Seismicity and seismic mode in Sverdlovsk Region

Abstract

Sverdlovsk region is a major industrial center. There are mining enterprises, chemical plants, reservoirs, and high-capacity power plants. These objects are located close to large settlements. Currently, about 400 seismic events are recorded in the region annually. These are industrial explosions, rock bursts, rock tectonic events and tectonic earthquakes. Tectonic earthquakes are rare. For the period 1788–2022, about 30 tectonic earthquakes were recorded in Sverdlovsk region. The intensity of earthquakes at the epicenters was up to 5.0–6.0 on the MSK-64 scale. To ensure the seismic safety of objects of increased responsibility and especially important engineering structures, it is necessary to carry out studies on detailed seismic zoning of the territory under consideration. The article presents the results of seismological studies. Consolidated unified catalogue of seismic events that occurred in the Urals region was compiled. Historical and instrumental catalogue data for the period 1788–2022 served as the basis. In this paper, a repeatability graph is presented. The graph position below the abscissa scale indicates weak seismic activity in the region. Earthquakes with a magnitude of 2.5 ≤ MS ≤ 5.5 occurred over the period 1788–2022 on average with a frequency of less than 1 event per year. The resulting slope of the b-value repeatability graph is 0.6446 ± 0.1093. For a detailed knowledge of the repetition of earthquakes of various magnitudes in the area under consideration, a matrix of seismic activity A3.3 was constructed. In general, the observed area is weakly differentiated in terms of seismic activity (A3.3), which varies in the range of 0.001 ≤ A3.3 ≤ 0.011. At the same time, the highest values of A3.3 are observed in the western part of Sverdlovsk region within the coordinates 5730′–58 N, 5830′–60 E. The background values of seismic activity (A3.3=0.001) are typical for the eastern part of the Sverdlovsk region, located within the West Siberian plate. In the study area, the sources of most of perceptible earthquakes are localized in the depth interval of 10–15 km, which corresponds to the depths of the pre-Riphean crystalline basement rocks.