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Materials on earthquakes in Samarkand and Ferhana regions (Republic of Uzbekistan) in 1868–1892 are presented based on original sources of information not used before. The epicenter location and magnitude for the earthquakes April 7, 1869, and March 2, 1892, are evaluated for the first time; for the other two earthquakes (April 3, 1868, and September 18, 1892), the uncertainty of previously published solutions is significantly reduced. Reduction of uncertainties of prior solutions is achieved owing to the formalized method of epicentral and magnitude assessment, which works successfully with sparse datasets. One of the restrictions on the entire set of solutions is association of the epicenter with certain active tectonic structures. This criterion is used only for selecting the preferable solution from the entire set of solutions obtained solely from macroseismic data. The complete set of solutions is retained and can be used to analyze the accuracy and objectivity of the preferable solution.

A method is proposed for calculating seismic hazard curves in a free-field. The applicability of the method is illustrated by a hypothetical situation characteristic to seismotectonic and ground conditions in platform areas: low local activity, proximity to a deep focal area, and a shallowly basement overlain by a consolidated soil profile. Presentation of the ground conditions by single parameter Vs30 (average velocity of transverse waves in upper 30 m of the soil profile) is not sufficient. Although such a description gives generally higher spectral amplitudes, it does not take into account amplification due to possible resonance phenomena; meanwhile, energy absorption in the soil profile due to inelastic behavior is ignored.

In the paper there are results of a recent study of the active faults in the Kerch Peninsula. There was compiled a Map of Active Faults - sources of the strong earthquakes occurred in Late Holocene. The map is a regional seismotectonic model of strong earthquake sources - detailed basis for a spatial prognosis of the seismic hazard. Results of the study show that the Kerch Peninsula demonstrates signs of the classical morphostructures, and a morphology of the modern peninsula contours is caused by the large active fault zones.

This paper reports recently obtained research data on active faults in the Kerch Peninsula. The compiled Map of Active Faults demonstrates foci of Late Holocene strong earthquakes. This map is a regional seismotectonic model of strong earthquake foci, and a detailed basis for prediction of spatial seismic hazards. According to the research results, the Kerch Peninsula is characterized by the features of classical morphostructures, while the morphology of recent peninsula contours is caused by large active fault zones.

The results of studying the geological and archaeological traces of the strong earthquakes on Cape Zyuk where the ancient settlement existed from the turn of the 6th to the 5th centuries B.C. to the first-third–middle of the 6th century A.D. are presented. The detailed knowledge gained on this monument allowed us to compile the timeline of the strong earthquakes for the past 2500 years. The detection of the seismotectonic deformation of the Late Holocene sediments indicates that the rupture of the source of a strong earthquake at Cape Zyuk extended to the surface. The dating of this event is constrained by the upper age of the second half of the 4th century B.C. to the beginning of the third century B.C. The previous event is dated to before the turn of the 6th–5th centuries B.C. Besides these events, there were presumably another four earthquakes in 63 B.C., before the second half of the 4th century B.C., in the first third to the mid-6th century A.D., and in the 18th century. Presumably Cape Zyuk was struck by four or five strong earthquakes during the past 2500 years. The lack of information about the earthquakes between the 6th and 18th centuries, i.e., during more than a 1000-year period, can probably be related to both the long period of quiescence between seismic activations and to the incompleteness of the collected data.

The paper investigates the effect of different methods for preprocessing earthquake catalogs (declustering, i.e., removal of dependent events from them, and selection of the magnitude of completeness) on seismic hazard assessment. Seismic catalogs of the Kamchatka and Caucasus regions have been used for the analysis, because synthetic catalogs do not always reflect the real features of regional seismicity. Test sites were selected for these regions. Three declustering methods are considered that leave different numbers of events in the catalogs. The plotted seismic hazard curves indicate a complex interaction of catalog declustering and selection of the magnitude of completeness. Since both methods affect the b-value, it cannot be predicted in advance, which will lead to an increase or decrease in the estimate for b. After it is applied, the declustering method leaves the largest number of events in the catalog, but does not always give the highest seismic hazard rating. Therefore, it is necessary to be extremely careful and attentive when declustering a catalog. At the very least, it should be borne in mind that the end result may be unpredictable.

