The rise and fall of periodic ‘drumbeat’ seismicity at Tungurahua volcano, Ecuador
| Autor: | Daniel Sierra, Mario Ruiz, Patricia Mothes, Andrew Bell, Santiago Aguaiza, Stephen Hernandez, H. Elizabeth Gaunt |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
geography
geography.geographical_feature_category 010504 meteorology & atmospheric sciences Lava Andesite Gas flux Induced seismicity 010502 geochemistry & geophysics 01 natural sciences Geophysics Volcano Space and Planetary Science Geochemistry and Petrology Long period Magma Earth and Planetary Sciences (miscellaneous) Seismology Geology 0105 earth and related environmental sciences |
| Zdroj: | Bell, A, Hernandez, S, Gaunt, H E, Mothes, P, Ruiz, M, Sierra, D & Aguaiza, S 2017, ' The rise and fall of periodic 'drumbeat' seismicity at Tungurahua volcano, Ecuador ', Earth and Planetary Science Letters, vol. 475, pp. 58-70 . https://doi.org/10.1016/j.epsl.2017.07.030 |
| ISSN: | 0012-821X |
| Popis: | Highly periodic ‘drumbeat’ long period (LP) earthquakes have been described from several andesitic and dacitic volcanoes, commonly accompanying incremental ascent and effusion of viscous magma. However, the processes controlling the occurrence and characteristics of drumbeat, and LP earthquakes more generally, remain contested. Here we use new quantitative tools to describe the emergence, evolution, and degradation of drumbeat LP seismicity at the andesitic Tungurahua volcano, Ecuador, in April 2015. The signals were recorded during an episode of minor explosive activity and ash emission, without lava effusion, and are the first to be reported at Tungurahua during the ongoing 17 yrs of eruption. Following four days of high levels of continuous and ‘pulsed’ tremor, highly-periodic LP earthquakes first appear on 10 April. Over the next four days, inter-event times and event amplitudes evolve through a series of step-wise transitions between stable behaviors, each involving a decrease in the degree of periodicity. Families of similar waveforms persist before, during, and after drumbeat activity, but the activity levels of different families change coincidentally with transitions in event rate, amplitude, and periodicity. A complex micro-seismicity ‘initiation’ sequence shows pulse-like and stepwise changes in inter-event times and amplitudes in the hours preceding the onset of drumbeat activity that indicate a partial de-coupling between event size and rate. The observations increase the phenomenology of drumbeat LP earthquakes, and suggest that at Tungurahua they result from gas flux and rapid depressurization controlled by shear failure of the margins of the ascending magma column. |
| Databáze: | OpenAIRE |
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