MIDDLE URAL EARTHQUAKE on October 18, 2015, ML=4.7, I0=6

Instrumental and macroseismic data on the earthquake of 18.10.2015 at 21h44m UTC, ML=4.7, I0=6 in the Sverdlovsk region, near the village of Sabik (Middle Urals) are presented. A significant amount of macroseismic data made it possible to build a map of the macroseismic field, taking into account the anisotropic nature of the propagation of the seismic effect. Taking into account the decision of the focal mechanism, the tectonic position of the source was substantiated.

Models of the macroseismic field earthquakes and their influence on seismic hazard assessment values for Central Asia

Seismic intensity assessment in points of a macroseismic scale plays an important role for researching the seismic history of areas characterized by active seismicity, as well as for construction (and updating) of seismic zoning maps in various scales. Macroseismic scale points are generally referred to in construction standards applied in the majority of post-Soviet states. In our study aimed to model the macroseismic field of earthquakes, a large volume of macroseismic data on Central Asia was analyzed, and coefficients used in Blake–Shebalin and Covesligeti equations were aligned. This article presents a generalized dependence model of macroseismic intensity attenuation with distance. The model takes into account seismic load features determined by various depths of earthquakes. The ratios of small and big axes of the ellipse, that approximates real isoseists, are estimated with respect to seismic scale points, earthquake depths and magnitudes. The East Uzbekistan area is studied as an example to investigate whether seismic hazard assessment values may differ depending on a chosen law of seismic influence intensity attenuation with distance.

Katav-Ivanovsk earthquake on 04.09.2018, mb=5.4 (Urals)

The article summarizes the instrumental and macroseismic data obtained in the area of Katav-Ivanovsk earthquake, which occurred on September 4, 2018, in Chelyabinsk region, Russia. The earthquake was the strongest instrumentally recorded earthquake in the Urals (mb=5.4) and at the same time, it had the most seismic intensity among other earthquakes in Russia in 2018 (I0=6 points). The uniqueness of this event was given by the fact that after it for the first time for the Urals the aftershock process was recorded, the active stage of which lasted more than 1 year. Like the mainshock, some aftershocks had a significant macroseismic effect. The work contains the results of studies that allowed to determine the exact coordinates of the epicenter in conditions of lack of near stations using the relative location technique. New processing approaches also made it possible to estimate the depth of the focus through a function of phase spectrum matching. Finally, a considerable amount of macroseismic data formed the basis of the macroseismic field map.

Determination of parameters of historical earthquakes based on macroseismic data

The paper attempts to determine the main parameters of historical earthquakes of the Carpathian region based on macroseismic data, using the macroseismic field equation, indirect parameters, and complex comparison with modern earthquakes. So far, the main source of information about the parameters of historical earthquakes in the Carpathian region has been "New catalog of strong earthquakes ...". In this catalog, all parameters are defined very ap-proximately, with a wide range of values. In addition, over the forty-year period since the release of the catalog, the initial macroseismic data of Carpathian region earthquakes have been substantially replenished and re-evaluated using the MSK-64 macroseismic scale. The study determined such basic parameters of historical earthquakes as the macroseismic epicenter, the intensity at the epicenter, focal depth, and magnitude. As well as additional parameters: direction of the maximum macro-seismic effect, area of intensity zones, distance, and azimuth to the extreme point where the earthquake was felt. The earthquake parameters were calculated using the attenuation formula of the macroseismic field with coefficients obtained by the R.Z. Burtiev for intermediate earthquakes of the Vrancea zone of the Carpathian region, separately in four azimuthal ranges. For crustal earthquakes, the general Blake-Shebalin macroseismic field equation was used. Despite possible errors associated with a correct assessment of intensity at observation points, as well as the accuracy of the coefficients of the macro-seismic field equation used for specific seismic events, it was possible to determine the type of each historical earthquake and obtain more accurate values of their parameters. The re-fined parameters of historical earthquakes will allow making a more holistic picture of the seismic hazard in the Carpathian region.

