TY - JOUR
T1 - Local seismicity near the actively deforming Corbetti volcano in the Main Ethiopian Rift
AU - Lavayssière, Aude
AU - Greenfield, Tim
AU - Keir, Derek
AU - Ayele, Atalay
AU - Kendall, J. Michael
PY - 2019/9/1
Y1 - 2019/9/1
N2 - 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.
AB - 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.
KW - East African rift
KW - corbetti volcano
KW - local seimicity
KW - main ethiopian rift
KW - continental tectonics
UR - http://www.scopus.com/inward/record.url?scp=85067853816&partnerID=8YFLogxK
U2 - 10.1016/j.jvolgeores.2019.06.008
DO - 10.1016/j.jvolgeores.2019.06.008
M3 - Article (Academic Journal)
AN - SCOPUS:85067853816
SN - 0377-0273
VL - 381
SP - 227
EP - 237
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
ER -