Saturday, October 4, 2008

Earthquakes Really Do Happen Just About Everywhere

"Earthquakes Really Do Happen Just About Everywhere" By Carolyn Nicolaysen

The crust of the earth is constantly moving. This movement is slow and, except in the case of an earthquake, it is unnoticeable. Movement of the crust creates stress. This stress can cause rocks and the geology of the area to change its shape and size. This change to the body of rock can also be called strain, the adjustment of the rock in response to stress.

An earthquake is a shaking or rolling of the ground caused by a sudden release of energy stored in the earth's crust. This happens when stress builds up until suddenly a rupture occurs and energy waves (seismic waves) are sent out through the earth. Volcanic activity can also cause earthquakes. The epicenter of an earthquake is the point of the greatest movement.

The size of an earthquake is directly related to the amount of energy released. Two factors are used to determine the true size of a quake: energy released and the damage caused.

The Richter scale measures the total amount of energy released by an earthquake. The scale uses numbers from 1 up to describe magnitude. Each number represents an earthquake ten times stronger than the next lower number. For example, an earthquake with a magnitude of 5 is ten times stronger than an earthquake with a magnitude of 4.

During the 20 years from 1975 to 1995 there were only four states in the United States that did not have any earthquakes: Florida , Iowa , North Dakota , and Wisconsin . The 1906 San Francisco earthquake registered 7.9 on the revised Richter scale. In 1954 a 7.3 magnitude hit Dixie Valley Nevada . The year 1959 saw a 7.3 at Hebgen Lake , Montana . Prince William Sound in Alaska had the biggest quake recorded in the United States : 9.2 in 1964. The 1983 Idaho Borah Peak earthquake had a magnitude of 7.3. And the 1994 Northridge quake was a 6.6.

Most people know earthquakes occur in California and Alaska , however, earthquakes are not unique to these regions. From December 1811 to February 1812, a series of the greatest earthquakes in history with an intensity at the top of the earthquake scale struck—not in California—but in a one million square mile area of the Midwest and southeastern portion of the United States: Missouri, Kentucky, Tennessee, Ohio, Georgia, and South Carolina. These quakes occurred along the New Madrid fault. Because of the limited population in the area at the time, the quakes resulted in only one death. If a quake of this size were to occur in these areas today the loss of life could be 50,000 or more.

On August 10, 1884 an earthquake measuring 5.2 on the Richter scale had its epicenter in New York south of Rockaway Beach . It caused chimneys to crumble and rang church bells in Connecticut and Pennsylvania . According to experts, a similar quake would cause major damage because of a much larger population today and the enormous buildings, bridges, and tunnels which were constructed without thought of earthquakes. New York , New Jersey , and Connecticut all sit on ancient geological faults.

The Wasatch Range runs north to south through Utah and like all mountain ranges it was produced by a series of earthquakes. The 240 mile long Wasatch Fault is made up of several segments, each capable of producing up to a 7.5 magnitude earthquake. See Meridian article Keeping Our Kids Safe While Away at College for more information on the Wasatch Range.

January 17, 1994 residents of Northridge , California were jolted out of bed at 4:31a.m. Apartment buildings pancaked, freeway overpasses fell, and fifty-seven people died—all in eight seconds. Seismologists consider Northridge to be only a strong quake, two steps below the magnitude 8 “big one.” Scientists believe the "big one" will cause an earthquake rupture which will extend ten to fifteen miles deep and 200 to 250 miles long, maybe more. It will be the size of twenty Northridge earthquakes laid end to end.

In October 2007 a 5.6 earthquake rocked the San Francisco Bay Area. This quake occurred on the Calaveras fault which runs adjacent to the Hayward Fault. The Hayward Fault moves about every 140 years producing catastrophic quakes. Experts fear the recent Calaveras quake could actually trigger the “big one” on the Hayward Fault. The Hayward fault last moved 140 years ago.

On January 26, 1700 a great earthquake shook the Pacific Northwest . This quake, with an estimated magnitude of 9.0, produced shaking which continued for several minutes and dropped the coastline of Washington State by nearly five feet.

Yes, several areas of the country are due for a “big one”, but the United States is not alone. Each day there are approximately 2,600 earthquakes somewhere in the world, or two per second. On October 14, 1968 a magnitude 6.9 earthquake hit east of Perth , Australia . The greatest recorded earthquake occurred in Chile on May 22, 1960. It was recorded as a 9.5 on the Richter scale and caused tsunamis in Chile , Japan , Hawaii , Philippines , New Zealand , Australia , and Alaska .

When a sizable earthquake occurs, there are many potential disasters that may follow during the next few days or weeks. With broken natural gas lines, fires are inevitable; dam failures, hazardous materials spills, power outages, natural gas leaks, landslides, loss of clean water supplies, road and bridge collapses, and even tsunamis may occur. Infrastructure may be destroyed: police and fire stations may be damaged or destroyed; hospitals may suffer severe damage just when they are needed most; jobs will be lost; banking and grocery store deliveries interrupted; gasoline may become scarce; telephone and internet services may be inoperable and garbage may pile up. With mail delivery spotty or nonexistent, bills will still need to be paid but might not be delivered.

While people are dealing with all of these hardships, first responders will have to choose between meeting the needs of their families and reporting for work. Who are first responders? We automatically think about fire fighters, police officers, and health care professionals but here are also many others. Utility workers will be needed immediately to restore power and water. Those who run your waste disposal plants will need to get those facilities up and running again.

Yes, earthquakes can happen where you live.

With all this to be concerned about, questions arise:

Can earthquakes be predicted? The answer is no. Scientists have never predicted a major earthquake. Scientists can, however, estimate the probability of an earthquake occurring by examining the records of past quakes.

Is there earthquake weather? Again, the answer is no. There is no connection between weather and the likelihood of an earthquake occurring. Earthquakes are not capable of altering the weather either.

Will California eventually fall into the ocean? Oh, I love that one! No. Earthquakes on the San Andreas Fault are a result of slip plate motion. The plates are moving horizontally past one another, so California is not going to fall into the ocean. Over thousands or millions of years Los Angeles could end up a neighbor of San Francisco , but the entire state will not fall into the ocean.

Which country has the most devastating earthquakes? Which has had the most damage and fatalities? China , Iran , and Turkey are in active areas which have a long history of catastrophic earthquakes.

Which country has the most earthquakes? Japan has more total earthquakes than anywhere else. Indonesia is a close second with Tonga and Fiji being very active zones.

Which country has the fewest earthquakes? Antarctica is the safest place to live if you are worried about earthquakes.

Why all this earthquake information without instructions of some kind? Well, I felt it was important for everyone to recognize the dangers they face from earthquakes even though they may live in an area we don't normally associate with them. Now, re-read the Meridian article Prepare Your Home for the Unexpected and, if you have not already done so, begin making the preparations that are suggested.

1 comments: said...

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