Measurement of Seismic Waves


 
 
Concept Explanation
 

Measurement of Seismic Waves

Measurement Of Seismic Waves:

The instrument used to measure seismic waves is called a seismograph. A typical seismological output, called a seismogram, looks like a series of waves as shown in figure. Scientists who study the behavior of earthquake are called seismologists

Earthquake are the breaking and cracking of the rocks inside the continental plates. The breakes happen after stress has built up in the surrounding area. There are usually very few or no quakes when the plates moves slowly. When there is a fast movement of the plate, there is a snap (like breaking a cracker ). The crack happens where the quakes starts. Ripples then move out in waves accross the plate. Those waves are called seismic waves. Those waves shakes everyone up within a specific area. When scientists analyze an earthquake they look at several parts.They find out where the focus is. The focus is the extact point where the earthquake started. It is usually many miles or kilometres below the surface of the Earth. Scientists also look to see where the epicenter was. The epicenter is the point on the surface directly above the focus. The national Earthquake information centre (NEIC) records an average of 20,000 earthquakes every year ( about 50 a day ) around the world.

                              

Measurements of the earthquake: Earthquake magnitude is calculated from the amplitude of the waves emitted as recorded by seismometers, and is expressed on 11 scale ranging from zero upwards. Each successive, point on the scale represents a factor of 10 increase in wave amplitude;so that, for example, a magnitude 5 earthquake emits waves 10 times that of a magnitude 4 event and 100 times that of a magnitude 3 event, and so on. In  other words, the magnitude scale is logarithmic. The magnitude scale is sometimes called the Richter Scale after its inventor Californian seismologist  Charles F. Richter.

Sample Questions
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Question : 1

Which of the following seismic waves travel deep inside the Earth ?

Right Option : D
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Question : 2

What is an instrument used to study earthquakes?

Right Option : D
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Question : 3

The machine that measures the strength of an earthquake is called ________________.

Right Option : B
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