Here we report the discovery of cold-seep ecosystem and shallow methane hydrates (2-3 mbsf) associated with methane gas flares in the water column from the Indian EEZ for the first time. The seep-sites are located in the Krishna-Godavari (K-G) basin at water depths of 900-1800 m and are characterized by gas flares in the water-column images. The occurrence of methane gas hydrates at very shallow depths (2-3 mbsf) at some of the seep-sites is attributed to high methane flux and conducive P-T conditions, necessary for the stability of methane hydrate. Chemosymbiont bearing Bivalves (Vesicomidae, Mytilidae, Thyasiridae and Solemyidae families); Polychaetes (Siboglinidae family) and Gastropods (Provannidae family) are also identified from seep-sites.
We observed a harmonic noise (HN) in DEutscher Geräte-Pool für Amphibische Seismologie ocean-bottom seismometers (OBSs) data recorded from the Andaman–Nicobar region. The HN is characterized by sharp spectral peaks with a fundamental frequency and several overtones occurring at integer multiples of the fundamental frequency. We used an automated algorithm to quantify the occurrence of HN for the entire four-month deployment period (1 January 2014 to 30 April 2014). The algorithm detected more than 23 days of HN for some OBS stations. The spectral analysis of the hourly count of HN shows distinct lunar and solar tidal periodicities at 4.14, 6.1, 6.22, 12, and 12.4 hr as well as 13.66 days. The observed periodicities provide evidence of tidal triggering of HN. The HN is generated by the strumming of head buoys due to seafloor currents initiated by oceanic tides in the Andaman–Nicobar region.
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