Coherent oscillations of the earth caused by earthquakes

Abstract

The records from the wideband IRIS seismic stations located in different regions of the world are analyzed. The phenomenon of emergence of regional- and global-scale coherent oscillations after earthquakes with M ≥ 7 is revealed. Coherence emerges irrespective of the epicentral location and source depth of the parental earthquake; it also does not depend on the location of the receiving stations. The effect is most clearly pronounced at the periods of the oscillations ranging from 5 to 10 min. Coherence is detected at the earliest 3.1 h after the parent earthquake and lasts for one to a few days, depending on the magnitude of the event. In the earthquakes with M ≥ 7 that occurred in the world during the studied period (from January 1, 2000 to March 11, 2011), a statistically significant increase is revealed in the number of repeated quakes within three days after the preceding event. This increase coincides with the periods of occurrence of the coherent oscillations and probably points to the influence of these oscillations on the potential sources of the earthquakes, which are on the metastable state. The results suggest the long-range interaction of the earthquakes as a probable cause of this phenomenon.