Why do earthquakes occur? It is common question in mind whenever we feel the surface under our feet moving. So, we discuss why and how earthquakes occur?
Earthquake is a sudden movement of land area when the entire affected area begins to shake. It results in destruction, sometimes excessive, depending upon its depth and strength.
Earthquakes usually occur when the deep rocks several meters beneath the land suddenly breaks and there is rapid motion along a fault. This sudden release of energy causes the seismic waves that make the ground shake.
During and after the earthquake, the plates or blocks of rock start moving and they continue to move until they get stuck again. The spot underground where the rock first breaks is called the focus, or hypocenter of the earthquake. The place right above the focus (at the ground surface) is called the epicenter of the earthquake.
Interestingly, earthquakes happen every day all over the world, along both tectonic plate edges and the inner area of the earth. Earthquakes occur along faults, which are fractures between blocks of rock that allow the blocks to move relative to one another. Faults are caused by the bumping and sliding that plates do and are more common near the edges of the plates.
Why do earthquakes occur?
The Earth’s crust (the outer layer of the planet) is made up of several pieces called tectonic plates and most earthquakes occur along their edges. The plates under the oceans are called oceanic plates. Plates that are not under the ocean are continental plates. The plates are moved around by the motion of a deeper part of the earth (the mantle) that lies underneath the crust, and by the weight of oceanic plates that pulls them down below oceanic plates. These plates are always moving apart, bumping, or sliding past each other at about the same speed that your fingernails grow. Earthquakes usually occur where two plates are running into each other or sliding past each other.
How do we measure the earthquake?
The earthquakes originate in tectonic plate boundary. The focus is point inside the earth where the earthquake started, sometimes called the hypocenter, and the point on the surface of the earth directly above the focus is called the epicenter.
There are two ways by which we can measure the strength of an earthquake: magnitude and intensity. Magnitude is proportional to the energy released by an earthquake at the focus. It is calculated from earthquakes recorded by an instrument called seismograph. It is represented by Numbers (e.g. 5.2, 7.7). Intensity on the other hand, is the strength of an earthquake as perceived and felt by people in a certain locality. It is a numerical rating based on the relative effects to people, objects, environment, and structures in the surrounding. The intensity is generally higher near the epicenter. It is represented by Romans (e.g. II, IV, IX). In the Philippines, the intensity of an earthquake is determined using the PHIVOLCS Earthquake Intensity Scale (PEIS).
The Three types of Earthquake
There are mainly three types of earthquakes:
- Induced Earthquakes. Induced quakes are caused by human activity, like tunnel construction, filling reservoirs and implementing geothermal or fracking projects.
- Volcanic Earthquakes. Volcanic quakes are associated with active volcanism. …
- Collapse Earthquakes.
How to protect yourself during an earthquake?
There is an earthquake happening everywhere around us any moment. Yet, we human are relatively unable to protect ourselves from earthquake. After all, it is a natural process. Yet, there are ways to protect yourself from an earthquake.
Follow these steps to protect yourself from impact of an earthquake:
- Look for a safer place and sit down
- Avoid places with ceilings, beams or light structures
- Immediately move out of a place which has any cracks
- Do not remain in a standing position as one can fall down and the fall during an earthquake is very dangerous