Low-frequency earthquakes beneath Tullu Moye volcano, Ethiopia, reveal fluid pulses from shallow magma chamber

Greenfield, Tim and Keir, Derek and Kendall, J-Michael and Ayele, Atalay (2019) Low-frequency earthquakes beneath Tullu Moye volcano, Ethiopia, reveal fluid pulses from shallow magma chamber. Earth and Planetary Science Letters, 526. p. 115782. ISSN 0012 821X DOI https://doi.org/10.1016/j.epsl.2019.115782

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Abstract

The active magmatic processes beneath volcanoes in continental rifts is poorly understood. For example, until recently in the East African rift (EAR), the majority of the young volcanoes were thought to be inactive. More recent studies have shown that numerous volcanoes in the EAR are seismically active and deforming rapidly. However, an unambiguous sign of actively degassing magma hosted in shallow magma bodies has eluded most investigators. Here we present detailed analysis of the first low-frequency (LF) earthquake swarms to be observed in the Main Ethiopian Rift. The earthquakes locate to beneath Tullu Moye volcano and are directly related to the presence of a shallow magma body with a high fluid content. Using spectral modelling we show that the LF earthquakes appear to have low stress-drops (1�50 kPa) which we interpret in terms of low rupture velocities and high pore-fluid pressure. Careful relocation of the LF earthquakes place them approximately 4 km below the surface within one of two possible clusters. However, analysis of the correlation between earthquake waveforms show that each swarm contains a range of earthquake families and as such a diversity of earthquake source mechanisms. To explain these observations, we propose the seismicity is induced by H2O/CO2 fluid pulses from the shallow magma body into a highly fractured region. Fluid pulses cause high pore fluid pressures, which also cause the low rupture velocities.

Item Type: Article
Uncontrolled Keywords: NILAREP;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
08 - Green Open Access
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 526
Page Range: p. 115782
Identification Number: https://doi.org/10.1016/j.epsl.2019.115782
Depositing User: Sarah Humbert
Date Deposited: 14 Sep 2020 15:05
Last Modified: 14 Sep 2020 15:05
URI: http://eprints.esc.cam.ac.uk/id/eprint/4880

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