Seismicity properties of the Chain Transform Fault inferred using data from the PI-LAB experiment
Seismicity properties of the Chain Transform Fault inferred using data from the PI-LAB experiment
Oceanic transform faults are intriguing in that they do not produce earthquakes as large as might be expected given their dimensions. We use 1-year of local seismicity (370 events above MC = 2.3) recorded on an array of ocean bottom seismometers (OBSs) and geophysical data to study the seismotectonic properties of the Chain transform, located in the equatorial Mid-Atlantic. We extend our analysis back in time by considering stronger earthquakes (MW ≥ 5.0) from global catalogs. We divide Chain into three areas (east, central, and west) based on historical event distribution, morphology, and multidimensional OBS seismicity cluster analysis. Seismic activity recorded by the OBS is the highest at the eastern area of Chain where there is a lozenge-shaped topographic high, a negative rMBA gravity anomaly, and only a few historical MW ≥ 5.5 events. OBS seismicity rates are lower in the western and central areas. However, these areas accommodate the majority of seismic moment release, as inferred from both OBS and historical data. Higher b-values are significantly correlated with lower rMBA and with shallower bathymetry, potentially related to thickened crust. Our results suggest high lateral heterogeneity along Chain. Patches with moderate to low OBS seismicity rates that occasionally host MW ≥ 6.0 earthquakes are interrupted by segments with abundant OBS activity but few historical events with 5.5 ≤ MW < 6.0. This segmentation is possibly due to variable fluid circulation and alteration, which may also change in time.
Mid Atlantic Ridge, OBS seismicity, fault segmentation, oceanic transform faults, seismotectonics
Leptokaropoulos, Konstantinos
6176f4d8-7af0-4575-bf2c-5aaba3d182ce
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Kendall, J. Michael
746f7fc0-ee9e-4436-89d6-a6f26cdec6aa
March 2023
Leptokaropoulos, Konstantinos
6176f4d8-7af0-4575-bf2c-5aaba3d182ce
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Kendall, J. Michael
746f7fc0-ee9e-4436-89d6-a6f26cdec6aa
Leptokaropoulos, Konstantinos, Rychert, Catherine, Harmon, Nicholas and Kendall, J. Michael
(2023)
Seismicity properties of the Chain Transform Fault inferred using data from the PI-LAB experiment.
Journal of Geophysical Research: Solid Earth, 128 (3), [e2022JB024804].
(doi:10.1029/2022JB024804).
Abstract
Oceanic transform faults are intriguing in that they do not produce earthquakes as large as might be expected given their dimensions. We use 1-year of local seismicity (370 events above MC = 2.3) recorded on an array of ocean bottom seismometers (OBSs) and geophysical data to study the seismotectonic properties of the Chain transform, located in the equatorial Mid-Atlantic. We extend our analysis back in time by considering stronger earthquakes (MW ≥ 5.0) from global catalogs. We divide Chain into three areas (east, central, and west) based on historical event distribution, morphology, and multidimensional OBS seismicity cluster analysis. Seismic activity recorded by the OBS is the highest at the eastern area of Chain where there is a lozenge-shaped topographic high, a negative rMBA gravity anomaly, and only a few historical MW ≥ 5.5 events. OBS seismicity rates are lower in the western and central areas. However, these areas accommodate the majority of seismic moment release, as inferred from both OBS and historical data. Higher b-values are significantly correlated with lower rMBA and with shallower bathymetry, potentially related to thickened crust. Our results suggest high lateral heterogeneity along Chain. Patches with moderate to low OBS seismicity rates that occasionally host MW ≥ 6.0 earthquakes are interrupted by segments with abundant OBS activity but few historical events with 5.5 ≤ MW < 6.0. This segmentation is possibly due to variable fluid circulation and alteration, which may also change in time.
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JGR Solid Earth - 2023 - Leptokaropoulos - Seismicity Properties of the Chain Transform Fault Inferred Using Data From the
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Accepted/In Press date: 16 February 2023
e-pub ahead of print date: 23 February 2023
Published date: March 2023
Additional Information:
Funding Information:
K. Leptokaropoulos, C. A. Rychert, and N. Harmon acknowledge funding from the Natural Environment Research Council (NE/M003507/1) and the European Research Council (GA 638665). J. M. Kendall was funded by the Natural Environment Research Council (NE/M004643/1). We thank the captain and crew of the R/V Marcus G. Langseth and the RRS Discovery, and the scientific technicians. We thank David Schlaphorst for discussions on magnitudes and focal mechanisms calculation. We thank Jochen Braunmiller and an anonymous reviewer, the Associate Editor, and Editor, Satoshi Ide, for their insightful comments and suggestions.
Publisher Copyright:
© 2023. The Authors.
Keywords:
Mid Atlantic Ridge, OBS seismicity, fault segmentation, oceanic transform faults, seismotectonics
Identifiers
Local EPrints ID: 475676
URI: http://eprints.soton.ac.uk/id/eprint/475676
ISSN: 2169-9356
PURE UUID: ba04858a-06c9-46cc-95ee-dcf3efbe3546
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Date deposited: 24 Mar 2023 17:30
Last modified: 17 Mar 2024 04:05
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J. Michael Kendall
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