Abstract:
On October 28th 2018, in the Focsani depression – the seismogenic zone of Vrancea, Romania, another earthquake occurred, with a large area of influence on the territory of Bulgaria. Based on an analysis if received reports, describing the feeling and other effects, an intensive map of the seismic impact on people and the environment on the territory of the country was built.The maximum intensity (Imax) with which the earthquake was felt in our country is from the 5th grade on the Medvedev–Sponheuer–Karnik scale (MSK-64). The seismic forecast properties of the microseismic noise in the minute range (i.e., half a minute report), recorded in seismic stations, located on the territory of the Balkan Peninsula were examined. It has been applied a methodology, developed by Lyubushin, A.A. (1998, 2007, 2009), corresponding to the specificity of the studied region. All calculations are done in MATLAB. Characteristic changes of the statistical parameters of the background seismic noise were determined a few days before the earthquake, expressed by the relative reduction of the parameters singular spectrum width (Δα, α *) and increase of the Hearst index (H). The effect of synchronization of ground seismic noise in the earthquake preparation stage was sought. On the basis of the study, characteristic changes of the statistical parameters of the background seismic noise were established several days before the Vrancea earthquake (28.10.2018) with Mw = 5.5, which represents a relative decrease of the parameters Δα, α* and an increase of the parameter H. A method is presented in the study of the dynamics of the seismic noise before the event with the use of continuous time series of the statistical parameters Δα, α* and H. The effect of synchronization of the seismic noise in the earthquake preparation stage was discovered near the epicenter and within a distance of 250 km from it.