Diurnal Periodicity of Weak Earthquakes in the Zhongar North Tian Shan Region

Abstract

A targeted exploration of the dependence of seismic activity on the time of day continues for about a century and a half. During this time, numerous scientific studies have been done on the diurnal periodicity in the occurrence of earthquakes. In this work, we present the first results of a study of diurnal periodicity in the occurrence of weak earthquakes by the example of individual seismically active zones of the Zhongar North Tian Shan region. The research was performed on the data on number of earthquakes with energy classes (K = logE, J) equal to 5, 6, 7 and 8, which arose within the North Tian Shan (1), Zhongar (2), Halyktau (3) and Ketmen (4) zones. To do this, by counting the number of earthquakes of corresponding energy that occurred during each hour, a time series of hourly values of number of shocks for the entire time period was compiled. Then, using the method of superposition of periods, the number of seismic events for each hour over the entire time interval is summed up, and a graph of the average daily course of the number of earthquakes was compiled. Studies have established the existence of diurnal periodicity in the realization of weak earthquakes and microquakes. It was most clearly observed for seismic events with K ≤ 6 for the North Tien Shan, Zhongar, Ketmen, and K ≤ 7 for Halyktau zones. With an increase in energy class (magnitude) of earthquakes, the observed pattern weakens and practically disappears for shocks with K ≥ 7 for the earthquakes, Zhongar, Ketmen and with K ≥ 8 for the Halyktau zones. The obtained graphs of the diurnal sequence of seismicity are identical to the analogous curves of diurnal variation in the numbers of weak earthquakes allocated for other regions (areas) of the globe.