Causes of Earthquakes

Earthquakes can arise from various natural phenomena, with tectonic earthquakes being the most prevalent. The occurrence of these seismic events is elucidated by the theory of plate tectonics, which describes the dynamics associated with continental drift and ocean floor expansion. According to this theory, the Earth’s surface is segmented into numerous rigid tectonic plates with a thickness ranging from 100 to 150 kilometers. These plates are in constant motion relative to one another, gliding over the asthenosphere, which is situated beneath the Earth’s crust. In addition to tectonic earthquakes, volcanic earthquakes occur due to active volcanic activity; however, they typically do not reach the intensity of tectonic earthquakes and are most often felt near the surface of the Earth, especially close to the hypocenter of the quake.

Earthquakes may also result from anthropogenic activities, known as induced earthquakes. These quakes can occur due to human interventions such as tunnel construction, large-scale reservoir filling, hydraulic fracturing projects, and geothermal energy extraction. Additionally, collapse earthquakes can take place as a consequence of cave and mining collapses.

Earthquake Hazards

Following an earthquake, several potentially destructive events can unfold, including:

Landslides: These may involve landslides and avalanches, as earthquakes can displace rocks or undermine soil cohesion on sloped terrains.
Flooding: Seismic activity can damage dams or trigger landslides into lakes or rivers, resulting in flooding.
Fires: Earthquakes can disrupt electrical lines and gas pipelines, leading to fires that may be difficult to extinguish if water supply pipes are also compromised.
Soil Liquefaction: An earthquake may cause water-saturated granular soil to lose its strength, transforming it into a liquid-like state, which can result in the tilting or sinking of structures and bridges.
Tsunamis: Underwater earthquakes or related landslides can generate tsunami waves, potentially causing significant loss of life.

Overview of Earthquakes

Earthquakes vary in magnitude and impact, with significant quakes capable of demolishing entire cities and resulting in substantial loss of life. An earthquake is defined as a sudden ground shaking caused by the ongoing movement of tectonic plates, which can lead to the accumulation of stress on rock layers along faults. This stress culminates in the breaking and sliding of rock blocks over one another, releasing stored energy in the Earth’s crust as a sudden movement. This energy results in seismic waves that propagate through the Earth’s materials and reach the surface, causing the perceptible seismic vibrations.

It is important to note that earthquakes primarily occur along geological faults, which are narrow zones where the movement of rocks affects one another. The main fault lines around the globe coincide with the edges of large tectonic plates that constitute the Earth’s crust. The crust consists of seven major tectonic plates, along with several smaller ones. These plates diverge at divergent boundaries, converge at convergent boundaries, and exhibit lateral sliding movements at transform boundaries.