主しゅ要よう動どう

noun

principal movement; principal shock

Seismological term for the main shaking phase of an earthquake, as opposed to preliminary tremors or aftershocks.

• 主しゅ要よう動どうの到とう達たつ前まえに緊きん急きゅう地じ震しん速そく報ほうが発はっ表ぴょうされた。

  An earthquake early warning was issued before the arrival of the principal shock.

• 主しゅ要よう動どうによる揺ゆれは約やく30秒びょう続つづいた。

  The shaking from the principal movement lasted about 30 seconds.