The shock wave of a powerful earthquake can easily destroy buildings and other structures, but there are some side-effects of the quake itself. Underground gas pipes may rupture, leading to serious fires and explosions. The health of survivors is but at risk by damaged sewerage systems allowing disease to spread. In mountainous areas, landslides or avalanches can be triggered, and an undersea earthquake can generate a huge wave called a tsunami.
An earthquake is a sudden shaking movement of the surface of the earth. It is known as a quake, tremblor or tremor. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to toss people around and destroy whole cities. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.
So far, there have been sixty-two earthquakes in India. The first recorded earthquake in India was on 6th June 1505 it occurred in Saldang, Karnali zone. And the most recent one happened in India as on 31st January 2018 and occurred in Kashmir, Pakistan, Afghanistan, and Tajikistan.
An earthquake is measured on Richter’s scale. A seismometer detects the vibrations caused by an earthquake. It plots these vibrations on a seismograph. The strength, or magnitude, of an earthquake, is measured using the Richter scale. Quakes measuring around 7 or 8 on the Richter scale can be devastating.
Most earthquake-related deaths are caused by the collapse of structures and the construction practices play a tremendous role in the death toll of an earthquake. In southern Italy in 1909 more than 100,000 people perished in an earthquake that struck the region. Almost half of the people living in the region of Messina were killed due to the easily collapsible structures that dominated the villages of the region. A larger earthquake that struck San Francisco three years earlier had killed fewer people (about 700) because building construction practices were different type (predominantly wood). Survival rates in the San Francisco earthquake was about 98%, that in the Messina earthquake was between 33% and 45%) (Zebrowski, 1997). Building practices can make all the difference in earthquakes, even a moderate rupture beneath a city with structures unprepared for shaking can produce tens of thousands of casualties.
Although probably the most important, direct shaking effects are not the only hazard associated with earthquakes, other effects such as landslides, liquefaction, and tsunamis have also played important part in destruction produced by earthquakes.
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