Vol 13, No 6 (2019)

This paper is concerned with results from ongoing work using the method of long-term earthquake prediction (LTEP) for the Kuril–Kamchatka island arc based on the seismic gap and seismic cycle patterns. We highlight the most important lines of research in the LTEP method during the preceding decade. A long-term forecast is provided using the basic method for the next 5 years, June 2019 through May 2024, for the most active part of the earthquake-generating zone in the region. The 20 segments of that zone have forecasts for the next 5 years, including the phases of the seismic cycle, the normalized rate of low-magnitude earthquakes (А₁₀), the magnitudes of moderate-size earthquakes that are expected to occur with probabilities of 0.8, 0.5, and 0.15, the maximum expected magnitudes and probabilities of great (М ≥ 7.7) earthquakes. This study continues the well-known work of S.A. Fedotov by examining space–time features of the regional seismic process for the period beginning 2017, including the great Near Islands (Aleutian) earthquake of July 17, 2017, M = 7.7. The results, as obtained here, corroborate a close relationship between the seismic process occurring in the segments that pose the highest earthquake hazard according to the LTEP and the great earthquakes in the region itself and in the adjacent seismic areas, as well as emphasizing a very high earthquake hazard for several areas at the Kuril–Kamchatka island arc; Thus it is necessary to continue and expand the ongoing work in earthquake strengthening and enhancing the level of seismic safety in those areas under the highest hazard, including the administrative center of Kamchatka Krai, the town of Petropavlovsk-Kamchatsky.

The explosive atmospheric electrogenic paragenesis we studied was found to contain over 100 mineral species, varieties, and non-crystalline phases (carbonaceous minerals, phases and compounds, native metals and alloys, carbides, silicides, nitrides, halides, chalcogenides, oxides, silicates and alumosilicates, and oxysalts. The paragenesis is characterized by an abnormally low level of mineralogical organization, which indicates a deep origin of the material in the explosive facies of volcanic eruptions, including carbonaceous minerals, phases, and organic compounds.

An analysis of deep structure for the East Greenland margin (Blosseville Kyst – Liverpool Land) and the Jan Mayen microcontinent yielded a common crustal model for the time before their dispersal. The joint model presents a visual picture of the net result from the Paleozoic, Mesozoic, and Cenozoic rifting phases. Beginning from the Devonian, a graben-like depression approximately 180 km wide has existed between Liverpool Land and the Jan Mayen Ridge. The depression resulted from downwarping of the crystalline basement that was not compensated by sedimentation. The sea basin was approximately 2 km deep at the end of the Devonian. The joint deep crustal section (from west to east) clearly shows three depths to the top of the upper mantle that can be fitted by dome-like surfaces superposed on one another. We interpret these surfaces as temperature fronts resulting from the formation of mantle plumes that took place during different epochs (Paleozoic, Mesozoic–Cenozoic, and Late Cenozoic). A basement high was identified beneath the edge of the present-day Blosseville Kyst and Liverpool Land shelf; the high correlates with the axis of a positive free-air gravity anomaly. East of the high, a continent–ocean boundary is tentatively identified along the axis of the anomaly. The present-day phase in the geological evolution of the Greenland–Norwegian region north of Iceland is characterized by a higher thermal state of the lithosphere and by intraplate tectonic occurrences.