Spectral analysis of a shallow earthquake and its comparison with the spectrum of a deep-focus earthquake

Introduction. The article is devoted to the processing of real seismic data (of unique shallow earthquake), analyzing the results in order to study the impact spectra and oscillator response and comparing them with the results of studies of a deep-focus earthquake. Aim. Matching and visual comparison of tripartite plots of total spectra of deep-focus and shallow earthquakes to reveal characteristic differences in their spectral characteristics. Materials and methods. Accelerograms were processed using Microsoft Excel and SeismoSignal programs from SeismoSoft. The total spectrum was calculated using the SRSS ("square root of the sum of squares") method. Results. A shallow earthquake impact spectrum was constructed for each direction, and the total spectrum was calculated using the «square root of sum of squares» (SRSS) method. The response spectrum of a system with one degree of freedom (oscillator) was matched to the impact spectrum. The total response spectra were calculated using five different methods, as a result of which the most appropriate one was determined. Tripartite plots of the spectra of impacts and reactions of deep-focus and shallow earthquakes along the X, Y, Z axes and total with envelopes of impacts and reactions are constructed and analyzed. Conclusions. It follows from the obtained results: the total envelopes of the response spectra have a larger width by periods in comparison with the envelopes of the impacts spectra; a deep-focus earthquake has higher dynamic coefficients than a shallow one; the region of the envelopes of the total spectra of the impacts of both types of earthquakes includes periods corresponding to the proper periods of civilian multi-storey buildings, which increases the probability of resonance.