Lower crustal earthquakes in the march 2018 sequence along the western margin of afar
Lower crustal earthquakes in the march 2018 sequence along the western margin of afar
During the evolution of continental rift systems, extension is thought to progressively focus in-rift to the future breakup boundary while faults along the rift margins progressively deactivate. However, observational constraints on how strain is partitioned between rift axis and rift margins are still lacking. The Afar rift records the latest stages of rifting and incipient continental breakup. Here, we analyzed the recent M
W 5.2 earthquake on the Western Afar Margin on March 24, 2018 and the associated seismic sequence of >500 earthquakes using 24 temporary seismic stations deployed during 2017–2018. We show seismicity occurring at lower crustal depths, from ∼15 to ∼30 km, with focal mechanisms and relocated earthquakes highlighting both west-dipping and east-dipping normal faults. We tested earthquake depth using InSAR by processing six independent interferograms using Sentinel-1 data acquired from both ascending and descending tracks. None of them shows evidence of surface deformation. We tested possible ranges of depth by producing forward models for a fault located at progressively increasing depths. Models show that surface deformation is not significant for fault slip at depths greater than 15 km, in agreement with the hypocentral depth of 19 km derived from seismic data for the largest earthquake. Due to the localized nature of deep earthquakes near hot springs coupled with subsurface evidence for magmatism, we favor an interpretation of seismicity induced by migrating fluids such as magma or CO
2. We suggest that deep fluid migration can occur at the rifted-margin influencing seismicity during incipient continental rupture.
Afar, deep seismicity, rift margins
La Rosa, Alessandro
3443c440-23fe-437e-b908-80f6b923c4ba
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Doubre, Cecile
9f348925-f5b6-445c-8663-7f58f58b97f3
Sani, Federico
6c59b4c4-ecca-4ecc-ba2c-66efa5e5e3df
Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Leroy, Sylvie
627c503b-1036-41fc-a24c-3d09954fab0a
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6
Pagli, Carolina
290edb22-712b-4563-a868-af4c21fdb6b0
April 2021
La Rosa, Alessandro
3443c440-23fe-437e-b908-80f6b923c4ba
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Doubre, Cecile
9f348925-f5b6-445c-8663-7f58f58b97f3
Sani, Federico
6c59b4c4-ecca-4ecc-ba2c-66efa5e5e3df
Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Leroy, Sylvie
627c503b-1036-41fc-a24c-3d09954fab0a
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6
Pagli, Carolina
290edb22-712b-4563-a868-af4c21fdb6b0
La Rosa, Alessandro, Keir, Derek, Doubre, Cecile, Sani, Federico, Corti, Giacomo, Leroy, Sylvie, Ayele, Atalay and Pagli, Carolina
(2021)
Lower crustal earthquakes in the march 2018 sequence along the western margin of afar.
Geochemistry, Geophysics, Geosystems, 22 (4), [e2020GC009614].
(doi:10.1029/2020GC009614).
Abstract
During the evolution of continental rift systems, extension is thought to progressively focus in-rift to the future breakup boundary while faults along the rift margins progressively deactivate. However, observational constraints on how strain is partitioned between rift axis and rift margins are still lacking. The Afar rift records the latest stages of rifting and incipient continental breakup. Here, we analyzed the recent M
W 5.2 earthquake on the Western Afar Margin on March 24, 2018 and the associated seismic sequence of >500 earthquakes using 24 temporary seismic stations deployed during 2017–2018. We show seismicity occurring at lower crustal depths, from ∼15 to ∼30 km, with focal mechanisms and relocated earthquakes highlighting both west-dipping and east-dipping normal faults. We tested earthquake depth using InSAR by processing six independent interferograms using Sentinel-1 data acquired from both ascending and descending tracks. None of them shows evidence of surface deformation. We tested possible ranges of depth by producing forward models for a fault located at progressively increasing depths. Models show that surface deformation is not significant for fault slip at depths greater than 15 km, in agreement with the hypocentral depth of 19 km derived from seismic data for the largest earthquake. Due to the localized nature of deep earthquakes near hot springs coupled with subsurface evidence for magmatism, we favor an interpretation of seismicity induced by migrating fluids such as magma or CO
2. We suggest that deep fluid migration can occur at the rifted-margin influencing seismicity during incipient continental rupture.
