Tag: structure of earth

Earth's crust is broken up into large pieces called tectonic plates. Tectonic plates are giant pieces of the Earth's crust that fit together and move around on the Earth's surface. Tectonic plates are constantly moving slowly, but sometimes friction between them causes them lock together and become unable to move. The rest of the plates carry on moving, which leads to increased pressure on the locked section. Eventually, the locked section succumbs to the pressure, and the plates move past each other rapidly. This movement causes a tectonic earthquake. The waves of released energy move through the Earth's crust in all direction and cause the shaking we feel at an earthquake site.

Most earthquakes are tectonic earthquakes, which happen when the large, thin plates of the Earth's crust called tectonic plates become stuck as they move past one another. They lock together, and pressure builds up. When they finally release, earthquakes occur.

As the magnitude records by seismograph at a place is more by 1, the magnitude of tremors will be 10 times more. Hence, the magnitude of tremors at 'B' are 100 times than at place 'A' since they differ by 2 in magnitude.

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included in the magnitude formula to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude of 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.
The Richter scale has the readings from 1 to 10. The reading of magnitude 3 on the Richter scale would be recorded by a seismograph. If the Richter scale gives a reading of magnitude 3, then the earthquake is not likely to cause much damage. Generally, earthquake of magnitudes higher than 7 is considered destructive in nature.

Richter scale is not a linear scale. It is a logarithmic scale. A difference in magnitude of $2$ implies a multiplication factor of $10^2 = 100$.

A Chinese mathematician, named Zhang Heng, inverted and constructed the first seismograph in A.D. 132.

Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake.

The outermost layer of the Earth is called as crust. It is not in one piece but fragmented. Each fragment is called as a plate. Such 7-8 major plates are present. Also, there are many minor plates. These plates are in continuous motion. When these plates brush past one another or a plate goes under another, it causes collision. This causes earthquake on the surface of the Earth. Earthquakes occur all the time around the world. But they are too small to be noticed. Major earthquakes are less frequent. Hence, given statement is true.

Earthquakes can causes floods, landslides and tsunamis, Earthquakes occurs all the time, all over the earth but at very less magnitude & earth's plates are in continual motion.