Space weather and earthquakes: possible triggering of seismic activity by strong solar flares

Abstract

The studies completed to-date on a relation of the Earth’s seismicity and solar processes provided the fuzzy and contradictory results. The main problem of this research is a lack of physical explanation of a mechanism of earthquake triggering by strong variations of space weather conditions. Based on results obtained in the field and laboratory experiments on earthquake triggering by DC pulses injection into the Earth crust we may assume that the similar triggering phenomena may occur after the strong electromagnetic impact to the earthquake source due to solar flares or geomagnetic storms. Numerical estimations demonstrated that telluric currents induced by geomagnetic pulsations generated by solar flare have the similar density at the depth of earthquake source location (10-6 A/m2) in comparison with the current density generated by artificial power sources (10-7 – 10-8 A/m2) resulted in observed spatiotemporal redistribution of seismic activity in the regions of Pamirs and Northern Tien Shan. For supporting the idea of a possible earthquake triggering by solar flares we carried out a statistical analysis of global and regional (Greece) seismicity behavior during the solar flare of X9.3 class occurred on September 6, 2017 (the strongest flare over the past thirteen years). We have discovered a new evidence of earthquake triggering due to the Sun-Earth interaction by simple comparison of a number of earthquakes before and after the strong solar flare. The global number of earthquakes (USGS catalog, M ≥ 4) for time window of ±11 days after the solar flare has increased by 68%, and the regional seismicity (Greece, EMSC catalog, M ≥ 3) has increased by 120%.