lake. A progressive lateral rupture of a seal below the crater lake and/or fluids migrating toward the surface is seismically recorded $$\sim$$ ∼ 15 min later as high-frequency bursts superimposed to tilt signals. At White Island, the hydrothermal system later ($$\sim$$ ∼ 25 min) responds by radiating harmonic tremor at a fixed location that could be generated through eddy-shedding. These seismic signals shed light on several aspects of phreatic eruptions, their generation and timeline. They are mostly recorded at periods longer than tens of seconds further emphasizing the need to deploy broadband seismic equipment close to active volcanic activity.