A deep-focus (H = 609 km) earthquake with Mw = 8.3 occurred in the Sea of Okhotsk on May 24, 2013. This earthquake was felt in Moscow at a distance of about 6500 km from the epicenter but barely felt on the western coast of Kamchatka, which is located within 200 km of the source. In this paper, an attempt is made to discover the probable causes of this phenomenon in the instrumental records of the earthquake. It is most probable that the anomalously high amplitudes in the group of SSS phases, which are observed in the vertical component, appear as the result of their superimposition on the surface waves. Different mechanisms can be suggested to interpret the formation of the observed wave pattern.

The points with normal, anomalously low, and anomalously high shaking intensities are recognized in the spatial distribution of macroseismic effects from the 1991 Racha earthquake, Greater Caucasus. Distribution of these points in the epicentral area is not random. Comparison between this distribution and the results of local tomography reveals that seismic wave velocities do not increase in the upper layers (from 0 to 3 km) beneath the points with anomalously high intensity, while a sharp increase in velocity is observed in the depth interval from 6 to 9 km. An original method of b-value mapping is suggested. Application of the method demonstrates that anomalously low intensities correlate to high b-values. This likely reflects higher intensity attenuation associated with higher b-value.

The epicentral zone and settlements that suffered from the MS = 6.1 earthquake in the northwest Amur oblast are examined. Only secondary seismic dislocations were revealed and mapped in detail. The inspection of settlements and inhabitansts inquiry allowed estimation of the intensity of the macroseismic effect based on the MSK-64 scale. These forthwith primary factual data give an idea on the shaking intensity at the distant and nearest zones and precise location of the earthquake focus. The map of isoseists of the highest (7–8) intensity is drawn.

The source of the 1991 Racha earthquake in the Greater Caucasus generally corresponds to thrusting, which is characteristic of the predominant regional compression stress field. A more adequate view of the rupture process is provided by a complex source model composed of three subsources. This model is reconstructed by the body-wave inversion and consistent with the spatial distribution of the aftershocks. In terms of the suggested model, at the last stage of the rupture process, the opposite slip type (normal faulting) is observed in the source, which seems to be objective. It compensates the rapid (probably short) local redistribution of stresses caused by the thrusts in the first two subsources. The surface deformations observed in the epicentral zones of strong earthquakes are probably the analogs of such a compensative mechanism. For example, in the rear parts of the thrusts associated with the surface ruptures, normal faults trending parallel to the strike of the thrust line occur. Another analog of the compensative motion is probably the peculiarities of the aftershock sources. It has long since been noted (Kuznetsova et al., 1976) that some fault plane solutions in the aftershock sequences of strong earthquakes are close to the main shock solution, while others are different. The explanation of this phenomenon is suggested in (Kuznetsova et al., 1976; Kostrov and Das, 1988). In (Kuznetsova et al., 1976), these events are referred to as the aftershocks due to the fracture growth and aftershocks of relaxation, respectively.

International audience; Relationship between the intensity of seismic shaking on the surface and the velocity structure of the medium at large depth is studied. The Spitak earthquake of December 7, 1988 is chosen as an object of study. A method to correlate the intensity of shaking in the localities to the geophysical parameters specified in the nodes of regular spatial grid is proposed. Formalized definition of anomalous intensity is suggested; it takes into account the distribution of distances from the localities with given intensity degrees to the hypo center or to the nearest segment of the surface fault. It is found that the seismic wave velocities at a depth of 1 km are higher (up to 0.2-0.6 km/s) under the localities with anomalously high intensity. No any certain reg ularity is found in deeper layers.