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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.

There are several ways of setting seismic impact on bedrock for calculating the impact on the free field. In the paper, two ways of setting the initial seismic impact on bedrock are analyzed: artificial and synthetic accelerograms. For assessing the effect of the soil profile in transferring seismic signals from bedrock to the free field, four seismogeological models were used. Linear and nonlinear (equivalent-linear approximation) behavior of soil profiles were studied. Summing all results of calculations, we conclude that there are no significant differences in expected seismic impact on the free-surface depending on how the input is set at bedrock. Systematically larger values when synthetic method is used is not more than 10%, which is not evaluated as being significant.

Archives and libraries were visited to find previously unknown documents testifying to the Lurøy, Norway, earthquake of 31 August 1819 in northernmost continental Europe. The focus here is on Sweden, Finland, and Russia, which are important for determining the area of perceptibility east of Norway. The new written sources include 12 notes or entries in original archived documents, six contemporary newspaper reports, and two recollections written down years later. The original documentation uncovered is contributory to establishing the authenticity of the observations in Finland and Sweden. The dates of the original documentation allow tracing of the dissemination of eyewitness accounts in writing from the inner area of perceptibility southward to the larger documentation and population centers. New sources of information include weather reports of the Royal Swedish Academy of Sciences, minutes of its meetings, and correspondence sent to the Senate in Finland. The minutes of meetings of the Academy indicate that ample data were collected in the Swedish province of Västerbotten. We found no original Russian documentation but uncovered national newspapers that are more reliable than the previously used Parisian newspaper. To increase transparency, we provide the first list of macroseismic data points (MDPs) including the respective documentation that testify to the Lurøy earthquake. A macroseismic intensity was assigned to a locality, using the European Macroseismic Scale of 1998, when adequate information was available. Accounting for the uncertainty of intensity assessment, the magnitude was estimated as moment magnitude M=5.9±0.2, reconfirming the ranking as the largest onshore or nearshore earthquake in the historical seismicity record of Fennoscandia. In addition to the reappraisal of the 31 August 1819 earthquake, a macroseismic map is provided for the earthquake of 17 February 1819, which was felt in northern Finland and Sweden. Some of its MDPs were previously associated with the Lurøy earthquake.

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.

When compiling historical earthquake catalogs, the main problem is to validate the reliability of information to exclude false reports. Detailed descriptions from reliable sources contribute to more precise intensity assessment. Additionally, in low-active territories, very important problem of identifying the nature of the event has to be solved. Earthquakes generated by tectonic or other activity (such as landslides or karst collapses) may have similar descriptions. Recently, cryoseisms have also been considered a possible source of the ground surface shaking. Seismic events in Belarus reported based on noninstrumental data and having fundamentally different interpretations in different publications are studied. The analysis is based on original information from primary sources. It is shown that two out of four seismic events are cryoseisms, while the other two are not related to the territory of Belorussia.

The Ganges–Brahmaputra Delta (GBD), the world’s largest delta, is composed of sediments eroded from the collision zone of Himalayas. These sediments moved the margin of the Indian Subcontinent for ~400 km and formed the thickest sedimentary sequence, which is subducted within the subduction zone of the Burma arc. A critical facility is located in the GBD central part. Although it is located for more than 300 km from the Indo-Burma subduction zone in the east and the continental collision zone in the north, these planetary structures significantly affects the seismic activity and seismic hazard of the GBD central part. Scarps exposed by trenches in the vicinities of this object were found in the surface and studied. The trench walls exhibit inclined layers with small vertical displacement, which could indicate a former paleoearthquake, however, they are underlain by horizontal layers without displacement. This pattern is interpreted as a result of erosion (neotectonic) activity related to repeated fluctuations of the Ganges River bed, which are traced in all trenches.

Earthquake environmental effects (EEEs) were compiled for the earthquakes of 1626, 1759, 1819, and 1904 in the Fennoscandian Peninsula, northern Europe. The principal source of information was the contemporary newspaper press. Macroseismic questionnaires collected in 1759 and 1904 were also consulted. We prepared maps showing newly discovered EEEs together with previously known EEEs and analyzed their spatial distribution. We assigned intensities based on the 2007 Environmental Seismic Intensity (ESI) scale to 27 selected localities and compared them to intensities assigned based on the 1998 European Macroseismic Scale. While the overall agreement between the scales is good, intensities may remain uncertain due to the sparsity of written documentation. The collected data sets are most probably incomplete but still show that EEEs are not unprecedented cases in the target region. The findings include landslides and rockfalls as well as cascade effects with a risk potential and widespread water movements up to long distances. The winter earthquake of 1759 cracked ice over a large area. This investigation demonstrates that the ESI scale also has practical importance for regions with infrequent EEEs.

