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20-Year Seismic Run-Up to the 2015-2016 Eruption of Volcan Momotombo, Nicaragua, and Final Acceleration by Adjacent 2014 m6.1 Tectonic Earthquake

Description: 

After 110 years of repose, Momotombo volcano began erupting on 1 Dec. 2015. Momotombo has very high temperature fumaroles (~800C) since at least 1978 and magma close to the surface. Since regional seismic monitoring began (1975), seismicity has been dominated by distal volcano tectonic earthquake (dVT) swarms. Precursory seismicity follows the Four Stage Conceptual Model of White and McCausland (2019), with Stage 1 (deep seismicity) and Stage 2 (dVTs) bot progressing since 1975, and Stage 3 (vent clearing seismicity) first prevalent in 2000. At least 56 dVT swarms occurred since 1975, indicating persistent small intrusions into the magma reservoir, helping to maintain the very high temperature summit fumaroles for decades. The recurrence rates of dVT swarms decreased from 261 days between 1975-83 and 1993-99, to 135 days between 2000-08, to 36 days in 2013, and to 23 days in the 17 months prior to the eruption. The latter decrease occurred immediately after nearby M6.1 and M5.3 tectonic events whose source models indicate both dextral and normal motion, with a combined net extensional change in the stress field at Momotombo (Higgins, 2021). We hypothesize that the resulting change facilitated increased magma supply. Seismicity reached Stage 3 (tremor and tornillos) twice prior to the eruption: in mid-2000 and in June 2006 when a phreatic emission occurred. After June 2006, seismicity was again dominated by Stages 1 and 2 with occasional Stage 3 tornillos. About 6 months before the eruption onset, two production wells at the geothermal plant (3 km south of the summit) recorded coincident, small, persistent, and unusual increases in water pressure. Four months prior to the eruption, unusually large numbers and magnitudes of Stage 1 deep earthquakes began to occur, reaching M3.8. No short-term forecast was provided nor was a final transition to Stages 3 and 4 observed, as the closest seismic station was inoperable. However, the Instituto Nicaragüense de Estudios Territoriales issued intermediate-term warnings based on the dramatic increases in Stage 1 and 2 seismicity during the 4 months prior to the eruption.

Session: Seismology's Role in Assessing Volcanic Hazard at Multiple Time Scales [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Wendy McCausland

Student Presenter: No

Invited Presentation: 

Authors