- An Introduction
is a sudden movement of the earth's surface. You can find out about
current earthquakes here.
are caused by the movement of the earth's tectonic plates. Earthquakes
occur where the earth's plates meet along plate boundaries (see
plate tectonics page for more infomration on this).For example
as two plates move towards each other, one can be pushed down
under the other one into the mantle. If this plate gets stuck
it causes a lot of pressure on surrounding rocks. When this pressure
is released it produces shock waves. These are called seismic
waves. This is an earthquake. The waves spread out from the point
where the earthquake started - the focus. More damage is done
near the focus. The point on the earth's surface directly above
the focus is the epicentre.
The effects of
earthquakes vary. This is a result of a variety of factors such
as the strength of the earthquake, the level of population in an
area and the level of economic development of the area struck.
magnitude (size) of an earthquake is measured using a seismometer.
This is a machine that measures movements in the earth's surface.
Scale measures earthquakes on a logarithmic scale - this means
that an earthquake of 6 is ten times more powerful than one with
a score of 5.
05.46 on 17th January 1995 an earthquake measuring 7.2 on the
Richter scale struck the heavily populated city of Kobe,
Japan. The earthquake occurred along the destructive plate boundary
where the Pacific and the Philippine Plate (oceanic) meet the
Eurasian (continental) plate.
Many freeways and buildings were destroyed, despite the strict
building regulations, and 5000 were killed. Fires spread as a
result of broken gas mains. 250,000 people were left homeless.
- What? Where? When? Why? So What? of the 1999 Turkish Earthquake
Turkish earthquake occurred on Tuesday 17th August 1999 at 3.02
a.m. local time (12 am GMT). The earthquake lasted 45 seconds
and measured 6.8 - 7.0 on the Richter Scale. See the BBC
News web site for detailed case study information and images
on the Turkish
can download a factfile about the Turkish Earthquake
(MS Word 97 - Size - 59kb)
lies on the conservative margin where the Pacific Plate slides
alongside the North American Plate (timeline
of movement). As a result it is susceptible to earthquakes.
The 1906 Earthquake almost destroyed San Francisco. Later, in
1989 an earthquake measuring 6.9 on the Richter Scale hit San