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Work was performed in 2008-2014 on the long-term prediction of great earthquakes at the Kuril-Kamchatka arc based on patterns that are observable in the locations of the rupture zones of great earthquakes (seismic gaps) and in the seismic cycle for such earthquakes. The prediction method has been successfully developed and applied to the region since 1965 (the LTEP method). This paper presents a long-term seismic forecast for the September 2013 to August 2018 period for the Kuril-Kamchatka arc earthquake-generating zone. The forecast predicts the following quantities for 20 constituent segments: phases of the seismic cycle, the normalized rate of small earthquakes A, the magnitudes of moderate-size earthquakes to be expected with probabilities 0.8, 0.5, and 0.15, the maximum possible magnitudes and probabilities of occurrence for great (M ≥ 7.7) earthquakes in the most active depth interval, viz., 0-80 km. We also discuss the seismic process in this region for the 2008-2013 period, namely, the patterns that are observable in the locations of earthquake swarms, the values of and changes in several characteristics of the seismic process in the Kuril-Kamchatka seismic zone during the period 2008-2013, which occurred in relation with great shallow earthquakes beneath the Sea of Okhotsk (July 5, 2008, M = 7.7; August 14, 2012, M = 7.7; May 24, 2013, M = 8.3, and the giant Tohoku earthquake of March 11, 2011 with M = 9.0). The results corroborate the high seismic hazard for the area of Petropavlovsk-Kamchatskii and the urgent necessity of continuing and intensifying the ongoing work on seismic retrofitting and seismic safety. [ABSTRACT FROM AUTHOR]

This paper presents results from a study of variations in short-period shear-wave attenuation in the lithosphere of the Baikal Rift Zone (BRZ). We used earthquake records made at the Ulan-Bator station (ULN) at epicentral distances of ∼400-1300 km. The ratios of maximum amplitudes in the Sn and Pn waves were considered. We show that these ratios are on the whole considerably higher than those in other areas of Central Asia. It was found that zones of low shear wave attenuation coincide with the rupture zones of large earthquakes that occurred during the 19th and 20th centuries. We identified zones of high attenuation where no large (M∼ > 7.0) seismic events have occurred during at least 180 years. The hypothesis we propose is that precursory processes before future large earthquakes may be occurring in these zones. We discuss the question of whether wave attenuation characteristics may be related to seismicity. [ABSTRACT FROM AUTHOR]

The area of western Transbaikalia is characterized by moderate seismic activity. Nevertheless, there is historical and instrumental evidence to show that rather strong seismic events have occurred in the area and caused considerable material damage to the population centers around their epicenters. Seismological knowledge of the region is scant. The earthquake catalogs for the area and for the historical period of time need to be corrected and supplemented. The present paper considers the earthquake of October 9, 1864, which has not been included in any parametric catalog thus far. New primary data that were found in the regional periodic press were used to determine the epicenter and magnitude (M = 5.1) for the event. The earthquake of October 9, 1864 is a 'forgotten' event, but is a significant addition to the catalog for western Transbaikalia. The materials presented here can be used to assess earthquake hazard for the area, as well as to aid in the search for other unknown or 'forgotten' earthquakes. [ABSTRACT FROM AUTHOR]

The conducted paleoseismological and archaeoseismological studies reveal three zones of concentration of the ancient and historical earthquakes in Gorny Altai which are related to the Kurai Fault zone, Katun, and South Terekta faults. The surface ruptures are detected within the Kurai Fault zone, which were formed in the epicentral zones of the paleoearthquakes that occurred 6500, 5800, 3200, and 1300 years ago and had magnitudes Mw = 6.7–7.6. The recurrence period of the paleoearthquakes is 700 to 2600 years. The detected secondary seismogenic deformations indicate that an epicentral zone of the paleoearthquake with an age of less than 12.5 ka (Mw = 7.2–7.6, intensity I = 10–11), the traces of earthquakes and their clusters with M ≥ 5–5.5 and I ≥ 6–7, which occurred about 150 and 90 ka ago, in the intervals of 38–19 ka ago (with a recurrence period of about 2 ka), and 19–12.5 ka ago are related to the southern part of the Katun Fault. The earthquake of I ≥ 5–6 which damaged the constructions of the Chultukov Log 1 burial mound in the period from IV century B.C. to the beginning of I century A.D. is associated with the northern part of the Katun Fault. In the zone of the South Terekhta Fault, the seismogenic displacements that occurred in VII–VIII centuries A.D. (Mw = 7.4–7.7, I = 9–11) and about 16 ka ago (M ≥ 7, I = 9–10) are revealed. The latter triggered the formation of a landslide-dammed lake which was destroyed by the earthquake about 6 ka ago (M ≥ 7, I = 9–10). Secondary paleoseismic deformations of the ancient earthquakes (M ≥ 5–5.5, I ≥ 6–7) are recorded in the sediments of the Uimon Basin with an age of 100–90 ka and about 77 ka. These results should be taken into account in designing a gas pipeline in the People's Republic of China, building infrastructure for tourism, and elaborating the seismic zoning maps for the territory of the Russian Federation. [ABSTRACT FROM AUTHOR]

