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Evidence of fluid induced earthquake swarms from high resolution earthquake relocation in the main Ethiopian rift

Evidence of fluid induced earthquake swarms from high resolution earthquake relocation in the main Ethiopian rift
Evidence of fluid induced earthquake swarms from high resolution earthquake relocation in the main Ethiopian rift

Fluid overpressure and fluid migration are known to be able to trigger or induce fault slip. However, relatively little is known about the role of fluids on generating earthquakes in some of the major continental rifts. To address this, we investigate the interaction between fluids and faults in the Main Ethiopian Rift (MER) using a large seismicity catalog that covers both the rift axis and rift margin. We performed cross-correlation analysis on four major earthquake clusters (three within the rift and one on the rift margin) in order to significantly improve accuracy of the earthquake relative relocations and to quantify families of earthquakes in which waveforms are similar. We also analyzed variation of seismicity rate and seismic moment release through time for the four clusters. The major results are that for all four clusters the earthquake relocations are 5–15 km deep, aligned to clear N-NNE striking, steeply (>60°) dipping planes. For the three clusters within the rift, the cross-correlation analysis identifies earthquake families that occur in short swarms during which seismic rate and moment release increases. Together, this space and time pattern of the seismicity strongly points toward them being fluid induced, with fluid likely sourced from depth such as mantle derived CO 2. In contrast, the seismicity on the rift margin lacks earthquake families, with occurrence of earthquakes more continuous in nature, which we interpret as pointing toward tectonic stress-driven microseismic creep. Overall, our results suggest that deep sourced fluid migration within the rift is an important driver of earthquake activity.

HypoDD, NonLinLoc, earthquakes, fluid, relocation, rift
1525-2027
Raggiunti, Martina
c9bb1c87-dabf-4c37-a3de-9fa0b4ef0de2
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Pagli, Carolina
290edb22-712b-4563-a868-af4c21fdb6b0
Lavayssiere, Aude
4754825b-d4c7-45ec-b715-b46a7c92f042
Raggiunti, Martina
c9bb1c87-dabf-4c37-a3de-9fa0b4ef0de2
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Pagli, Carolina
290edb22-712b-4563-a868-af4c21fdb6b0
Lavayssiere, Aude
4754825b-d4c7-45ec-b715-b46a7c92f042

Raggiunti, Martina, Keir, Derek, Pagli, Carolina and Lavayssiere, Aude (2023) Evidence of fluid induced earthquake swarms from high resolution earthquake relocation in the main Ethiopian rift. Geochemistry, Geophysics, Geosystems, 24 (4), [e2022GC010765]. (doi:10.1029/2022GC010765).

Record type: Article

Abstract

Fluid overpressure and fluid migration are known to be able to trigger or induce fault slip. However, relatively little is known about the role of fluids on generating earthquakes in some of the major continental rifts. To address this, we investigate the interaction between fluids and faults in the Main Ethiopian Rift (MER) using a large seismicity catalog that covers both the rift axis and rift margin. We performed cross-correlation analysis on four major earthquake clusters (three within the rift and one on the rift margin) in order to significantly improve accuracy of the earthquake relative relocations and to quantify families of earthquakes in which waveforms are similar. We also analyzed variation of seismicity rate and seismic moment release through time for the four clusters. The major results are that for all four clusters the earthquake relocations are 5–15 km deep, aligned to clear N-NNE striking, steeply (>60°) dipping planes. For the three clusters within the rift, the cross-correlation analysis identifies earthquake families that occur in short swarms during which seismic rate and moment release increases. Together, this space and time pattern of the seismicity strongly points toward them being fluid induced, with fluid likely sourced from depth such as mantle derived CO 2. In contrast, the seismicity on the rift margin lacks earthquake families, with occurrence of earthquakes more continuous in nature, which we interpret as pointing toward tectonic stress-driven microseismic creep. Overall, our results suggest that deep sourced fluid migration within the rift is an important driver of earthquake activity.

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Geochem Geophys Geosyst - 2023 - Raggiunti - Evidence of Fluid Induced Earthquake Swarms From High Resolution Earthquake - Version of Record
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Published date: 23 April 2023
Additional Information: Funding Information: MR., DK., and CP. are funded by 2017 PRIN project—protocol MIUR: 2017P9AT72 PE10. DK is also supported by Natural Environment Research Council under NERC Grant NE/L013932/1. M.R. was also supported by PhD studentship from University of Pisa. Publisher Copyright: © 2023. The Authors.
Keywords: HypoDD, NonLinLoc, earthquakes, fluid, relocation, rift

Identifiers

Local EPrints ID: 476896
URI: http://eprints.soton.ac.uk/id/eprint/476896
ISSN: 1525-2027
PURE UUID: 7b22815d-af15-43e5-92fc-7fd61279b38e
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 18 May 2023 17:00
Last modified: 19 May 2023 01:40

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Contributors

Author: Martina Raggiunti
Author: Derek Keir ORCID iD
Author: Carolina Pagli
Author: Aude Lavayssiere

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