Vol 13, No 4 (2019)

The edifices of many active volcanoes on the Kuril Islands contain hydrothermal systems whose surface manifestations include springs with diversity in their chemical compositions and in their physical and chemical parameters. Thermal waters of Kuril Islands were found to exhibit four main isotopic shifts relative to the local meteoric water line. The ultra-acid Cl–SO₄ (SO₄–Cl) waters show a mixing trend between the meteoric component and volcanic steam. Acid steam-heated SO₄ waters demonstrate trends indicating kinetic fractionation at temperatures near the boiling point. The isotope compositions for coastal springs plot at the line of mixing between meteoric and sea water. The oxygen isotope shift for the thermal waters that from geothermal wells is formed by isotope exchange with the host rock. The latitude effect detected in the isotope composition of meteoric water is also seen to varying degrees in the isotope composition of thermal water.

This paper provides information on the structure, chemical composition, and concentrations of microelements in ferromanganese crusts and siliceous crusts sampled on the Pervenets Rise, Sea of Japan. The crusts were formed by cementation of small fragments of green clays (celadonite) by manganese hydroxides (todorokite and birnessite) or by silica. The primary process involved the generation of celadonite, which was deposited as ore-bearing hydrothermal brine that was discharged in the caldera of the volcano or on its slopes. The crusts have a structure that indicates their formation during diffuse percolation of gas-charged hydrothermal brine along fissures or weakened zones in volcanic rocks and subsequent cementation of the resulting celadonite deposits with manganese or siliceous oxides. The manganese and the siliceous mineralization are separated over time, as well as, frequently, in space, and are more local.

This paper reviews high precision measurements of distances by geodimeters and elevations by first-order leveling between permanent geodetic monuments in local strain measurement patches on the coast of the Avacha Bay in order to detect strain precursors of a probable large (М > 7.0) near earthquake and to obtain quantitative characteristics of coseismic strain. We report the results of all 1984–1995 measurements in tabular form. These data are necessary for future researchers, since the extant monuments (benchmarks) can be surveyed in the future using any precision methods, to compare with the past results to derive objective inferences. No significant changes (those in excess of the double uncertainty) in elevations and distances between geodetic monuments have occurred. The large (М = 6.8) earthquake of March 2, 1992 whose epicenter was in the Avacha Bay did not give rise to any strain; no coseismic strain has been observed either. They may still have occurred, but the sensitivity of the method and the considerable distance between the strain measurement patches and the earthquake epicenter prevented detection.