seismic moment

例句：

1. 1. The seismic activity in the region has been increasing recently.
   该地区的地震活动最近有所增加。
2. 2. The seismologist is studying the causes of this earthquake.
   地震学家正在研究这次地震的原因。
3. 3. The seismic waves are traveling through the earth's crust at a speed of about 7.8 kilometers persecond.
   地震波以大约每秒7.8公里的速度穿越地球地壳。