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Ichihara M, Ohminato T, Konstantinou KI, Yamakawa K, Watanabe A, Takeo M. Seismic background level (SBL) growth can reveal slowly developing long-term eruption precursors. Sci Rep 2023; 13:5954. [PMID: 37045890 PMCID: PMC10097692 DOI: 10.1038/s41598-023-32875-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 04/04/2023] [Indexed: 04/14/2023] Open
Abstract
The accelerating growth of seismic unrest before eruptions has been observed at many volcanoes and utilized for eruption forecasts. However, there are still many eruptions for which no precursory unrest has been identified, even at well-monitored volcanoes. The recent eruptions of Shinmoe-dake, Japan, have been another negative example of this kind. Here we present seismological evidence that the eruption preparation had been ongoing at the shallow depths beneath Shinmoe-dake for several months to a year. We investigated the seismic background level (SBL) of eleven-year data recorded around the volcano, including two stations about 1 km from the eruptive crater. We searched for persistent weak signals, focusing on low-amplitude time windows recorded during quiet nighttime. Then the spectra of daily background noise were classified by clustering analysis. The SBL analysis successfully revealed very weak precursory tremors from more than several months before the eruption, and residual tremors to the end of the eruptive period. The precursory signals grew acceleratory in a similar way as is assumed in the material failure forecast method applied to eruption forecasts. However, their growth was significantly slower and longer compared to other cases reported in the literature. Such slow and quiet eruption preparations would not be captured by conventional seismological methods. We expect that long-term SBL analyses on proximal seismic data will help detect early precursors, even at seismically quiet volcanoes, and will also help towards judging the end of an eruptive period.
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Affiliation(s)
- Mie Ichihara
- Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032, Japan.
| | - Takao Ohminato
- Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Kostas I Konstantinou
- Department of Earth Sciences, National Central University, Jhongli, 320, Taoyuan, Taiwan
| | - Kazuya Yamakawa
- Mount Fuji Research Institute Yamanashi Prefectural Government, 5597-1 Kenmarubi, Kamiyoshida, Fujiyoshida, Yamanashi, 403-0005, Japan
| | - Atsushi Watanabe
- Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Minoru Takeo
- Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo, 113-0032, Japan
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Lebrato M, Wang YV, Tseng LC, Achterberg EP, Chen XG, Molinero JC, Bremer K, Westernströer U, Söding E, Dahms HU, Küter M, Heinath V, Jöhnck J, Konstantinou KI, Yang YJ, Hwang JS, Garbe-Schönberg D. Earthquake and typhoon trigger unprecedented transient shifts in shallow hydrothermal vents biogeochemistry. Sci Rep 2019; 9:16926. [PMID: 31729442 PMCID: PMC6858458 DOI: 10.1038/s41598-019-53314-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 10/30/2019] [Indexed: 12/03/2022] Open
Abstract
Shallow hydrothermal vents are of pivotal relevance for ocean biogeochemical cycles, including seawater dissolved heavy metals and trace elements as well as the carbonate system balance. The Kueishan Tao (KST) stratovolcano off Taiwan is associated with numerous hydrothermal vents emitting warm sulfur-rich fluids at so-called White Vents (WV) and Yellow Vent (YV) that impact the surrounding seawater masses and habitats. The morphological and biogeochemical consequences caused by a M5.8 earthquake and a C5 typhoon (“Nepartak”) hitting KST (12th May, and 2nd–10th July, 2016) were studied within a 10-year time series (2009–2018) combining aerial drone imagery, technical diving, and hydrographic surveys. The catastrophic disturbances triggered landslides that reshaped the shoreline, burying the seabed and, as a consequence, native sulfur accretions that were abundant on the seafloor disappeared. A significant reduction in venting activity and fluid flow was observed at the high-temperature YV. Dissolved Inorganic Carbon (DIC) maxima in surrounding seawater reached 3000–5000 µmol kg−1, and Total Alkalinity (TA) drawdowns were below 1500–1000 µmol kg−1 lasting for one year. A strong decrease and, in some cases, depletion of dissolved elements (Cd, Ba, Tl, Pb, Fe, Cu, As) including Mg and Cl in seawater from shallow depths to the open ocean followed the disturbance, with a recovery of Mg and Cl to pre-disturbance concentrations in 2018. The WV and YV benthic megafauna exhibited mixed responses in their skeleton Mg:Ca and Sr:Ca ratios, not always following directions of seawater chemical changes. Over 70% of the organisms increased skeleton Mg:Ca ratio during rising DIC (higher CO2) despite decreasing seawater Mg:Ca ratios showing a high level of resilience. KST benthic organisms have historically co-existed with such events providing them ecological advantages under extreme conditions. The sudden and catastrophic changes observed at the KST site profoundly reshaped biogeochemical processes in shallow and offshore waters for one year, but they remained transient in nature, with a possible recovery of the system within two years.
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Affiliation(s)
- Mario Lebrato
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany. .,Bazaruto Center for Scientific Studies (BCSS), Benguerra Island, Mozambique.
| | - Yiming V Wang
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany.,Max Planck Institute for the Science of Human History, Jena, Germany
| | - Li-Chun Tseng
- National Taiwan Ocean University, Keelung City, Taiwan
| | | | - Xue-Gang Chen
- Ocean College, Zhejiang University, Zhoushan City, China
| | - Juan-Carlos Molinero
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany.,Marine Biodiversity, Exploitation and Conservation (MARBEC), IRD/CNRS/IFREMER/University of Montpellier, Montpellier, France
| | - Karen Bremer
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany
| | | | - Emanuel Söding
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany
| | | | - Marie Küter
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany
| | - Verena Heinath
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany
| | - Janika Jöhnck
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany
| | | | | | | | - Dieter Garbe-Schönberg
- Institute of Geosciences, Kiel University (CAU), Kiel, Germany.,Jacobs University Bremen gGmbH, Bremen, Germany
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Glynn CC, Konstantinou KI. Reduction of randomness in seismic noise as a short-term precursor to a volcanic eruption. Sci Rep 2016; 6:37733. [PMID: 27883050 PMCID: PMC5121890 DOI: 10.1038/srep37733] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 10/31/2016] [Indexed: 11/09/2022] Open
Abstract
Ambient seismic noise is characterized by randomness incurred by the random position and strength of the noise sources as well as the heterogeneous properties of the medium through which it propagates. Here we use ambient noise data recorded prior to the 1996 Gjálp eruption in Iceland in order to show that a reduction of noise randomness can be a clear short-term precursor to volcanic activity. The eruption was preceded on 29 September 1996 by a Mw ~5.6 earthquake that occurred in the caldera rim of the Bárdarbunga volcano. A significant reduction of randomness started occurring 8 days before the earthquake and 10 days before the onset of the eruption. This reduction was observed even at stations more than 100 km away from the eruption site. Randomness increased to its previous levels 160 minutes after the Bárdarbunga earthquake, during which time aftershocks migrated from the Bárdarbunga caldera to a site near the Gjálp eruption fissure. We attribute this precursory reduction of randomness to the lack of higher frequencies (>1 Hz) in the noise wavefield caused by high absorption losses as hot magma ascended in the upper crust.
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Affiliation(s)
- C C Glynn
- Dept of Earth Sciences, National Central University, Jhongli, 320 Taiwan
| | - K I Konstantinou
- Dept of Earth Sciences, National Central University, Jhongli, 320 Taiwan
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