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The present paper gives a scale of earthquake energy class KF that is to standardize the relevant data based on the existing scales: MS, MW, mb, KS, among many others. The conceptual novelty of the scale we propose consists in shifting the emphasis from seismometric issues that are traditional in such cases, which are concerned with the recording of seismic waves, as well as with issues arising in discussions of their generation and propagation, toward an effective use of basic energy properties of the seismic process (the Gutenberg–Richter law). In the most general case, this approach can significantly simplify the development of regression relations between different earthquake size scales, but the most promising problem consists in developing a single generalized scale. A particular solution of the problem is presented as the development of such a scale for earthquakes of Kamchatka. The KF scale rests on the energy class proposed by S.A. Fedotov (KS at the Kamchatka Branch (KB) of the National Seismological Centre, Geophysical Survey, Russian Academy of Sciences (NSC GS RAS) and on the generally accepted mb magnitude (ISC). [ABSTRACT FROM AUTHOR]

This paper describes the behavior of several seismic precursors prior to the 2016–2019 activation in an area of a complex geodynamic setting at the boundary of the Pacific, North American, and Eurasian plates. We used an integrated approach to combine identified precursors with a view to getting more accurate locations of possible rupture zones of future large earthquakes. The precursors include quiescence based on the RTL parameter and the "Z-function", variations in the slope of the earthquake recurrence graph (γ-value), and the areas of seismic ruptures dS. For the first time in Kamchatka, we analyze anomalies in the parameter dS interpreted as seismic activations to show the presence of a precursory component before the onset of the foreshock activation. Examples include increases in the values of that parameter before events that were the largest for the areas where they occurred: the Near-Islands Aleutian earthquake of July 17, 2017, Mw = 7.8 and the Uglovoe Podnyatie earthquake of December 20, 2018, Mw = 7.3. The overall extent of the anomalous area, which still exists and includes consecutive quiescence and foreshock phases, is ~900 km, which creates conditions for possible occurrence of a new great earthquake in the junction zone of the three plates with a magnitude that can exceed whatever has been recorded in the region so far. [ABSTRACT FROM AUTHOR]

This paper describes a method for calculating the earthquake energy class for the Kamchatka region from coda records in the 0.8–1.8 Hz frequency band. The method is based on an empirical correlative relationship between the coda level and the Fedotov earthquake class. The coda level is found as the mean power of the ground velocity in an interval of 30 s. Five seismic dipping zones have been identified in Kamchatka, each having its own expression for converting the coda level to the energy class. [ABSTRACT FROM AUTHOR]

Data on the stress–strain state of the Earth's crust obtained by precision observations were studied using strain-gage analysis based on the geometric theory of deformation. Ground-based optical distance observations were made on one of the geodynamic polygons in Petropavlovsk-Kamchatsky to calculate the major axes of compression and tension. Out of ten baselines, four variants of the strain-gauge rosette were taken to calculate the invariant characteristics of deformation from measured displacements of the Earth's surface. The strain-gage analysis of the observation results made it possible to determine the main deformations and calculate the angle between the dominant loading axis and the shortening axis. Two sources of impact were proposed as factors that specify the dominant loading axis: magmatism (nearby active volcanoes) and the subduction zone (the impact of the subducting Pacific Plate). Since the region is seismically active, the analysis involved strong (M > 5.5) earthquakes to identify a possible relationship between earthquakes and deformation characteristics. [ABSTRACT FROM AUTHOR]

The Vp/Vs kinematic parameter for the Kamchatka seismic subduction zone has been long monitored on a regular basis. This has allowed estimating the behavior of the parameter and revealing its features during the precursory period and actual rupturing of the March 25, 2020 earthquake which occurred in the Pacific plate at the contact between the Pacific plate and the continental slope of Kamchatka. The March 25, 2020 earthquake with its high magnitude (ML = 7.6, MW = 7.5) is a rare enough event to occur in the Pacific plate. Knowledge of earth structure in the source region of the earthquake was updated based on the results of deep seismic sounding and continuous seismic profiling which was carried out in the area in the past. It was shown that the earthquake source area is at an inflection in the descending Pacific plate. The source area lies in the layer at the boundary between the asthenosphere and the crust and mantle. The layer is at depths of 30‒60 km and has lower Vp and Vs velocities. The inflection region along Kamchatka shows lower Vp/Vs values, which is a sign of extension along the plate. The source area is in the contact between the Pacific plate, which is subducting under the southern end of Kamchatka, and the North Kuril Islands, as well as the Sea-of-Okhotsk plate. The region shows a distinct change in the anomalous values of the parameter from lower to higher, with the latter being typical for compression. Our study has allowed estimating possible regions of tension and compression in the geological medium. [ABSTRACT FROM AUTHOR]

The characteristics of the distributions of the time differences occurrence of the consecutive earthquakes in the Kuril-Kamchatka zone, including the Hokkaido Island area, have been investigated in various magnitude ranges. For the purpose of the analysis, we used the data from the regional and world earthquake catalogs for the last 20 years. As a result of this analysis, a new intermediate-term precursor effect has been found: a quiescence period observed prior to the strongest earthquakes. This precursor manifests itself in the form of the long-term (2-6 months) absence of events with M ≥ 5.5 within the territory. For the predictive purposes, it was proposed to replace the quiescence period by such a more stable parameter as the sum of the three longest intervals between the earthquakes with M ≥ 5.0 in a sliding time window. The prognostic informativeness of this parameter has been assessed. [ABSTRACT FROM AUTHOR]