MARJANBULAK EARTHQUAKE on MAY 25, 2013 with КР=14.1, МS=5.2, I0=7 (Djizakh province, Uzbekistan)

The instrumental data and the results of the macroseismic survey of the Marjanbulak earthquake MwMOS=6.2 with an intensity of 8 on the MSK-64 scale, which occurred in Uzbekistan, are presented. The isoseismal map is given. Correspondence between the intensity of the earthquake manifestation and the regional macroseismic field equation is shown. Geological and geophysical, engineer-geological conditions in the epicentral zone are described. The seismicity of the observation area is reviewed.

TUYABUGUZ EARTHQUAKE on May 25, 2013 with КР=14.1, МS=5.2, I0=7 (Tashkent district, Uzbekistan)

The results of instrumental and macroseismic observations of the Tuyabuguz earthquake on May 24, 2013, with КР=14.1, МS=5.2, I0=7 (MSK-64) are presented. The earthquake occurred 35 km southwest of Tashkent and was felt up in many settlements of Uzbekistan. The isoseismal map is given. Correspondence between the intensity of the earthquake manifestation and the regional macroseismic field equation is shown. Geological and geophysical conditions in the epicentral zone are described. The seismicity of the observation area is reviewed. The focal area of the Tuyabuguz earthquake is located in the seismically active zone, where strong historical and instrumentally recorded events occurred with intensity I=7–8 point.

Influence of shaking intensity attenuation peculiarities on reliability of earthquake loss estimation in emergency mode

The methods and results of seismic hazard zoning are investigated for the Russian Federation territory and abroad. The input data used in the zoning procedure, aimed at revealing the boundaries of areas with stable seismic intensity attenuation parameters have been analyzed. The zoning procedure has been developed for determining the boundaries of territories, within which the macroseismic field parameters (i.e., the coefficients in N.V. Shebalin’s equation; the orientation of the elliptic isoseist axes, as well as the ratio of their semi-axes) show close values in each point. Examples are given in distinguishing zones characterized by quasi-stable parameters for separate regions, as well as in calibrating the computer model of the macroseismic field. The case studies are considered in the presence of a complete set of input data and under conditions of their insufficiency. The efficiency of the macroseismic field calibrated models application in the Extremum system in order to increase the reliability of near real time earthquake loss estimations is shown.

Macroseismic Field Anisotropy of the ML 4.7 Earthquake of 18 October 2015 in Central Urals, Russia

Ruslan A. Dyagilev, Natalia S. Guseva, Filipp G. Verkholantsev report on macroseismic field anisotropy of a rare ML 4.7 tectonic event in the Ural Mountains on 18 October 2015. This publication is an English adaption of an article that was first published in Russian in the Russian Geophysics Journal (2016, Vol. 5, pp. 42–46).

Regional macroseismic field and intensity residuals of the August 24, 2016, Mw=6.0 central Italy earthquake

A macroseismic investigation of the August 24, 2016, Mw=6.0 Central Italy earthquake, was carried out through an online web survey. Data were collected through a macroseismic questionnaire available at the website www.haisentitoilterremoto.it, managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). Over 12000 questionnaires were compiled soon after the seismic occurrence, coming from over 2600 municipalities. A statistical analysis was applied to the data collected in order to investigate the spatial distribution of intensity of the earthquake. The macroseismic intensity field (I) was described by identifying three main components: an isotropic component (II), a regional anisotropic component (IA) and a local random variations parameter (). The anisotropic component highlighted specific and well-defined geographical areas of amplification and attenuation. In general, the area between the Adriatic coast and Apennines Chain was characterized by an amplification of intensity, while the West side of the Apennines showed attenuation, in agreement with the domains found by other works focused on the analysis of instrumental data. Moreover, the regional macroseismic field showed similarities with instrumental PGA data. The results of our analysis confirm the reliability of web questionnaire data.