Low-Frequency hybrid earthquakes near a magma chamber in Afar: quantifying path effects
Low-Frequency hybrid earthquakes near a magma chamber in Afar: quantifying path effects
Areas of active volcanism contain elaborate velocity structures that complicate interpretations of earthquake source mechanisms. We examine the spectral characteristics of 805 earthquakes that immediately followed a large volume basaltic dike intrusion and associated silicic flank eruption of Dabbahu volcano in the Afar Depression as recorded on near-source seismometers. We use these results to quantify the contribution of scattering and attenuation to the observed spectra of low-frequency hybrid and volcano-tectonic earthquake clusters from beneath Dabbahu volcano and around the dike zone. We find strong variations in the signal amplitude and frequency content of earthquakes recorded at stations separated by as little as 2 km, caused by preferential attenuation of high frequencies depending on the vantage point. These observations imply that there are large impedance contrasts near the cooling, solidifying, and recently intruded dike. We estimate the intrinsic absorption attenuation coefficient, QI, and inverse scattering length, g0, averaged over a 300-sq-km area beneath Dabbahu. Our results are consistent with the highest attenuation coefficients from studies of volcanic provinces in Italy (QI-1 ? 0.02, g0?0.1 km-1 for a signal at 2 Hz). The magnitude of these two parameters indicates there are large impedance contrasts present in the area due to the recent intrusion of magma and associated fracturing.
1892-1903
Cote, Dustin M.
7823f61b-8efd-4590-b0b3-36c263a3a978
Belachew, Manahloh
7ee40db0-a3cc-40d0-805b-97ce19d6e4df
Quillen, Alice C.
72514038-d26a-43dd-a435-c61e879f83cf
Ebinger, Cynthia J.
d1ca4ec3-6eaf-4d0d-91a2-c0db40db7972
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6
Wright, Tim
5553bb25-2bd4-4629-bc93-d81bb12f5acb
October 2010
Cote, Dustin M.
7823f61b-8efd-4590-b0b3-36c263a3a978
Belachew, Manahloh
7ee40db0-a3cc-40d0-805b-97ce19d6e4df
Quillen, Alice C.
72514038-d26a-43dd-a435-c61e879f83cf
Ebinger, Cynthia J.
d1ca4ec3-6eaf-4d0d-91a2-c0db40db7972
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6
Wright, Tim
5553bb25-2bd4-4629-bc93-d81bb12f5acb
Cote, Dustin M., Belachew, Manahloh, Quillen, Alice C., Ebinger, Cynthia J., Keir, Derek, Ayele, Atalay and Wright, Tim
(2010)
Low-Frequency hybrid earthquakes near a magma chamber in Afar: quantifying path effects.
Bulletin of the Seismological Society of America, 100 (5A), .
(doi:10.1785/0120090111).
Abstract
Areas of active volcanism contain elaborate velocity structures that complicate interpretations of earthquake source mechanisms. We examine the spectral characteristics of 805 earthquakes that immediately followed a large volume basaltic dike intrusion and associated silicic flank eruption of Dabbahu volcano in the Afar Depression as recorded on near-source seismometers. We use these results to quantify the contribution of scattering and attenuation to the observed spectra of low-frequency hybrid and volcano-tectonic earthquake clusters from beneath Dabbahu volcano and around the dike zone. We find strong variations in the signal amplitude and frequency content of earthquakes recorded at stations separated by as little as 2 km, caused by preferential attenuation of high frequencies depending on the vantage point. These observations imply that there are large impedance contrasts near the cooling, solidifying, and recently intruded dike. We estimate the intrinsic absorption attenuation coefficient, QI, and inverse scattering length, g0, averaged over a 300-sq-km area beneath Dabbahu. Our results are consistent with the highest attenuation coefficients from studies of volcanic provinces in Italy (QI-1 ? 0.02, g0?0.1 km-1 for a signal at 2 Hz). The magnitude of these two parameters indicates there are large impedance contrasts present in the area due to the recent intrusion of magma and associated fracturing.
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Published date: October 2010
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Local EPrints ID: 175167
URI: http://eprints.soton.ac.uk/id/eprint/175167
ISSN: 0037-1106
PURE UUID: 2e1c3270-6920-48c3-afd5-9a5c4e7251c7
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Date deposited: 22 Feb 2011 16:46
Last modified: 14 Mar 2024 02:57
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Contributors
Author:
Dustin M. Cote
Author:
Manahloh Belachew
Author:
Alice C. Quillen
Author:
Cynthia J. Ebinger
Author:
Atalay Ayele
Author:
Tim Wright
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