TY - JOUR
T1 - Shear velocity structure of the crust and upper mantle of Madagascar derived from surface wave tomography
AU - Pratt, Martin J.
AU - Wysession, Michael E.
AU - Aleqabi, Ghassan
AU - Wiens, Douglas A.
AU - Nyblade, Andrew A.
AU - Shore, Patrick
AU - Rambolamanana, Gérard
AU - Andriampenomanana, Fenitra
AU - Rakotondraibe, Tsiriandrimanana
AU - Tucker, Robert D.
AU - Barruol, Guilhem
AU - Rindraharisaona, Elisa
N1 - Funding Information:
We thank Peter Shearer, Nathan Simmons and one anonymous reviewer for providing productive comments that helped improve this manuscript. We would like to acknowledge the IRIS/PASSCAL instrument center for providing instrumentation for the MACOMO project. The Missouri Botanical Gardens provided invaluable guidance regarding site selection and security. Thanks also go to Frederik Tilmann and Karin Sigloch for providing additional datasets and comments, and to Franklin Koch for help deploying stations. Funding for the MACOMO project was provided by NSF award EAR-0838426 . RHUM-RUM seismological deployments were supported by the French CNRS-INSU (Institut National des Sciences de l'Univers), program SYSTER, by the CNRS-INEE (Institut National Ecologie et Environnement), the TAAF (Terres Australes et Antarctiques Françaises), by the French ANR (Agence Nationale de la Recherche, project ANR-11-BS56-0013 ), and by the DFG (Deutsche Forschungsgemeinschaft) grant SI1538/2-1 RHUM-RUM in Germany. RHUM-RUM equipments were provided by the Alfred Wegener Institut (AWI) in Bremerhaven, Germany, and by RESIF-SISMOB in Grenoble, France.
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2017/1/15
Y1 - 2017/1/15
N2 - The crust and upper mantle of the Madagascar continental fragment remained largely unexplored until a series of recent broadband seismic experiments. An island-wide deployment of broadband seismic instruments has allowed the first study of phase velocity variations, derived from surface waves, across the entire island. Late Cenozoic alkaline intraplate volcanism has occurred in three separate regions of Madagascar (north, central and southwest), with the north and central volcanism active until <1 Ma, but the sources of which remains uncertain. Combined analysis of three complementary surface wave methods (ambient noise, Rayleigh wave cross-correlations, and two-plane-wave) illuminate the upper mantle down to depths of 150 km. The phase-velocity measurements from the three methods for periods of 8–182 s are combined at each node and interpolated to generate the first 3-D shear-velocity model for sub-Madagascar velocity structure. Shallow (upper 10 km) low-shear-velocity regions correlate well with sedimentary basins along the west coast. Upper mantle low-shear-velocity zones that extend to at least 150 km deep underlie the north and central regions of recent alkali magmatism. These anomalies appear distinct at depths <100 km, suggesting that any connection between the zones lies at depths greater than the resolution of surface-wave tomography. An additional low-shear velocity anomaly is also identified at depths 50–150 km beneath the southwest region of intraplate volcanism. We interpret these three low-velocity regions as upwelling asthenosphere beneath the island, producing high-elevation topography and relatively low-volume magmatism.
AB - The crust and upper mantle of the Madagascar continental fragment remained largely unexplored until a series of recent broadband seismic experiments. An island-wide deployment of broadband seismic instruments has allowed the first study of phase velocity variations, derived from surface waves, across the entire island. Late Cenozoic alkaline intraplate volcanism has occurred in three separate regions of Madagascar (north, central and southwest), with the north and central volcanism active until <1 Ma, but the sources of which remains uncertain. Combined analysis of three complementary surface wave methods (ambient noise, Rayleigh wave cross-correlations, and two-plane-wave) illuminate the upper mantle down to depths of 150 km. The phase-velocity measurements from the three methods for periods of 8–182 s are combined at each node and interpolated to generate the first 3-D shear-velocity model for sub-Madagascar velocity structure. Shallow (upper 10 km) low-shear-velocity regions correlate well with sedimentary basins along the west coast. Upper mantle low-shear-velocity zones that extend to at least 150 km deep underlie the north and central regions of recent alkali magmatism. These anomalies appear distinct at depths <100 km, suggesting that any connection between the zones lies at depths greater than the resolution of surface-wave tomography. An additional low-shear velocity anomaly is also identified at depths 50–150 km beneath the southwest region of intraplate volcanism. We interpret these three low-velocity regions as upwelling asthenosphere beneath the island, producing high-elevation topography and relatively low-volume magmatism.
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U2 - 10.1016/j.epsl.2016.10.041
DO - 10.1016/j.epsl.2016.10.041
M3 - Article
AN - SCOPUS:85003721954
VL - 458
SP - 405
EP - 417
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
ER -