Electrical resistivity tomography combined with seismic data estimates heterogeneous distribution of near-seafloor concentrated gas hydrates within gas chimneys

Abstract

Near-seafloor concentrated gas hydrates (GHs) containing large amounts of methane have been identified at various gas chimney sites. Although understanding the spatial distribution of GHs is fundamental for assessing their dissociation impact on aggravating global warming and resource potential, the spatial distribution of GHs within gas chimneys remains unclear. Here, we estimate the subseafloor distribution of GHs at a gas chimney site in the Japan Sea using marine electrical resistivity tomography data. The resulting two-dimensional subseafloor resistivity structure shows high anomalies (10–100 Ωm) within seismically inferred gas chimneys. As the resistivity anomalies are aligned with high amplitude seismic reflections and core positions recovering GHs, we interpret the resistivity anomalies are near-seafloor concentrated GH deposits. We also detect various distribution patterns of the high resistivity anomalies including 100-m wide and 40-m thick anomaly near the seafloor and 500-m wide anomaly buried 50 m below the seafloor, suggesting that GHs are heterogeneously distributed. Therefore, considering such heterogeneous GH distribution within gas chimneys is critical for in-depth assessments of GH environmental impacts and energy resources.