Earthquake is one of the worst natural disasters. It causes a catastrophe. But do you know why do earthquakes occur? What are its after-effects? Let’s find out more about it.
Introduction to Earthquake
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.
Learn more about Shape of Earth here in detail.
Causes of Earthquake
Earthquakes are caused by sudden tectonic movements in the Earth’s crust. The main cause is that when tectonic plates, one rides over the other, causing orogeny collide (mountain building), earthquakes. The largest fault surfaces on Earth are formed due to boundaries between moving plates.
The stress increases when they stick, relative motion between the plates. This continues until the stress rises and breaks, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy as shock waves. Such faults are San Andreas fault in San Francisco, Rift valley in Africa etc.
Effects of Earthquake
The effects of an earthquake are terrible and devastating. Many building, hospitals, schools, etc are destroyed due to it. A lot of people get killed and injured. Many people lose their money and property. It affects the mental health and emotional health of people.
The environmental effects of it are that including surface faulting, tectonic uplift and subsidence, tsunamis, soil liquefaction, ground resonance, landslides and ground failure, either directly linked to a quake source or provoked by the ground shaking.
Read about The Earth in more detail here.
Solved Examples for you
Q. The earth shakes when _________ occurs.
Sol. The correct answer is option ”c”. 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.
Q. What was the measurement of the intensity of earthquake occurred in Bhuj on Richter scale?
- one to two
- eight to nine
- seven to eight
- five to six
Sol. The correct answer is option ”c”. The intraplate earthquake reached 7.7 on the moment magnitude scale and had a maximum felt intensity of X (Extreme) on the Mercalli intensity scale.