The effect of the upper part of a layered profile on calculated seismic hazard parameters is analyzed. The behavior of the soil profile is studied as part of equivalent linear modeling with the example of six seismogeological models. Peak ground acceleration of the input signal varies from 0.1 to 0.6 g. It is shown that the character of the dependence of physicomechanical properties in the layer on the strain value leads to variations in the amplitudes of the response spectrum on the free surface and displacement of the maximum of the frequency spectrum. An increase in the thickness of the upper layer significantly influences the shape of the response spectra. Variations in the PGA values, damping coefficients, strain values with depth are calculated, as well as the velocity profiles for different soil layers with respect to the degradation curves. It is demonstrated that restricting the upper limit of the damping coefficient to 15% does not lead to noticeable changes in the shape of the response spectra on the free surface. The soil column begins to decrease the peak value of the input signal when its level exceeds 0.3 g.

The ground layer response to seismic loading is analyzed in the paper. Two approaches to the site profile behavior are considered: elastic (linear) and viscoelastic (equivalent linear modeling). Four typical soil profiles are taken into account; input peak values are within the range from 0.1 to 0.6g. In all profiles, when ignoring the nonlinear behavior, the calculated impacts are still within the standard response spectrum. When the nonlinearity is taken into account, the pattern is completely different. The standard spectrum is abundantly conservative for high frequencies; meanwhile, it substantially underestimates the level of hazard at low frequencies. Therefore, the shape of standard spectra as a whole does not adequately describe a seismic hazard, especially when the input signal is higher than 0.2g.

The data on the earthquakes of April 13 and 25, 1914 in Altai from (Novyi katalog…, 1977) have been summarized. Based on an analysis of the earlier publications and the new data from the initial sources, it has been shown that the only seismic event occurred on April 25 (12 old style), 1914. The weak differentiation of macroseismic effects over the area does not allow us to reliably locate the epicenter; the best spatial accuracy is ±50 km. Based on the entire data volume, the magnitude is estimated at 5.5 ± 0.3 which is slightly higher than was believed earlier.

The parameters of the September 3, 1978, earthquake in the Western Caucasus are presented according to data from different seismological agencies. This event, along with the 1966 earthquake in Anapa, is the strongest seismic event in the region. The solutions suggested in the main international and national seismological agencies contradict the well-known fact that the earthquake did not have catastrophic consequences. This is confirmed only by the position of the epicenter according to GCMT data intended for determining somewhat different earthquake parameters: the focal mechanism and seismic moment. Despite the fact that there was no expedition to perform a macroseismic study of the earthquake, some information was collected by phone survey. Information on the spatial distribution of the macroseismic effect made it possible to more accurately determine the epicenter position according to the GCMT data.

Historical earthquakes have to be parameterized for seismic‐hazard analyses, although there may be only a few intensity assignments available for them. We studied epicenter determination for 18 million synthetic samples of 3–11 intensity data points (IDPs). The IDP distributions corresponded to earthquakes that occurred offshore, close to the coast, or onshore. We assumed an ordinal variable, an attenuation relationship, and a point source. The attenuation relationship was utilized to encompass every IDP of a sample using a lower and upper radius that corresponded to the respective intensity. The epicenter must fit all the intensity rings simultaneously. The successes and failures of epicenter determination were monitored for a fixed magnitude and depth. We investigated where the epicenter was found, its uncertainty, and its uniqueness. Small location uncertainties may be obtained for the smallest samples but increasing the sample size led to a larger proportion of small uncertainties provided that intensities were error‐free. A large range of intensities in the sample, a short distance to the true epicenter, and, to a lesser extent, a small azimuthal gap were indicators of a good solution. A location uncertainty of 20 km and smaller is realistic in many cases, but uncertainties of 5 km are extremely seldom occurrences. The proportion of good locations was reduced when the intensities were erroneous. Epicenters were determined for the earthquakes of 26 April 1458 in central Italy, 14 July 1765 in Sweden, and 23 December 1875 in the eastern United States.

