During the geological survey and prospecting, helium and hydrogen are recognized indicators of minerals, deep-seated faults, seismic activity, and ascending deep fluids. Their anomalous concentrations also serve as a marker of metamorphic processes. Helium survey is applied for tracing deep-seated faults and mapping permeable zones. In this work, the first results of gas geochemical survey in marine sediments and water to study the distribution of helium and hydrogen and their relation with the seismic activity of some geological structures in the southwestern Sea of Okhotsk and northern Sea of Japan. Anomalies of these gases (He up to 60 ppm, H up to 120 ppm) were identified in the hydrate-bearing sediments in the fault zones. It was also found that helium concentrations in the water column of the Tatar Strait are higher than in the studied area of the Sea of Okhotsk, possibly, due to the difference in geological structure and seismotectonic activation. Moreover, coal layers could be a significant source of methane in the gashydrate-bearing layers of the Tatar Strait.

The Red River delta with an area of about 12 620 km² is one of the largest deltas of Viet Nam and it also is one of the remarkable deltas of Asia. The delta was formed during the Holocene, mainly from 9000 years ago to the present. The Red River delta belongs to the NW tip of the large tertiary basin that is the Red River basin (Song Hong basin). The NW tip of the Red River basin presents as Ha Noi graben, which is controlled by the Chay River fault in the SW and the Lo River fault in the NW. Both faults are belonging to the regional Red River fault zone that is a boundary between the South China block and the Indochina blocks. The Red River delta was formed on the top of tectonic active area. Due to tectonic activity the Red River bed is differentiated and revealed as in-uniform distribution of the Quaternary sediments. Evolution of the Red River delta has been closely connected with the Pliocene‒Quaternary tectonics, specifically during transgression period after the last glacial maximum. The submarine area advanced along the NE and SW subsidence zones of the Red River delta area and created two remarkable lagoons, meanwhile the central part it had resisted transgression process and created a protrusive zone. Our study recognized that there were at least two tectonic movements occurred in the region since the Late Miocene, after a cessation of left-lateral strike slip of the Red River fault zone: those are NE‒SW compression and then NE‒SW extension under the general right-lateral strike slip of the Red River Fault Zone.

Two major groups of the lithosphere sources of methane are distinguished, i.e., the lithosphere sources proper (metamorphism, and serpentinization and spreading zones) and organic fuel deposits in the Earth’s crust. Hydrocarbon deposits, mud volcanoes, geothermal systems, and mineral sources are located on Sakhalin Island. All investigated objects are associated with large tectonic faults: the Yuzhno-Sakhalinsky and Main Pugachiovsky mud volcanoes are controlled by the Central Sakhalin fault; the Shakhterskoe coal deposit is confined to the West Sakhalin fault, while the Daginskaya geothermal system and the studied oil- and-gas fields are associated with the Hokkaido-Sakhalin fault. The authors’ studies of natural gases allow allocating two basic zones on the Sakhalin island with different types of hydrocarbon-carbon dioxide sources: Oil-and-gas (mostly methane; north-east) area and Coal-Gas area (carbon-dioxide-methane; west, south-west). Those areas differ in both chemical and isotope composition of natural gases. Some gashazardous areas have also been identified along tectonic faults, where they are due to gas release on the land surface. The populated localities on Sakhalin are shown to be situated near fault zones; therefore, the problem of gas hazard control is of critical importance.

This paper reports on the heaviest submarine fluxes of natural gas bubbles (flares) that have occurred in the Sea of Okhotsk, the Laptev Sea, and Lake Baikal. It has been concluded that there is a “ga