Seismicity and active accretion processes at the ultraslow-spreading Southwest and intermediate-spreading Southeast Indian ridges from hydroacoustic data

Type Article
Date 2016-08
Language English
Author(s) Tsang-Hin-Sun Eve1, 2, Royer Jean-YvesORCID1, 2, Perrot Julie1, 2
Affiliation(s) 1 : Univ Brest, Lab Domaines Ocean, Brest, France.
2 : CNRS, Lab Domaines Ocean, Brest, France.
Source Geophysical Journal International (0956-540X) (Oxford Univ Press), 2016-08 , Vol. 206 , N. 2 , P. 1232-1245
DOI 10.1093/gji/ggw201
WOS© Times Cited 9
Keyword(s) Seismicity and tectonics, Acoustic properties, Mid-ocean ridge processes, Indian Ocean
Abstract Volcanic and tectonic events are the main processes involved in the generation of the oceanic crust and responsible for the seismicity associated with seafloor spreading. To monitor this activity, usually not or poorly detected by land-based seismological stations, we deployed from February 2012 to February 2013 a network of autonomous hydrophones to compare the behaviour of the ultraslow-spreading Southwest (SWIR) with that of the intermediate-spreading Southeast Indian ridges (SEIR). The rate of seismicity is similar for both ridges, suggesting that there is no systematic relationship between seismicity and spreading rates. The along-axis distribution of the seismic events, however, does differ, reflecting the rate-dependence of accretion modes. Earthquakes are sparse and regularly spaced and scattered along the SWIR, reflecting prevailing tectonic processes. By contrast, along the SEIR, events are irregularly distributed and focus at ridge-segment ends and transforms faults, reflecting the ridge segmentation; only two swarms occurred at a segment centre and are probably caused by a magmatic event. This seismicity distribution thus looks controlled by segment-scale crustal heterogeneities along the SEIR and by regional-scale contrasting accretion processes along the SWIR, probably driven by different lithospheric and asthenospheric dynamics on either side of the Melville FZ. The comparison of hydroacoustic and teleseismic catalogues shows that, along these spreading ridges, the background seismicity observed in one year by a hydroacoustic network is representative of the seismicity observed over two decades by land-based networks.
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Tsang-Hin-Sun Eve, Royer Jean-Yves, Perrot Julie (2016). Seismicity and active accretion processes at the ultraslow-spreading Southwest and intermediate-spreading Southeast Indian ridges from hydroacoustic data. Geophysical Journal International, 206(2), 1232-1245. Publisher's official version : https://doi.org/10.1093/gji/ggw201 , Open Access version : https://archimer.ifremer.fr/doc/00340/45165/