Text
2020GC009614
- Accepted Manuscript
More information
Published date: April 2021
Additional Information:
Funding Information:
This study was developed in the framework of the PhD project of A. La Rosa (XXXIII cycle of the Dottorato Regionale Pegaso in Earth Sciences) and is supported by the Ministero Università e Ricerca (MiUR) through PRIN Grant 2017P9AT72. A. La Rosa and C. Pagli acknowledge partial support by the University of Pisa Grant PRA_2018_19. Sentinel‐1 IW SLCs are provided by the Copernicus Open Access Hub (Sentinel‐1) ( https://scihub.copernicus.eu/ ). Shuttle Radar Topography Mission Digital Elevation Models (SRTM‐DEM) can be downloaded from the U.S. Geological Survey Earth Explorer web service ( https://earthexplorer.usgs.gov ). Seismic instruments (USGS NEIC) were loaned by SEIS‐UK. The facilities of SEIS‐UK are supported by the Natural Environment Research Council (NERC) under agreement R8/H10/64. Instruments for the Southern profile belong to the French national pool of portable seismic instruments SISMOB‐RESIF (INSU‐CNRS). The temporary network deployments were part of an Actions‐Marges and ISTeP project (#2016‐82). We thank the regional authorities of the Afar, Tigray and Amhara for their administrative support. We also thank the wider staff body at the IGSSA of Addis Ababa University and the Centre Français d'Etudes Ethiopiennes (CFEE, IFRE23, USR3117) for the support in Ethiopia.
Funding Information:
This study was developed in the framework of the PhD project of A. La Rosa (XXXIII cycle of the Dottorato Regionale Pegaso in Earth Sciences) and is supported by the Ministero Universit? e Ricerca (MiUR) through PRIN Grant 2017P9AT72. A. La Rosa and C. Pagli acknowledge partial support by the University of Pisa Grant PRA_2018_19. Sentinel-1 IW SLCs are provided by the Copernicus Open Access Hub (Sentinel-1) (https://scihub.copernicus.eu/). Shuttle Radar Topography Mission Digital Elevation Models (SRTM-DEM) can be downloaded from the U.S. Geological Survey Earth Explorer web service (https://earthexplorer.usgs.gov). Seismic instruments (USGS NEIC) were loaned by SEIS-UK. The facilities of SEIS-UK are supported by the Natural Environment Research Council (NERC) under agreement R8/H10/64. Instruments for the Southern profile belong to the French national pool of portable seismic instruments SISMOB-RESIF (INSU-CNRS). The temporary network deployments were part of an Actions-Marges and ISTeP project (#2016-82). We thank the regional authorities of the Afar, Tigray and Amhara for their administrative support. We also thank the wider staff body at the IGSSA of Addis Ababa University and the Centre Fran?ais d'Etudes Ethiopiennes (CFEE, IFRE23, USR3117) for the support in Ethiopia.
Publisher Copyright:
© 2021. The Authors.
Keywords:
Afar, deep seismicity, rift margins
Identifiers
Local EPrints ID: 448961
URI: http://eprints.soton.ac.uk/id/eprint/448961
ISSN: 1525-2027
PURE UUID: b4ce4bfd-4637-4665-880e-a93e8403535d
Catalogue record
Date deposited: 12 May 2021 16:30
Last modified: 17 Mar 2024 03:24
Export record
Altmetrics
Contributors
Author:
Alessandro La Rosa
Author:
Cecile Doubre
Author:
Federico Sani
Author:
Giacomo Corti
Author:
Sylvie Leroy
Author:
Atalay Ayele
Author:
Carolina Pagli
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
