ИСТИНА

The existence of the effect of the round-the-world surface seismic waves (“seismic echo”) in evolution of aftershock process was shown in the work on a broad evidence base, including hundreds of the main shocks and thousands of aftershocks. At the same time, we by no means believe this effect has been fully proven. We only present a version of our own understanding of the physical causes of the observed phenomenon and analyze the regularities in its manifestation. The effect is that the surface seismic waves excited in the earthquake source by the main shock makes a complete revolution around the Earth and excites strong aftershock in the epicentral area of the main shock at the time T = 3 +/- 0.5 hours after the moment of main shock. The physical nature of the effect is that a critical concentration of wave energy in epicenter is created by converging surface waves under achieving of epicentral area (cumulative effect). Effect of the first seismic echo is manifested most clearly. For the statistical analysis of the dynamics of the seismic events flow after strong earthquakes (main shocks), we selected several datasets from a long time series of the earthquakes contained in the global catalog USGS/NEIC for the period 1973-2014 and in the regional catalog of Northern California for the period 1968-2007. For data processing and efficiently detecting the effect of a seismic echo, we used an algorithm based on the well-known superposed epoch analysis, or synchronous detection method. Thus, the present work supports our hypothesis of the activation of rock failure under the cumulative impact of an round-the-world seismic echo on the source area which is releasing (“cooling”) after the main shock. The spatial regularities in the manifestations of this effect are established, and the independence of the probability of its occurrence on the main shock magnitude is revealed. The detected phenomenon of the seismic echo can be used to increase the probability of a forecast of a strong aftershock in determining the scenario of seismic process in the epicentral zone of occurred strong earthquake. This work was partially supported by the Russian Foundation for Basic Research (project # 18-05-00096) and Russian Governmental assignment programs of the Schmidt Institute of Physics of the Earth RAS. References: 1. Guglielmi A.V., Zotov O.D., Zavyalov A.D. The Aftershock Dynamics of the Sumatra-Andaman Earthquake // Izvestiya, Physics of the Solid Earth, 2014, Vol. 50, No. 1, pp.64-72. ISSN: 1069-3513. DOI: 10.1134/S1069351313060037 2. Guglielmi A.V., Zavyalov A.D., Zotov O.D., Lavrov I.P. Dependence of the Aftershock Flow on the Main Shock Magnitude // Izvestiya, Physics of the Solid Earth, 2017, Vol. 53, No. 1, pp.10-17. DOI: 10.1134/S1069351317010086 3. Zotov O.D., Zavyalov A.D., Guglielmi A.V., Lavrov I.P. On the Possible Effect of Round-the-World Surface Seismic Waves in the Dynamics of Repeated Shocks after Strong Earthquakes // Izvestiya, Physics of the Solid Earth, 2018, Vol. 54, No. 1, pp. 178-191. DOI: 10.1134/S1069351318010159