The 18 September 2011 Sikkim Himalaya earthquake of Mw 6.9 (focal depth 50 km, NEIC report) with maximum intensity of VII on MM scale (www.usgs.gov) occurred in the Himalayan seismic belt (HSB), to the north of the main central thrust. Neither this thrust nor the plane of detachment envisaged in the HSB model, however, caused this strong devastating earthquake. The Engdahl–Hilst–Buland (EHB) relocated past earthquakes recorded during 1965–2007 and the available global centroid moment tensor) solutions are critically examined to identify the source zone and stress regime of the September 2011 earthquake. The depth section plot of these earthquakes shows that a deeper (10–50 km) vertical fault zone caused the main shock in the Sikkim Himalaya. The NW (North-West) and NE (North-East) trending transverse fault zones cutting across the eastern Himalaya are the source zones of the earthquakes. Stress inversion shows that the region is dominated by horizontal NNW-SSE (North of North-West-South of South-East) compressional stress and low angle or near horizontal ENE-WSW (East of North-East-West of South-West) tensional stress; this stress regime is conducive for strike-slip faulting earthquakes in Sikkim Himalaya and its vicinity. The Coulomb stress transfer analysis indicates positive values of Coulomb stress change for failure in the intersecting deeper fault zone that produced the four immediate felt aftershocks (M ≥ 4.0).

The main objective of this paper was to introduce the Environmental Seismic Intensity scale (ESI), a new scale developed and tested by an interdisciplinary group of scientists (geologists, geophysicists and seismologists) in the frame of the International Union for Quaternary Research (INQUA) activities, to the widest community of earth scientists and engineers dealing with seismic hazard assessment. This scale defines earthquake intensity by taking into consideration the occurrence, size and areal distribution of earthquake environmental effects (EEE), including surface faulting, tectonic uplift and subsidence, landslides, rock falls, liquefaction, ground collapse and tsunami waves. Indeed, EEEs can significantly improve the evaluation of seismic intensity, which still remains a critical parameter for a realistic seismic hazard assessment, allowing to compare historical and modern earthquakes. Moreover, as shown by recent moderate to large earthquakes, geological effects often cause severe damage''; therefore, their consideration in the earthquake risk scenario is crucial for all stakeholders, especially urban planners, geotechnical and structural engineers, hazard analysts, civil protection agencies and insurance companies. The paper describes background and construction principles of the scale and presents some case studies in different continents and tectonic settings to illustrate its relevant benefits. ESI is normally used together with traditional intensity scales, which, unfortunately, tend to saturate in the highest degrees. In this case and in unpopulated areas, ESI offers a unique way for assessing a reliable earthquake intensity. Finally, yet importantly, the ESI scale also provides a very convenient guideline for the survey of EEEs in earthquake-stricken areas, ensuring they are catalogued in a complete and homogeneous manner

Descriptions of the macroseismic effects of Altai earthquakes (1764–1913) from primary sources are presented. Though the main result of the study is a compilation of felt reports in the Altai region more complete than before, parametric solutions are proposed, when it is possible. “More complete” means not only more macroseismic information in some localities on known earthquakes or discovering previously unknown seismic events. It is important that sources of primary information are sought out and presented. As far as concerns earthquake parameters, for some seismic events they are conventional (taking into account the limited macroseismic data available). It is supposed that actual macroseismic effects for most (if not all) earthquakes in the region are available only in the far-field area of strong seismic events, whose sources are located in sparsely populated mountains. If true, modern methods of seismic hazard assessment using parametric earthquake catalogs may give inadequate results.

On October 14, 2011, an earthquake with the magnitude Mw = 6.0 occurred 15 km northwest of the town of Skovorodino in East Siberia. This earthquake aroused interest among geophysicists. In this paper, we present some results on the prior seismicity in the region, which are based on the macroseismic and instrumental data. The assessment of the seismic regime immediately before the main shock and the analysis of the aftershock sequence rely on the data provided by the field network of the Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. The network was in operation from the end of July 2011 to January 2012. The analysis of the entire dataset suggests that the Skovorodino earthquake was outstanding in a vast region: only seismic events with low magnitudes (at most 4) occurred in the epicentral zone of this earthquake and its nearest neighborhood. The positions of the source of the main shock and the hypocenters of the after-shocks (more than 1300 events) are determined. The aftershock sequence is anomalous—it lacks sufficiently strong seismic events (M ≥ 3.5). The spatiotemporal distribution of the aftershocks shows two clusters of the epicenters to the west and east of the epicentral zone. These clusters drastically differ in their parameters, indicating that the source has a complex structure. Generally, the source can be understood as a shear displacement on the subvertical fault plane trending approximately along the latitude. The size of the source is 17 × 17 km; the average slip is 63 cm, which is at least 30% larger than the characteristic values for the earthquakes with M = 6.0.