The evolution of scientific views on the structure of the sources of strong earthquakes at the end of the 20th and beginning of the 21th century in Russia is considered. The lack of a clear, consistent understanding of the structure of sources of the strongest seismic events was initially typical of the scientific concepts that emerged in the main developed countries. In the 1950s, at the Schmidt Institute of Physics of the Earth of the USSR Academy of Sciences, G.A. Gamburtsev formulated a hypothesis about the stability of the seismic regime of a system of seismic sutures over a long period of time (a few hundred years). The seismic sources of the recently studied earthquakes are located in the regions of large faults. With the increase in magnitude, they become more extended and structurally complex. In the considered cases, there are sources that are relatively simply to reconstruct, which encompass the fault planes of the large existing faults (Spitak source, M = 6.8), as well as sources that are more complex, formed in the disjunctive nodes, or those that encompass the crustal blocks. For example, the seismic source of the Altai earthquake (M = 7.3) is characterized by a volumetric structure and is developed along the boundaries of the large seismogenic blocks. The source of the Wenchuan earthquake (M = 7.9) is most complicated. It appears as a three-dimensional (3D) structure composed of a few crustal blocks framed by two extended northeast striking faults and separated by a transverse fault of the northwestern orientation. The sources having a different focal structure differently manifest themselves in the structure of seismic dislocations on the surface and in the distribution of aftershock hypocenters at depth. The anomalously low velocity "pockets" that were identified by the method of local seismic tomography in the source areas of the Spitak and Altai earthquakes and that accompany the main and secondary faults at depth are likely to be the zones of the dynamic influence of these faults. The damaged near-fault zones, with abundant cracks and fractures, are the severely destroyed inclusions in the crustal rocks, and they hamper the propagation of seismic waves. Therefore, within these pockets, the P-waves propagate at a lower velocity than the undamaged geological medium. The results of the paleoseismological study of seismic faults in the trenches showed that strong earthquakes also occurred in the same sources in the past, and the period of recurrence of the strongest seismic events ranges from a few hundred to the first thousand years. Thus, the integrated studies of the source zones of the strongest earthquakes that were conducted in the past decades in different regions of Eurasia have shown that the hypothesis of Gamburtsev has remained relevant. [ABSTRACT FROM AUTHOR]

This report continues a series of works by the authors on earthquake-prone areas recognition by the algorithmic system FCAZ. For the first time, successive earthquake-prone areas recognition for several magnitude thresholds in the same seismic region is conducted. This can be done by iteratively narrowing the set of recognition objects of the FCAZ system. Earthquake-prone areas for a given magnitude threshold are recognized within zones already recognized as dangerous for a smaller threshold magnitude. The reproducibility of the study is ensured by the fact that at all stages the recognition algorithm remains unchanged. Earthquakeprone areas with magnitude thresholds of М ≥ 5.5, М ≥ 5.75, and М ≥ 6.0 in the Baikal-Transbaikal region are studied successively. [ABSTRACT FROM AUTHOR]

The stress state of the Earth's crust in the region of the Chuya earthquake of 2003 (Gorny Altay) is studied using the data of long-term epicentral observations by dense networks of temporary stations. These data comprise 545 seismic events, which widely vary in energies and whose parameters are determined highly accurately. Two hierarchical levels of the stress field are revealed and their spatial structure and temporal behavior are investigated. It is shown that the subregional stress field, which is determined from the data on strong earthquakes, is predominantly stable across the studied area, where the regime of horizontal shear with submeridional orientation of principal pressure axes is observed. The local stress field calculated from the weak seismic events experiences regular variations, which are consistent with the block structure of the crust; this field is heightand time-dependent. [ABSTRACT FROM AUTHOR]

