An earthquake can be both a man-made and natural disaster. It is difficult to control the magnanimity and fierceness of such an attack when an earthquake comes. The recent Nepal example is in itself a testimony of how necessary it has become to be aware of some of the earthquake preventive measures. But before that one must know how an earthquake is caused. Read up:-
This is one of the major causes of an earthquake. There are several types of earthquake waves including primary waves and also secondary waves. However, Surface waves consist of several major types and are known as long waves. These waves then cause heavy disruption when they flow as they are affected by changes in the density and also the rigidity of the material through which they pass. Major examples of such an earthquake were in Assam, India (1897 and 1950).
Compression in the earth’s crust
There have been many examples of Earthquakes in Australia being caused because of the movements along faults. This could be a result of the compression in the Earth’s crust. You can determine the size or magnitude of earthquakes by measuring the actual amplitude of the seismic waves which gets recorded on a seismograph.
Dams and reservoirs
This can be one of the major causes. The rupture in the million tons of water would have hastened the earth’s shaking. No geological process can actually come up with such a huge concentration of mass in such a small area except for a volcano. It is history which has proved how large reservoirs of water created by dams have caused earthquakes. Examples include from Zambia to Greece to India. Example: – 2008 Sichuan, China earthquake- killed nearly 70,000 people. It is believed that it was triggered by the construction of the Zipping Dam nearby.
Taking water out of ground is another example through which earthquakes have been necessarily initiated. The act causes the water table to drop thus destabilizing an existing fault. For example: – 2011 Lorca earthquake. This 2011 earthquake in Lorca, Spain caused a huge amount of destruction for its 5.1 magnitude as was recorded in the Richter scale. It was also because the epicenter of the mountain was located so close to the surface. Its shallow epicenter could have had a relation with that of the act of groundwater extraction near Lorca. Since 1960, water extraction has been one of the main reasons as to why the region’s water table dropped by an incredible 250 meters.
Geothermal power plants — Salton Sea Geothermal Field and The Geysers Geothermal Field
According to a 2011 study published, it was clear that researchers at the University of California had discovered that seismic activity had increased around the Salton Sea as geothermal field operations around the area had ramped up. While these earthquakes in themselves may not be the main cause of damage but the other interaction with bigger faults like San Andreas could be one. Earthquake swarms include bursts of dozens of small quakes prevailing below magnitude 6 or so—happen regularly along the Salton Sea. Example of such an earthquake include: – Salton Sea Geothermal Field and The Geysers Geothermal Field
Tracking and injection wells — 2011 Oklahoma earthquake
The process of hydraulic fracturing, or fracking is not actually the main cause of earthquakes. It is when the waste fracking liquid is injected back underneath into the deep wells that cause rupture. The fluid caused due to the extraction of liquids can seep out and also lubricate faults. This can cause them to slip more easily. For example:- 2011 Oklahoma earthquake- A study had pointed out that Seismic activity in Oklahoma has shot up along with the rise of fracking. Earthquake swarms have become a regular occurrence in the region. The number of earthquakes had shot up from a dozen in 2008 to over 1,000 in 2010.
Big skyscrapers and buildings can put immense pressure on the earth’s surface. It can cause the rudimentary rocks to even crack. As a study points out, Taipei 101’s especially huge mass of 770,000 tons is presently putting too much pressure on the soft sedimentary rock below. It comes because of the extra steel and concrete which is being used to make the skyscraper solid enough to withstand earthquakes. Since construction began on the building of Taipei 101, the region began to receive several micro-earthquakes and even two larger earthquakes which went directly underneath the building.
Tectonic movements of the earth
Tectonic Earthquakes are caused when the crust becomes subjected to strain, and eventually starts moving. The theory of plate tectonics explains how when the crust of the Earth is made of several plates, there are large areas of crust which float on the Mantle. Since these plates are small and are free to slowly move, they undergo a lot of movement.Many of these earthquakes which we feel are may be located in the areas where these plates could collide can even slide past each other.
Example: – Due to tectonic movements, San Francisco has noticed many small shakes.
Volcanic earthquakes are very less likely than Tectonic ones. They are triggered when there is an explosion of an explosive volcano. It depends from volcano to volcano. If they are quite, chances are less. For example: – In the case of Mt Pele, the lava has solidified before it flew down the sides of the volcano. At least around 20 miles of the area around is affected when a volcano explodes. However for a tectonic earthquake, effects may be felt around the globe.
Any disturbance on the surface
All earthquakes are majorly caused by disturbance of the outside crust on the ephemeral surface of the earth. Anything which will tend to destroy the perfect equilibrium or the balance of the globe will likely cause an earthquake. Each side and every part must necessarily carry the same weight. There is the perfect nature’s balance required which man spoils due to his removals of earth, ores, oil, rock, coal, and the building of cities, that is continually changing.
Example: – The Himachal Pradesh Earthquake in India, 2014.