The Earth is an active and constantly changing planet, with its surface in a state of continuous movement as a result of forces within. The most important geological process to shape the planet is the movement of tectonic plates. These enormous pieces of the Earth's lithosphere ride on top of the semi-fluid asthenosphere, and their interaction produces a variety of geological phenomena. Among the most devastating of these is the earthquake, which can level cities, produce tsunamis, and result in massive loss of life and property. Knowing how tectonic plate motions generate seismic activity is essential for forecasting, preparing, and reducing the destructive power of earthquakes.
These tectonic plates consist of large and somewhat rigid blocks forming the outer shell of the Earth. These blocks of tectonic plates are, however, very slow. This slow movement of the plates is such that they are finally brought into contact with each other. Convection currents operate under the internal heat of the Earth in the mantle, causing movement in the plates. Over millions of years, the movements of the Earth's crust gave rise to mountain ranges, ocean basins, and deep-sea trenches.
Plate motion is far from smooth and continuous. Instead, stress builds up along fault lines where plates come into contact with one another. When this stress is more than the rocks can withstand, it is released in the form of seismic waves, producing an earthquake. The severity of an earthquake would depend on such things as the nature of the plate boundary, the depth of the earthquake, and the released energy.
The two plates are coming together the convergent boundaries in the most earthquake-prone area on earth. Most of the time, one of the converging plates is forced under the other in a mechanism known as subduction. The subduction zones bear such extreme pressure and friction that they become the birthing place of major earthquakes.
The Pacific Ring of Fire is a paper-shaped area around the Pacific Ocean. Above this zone are the majority of significant destructive earthquakes that were attributed to subduction. One such earthquake occurred in Japan in 2011 with a magnitude of 9.0 on the Richter scale, triggering a destructive tsunami that resulted in the Fukushima nuclear disaster.
Where there are divergent boundaries, plates are moving apart and producing new crust as the magma ascends to the Earth's surface. Although these zones are usually implicated in volcanism, they cause earthquakes too. The Mid-Atlantic Ridge, an oceanic mountain range that is a consequence of the opening up of the Eurasian and North American plates, has much more frequent but lighter seismic activity.
At transform faults, plates move past one another horizontally. Because of the friction between the plates, they can't move easily, and the stress builds up. When stress is released, earthquakes happen.
One well-known example is California's San Andreas Fault, which has the Pacific and North American plates moving past one another. This fault produced major earthquakes such as the 1906 San Francisco earthquake that devastated much of the city.
Fault lines are cracks in the Earth's crust along which there is movement. The faults are the points of fracture where stress caused by tectonic plate movement is released. There are three types of faults:
These faults are located where the world's earthquakes are said to be concentrated. California, Japan, and Indonesia are examples of some areas subject to great risk due to their location near major fault lines.
Continental drift, originally put forth by Alfred Wegener, is the theory that continents are no longer stationary but instead, gradually advance over the face of the earth. The movement of the continents is somehow influenced by the movements of the tectonic plates beneath. Continental movement is accompanied by interactions with other plates that cause stress and deformation of the crust. These actions have, over millions of years, led to the formation of mountain ranges and ocean basins and have also caused earthquakes.
For instance, the collision of the Eurasian plate with the Indian plate has created the Himalayas and recurring earthquakes in northern India and Nepal. The destructive 2015 Nepal earthquake, which registered 7.8 on the Richter scale, was a consequence of this continued collision.
Scientists employ several methods of measuring and forecasting earthquakes. The seismometer is the most frequently used tool; it registers seismic waves and is used to measure the magnitude and location of an earthquake. The Richter scale and the Moment Magnitude Scale (Mw) are commonly used to measure the strength of earthquakes.
While it is still difficult to predict the exact location and timing of an earthquake, scientists research fault lines, records, and current seismic activity to predict the probability of future occurrences. Early warning systems, like Japan's Earthquake Early Warning (EEW) system, assist in issuing warnings seconds to minutes before an earthquake, providing individuals with a chance to seek shelter and reduce damage.
Several strong earthquakes have had a lasting effect on human civilization. Some of the most destructive events are:
Earthquakes cannot be avoided, but their effects can be reduced by being prepared and enhancing infrastructure. Governments and scientists concentrate on:
Although, earthquakes originate mostly from the action of tectonic plates whereas some have been triggered by human activities. Activities such as mining have observed that reservoir-caused seismicity from large dams and hydraulic fracturing (fracking) change the distribution of stress in the Earth's crust, which causes tremors. It is stated that the Zipingpu Dam in China was associated with the 2008 Sichuan earthquake. Knowing this hazard will help regulate industrial practices to minimize human-induced seismicity.
The movements of tectonic plates are responsible for the major changes in the Earth's surface and are associated with great hazards that include earthquakes. Scientists and government officials draw from their knowledge of how plate interaction, fault zones, and continental drift trigger seismic activities to implement measures that can prevent damage and allow some casualties to be saved. Although the prediction of earthquakes is not presently realized, gathering prowess and preparedness strategies have grown so that a measure of resistance can now be produced against such disasters. The more research is carried out, the more humanity adjusts itself to the abuse the changeable Earth presents.
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