This article presents original macroseismic information on earthquakes in Eastern Siberia from the eighteenth century to the first half of the nineteenth century, derived from primary sources. The analysis of this information has enabled us to identify previously unknown earthquakes and reveal false seismic events. We traced the origin of errors and false interpretations in some basic descriptive and parametric earthquake catalogs that have arisen due to the use of secondary compilations and sources. New parametric solutions for some known earthquakes are proposed. When there are several equally credible solutions to an observed macroseismic effect, it seems reasonable to present all alternatives rather than arbitrarily to choose one of them. If the location of the epicenter and magnitude of an earthquake cannot be determined with reasonable accuracy, it is proposed to retain only information about the felt effects of a seismic event in a given populated locality.

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.

Historical seismology suggests certain recommendations to assess the reliability of macroseismic information. These recommendations are quite general and have proved their efficiency in many cases. But they should be very carefully applied, because the formal approach used in them is not always reasonable. Based on the analysis of sources relevant to the 1542 earthquake in the north of Russia, it is shown that though the distribution of priorities for sources relying on how close they are to the event works well, it can not be considered a universal rule. Many other details, such as characteristic of the person compiling the document, one’s interests, how free one could access the non-public achirves, and the goal of writing the document, have to be taken into account.

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 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.

Problems of physical basis of earthquake source mechanics are discussed. Results of stress state reconstruction based on the cataclastic analysis of discontinuous dislocations in some seismotectonic active earth crust domains are presented. Common features of the stress state in areas of preparation of strong earthquake in this century are revealed. It is demonstrated that the distribution of the effective isotropic pressure and of the maximal shear stress in areas of earthquake source preparation is characterized by essential heterogeneity. The main part of the source is always associated to crust domain under low effective confining pressure. Specific role of crust domains characterized by high stress gradients is recognized. The nucleation point of the earthquake is usually associated to such domains. Based on some strong earthquake case studies it is demonstrated that usually the rupture propagates from the region of high gradients of stresses toward the crust domains characterized by low effective compression.

Earthquakes that occurred in the Baikal seismic region in 1725, 1742, 1769, and 1829 are studied on the basis of original macroseismic information. Due to the fact that their parameters were previously determined using the combination of macroseismic and paleoseismic data, the goal of our investigation is to verify how well the solutions agree with the macroseismic evidence. Careful examination of macroseismic data includes, first of all, the searching for original sources, which cannot be replaced by any other data types, for instance, paleoseismic information characterized by questionable reliability. The completeness of analysis is achieved when different components are inspected separately before mixing. In the case when unequivocal data interpretation is impossible, it is better to consider different alternative solutions characterized by relatively narrow error ranges. Variants can be weighted correspondingly (at least, evaluated qualitatively). Otherwise we have to deal with the so-called “average” solutions, often useless due to great determination errors. Magnitudes of all earthquakes estimated previously on the basis of macroseismic and paleoseismic data are not confirmed by the original macroseismic information, and revised magnitudes are essentially lower.

Parameters for historical earthquakes have to be derived from written documentary materials. We argue that the steps involved can be approached through a defined theoretical framework using precise terminology. More pervasive use of the concept of ordinal variable is advocated when discussing earthquake intensity. The essential information available for parameter derivation consists of earthquake intensities and hierarchies between them as a function of space. To get error limits for earthquake parameters derived from sparse data, we propose to construct and illustrate possible earthquake occurrences of the past (so-called earthquake scenarios) that fit the available observations. Each possible scenario is associated with a probability, whose derivation involves expert judgment.

Algorithm of natural stress reconstruction based on data on slip fault sets is presented. Also additional physical principles following from generalization of experimental geomechanics and theoretical tectonophysics are considered. It gives possibility to define not only orientation of stress tensor principal axis but also the ratio of its spherical and deviatory components. The characteristic feature of the method is that it simultaneously calculates mutually consistent components of stress tensor and increment tensor of seismotectonic deformations, what was missing in previously known methods of tectonophysics. The application of the method is illustrated by two case studies in seismoactive zones of Central Asia: a) Altai and Sayan and b) Northern Tien Shan. Results of stress reconstruction in this intra-plate faulted and folded domains demonstrate that the impact of crust flow and mantle heterogeneity on stresses is great. These processes can contribute much more in generating stresses in crust than interaction of lithosphere plates at distant borders.

