Facts About Earthquake
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What is an Earthquake?
An earthquake is the sudden, sometimes violent movement of the earth's surface from the release of energy in the earth's crust. -
What Causes Most Earthquakes?
When the crust of the earth is subjected to tectonic forces,it bends slightly. But, because the crust is rigid,so when the stress or pressure exceeds the strength of the rocks, the crust breaks and snaps into a new position. Vibrations called seismic waves are generated and travel both through the earth and along its surface. These seismic waves cause the movement we call earthquakes. -
Where Are Earthquakes Likely to Occur?
Within the areas of the crust are fractures, known as faults, along which two crustal blocks have slipped or moved against each other. One block may move up while the other moves down, or one may move horizontally in one direction and the other in the opposite direction. Geologists and seismologists (scientists who study earthquakes and the processes that create them) have found that earthquakes occur repeatedly at faults, which are zones of weakness in the earth's crust. -
How Many Earthquakes Happen Each Year?
There are over a million quakes annually, including those too small to be felt. The following table shows the average frequency of different magnitudes.Description Magnitude Frequency per year Great 8.0+ 1 Major 7.0-7.9 18 Large (destructive) 6.0-6.9 120 Moderate (damaging) 5.0-5.9 1,000 Minor (damage slight) 4.0-4.0 6,000 Generally felt 3.0-3.9 49,000 Potentially perceptible 2.0-2.9 300,000 Imperceptible less than 2.0 600,000+ -
Where do most earthquake occur in India ?
Most of the earthquakes occur in Himalayan region. -
Where did the largest earthquake occurred in India ?
Assam earthquake (1950) of magnitude 8.7. -
How Many Earthquakes Happen Every Month , Day , Minute?
Using the previous table:
Per month..........................................Approximately 80,000
Per day.............................................Approximately 2,600
Per minute.........................................Approximately 2
And, per second, one earthquake is felt approximately every 30 seconds. Of these only a relative few are capable of causing damage. Earthquakes are common natural events. -
How Deep Do Earthquakes Occur in the World?
Earthquakes occur in the crust or upper mantle, which ranges from the surface to about 800 kilometers deep (about 500 miles). -
Where Do Most Earthquakes Occur in the World?
The surface of the earth is divided like a jigsaw puzzle into giant pieces called tectonic or crustal plates. These giant pieces move slowly over partially melted rock known as the mantle. As they move, they slide along each other, move into each other, move away from each other, or one slips under another. On these active plate boundaries about 95% of all the world's earthquakes occur. California, Alaska, Japan, South America, and the Philippines are all on plate boundaries. Only 5% are in areas of the plates far away from the boundaries. These are called mid-plate or intra-plate earthquakes and are, as yet, poorly understood. -
When was the First Instrument for Detecting Earthquakes Invented?
The earliest known earthquake detection instrument was invented in 132 A.D. by Zhang Heng, a Chinese philosopher. The instrument was a large (2 meters or 6.5 feet in diameter) bronze jar, with a central pendulum inside. Decorating the jar on the outside were a series of dragon heads connected to a pendulum, each with a ball in a hinged mouth. Directly beneath each dragon head, on the surface of the stand, was a bronze toad, head up, mouth open to receive a ball from the dragon's mouth. During an earthquake, the ground motion would move the pendulum and cause one or more balls to fall from a dragon's mouth into a toad's mouth. The direction of the earthquake was indicated by which of the dragon heads had dropped a ball. This instrument was sensitive enough to perceive shaking too small to be felt, as it detected an earthquake over 600 kilometers (372 miles) away, news of which arrived several weeks later. Earthquake detectors are mentioned later in oriental manuscripts, but in the west earthquake detection instruments did not emerge until centuries later. -
What is the Difference Between an Earthquake Prediction And a Forecast?
An earthquake prediction involves assigning a specific date, location, and magnitude for an earthquake. A forecast assigns a series of probabilities and a range of years and magnitudes to a region. There is no way to accurately predict earthquakes, but forecasts have been calculated for different areas of the United States. The earthquake in northern California on October 17, 1989 was not predicted, but did fall within the magnitude range, time span, and region forecast by U.S. Geological Survey staff. -
Does Animal Behavior Change Before Earthquakes?
Changes in animal behavior before earthquakes have been observed and documented in different parts of the world, most recently in the northern California earthquake of October 17, 1989. It has been recorded that a fish in a high school biology lab in California would flip on its side before some earthquakes.
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Does the Ground Really Open Up and Swallow People?
This is an earthquake myth. Cracks and fissures appearing in the ground are a common effect of earthquakes. Most of these are narrow and shallow. In very large earthquakes changes in the level of the land can result in larger cracks that can cause a lot of damage to buildings, but the ground does not swallow people and buildings. -
Do Earthquakes Cause Volcanoes?
No, there are different earth processes responsible for volcanoes. Earthquakes may occur in an area before, during, and after a volcanic eruption, but they are the result of the active forces connected with the eruption, and not the cause of volcanic activity. -
Are Earthquakes Weather Related?
In the 4th Century B.C., Aristotle proposed that earthquakes were caused by winds trapped in subterranean caves. Small tremors were thought to have been caused by air pushing on the cavern roofs, and large ones by the air breaking the surface. This theory lead to a belief in earthquake weather, that because a large amount of air was trapped underground, the weather would be hot and calm before an earthquake. A later theory stated that earthquakes occurred in calm, cloudy conditions, and were usually preceded by strong winds, fireballs, and meteors. There is no connection between weather and earthquakes. They are the result of geologic processes within the earth and can happen in any weather and at any time during the year. -
Do All Large Magnitude Earthquakes Result in Great Amounts of Death and Destruction?
No.The destructive forces of an earthquake depends on many factors. Large earthquakes commonly occur in remote areas of the world, with no buildings or people, and are not destructive. In addition to magnitude, some of the factors that determine damage and deaths are: population densities, the density and types of building construction, local geologic conditions, distance from the epicenter, earthquake depth, how long the shaking continues, and the degree of earthquake preparedness in the region. -
Can Earthquakes Be Prevented?
There is no known way to prevent earthquakes, but it is possible to lessen the impact. The amount of devastation from an earthquake can be greatly diminished by building structures using earthquake resistant design, making the interiors of buildings safe from falling objects, and educating people about earthquake safety.