noun
epicentral distance
Technical term in seismology; the distance from the epicenter to a given observation point.
震央距離が大きいほど、地震波の到達時間は遅くなる。
The greater the epicentral distance, the later the arrival time of seismic waves.
震源距離 is the distance from the hypocenter (focus), while 震央距離 is the distance from the epicenter (surface point directly above the hypocenter).
Compound of 震央 (epicenter) and 距離 (distance).