noun
main shock (of an earthquake)
Seismological term for the largest earthquake in a sequence, contrasted with foreshocks (前震) and aftershocks (余震).
本震の後も、大きな余震が続いた。
Even after the main shock, large aftershocks continued.
気象庁は、今回の地震を本震と判断した。
The Japan Meteorological Agency determined that this earthquake was the main shock.