Information on the earthquake in Altai in 1887 is supplemented by information from the Kavkaz newspaper (The Caucasus) published in Tiflis (Tbilisi). It is concluded that it is necessary to carry out systematic work to search for sources of information while organizing research based on the history of the regional and central press and developing archival and library science; episodic surveys from project to project, limited only to sources in the study area, create the risk of missing the original macroseismiс information. New data and the use of a strictly formalized procedure for determining the position of the epicenter have led to a revision of the previous decision of the earthquake on January 2/14, 1887.

Abstract—Deep earthquakes occur in subduction zones—they play a key role in the global tectonic model. There are only a few places on the Earth where deep-focus seismicity is observed on the continents in small localized areas at a considerable distance from the present-day subduction zones, in particular in the Vrancea region of the Carpathians. The strongest deep Vrancea earthquakes are felt at a distance of over 1000 km. They essentially define the seismic hazard for the East European platform, where either there are no local focal zones or these zones have small magnitudes. Therefore, studying deep Carpathian earthquakes is very important for adequate assessment of seismic hazard for the East European platform. We assume that although the strongest deep Carpathian earthquakes have been studied quite fully and thoroughly, not all existing information has been exhausted. The search for previously unknown primary sources may reveal new information about the macroseismic effect and, consequently, lead to more reliable and accurate earthquake parameter evaluations. This article examines the 1838 deep Carpathian earthquake using the original descriptions from primary sources. The earthquake magnitude has been determined by means of a new approach based on minimizing the discrepancies between the calculated and observed shaking intensities at all localities. It is shown that the magnitude of the 1838 earthquake is underestimated in the published catalogs by about 0.5 unit. We believe that the main reason is that the previously used macroseismic data in the far-field zone are not sufficiently complete.

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.

Освещены результаты новейших исследований активных разломов Керченского п-ова. Составлена карта активных разломов - очагов сильных землетрясений, проявивших себя в позднем голоцене. Карта активных разломов представляет собой региональную сейсмотектоническую модель очагов сильных землетрясений - детальную основу для пространственного прогноза сейсмической опасности. Результаты исследований показывают, что Керченский п-ов демонстрирует признаки классических морфоструктур, а морфология современных очертаний полуострова обусловлена зонами крупных активных разломов.

Приводятся результаты изучения геологических и археологических следов сильных землетрясений на мысе Зюк, где расположено античное городище, существовавшее с рубежа VI–V вв. до н. э. до первой трети–середины VI в. н. э. Хорошая изученность памятника дала возможность составить хронологию сильных землетрясений за последние 2.5 тыс. лет. Обнаружение сейсмо­тектонической деформации позднеголоценовых отложений свидетельствует о выходе очага сильного землетрясения на мысе Зюк. Датировка этого события ограничена верхней возрастной рамкой – вторая половина IV в. до н. э. – начало III в. до н. э. Предыдущее событие датируется до рубежа VI–V вв. до н. э. Кроме них, предположительно можно говорить еще о четырех событиях: 63 г. до н. э.; до второй половины IV вв. н. э.; первой трети–середины VI в. н. э. и XVIII столетия. Можно предполагать, что за последние 2.5 тыс. лет мыс Зюк подвергался сильным землетрясениям 4–5 раз. Отсутствие сведений о землетрясениях между VI и XVIII столетиями, т. е. за период продолжительностью более 1000 лет, может быть связано как с продолжительной эпохой затишья между сейсмическими активизациями, так и с неполнотой собранных данных.

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.

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 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.

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.

Руины хорошо изученного древнего города Фанагория предоставили уникальную возможность для восстановления неизвестной ранее страницы сейсмической истории Таманского полуострова. На основе собранных геологических, геофизических и археосейсмологических данных выдвинута гипотеза о гибели средневекового города Фанагория в результате катастрофического землетрясения в X веке. Город оказался прямо в месте выхода очага сильнейшего (9?10 баллов по шкале MSK-64) землетрясения на поверхность, связанного с Фанагорийской флексурно-разрывной зоной. Ruins of well studied ancient settlement Phanagoria have given a unique opportunity for recovery of unknown earlier seismic history of Taman Peninsula. On the basis of collected geological, geophysical and archeoseismological data the hypothesis of death of the medieval settlement Phanagoria as a result of a catastrophic earthquake in the 10th century is made. The deep and near-surface structure of the Phanagoria deformation zone has been studied by seismic exploration. Along the southern coast of the Gulf of Taman the subvertical low-weak zone is detected. In outcrops the flexures of the neogen-quarternary layers and their immersion towards the sea are revealed. Deformation zone has been traced on the ancient settlement Phanagoria. On an excavation of the late medieval hillfort we have detected a ground flexure – to a surface on which ancient buildings of the 9-10th centuries were constructed. The settlement Phanagoria has appeared directly in the place of an exit of the source of the strongest (IX-X on MSK-64 scale) earthquake on a surface connected with the Phanagoria deformation zone.

