FN Archimer Export Format PT J TI Tomography of crust and lithosphere in the western Indian Ocean from noise cross-correlations of land and ocean bottom seismometers BT AF HABLE, Sarah SIGLOCH, Karin STUTZMANN, Eleonore KISELEV, Sergey BARRUOL, Guilhem AS 1:1;2:2;3:3;4:4;5:3; FF 1:;2:;3:;4:;5:; C1 Department of Earth- and Environmental Sciences, Ludwig-Maximilians-University, Munich, Germany Department of Earth Sciences, University of Oxford, Oxford, United Kingdom Institut de Physique du Globe de Paris, Sorbonne Paris Cite, Universite Paris Diderot, UMR 7154 CNRS, 75005 Paris, France Institute of Physics of the Earth, Moscow, Russia C2 UNIV MUNICH, GERMANY UNIV OXFORD, UK IPGP, FRANCE RUSSIAN ACAD SCI, RUSSIA IF 2.574 TC 19 UR https://archimer.ifremer.fr/doc/00508/61988/66099.pdf https://archimer.ifremer.fr/doc/00508/61988/66101.zip LA English DT Article CR MD 192 / RHUM-RUM BO Marion Dufresne DE ;Crustal imaging;Seismic instruments;Seismic interferometry;Seismic noise;Seismic tomography AB We use seismic noise cross-correlations to obtain a 3-D tomography model of SV-wave velocities beneath the western Indian Ocean, in the depth range of the oceanic crust and uppermost mantle. The study area covers 2000×2000 km2 between Madagascar and the three spreading ridges of the Indian Ocean, centred on the volcanic hotspot of La Réunion. We use seismograms from 38 ocean bottom seismometers (OBSs) deployed by the RHUM-RUM project and 10 island stations on La Réunion, Madagascar, Mauritius, Rodrigues, and Tromelin. Phase cross-correlations are calculated for 1119 OBS-to-OBS, land-to-OBS, and land-to-land station pairs, and a phase-weighted stacking algorithm yields robust group velocity measurements in the period range of 3-50 s. We demonstrate that OBS correlations across large interstation distances of >2000 km are of sufficiently high quality for large-scale tomography of ocean basins. Many OBSs yielded similarly good group velocity measurements as land stations. Besides Rayleigh waves, the noise correlations contain a low-velocity wave type propagating at 0.8-1.5 km/s over distances exceeding 1000 km, presumably Scholte waves travelling through seafloor sediments. The 100 highest-quality group velocity curves are selected for tomographic inversion at crustal and lithospheric depths. The inversion is executed jointly with a data set of longer-period, Rayleigh-wave phase and group velocity measurements from earthquakes, which had previously yielded a 3-D model of Indian Ocean lithosphere and asthenosphere. Robust resolution tests and plausible structural findings in the upper 30 km validate the use of noise-derived OBS correlations for adding crustal structure to earthquake-derived tomography of the oceanic mantle. Relative to crustal reference model CRUST1.0, our new shear-velocity model tends to enhance both slow and fast anomalies. It reveals slow anomalies at 20 km depth beneath La Réunion, Mauritius, Rodrigues Ridge, Madagascar Rise, and beneath the Central Indian spreading ridge. These structures can clearly be associated with increased crustal thickness and/or volcanic activity. Locally thickened crust beneath La Réunion and Mauritius is probably related to magmatic underplating by the hotspot. In addition, these islands are characterised by a thickened lithosphere that may reflect the depleted, dehydrated mantle regions from which the crustal melts where sourced. Our tomography model is available as electronic supplement. PY 2019 PD NOV SO Geophysical Journal International SN 0956-540X PU Oxford University Press (OUP) VL 219 IS 2 UT 000491050200013 BP 924 EP 944 DI 10.1093/gji/ggz333 ID 61988 ER EF