To estimate seismic hazard, the basic law of seismicity, the Gutenberg-Richter recurrence relation, is applied in a modified form involving a spatial term: $$\log N\left( {M,\;L} \right) = A - B\left( {M - 5} \right) + C\log L$$ , where N( M,L) is the expected annual number of earthquakes of a certain magnitude M within an area of linear size L. The parameters A, B, and C of this Unified Scaling Law for Earthquakes (USLE) in the Himalayas and surrounding regions have been studied on the basis of a variable space and time-scale approach. The observed temporal variability of the A, B, and C coefficients indicates significant changes of seismic activity at the time scales of a few decades. At global scale, the value of A ranges mainly between −1.0 and 0.5, which determines the average rate of earthquakes that accordingly differs by a factor of 30 or more. The value of B concentrates about 0.9 ranging from under 0.6 to above 1.1, while the fractal dimension of the local seismic prone setting, C, changes from 0.5 to 1.4 and larger. For Himalayan region, the values of A, B, and C have been estimated mainly ranging from −1.6 to −1.0, from 0.8 to 1.3, and from 1.0 to 1.4, respectively. We have used the deterministic approach to map the local value of the expected peak ground acceleration (PGA) from the USLE estimated maximum magnitude or, if reliable estimation was not possible, from the observed maximum magnitude during 1900-2012. In result, the seismic hazard map of the Himalayas with spatially distributed PGA was prepared. Further, an attempt is made to generate a series of the earthquake risk maps of the region based on the population density exposed to the seismic hazard. [ABSTRACT FROM AUTHOR]

The spatial-temporal distributions of earthquakes in the Kuril-Okhotsk region were analyzed. The events with Ms ≥ 4 from 1980 until 2009 and Ms ≥ 7 from 1910 until 2009 (20576 and 76 earthquakes, respectively) were studied. The specially developed program complex allowed us to obtain the 4-D distribution of the seismic events (along the sections, depths, temporal intervals, and energetic levels). It was shown that the seismic events obviously tend to cluster both along the surface and depth directions. The spatial-temporal analysis of the events (with Ms ≥ 4) in six five-year intervals from 1980 until 2009 has revealed a cyclic increase and decrease in the seismic activity in different time intervals and its cyclic migration from the South through the Central to the North Kuriles and back. The analysis of the strong events with Ms ≥ 7 in twenty 5-year intervals during 1910-2009 has shown that their amount significantly decreased for the last 30 years and the location of the hypocenter depths also changed (only shallow-focus earthquakes have been observed since 1975). The peaks of the seismic activity (1915-1919, 1955-1969, and 2005-2009) are separated by 35-year periods of its decrease. [ABSTRACT FROM AUTHOR]

The results of the instrumental and macroseismic studies are reported for the tangible earthquake with intensity of up to 5-6 and amplitude of MLH = 4.8 that occurred near the western coast of Sakhalin Island. The main parameters of the Kostromskoe earthquake have been estimated in two versions: (1) based on the data from the local network of digital stations located in southern Sakhalin, and (2) from the complex of local, regional, and global observations. It has been noted that the development of the local network in southern Sakhalin allowed the seismic regime in the earthquake area to be investigated in more detail and the mechanisms of both the individual weak and group events to be derived. The acquired data on the dislocation style of the main shock and aftershocks in the days following the event were used for the geological-tectonic interpretation of the Kostromskoe earthquake. [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]

The article presents a study which examines the earthquakes distribution according to their type of motions in the Kuril-Okhotsk region in Russia and the mechanisms of earthquake sources. The study uses data from the GlobalCMT catalogue to analyze the earthquake epicenters and evaluates distribution using the three vertical projections of earthquake sources by the direction orthogonal to the Kuril-Kamchatka arc position. Result shows that earthquake sources mechanism are at depths of up to 80 kilometers (km) in the southeastern part of the regions considered close to ocean. The analysis of the epicenter locations normal to the seismic focal zone (SFZ) reveals three zones from east to west, to which faults are found.