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.

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 earthquake with Mw=6.0 occurred on October 14, 2011 in the southeastern Siberia (Russia) in the zone of junction of Kalatur and Tukuringra mountain ranges near the town of Skovorodino. This earthquake aroused a great interest among specialists due to its strength and location. The magnitude of the Skovorodino earthquake is the largest in the known seismic history of the region and is close to the maximum value expected for the region. Besides, presently this region is actively developed; including the construction of oiland gas-pipelines. The exact knowledge of the source zone and the specific geologic structures is of primary importance for the correct seismic hazard assessment. Although the world and regional seismological networks adequately reflect the seismicity of the area, they do not provide the necessary quality of location of even strongest events. The epicentral observations of the Skovorodino earthquake were carried out by the network of Institute of Physics of the Earth, RAS, during October-December 2011 and made it possible to monitor the aftershock activity. More than 1300 events were recorded. Map of epicenters together with the cross-sections by depth and the fault plane solution are shown in Fig.1. The analysis of more than 10000 waveforms led to the following conclusions (Bykova et al., 2014) 1. The Skovorodino, 2011, earthquake is an outstanding event in the region. Its magnitude exceeds previously known values by 2 – 2.5. 2. Two clusters of epicenters are clearly expressed in the aftershock cloud: west and east (Fig. 1). They differ in the recurrence plots, in the level and time variations of the energy released, and in the depths of hypocenters, which implies the complex structure of the source. Generally, the source can be represented as a strike-slip in a plane striking EW and dipping steeply to the North. Its sizes are about 17 km × 17 km, the mean value of the displacement is about 63 cm, exceeding the values characteristic for M=6.0 events by about 30%. 3. The aftershock sequence is anomalous: rather strong (M≥3.5) aftershocks are absent. It is consistent with the anomalously large displacement in the source and the rather large magnitude of the mainshock with respect to events previously recorded in the region. The study of the source zone of the Skovorodino earthquake was continued in 2013 using the methods of microseismic sounding. The aim was to reveal 3D heterogeneities in the source zone and to construct the more precise model. The region studied is shown by the frame in Fig. 1. In the method proposed the spatial properties of spectral characteristics of microseismic signal recorded by one or several stations along profiles within the specific site are used to identify the heterogeneities of the medium (Kalinina et al., 2009). The analytical solutions proved that in the Rayleigh fundamental mode the zone of maximum shear stresses is located at a depth equal to half of

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.

Движение в очаге Рачинского землетрясения 1991 г. на Большом Кавказе в целом соответствует взбросу, что характерно для доминирующего напряжения сжатия в регионе. Более адекватно процесс вспарывания может быть представлен сложным очагом из трех субисточников. Данная модель получена путем инверсии объемных волн; она согласуется с пространственным распределением афтершоков. На последнем этапе развития разрыва наблюдается обратный тип движения в очаге – сброс. Его наличие в предложенной модели представляется объективным, призванным компенсировать быстрое (возможно, кратковременное) локальное перераспределение напряжений, вызванное взбросовыми движениями в первых двух субочагах. Аналогами такого компенсационного механизма могут быть наблюдения поверхностных деформаций в эпицентральных зонах сильных землетрясений. Так в тылу взбросов, связанных с выходом разрыва в очаге на поверхность, обнаруживаются сбросы, простирающиеся параллельно линии взбросов. Другим аналогом компенсационных движений могут рассматриваться особенности механизмов афтершоков. Давно уже замечено [Кузнецова и др., 1976], что в афтершоковых последовательностях сильных землетрясений некоторые механизмы очагов близки к механизму главного толчка, а некоторые имеют иной механизм. В [Кузнецова и др., 1976; Kostrov, Das, 1988] предложено объяснение этого наблюдения. В [Кузнецова и др., 1976] они называются соответственно афтершоки развития и афтершоки последействия.

The epicentral zone and settlements that suffered from the M S = 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.

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 hypocenter 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 regularity is found in deeper layers.