Epicentral distance

Epicentral distance refers to the ground distance from the epicenter to a specified point. Generally, the smaller the epicentral distance of an earthquake of the same scale, the heavier the damage caused by the earthquake. On the contrary, with the increase of epicentral distance, the damage caused by the earthquake is gradually reduced. Due to the limitation of seismometers designed in the early years, some seismic magnitude scales began to show errors when the epicentral distance exceeded a certain range from the observation points. In seismology, the unit of far earthquakes is usually ° (degree), while the unit of near earthquakes is km. But regardless of distance, Δ is used as a symbol for the epicentral distance.