Local seismicity near the actively deforming Corbetti volcano in the Main Ethiopian Rift

Aude Lavayssière*, Tim Greenfield, Derek Keir, Atalay Ayele, J. Michael Kendall

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

3 Citations (Scopus)
26 Downloads (Pure)

Abstract

Corbetti is currently one of the fastest uplifting volcanoes globally, with strong evidence from geodetic and gravity data for a subsurface inflating magma body. A dense network of 18 stations has been deployed around Corbetti and Hawassa calderas between February 2016 and October 2017, to place seismic constraints on the magmatic, hydrothermal and tectonic processes in the region. We locate 122 events of magnitudes between 0.4 and 4.2 using a new local velocity model. The seismicity is focused in two areas: directly beneath Corbetti caldera and beneath the city of Hawassa. The shallower 0–5 km depth below sea level (b.s.l.) earthquakes beneath Corbetti are mainly focused in EW- to NS-elongated clusters at Urji and Chabbi volcanic centres. This distribution is interpreted to be mainly controlled by a northward propagation of hydrothermal fluids away from a cross-rift pre-existing fault. Source mechanisms are predominantly strike-slip and different to the normal faulting away from the volcano, suggesting a local rotation of the stress-field. These observations, along with a low Vp/Vs ratio, are consistent with the inflation of a gas-rich sill, likely of silicic composition, beneath Corbetti. In contrast, the seismicity beneath Hawassa extends to greater depth (16 km b.s.l.). These earthquakes are focused on 8–10 km long segmented faults, which are active in seismic swarms. One of these swarms, in August 2016, is focused between 5 and 16 km depth b.s.l. along a steep normal fault beneath the city of Hawassa, highlighting the earthquake hazard for the local population.

Original languageEnglish
Pages (from-to)227-237
Number of pages11
JournalJournal of Volcanology and Geothermal Research
Volume381
Early online date17 Jun 2019
DOIs
Publication statusPublished - 1 Sep 2019

Keywords

  • East African rift
  • corbetti volcano
  • local seimicity
  • main ethiopian rift
  • continental tectonics

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