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Russian Geology and Geophysics

2018 year, number 9

FORMATION OF METHANE CONCENTRATION AND ELECTROMAGNETIC-FIELD ANOMALIES IN SOUTHWESTERN PETER THE GREAT GULF (Sea of Japan)

B.A. Burov, A.I. Obzhirov, A.I. Gresov, A.S. Salomatin, E.V. Maltseva, Yu. A. Telegin, I.G. Yugai, A.V. Yatsuk
V.V. Ilichev Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, ul. Baltiiskaya 43, Vladivostok, 690041, Russia
Keywords: Free methane in the pore space of bottom sediments, methane seep, electrical conductivity of bottom sediments, Schumanns resonances in the Earths natural electric field

Abstract

We report methane concentrations in the bottom water layer and the upper layer of bottom sediments and the results of acoustic explorations of methane seeps on the shelf bordering the continental slope of the Sea of Japan region, in which electromagnetic Schumanns resonance oscillations were earlier recorded at continental-slope water depths of 500, 1000, and 2000 m. The occurrence of Schumanns resonances at such great depths is explained by an increase (a factor of more than 25) in the electrical resistivity of a ~2000 m thick sediment layer with the pore space largely filled with free methane. A new method is proposed for determining the depth of the sources of anomalous concentrations of methane in bottom sediments or in the bottom water layer on a deep shelf. The method is based on recording Schumanns resonances during measurements of the natural electric field at a series of increasing depths in areas bordering the continental slope.