The first tremors occurred at 2:41 a.m. local time in the Pacific Ocean, 175 kilometers south of Simushir Island. The magnitude of the seismic event was 5.0. Three hours later, a second earthquake struck 145 kilometers southwest of the city of Severo-Kurilsk on the island of Paramushir. Its magnitude was 4.7.
In both cases, the incidents went unnoticed by the neighbors.