The tectonic model of the Shillong plateau and Assam valley in the northeast India region, the source area for the 1897 great earthquake (Ms ~ 8.7) and for the four (1869, 1923, 1930 and 1943) large earthquakes (M. ≥ 7.0), is examined using the high precision data of a 20-station broadband seismic network. About 300 selected earthquakes M ≥ 3.0 recorded during 2001–2009 are analysed to study the seismicity and fault plane solutions. The dominating thrust/reverse faulting earthquakes in the western plateau may be explained by the proposed pop-up tectonics between two active boundary faults, the Oldham–Brahmaputra fault to the north and the Dapsi–Dauki thrust to the south, though the northern boundary fault is debated. The more intense normal and strike-slip faulting earthquakes in the eastern plateau (Mikir massif) and in the Assam valley, on the other hand, are well explained by transverse tectonics at the long and deep rooted Kopili fault that cuts across the Himalaya and caused the 2009 Bhutan earthquake (Mw 6.3). It is conjectured that the complex tectonics of the Shillong plateau and transverse tectonics at the Kopili fault make the region vulnerable for impending large earthquake(s).

Some factors affecting the accuracy of magnitude calibration of palaeoearthquakes are discussed. The general problem is illustrated by two case studies. First, the 2003 strong earthquake in the Altai region (Russia–Mongolia border), which has generated co-seismic surface faulting is considered. An analysis is conducted to determine how accurately its magnitude could be defined after 2000 years based on surface faulting parameters, retrieved when future palaeoearthquake studies are launched. This example demonstrates that accurate evaluation of magnitude is possible if specific regional seismotectonic features are taken into account and surface faulting parameters are measured over a dense grid. Next, the Muya earthquake that occurred in the Baikal seismic region in 1957 is studied with respect to the problem of palaeoearthquake magnitude calibration in this region. The intensity of the Muya earthquake is assessed based on macroseismic and geological data. Macroseismic effect distribution confirms source depth at 20–22 km, agreeing with a seismic rupture length of 25 km: only a part of the source is exposed on the surface. Comparison with length of paleoseismodislocations shows that it is a regional feature. The source mechanism with three sub-sources is in agreement with the segmentation of surface ruptures. Sub-sources are of strike-slip type with small normal components. Essential normal slip at surface is probably not representative for the source and is due to accommodation of strike-slip movement along with a system of sub-parallel en echelon ruptures under tension.

Coherency of the source model of the 1991 Racha earthquake in the Greater Caucasus with different data types is analyzed. Authors, when interpreting macroseismic data, accept complex nature of macroseismic effects generation but, nevertheless, consider that its spatial distribution follows certain regularities. First time in the practice, method of evaluation of the mecroseismic material completeness is proposed based on the intensity attenuation along with distance. It is demonstrated the character of macroseismic intensity attenuation can be used for verification of the source model elements constructed based on other seismological data. Dependence of the macroseismic effect distribution on azimuth in near field of the 1991 Racha earthquake is recognized.

This study starts from the earthquakes of May 14, 1626 and June 22, 1626 as given in existing parametric catalogs for the Baltic (Fennoscandian) Shield. The first shock is located in North-western Russia, the second in Finland that belonged to Sweden at that time. A search for previously unknown Russian sources of information is performed, and secondary Swedish sources are replaced by primary ones. The contemporary sources are two Russian chronicles and two Swedish manuscripts. In addition, a later reminiscence is used. The contents of the sources are critically analyzed and augmented with background information. A new interpretation of one Swedish manuscript is presented. The earthquake dates are analyzed. A credible source of errors follows from the different calendars used. Macroseismic intensity assessment is possible for two places. A new solution of one earthquake felt in both territories is proposed. The available data are too fragmentary to prove it beyond doubt, but the scenario is feasible in many ways. Tentative earthquake parameters are calculated. Epicentral intensity is assessed at 6–7 (EMS), magnitude is estimated at 4.7–5.7. The epicenter is located in Russia close to the border between the two territories.

