Formation of methane concentration and electromagnetic-field anomalies in southwestern Peter the Great Gulf (Sea of Japan)

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 Schumann’s resonance oscillations were earlier recorded at continental-slope water depths of 500, 1000, and 2000 m. The occurrence of Schumann’s 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 Schumann’s resonances during measurements of the natural electric field at a series of increasing depths in areas bordering the continental slope.