Earthquake may cause additional damage and hampering recovery if continuous. Since 2015 over 10,000 people died due to earthquakes and tsunamis.
Little was understood about earthquakes until emergence of seismology at the begining of 20th century.seismology which involves the study of all aspects of earthquakes,has yielded answers to such long standing questions as why and how earth quake occurs.
An Earthquake is a perceptible shaking of the surface of the Earth,resulting from sudden release of energy in the earth's crust that creates seismic waves.
Major Earthquake mainly occurs in belts coinciding with the margins of tectonic plates. The most important Earthquake belt is the Circum -pacific belt, which mainly affects coastal religion of pacific ocean - those of New zealand ,New Guinea,Japan,The Aleutian Islands,Alaska, the western coast of North and South America.80% energy released in earthquake come from this. It is known as pacific ring of fire as associated with volcanic activity. The 2nd is alpide Belt passes through mediterranean region eastwards from Asia and join circum -pacific belt in the East Indies. 15% energy released here .
FORMS
The energy released by elastic strain,gravity,chemical reaction or even the motion of massive bodies. All of these elastic strain is the most important cause as this energy is only that is stored in sufficient quantity in the earth to produce major disturbances known as tectonic earthquakes.
Some earthquakes are associated with volcanic activity.circum -pacific Belt are example.
Man made earthquakes due to poor planning in infrastructural activities like fracking for oil,dambuliding etc.
Another reason can be cooling of earth detected by scientists. It cause contraction of the earth's crust which also volcanic disturbance causing.
Particularly In Indian perspective in 2017 suspected ,Indian tectonic plate is slowly going underneath Eurasian plate per year. May be due to this energy accumulation in this region there is greater magnitude Earthquake.