A similarity in patterns of global seismicity after St. Patrick's Day geomagnetic storms of 2013 and 2015

We present the results of a response of global seismicity to St. Patrick's Day (March 17) geomagnetic storms in 2013 and 2015, which occurred during rather similar solar flux levels and nearly identical storm sudden commencement times. A similar pattern of most substantial earthquake occurrence after storms is revealed. Namely, with a time delay of ~30 and ~39 days after storm onsets in 2013 and 2015, respectively, the strong crust earthquakes occurred at continental areas in Iran (M7.7, April 16, 2013) and Nepal (M7.8, April 25, 2015). Then, with a time delay of ~68 and ~74 days after storm onsets in 2013 and 2015, respectively, the strong deep-focused earthquakes occurred beneath the Sea of Okhotsk (M8.3, May 24, 2013, Russia) and beneath the Pacific Ocean (M7.8, May 30, 2015, Japan). It is shown that in the time of geomagnetic storm onsets (06:04 UT in 2013 and 04:48 UT in 2015), the longitudes at which the future strong earthquakes occurred were located under the polar cusps where the solar wind plasma would have direct access to the Earth's environment. The results support our earlier findings [Ouzounov and Khachikyan, 2022] that seismic activity may respond to geomagnetic storm onset with a time delay of up to ~ two months.