Title

Temporal Relationships of the Global Volcanic Earthquake Swarm Model

Document Type

Presentation

Publication Date

12-10-2018

Abstract

The Global Volcanic Earthquake Swarm Model (GVESD) was developed 23 years ago as a conceptual model to aid in identifying patterns and processes in volcanic earthquake swarms. The sequence of events – background, high-frequency (HF) events, relative quiescence, low-frequency (LF) events, tremor, eruption – is similar for long and short swarms, and similar whether preceding basaltic, andesitic, or dacitic eruptions. However, the details of the time sequences have not previously been studied. Here we examine 23 swarms that show many or all of the elements of the GVESD. Durations range from 5 to 366 days. In addition to durations, we also normalize time by choosing 0% at the first event and 100% at the onset of eruption. This allows determination of the relative time of occurrence of different components. We tested the data for correlations with VEI, SiO2 content, depth, duration, time to LF event onset, time to tremor onset, time of peak rate, time of max M, and time since last eruption. Highlights include the following: VEI correlates with time to last eruption for VEI >2. The onset of LF events and tremor is systematically earlier for large VEI eruptions: max M is also earlier. Both LF and tremor onset occur later for lower SiO2 values. In general, LF event onset occurs about half way through swarms regardless of duration. LF events occurred before tremor in nearly all cases (two were simultaneous). The peak rate occurs relatively earlier for shorter swarms, and the max M is larger for shorter swarms. Computed ascent velocities are higher for lower SiO2 values (more fluid magmas). Ascent velocity is slower for deeper swarms, and also slower for longer swarms. We found no simple correlation between duration and VEI, SiO2, and depth. For most parameters, there is significant variance in the data. This suggests that the physical processes that control the observed parameters are complex. Nevertheless, the GVESD is still a useful guide to help assess the overall development of earthquake swarms at volcanoes.

Citation / Publisher Attribution

Presented at the AGU Fall Meeting on December 10, 2018 in Washington, D.C.

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