Earthquake Terminology

Term

Definition

  Felt Tremors

Tremors felt in Malaysia

  Depth

Earthquake depth measured from the earth surface to focal point. (Measured in kilometres).

  Epicentre

The epicentre is the point on the earth surface vertically above the hypocentre (or focus point).

  Hypocentre

The hypocentre is the point within the earth crust where an earthquake rupture starts.

  Foreshocks

A series of small earthquakes that occurs before the mainshock.

  Mainshocks

The largest earthquake in a sequence of earthquakes.

  Aftershocks

A series of weak or moderate earthquakes that occurs after the mainshock.

  Magnitude

The magnitude is a number that characterizes the relative size of an earthquake. Magnitude is based on measurement of the maximum amplitude of seismic wave recorded by a seismograph.

  Intensity

The intensity is a number (written as a Roman numeral) describing the severity of an earthquake in terms of its effects on the earth surface and on humans and their structures.

 

Tsunami Terminology

Term

Definition

  Local tsunami

A tsunami from a nearby source for which its destructive effects are confined to coasts within 100 km of the source or less than an hour tsunami travel time from its source.

  Regional tsunami

A tsunami capable of destruction in a particular region, generally within 1,000 km or 1 – 3 hours tsunami travel time from its source.

  Ocean-wide or distant tsunami

A tsunami originating from a faraway source, generally more than 1,000 km or more than 3 hours tsunami travel time from its source.