Special report: Strong Earthquake Jolts SW China
BEIJING, May 13 -- What is an earthquake? An earthquake is what happens when two blocks of the earth suddenly slip past one another.
The surface where they slip is called the fault or
fault plane.
The location below the earth's surface where the
earthquake starts is called the hypocenter, and the location directly above it
on the surface of the earth is called the epicenter.
Sometimes an earthquake has foreshocks. These are
smaller earthquakes that happen in the same place as the larger earthquake that
follows.
Scientists can’t tell that an earthquake is a
foreshock until the larger earthquake happens.
The largest, main earthquake is called the mainshock.
Mainshocks always have aftershocks that follow. These
are smaller earthquakes that occur afterwards in the same place as the
mainshock.
Depending on the size of the mainshock, aftershocks
can continue for weeks, months, and even years after the mainshock!
(Source: USGS)