Seismotectonics of the two recent earthquakes, one Mw 6.3 in the Bhutan Himalaya on 21 September 2009 and the other Mw 5.1 in the Assam valley on 19 August 2009, are examined here. The recent seismicity and fault plane solutions of these two felt earthquakes suggest that both the events occurred on the Kopili fault zone, a known active fault zone in the Assam valley, about 300 km long and 50 km wide. The fault zone is transverse to the east–west Himalayan trend, and its intense seismicity indicates that it transgresses into the Himalaya. The geologically mapped curvilinear structure of the Main Central Thrust (MCT) in the Himalaya, where the epicentre of the Bhutan earthquake is located, is possibly caused by the transverse Kopili fault beneath the MCT. This intensely active fault zone may be vulnerable to an impending larger earthquake (M > 7.0) in the region.

Intensity of the Muya, 1957 earthquake is assessed in localities based on macroseismic data and in epicentral area based on effects in natural environment; it is analyzed how these assessments correspond to each other and to instrumental location of epicenter, hypocentral depth, and magnitude; it is evaluated, how seismodislocations of the Muya earthquake could serve as control of palaeoseismostructure parameters in this region. Spatial distribution of macroseismic effect confirms relatively deep source (20–22 km). Deep source agrees with anomalously short surface rupture length (not more than 25 km); only a part of the source exposed on the surface. Comparison with length of palaeoseismostructures shows that it is a regional feature. Epicentral intensity based on surface ruptures is assed X degrees in ESI2007 scale. Ignoring geological effects will underestimate epicentral intensity up to two degrees. Source mechanism with three sub-sources is in agreement with segmentation of surface ruptures. Sub-sources are of strike-slip type with small normal component; essential normal slip at surface is probably not representative for the source and is due to accommodation of strike-slip movement along with a system of sub-parallel en echelon ruptures under tension.

Earthquake catalogues for Romania supply for 11th–15th century earthquakes located in the region of Vrancea records that consist of a complete set of parameters, including magnitude and depth. Scope of this paper is to verify the reliability and consistency of these parameters with the informative background as explicitly referenced by the catalogues. After retrieving the original sources they mention, the set of data appeared to be related almost exclusively to the Russian plain and too poor to be at the very origin of the parameter assessment. Data for 19th–20th century earthquakes, such as instrumental locations and CMT solutions, added to the understanding of the macroseismic response of the Russian plain to Vrancea earthquakes. On the one hand, the investigation and analysis of historical earthquake records for the fourteen events listed by the catalogues in the 11th–15th centuries has shown that for three earthquakes (1022, 1038, 1258) no primary sources could be traced, and three more earthquakes (1091, 1170 and 1328) are attested only by scarcely reliable records and had to be classified as doubtful, and one (1473) is simply a duplication of the 1471 event. On the other hand, the availability of data on recent earthquakes that may be compared to historical ones in terms of macroseismic effects allowed the authors to agree with the previous catalogue compilers’ solution with regard to both magnitude and depth of the past earthquakes for which do exist reliable primary historical records.

The comparison of intensity assessments based on macroseismic data and Earthquake Environmental Effects (EEE) is presented. Specific problems faced when assessing intensities using different types of scales are discussed. Two case studies of recent earthquakes with magni- tudes MS ¼ 7.4 (Altai, 2003, and Neftegorsk, 1995) are used to illustrate the applicability of the INQUA EEE scale. The Altai earthquake was accompanied by surface faulting of c. 70 km length and up to 2 m of horizontal and 70 cm of vertical offset; secondary EEE were observed over 3000 km 2 . The dominant type of surface faulting during the Neftegorsk earthquake was strike-slip. The length of surface faulting was up to 46 km, maximum horizontal offset was 8.1 m, and average offset coherent with seismic momentwas 3.9 m; secondary EEE were observed occasionally at considerable distance from the epicentre on wet seashore sands. Application of the INQUA scale shows the epicentral intensity of the Altai earthquake to be X degrees. Most consist- ent with all types of data (rupture length, maximum and average offsets) intensity assessment for the Neftegorsk earthquake which is within the X-XI degree range. Taking into account environ- mental effects in intensity scales is an essential requirement: it follows from the complex nature of an earthquake impact, which spans a very broad frequency range, including static deformations. The case studies illustrate that the intensity assessment of an earthquake, based only on damage to buildings, will be essentially incomplete.

