The Reason for Earthquakes

Once there was just one massive continent in one ocean . Because of the earth's rotation the land splitted and formed new continents and the earth's plates. The plates float on the earth's magma.

The pacific plate drifts up to 3 cm per year along the seams of the moving plates. There is an area of friction which can be from 15 to 50 kilometres deep. Nearly all earthquakes originate from a friction area. An extreme power is released when the earth's plates grind against each other which tears through the earth's crust causing an earthquake.

In California there are hundreds of these tears in the earth's crust.


MORE FACTS

There are up to 14 earth tremors daily in California, but many of them are so slight that they go unnoticed. Since the beginning of this century there have been 3600 tremors which have registed over 4.0 on the Richter scale. In 1906, there was an earthquake measuring 8.3 which nearly flattened San Francisco.Because of the terrible destruction this earthquake caused new laws were passed for building construction. This turned out to be useful in 1989, when a quake measuring 7.1 shook the city : Another catastrophe was prevented.

It is estimated that sometime within the next 30 years there will be another quake of the 8.3 magnitude. Residents are told to avoid putting heavy objects on shelves, to fasten cupboards to walls and in the case of a quake to get under a bed or table.Californians live under the constant threat of earthquakes.

GREAT EARTHQUAKES DURING THE LAST CENTURY

1 1906 SAN FRANCISCO, 8.3 Richter Scale
Damage to homes built before earthquake codes.

2 1983 COALINGA, 6.7 Richter Scale
Damage to older homes built before earthquake codes.
3 1971 SAN FERNANDO, 6.6 Richter Scale
Damage to newer homes improperly designed or constructed.
4 1984 MORGAN HILL, 6.2 Richter Scale
Damage to homes built before earthquake codes.
5 1989 LOMA PRIETA, 7.1 Richter Scale
Damage to homes built before earthquake codes.
6 1994 NORTHRIDGE, 6.7 Richter Scale
Damage to modern houses.

http://www.eqe.com/nathazards/eqk.htm

http://pc-78-120.udac.se:8001/www/Geography.html

 

Why California has Earthquakes

California has a lot of earthquakes.

Ever wondered why?

It's because of the population shift that happens every weekend. Most of California's population lives on the coast. On Friday, a significant percentage of the San Francisco Bay Area population gets on Highway 80 and heads for Tahoe/Reno. If it's summer, they go water skiing. If it's winter, then they go snow-skiing. On Sunday night, everyone heads back to the Bay Area. It's this constant teeter-totter effect that creates earthquakes.

Copyright 1997 Stacey Irvine, San Jose, California. stacey@spies.com

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