FN Archimer Export Format PT J TI Ambient noise Rayleigh wave tomography across the Madagascar island BT AF Adimah, N I Padhy, S AS 1:1,2;2:1,2; FF 1:;2:; C1 Seismological Observatory, National Geophysical Research Institute (Council of Scientific and Industrial Research), Uppal Road, Hyderabad-500007, India Academy of Scientific and Innovative Research (AcSIR), AcSIR Headquarters CSIR-HRDC Campus, Postal Staff College Area, Sector 19, Kamla Nehru Nagar, Ghaziabad-201002, India C2 CSIR (INDIA), INDIA ACSIR, INDIA IF 2.574 TC 5 UR https://archimer.ifremer.fr/doc/00600/71184/69539.pdf https://archimer.ifremer.fr/doc/00600/71184/69540.pdf LA English DT Article CR MD 192 / RHUM-RUM BO Marion Dufresne DE ;Seismic tomography;Africa;Crustal structure;Surface waves and free oscillations;Seismic noise AB The unusual complex lithospheric structure of Madagascar is a product of a number of important geological events, including: the Pan-African Orogeny, episodes of Late Cenozoic intraplate volcanism and several phases of deformation and metamorphism. Despite this rich history, its detailed crustal structure remains largely underexplored. Here, we take advantage of the recently obtained data set of the RHUM-RUM (Réunion Hotspot and Upper Mantle–Réunions Unterer Mantel) seismological experiment, in addition to previously available data sets to generate the first Rayleigh wave group velocity maps across the entire island at periods between 5 and 30 s using the ambient noise tomography technique. Prior to preliminary data preparation, data from Ocean Bottom Seismometers are cleaned of compliance and tilt noise. Cross-correlating noise records yielded over 1900 Rayleigh wave cross-correlation functions from which group velocities were measured to perform surface wave tomography. Dispersion curves extracted from group velocity tomographic maps are inverted to compute a 3-D shear velocity model of the region. Our velocity maps have shown relative improvement in imaging the three sedimentary basins in the western third of the island compared to those of previous studies. The Morondava basin southwest of the island is the broadest and contains the thickest sedimentary rocks while the Antsirinana basin at the northern tip is narrowest and thinnest. The lithosphere beneath the island is characterized by a heterogeneous crust which appears thickest at the centre but thins away towards the margins. A combined effect of uneven erosion of the crust and rifting accommodates our observations along the east coast. Average 1-D shear velocity models in six different tectonic units, support the causes of low velocity zones observed in the west coast of the island and reveal an intermediate-to-felsic Precambrian upper and middle crust consistent with findings of previous seismic studies. Our findings, especially at short periods provide new constraints on shallow crustal structure of the main island region. PY 2020 PD MAR SO Geophysical Journal International SN 0956-540X PU Oxford University Press (OUP) VL 220 IS 3 UT 000525944600015 BP 1657 EP 1676 DI 10.1093/gji/ggz542 ID 71184 ER EF