Analysis of aftershock sequences of the strongest earthquakes of the world showed that previously discovered empirical relations are not universal. Bath’s law is found to be invalid in the majority of cases, while Omori’s law is valid only in a short initial interval of aftershock activity. It is supposed that aftershocks of the strongest earthquakes of normal depths are related initially to fracture of zones that preserved their integrity after the rupture in the source of the main shock and at a later stage to relaxation of stresses in the medium adjacent to the rupture.

The INQUA scale, based on coseismic environmental effects, appears to be a very promising tool to get long-term and reliable information on seismicity. However, it has to pass through comprehensive testing procedures. Results of the INQUA scale application to earthquake intensity calibration are presented, part of the worldwide testing of the scale. As a case study, the Verny, 1887, earthquake in Central Asia has been chosen. It was a large earthquake (felt over 2,000,000 km 2 ) located in a region with a specific temporal and spatial organization of seismicity. Verification of magnitudes of some large past earthquakes is important for the correct understanding of regional seismotectonics and seismic hazard assessment. The work is based on the original materials collected by the expedition soon after the earthquake in the epicentral area. It is demonstrated that assessment of epicentral intensity derived from total area of secondary environmental effects is reliable. This enables evaluation of the parameters of historical earthquakes based on generalized information of observed earthquake environmental effects (EEE). The epicentral intensity I 0 is assessed to be IX-X degrees; the highest observed local intensities are coherent with I 0 assessment.

The possibility to obtain a more complete and unbiased long-term history of seismic shakings over large territories than is explicitly reported from inhabited localities is discussed in the paper. An approach proposed for this purpose consists in complementing the spatial distribution of the macroseismic effect of earthquakes by calculated intensities at localities where information on felt shakings is absent. The calculated intensity is obtained on the basis of data on the epicentral intensity and location of epicenters provided by earthquake catalogs. This approach is applied to the analysis of the history of seismic shaking in Spain. The calculated intensities are shown to be comparable in accuracy with the ordinary practice of intensity determinations at national seismological centers.

On 27 May 1995, a large earthquake (Ms 7.6) occurred in the northern part of Sakhalin Island near an uncertain plate boundary between the Okhotsk (or the North American) plate and the Eurasian (or the Amurian) plate. The source process of the mainshock, the detailed aftershock activity, the b-value of the fre- quency-magnitude relationship for aftershocks, and the 3D P-wave velocity distri- bution have been investigated. Thirty-one body-wave records were inverted to de- termine the sequence of subevents of the mainshock using an iterative deconvolution method. The source parameters obtained are the location of the initial epicenter (52.64 N, 142.83 E); the centroid depth (9 km); strike, dip, and slip, equal to (191, 87, 172) for the first subevent, (198 ,7 6, 175) for a second subevent, and (196 ,7 9, 174) for the combined source; and the total seismic moment M0 (4.2 10 19 N m) and Mw (7.0). We also deployed 12 temporary seismographic stations in the focal area from 7 June to 8 July 1995. More than 2000 events were located in an aftershock area of 60 km 10 km that trends in a N15E direction, which is consistent with the location of the surface rupture tracing the Gyrgylan'i-Ossoy fault. The P-wave velocity patterns were compared with the aftershock seismicity and the spatial distribution of the b-values, with results suggesting that high velocity corre- lates with high seismicity and small b-value. Our research strongly suggests that the 1995 Sakhalin earthquake was one of the outstanding events that define the uncertain plate boundary.

In the frame of the European Commission project “Seismic Hazard Harmonization in Europe” (SHARE), aiming at harmonizing seismic hazard at a European scale, the compilation of a homogeneous, European parametric earthquake catalogue was planned. The goal was to be achieved by considering the most updated historical dataset and assessing homogenous magnitudes, with support from several institutions. This paper describes the SHARE European Earthquake Catalogue (SHEEC), which covers the time window 1000–1899. It strongly relies on the experience of the European Commission project “Network of Research Infrastructures for European Seismology” (NERIES), a module of which was dedicated to create the European “Archive of Historical Earthquake Data” (AHEAD) and to establish methodologies to homogenously derive earthquake parameters from macroseismic data. AHEAD has supplied the final earthquake list, obtained after sorting duplications out and eliminating many fake events; in addition, it supplied the most updated historical dataset. Macroseismic data points (MDPs) provided by AHEAD have been processed with updated, repeatable procedures, regionally calibrated against a set of recent, instrumental earthquakes, to obtain earthquake parameters. From the same data, a set of epicentral intensity-to-magnitude relations has been derived, with the aim of providing another set of homogeneous Mw estimates. Then, a strategy focussed on maximizing the homogeneity of the final epicentral location and Mw, has been adopted. Special care has been devoted also to supply location and Mw uncertainty. The paper focuses on the procedure adopted for the compilation of SHEEC and briefly comments on the achieved results., Journal of Seismology, 17 (2), ISSN:1383-4649, ISSN:1573-157X

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.

