On the origin of recent seismic unrest episodes at Deception Island volcano, Antarctica

• Published in: Journal of Volcanology and Geothermal Research
• Main Authors: Moreno Vacas, Alejandro, Almendros González, Francisco Javier
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2021
• Subjects: Volcano-tectonic earthquakes; Seismic swarms; Magma intrusions; Failed eruptions; Volcano seismicity; Deception Island volcano; Antarctica; Deception Island; Livingston Island; South Shetland Islands; Antarc*; Antarctica Journal
• Online Access: http://hdl.handle.net/10481/71241; https://doi.org/10.1016/j.jvolgeores.2021.107376

Thework of AMVwas funded by a Grant for Young Researchers (ref. 2018-6032) under the Youth Employment Program of the Junta de Andalucia, Spain. Additional support comes from project BRAVOSEIS funded by the Spanish Ministry of Science (MINECO) under grant CTM2016-77315-R. Funding for the open access charges comes from Univeristy of Granada/CBUA. Deception Island (South Shetland Islands, Antarctica) is an active volcano characterized by a moderate level of seismic activity, dominated by long-period seismicity related to hydrothermal processes in a shallow aquifer. Nevertheless, in the last few decades the volcano has undergone at least three episodes of seismic unrest, in 1992, 1999, and 2015. During these episodes, the pattern of seismicity changed, and swarms of volcanotectonic earthquakes with hundreds of events in time spans of a few months were detected. These episodes are interpreted as consequences of magmatic intrusions. However, the seismic series display significant differences that lead us to think that the processes initiating the series are not exactly the same in all cases. The 1999 series comprisedmostly small-magnitude earthquakes, produced regularly during 1.5 months, and located at shallow depths (<4 km) within the caldera, mostly along a WSW-ENE trend that parallels the Bransfield rift. No precursory seismic activity was reported, and a few months after the series onset the seismicity was back to normal levels. The 2015 series included earthquakes with largermagnitudes, occurring during 5 months in temporal clusters separated by aseismic periods. They were located at deeper levels (<10 km) with epicenters distributed all around Deception Island, at distances up to 30 km. Additionally, distal (~35 km) VT seismicity was reported SE of Livingston Island months before the 2015 series onset, and the seismicity at Deception Island remained anomalously high during a few years. Taking into account the limited data available for the 1992 unrest, we conclude that the 1992 and 1999 series were produced by shallow, short-lived, small-volume (~4·104m3) intrusions that affected the shallowmost part of the volcanic edifice. On the contrary, the 2015 series was consequence of a deep, long-lasting intrusion that involved a larger volume of ~5·106 m3 (in the range of a VEI 2 eruption) and modified the stress field of the whole volcanic edifice. Youth Employment Program of the Junta de Andalucia, Spain 2018-6032 project BRAVOSEIS - Spanish Ministry of Science (MINECO) CTM2016-77315-R Univeristy of Granada/CBUA