TY - JOUR
T1 - Seismicity and seismotectonics of Madagascar revealed by the 2011–2013 deployment of the island-wide MACOMO broadband seismic array
AU - Rakotondraibe, Tsiriandrimanana
AU - Nyblade, Andrew A.
AU - Wysession, Michael E.
AU - Durrheim, Raymond J.
AU - Rambolamanana, Gérard
AU - Aleqabi, Ghassan I.
AU - Shore, Patrick J.
AU - Pratt, Martin J.
AU - Andriampenomanana, Fenitra
AU - Rümpker, Georg
AU - Rindraharisaona, Elisa
N1 - Funding Information:
We gratefully acknowledge the field support from IRIS-PASSCAL, which provided the seismic equipment for the MACOMO project (FDSN code: XV, doi:https://doi.org/10.7914/SN/XV_2011); SELASOMA project (FDSN code: ZE, doi:10.14470/MR7567431421), IRIS (FDSN code: II, doi:https://doi.org/10.7914/SN/II),CEA/DASE (FDSN code: RD, doi.org/10.15778/RESIF.RD) GEOFON (FDSN code: GE, doi:10.14470/TR560404), and GEOSCOPE (FDSN code: G, doi:10.18715/GEOSCOPE.G) for additional seismic data. Figures in this paper have been produced with GMT (Wessel and Smith, 1998). This study was funded by NSF awards EAR-0838426 and 0838387, and supported by the AfricaArray program. R. Durrheim acknowledges the support of the National Research Foundation through the South African Research Chairs Initiative. We also acknowledge two anonymous reviewers and Cynthia Ebinger and Derek Keir for providing insightful reviews that helped to improve the paper.
Funding Information:
We gratefully acknowledge the field support from IRIS -PASSCAL, which provided the seismic equipment for the MACOMO project (FDSN code: XV, doi: https://doi.org/10.7914/SN/XV_2011 ); SELASOMA project (FDSN code: ZE, doi: 10.14470/MR7567431421 ), IRIS (FDSN code: II, doi: https://doi.org/10.7914/SN/II ),CEA/DASE (FDSN code: RD, doi.org/10.15778/RESIF.RD ) GEOFON (FDSN code: GE, doi: 10.14470/TR560404 ), and GEOSCOPE (FDSN code: G, doi: 10.18715/GEOSCOPE.G ) for additional seismic data. Figures in this paper have been produced with GMT ( Wessel and Smith, 1998 ). This study was funded by NSF awards EAR-0838426 and 0838387, and supported by the AfricaArray program. R. Durrheim acknowledges the support of the National Research Foundation through the South African Research Chairs Initiative. We also acknowledge two anonymous reviewers and Cynthia Ebinger and Derek Keir for providing insightful reviews that helped to improve the paper.
Publisher Copyright:
© 2020
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/9/5
Y1 - 2020/9/5
N2 - The seismicity and seismotectonics of Madagascar have been studied using an island-wide distribution of broadband seismic stations. The 28-station MAdagascar-COmoros-MOzambique (MACOMO) array was deployed for a 23-month period between 2011 and 2013. MACOMO data were supplemented by seven temporary stations from the Seismological Signatures in the Lithosphere/Asthenosphere system of Southern Madagascar (SELASOMA) project, ten temporary stations from the Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel project (RHUM-RUM), and 11 permanent stations. A total of 695 earthquakes with magnitudes between ML1 and ML5.3 located within Madagascar were recorded, a new local magnitude scale was developed, and focal mechanisms were determined for 23 well-recorded events. Most of the seismicity is clustered within central Madagascar, forming NW-SE trends in the Ankaratra region and NE-SW trends in the Alaotra and Ankay regions that roughly align with extensional tectonic features. The northern and southern parts of Madagascar also show seismicity clusters that align parallel to existing tectonic features, primarily Precambrian shear zones. Focal mechanisms exhibit a wide orientation of nodal planes, show predominantly normal faulting throughout Madagascar, and provide no evidence for a sharp east-west striking plate boundary between the Lwandle and Somalian plates in the middle of the island. However, a diffuse plate boundary cannot be excluded. We suggest that topographically-generated extensional stresses is the cause of most seismicity, given that significantly fewer earthquakes are located in the lower elevation areas of the island compared to regions of higher elevations. The frequency-magnitude distribution has a b-value of ~1.2 and indicates that events with magnitude ML5 or greater should occur with an average repeat time of ~1.4 years. However, no earthquake exceeding ML6 has been recorded in the last century, suggesting that the frequency-magnitude distribution could be truncated.
AB - The seismicity and seismotectonics of Madagascar have been studied using an island-wide distribution of broadband seismic stations. The 28-station MAdagascar-COmoros-MOzambique (MACOMO) array was deployed for a 23-month period between 2011 and 2013. MACOMO data were supplemented by seven temporary stations from the Seismological Signatures in the Lithosphere/Asthenosphere system of Southern Madagascar (SELASOMA) project, ten temporary stations from the Réunion Hotspot and Upper Mantle - Réunions Unterer Mantel project (RHUM-RUM), and 11 permanent stations. A total of 695 earthquakes with magnitudes between ML1 and ML5.3 located within Madagascar were recorded, a new local magnitude scale was developed, and focal mechanisms were determined for 23 well-recorded events. Most of the seismicity is clustered within central Madagascar, forming NW-SE trends in the Ankaratra region and NE-SW trends in the Alaotra and Ankay regions that roughly align with extensional tectonic features. The northern and southern parts of Madagascar also show seismicity clusters that align parallel to existing tectonic features, primarily Precambrian shear zones. Focal mechanisms exhibit a wide orientation of nodal planes, show predominantly normal faulting throughout Madagascar, and provide no evidence for a sharp east-west striking plate boundary between the Lwandle and Somalian plates in the middle of the island. However, a diffuse plate boundary cannot be excluded. We suggest that topographically-generated extensional stresses is the cause of most seismicity, given that significantly fewer earthquakes are located in the lower elevation areas of the island compared to regions of higher elevations. The frequency-magnitude distribution has a b-value of ~1.2 and indicates that events with magnitude ML5 or greater should occur with an average repeat time of ~1.4 years. However, no earthquake exceeding ML6 has been recorded in the last century, suggesting that the frequency-magnitude distribution could be truncated.
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U2 - 10.1016/j.tecto.2020.228547
DO - 10.1016/j.tecto.2020.228547
M3 - Article
AN - SCOPUS:85089083286
SN - 0040-1951
VL - 790
JO - Tectonophysics
JF - Tectonophysics
M1 - 228547
ER -