To evaluate the completeness of modern knowledge on historical seismicity it is necessary to know the general geopolitical and socio-cultural background in the country. It determines the possibility to record the evidence of an earthquake and conserve the record in original form for a long time-period. The potential duration of historical earthquake study in Russia is assessed based on these considerations. Certain stages of earthquake study in Russia have been detected. Specific problems of seismicity studies of low active areas are discussed as an example of Russian platform. The value of each (even moderate magnitude) event becomes crucial for seismic hazard assessment in such territories. A correct identification of event nature (tectonic earthquake or exogenous phenomena - landslides, karsts, etc.) is practically impossible without using primary sources with detailed descriptions. Occurrence of modern earthquakes can be used to assess the accuracy of historical seismicity knowledge.

Summary The Neftegorsk 1995 May 27 earthquake (MS = 7.6) occurred in the northern part of Sakhalin Island in a region considered to be a fairly inactive plate boundary between the North American and Eurasian plates. Coseismic surface ruptures are associated with the Upper Piltoun fault, a secondary feature joining the Sakhalin–Hokkaido and Middle Sakhalin faults, which are the main tectonic elements of the region. Observations obtained during a field experiment that included a local seismic network, neotectonics and geodetic measurements are combined with the analysis of satellite images and a broad-band body wave inversion. A complex source model consisting of four branches is proposed. The two main branches, oriented N–S, show right-lateral strike-slip motion. The rupture nucleates between these two segments and propagates bilaterally. We estimate a total rupture length of 46 km, a width of 12 km, and an average slip value of 3.9 m. However, the maximum observed value of surface slip is 8.1 m, an unusually large value for an event of this magnitude. This earthquake supports the model of a North American plate rotating clockwise with respect to Eurasia.

SUMMARY The aftershock sequence of the Spitak earthquake, as recorded by a dense portable network deployed around the source region, is analysed in order to obtain a precise description of the mechanics of the rupture. A collection of 708 well-recorded events corresponding to a period of about two weeks is studied, their hypocentres are accurately located, and their focal mechanisms are calculated individually as well as by a joint procedure that permits us to estimate the stress regime. The epicentral distribution of these aftershocks indicates that the fault at depth extends well beyond the surface rupture towards the west and northwest. Neotectonic and seismic observations permit us to identify five segments broken during the earthquake. The southeastern one, oriented N140°, corresponds to the surface ruptures along the Alavar right lateral shear fault. The main surface ruptures, between Spitak and Gekhasar, correlate well with aftershocks showing a N120° trending fault surface, dipping 50" to the NE and acting as a thrust with a right lateral component. Two similar segments towards the west, are offset and hidden under active folds. A fifth segment, towards the NW, corresponds to a right lateral blind shear fault buried in depth, in the vicinity of the large Pambak-Sevan fault. 14 vertical sections across the fault, including focal mechanisms, illustrate these features. A relocation of the main shock and aftershocks for the period before the installation of the portable network, confirms the spatial extent of the seismicity. The foreshock, the main shock and the strongest aftershock (4min 20s after the main shock) have approximately the same epicentre. Thus the rupture started at the crossing of the Pambak-Sevan and Alavar faults and propagated bilateraly from there, although the seismic moment associated to the Alavar branch is only about one sixth of the total moment. The stress regime is one of triaxial compression with a a, axis oriented N344". The same orientation is given by the microtectonic observations made on the central segment of the surface ruptures, a result that agrees with previous estimates for the Georgian Caucasus.

The epicentre of the destructive earthquake that devastated northern Armenia, the strongest in the region since historical times, is located within the Lesser Caucasus, a mountain country subjected to north–south compression by the push of the Arabian plate. A French-Soviet field expedition studied surface breaks and aftershock activity. The fault scarp could be followed for 13 kilometres and showed a reverse dislocation of 1.6 metres. Aftershocks are shallower than 13 kilometres, and delimit a ruptured surface of about 300km2.