ProLom Program for Probabilistic Location of Earthquakes Using Macroseismic and Instrumental Data

Abstract

The article is devoted to addressing the critical issue of increasing the reliability of estimates of the parameters of seismic events that occurred during the formation of instrumental observational seismology. Catalogs of this period are characterized by an extremely limited set of instrumentally determined phases, but are accompanied by descriptions of observed macroseismic effects. Previously, the authors proposed a probabilistic method for determining the epicenters and magnitudes of earthquakes based on a joint analysis of their macroseismic and instrumental data. For software implementation of the method, the ProLom program (Probabilistic Locator by Macroseismics) was created. The input data of the program are the values of intensity data points (IDP’s) on the MSK-64 scale and the coordinates of points where the earthquake was observed with these intensities, as well as the arrival times of seismic phases from the bulletins of seismic stations and their coordinates. Based on instrumental and macroseismic data for the test earthquake of May 20, 1967, various combinations of initial data were prepared in order to assess the applicability of the method depending on the distance of seismic stations, the amount of macroseismic information (IDP’s), azimuthal coverage of the source points-intensity values and the range of variations in intensity values. The minimum (boundary) conditions for the applicability of the method were identified: the presence of seismic stations, regardless of the number, at a distance of up to 2000 km from the epicenter and recording of at least two seismic phases, at least 7 IDP’s, and azimuthal coverage of the source with points-intensity values of at least 155°.