Recent Japan quake confirmed aftershock of deadly 2011 event Nathan Howes Tuesday, February 16th 2021, 2:34 pm - Aftershock sequences may persist for more than 2,000 years on the slowest-slipping faults, according to research. After an earthquake strikes, its ripple effects can occur for years, perhaps decades or centuries, afterwards. The Feb. 13 earthquake in Japan is a perfect example of this. The powerful 7.1-magnitude tremor that struck 89 km southeast of Sendai, Japan Saturday was an actual aftershock of the destructive and deadly 9.0-magnitude quake that rattled the same area nearly 10 years ago, according to the country's national meteorological agency. Dozens of injuries were reported in the Fukushima and Miyagi prefectures after the Feb. 13 event, according to local media outlets, but there were no significant casualties.