Earthquake - Facts and Information

An Earthquake is a phenomenon of a sudden shaking of the ground. In the Philippines, earthquakes are common, as it is located in the Pacific Ring of Fire where a looooot of tectonic plates meet. There are five active fault lines in the country namely the Western Philippine Fault, the Eastern Philippine Fault, the South of Mindanao Fault, Central Philippine Fault and the Marikina/Valley Fault System.

Earthquakes are caused by the sudden movement of masses of rocks that releases seismic waves under the Earth’s surface. It mostly occurs in areas called "fault" or fault line where rock masses usually move with one another. Major fault lines are commonly located at the edges of the tectonic plates of the Earth’s crust.

Anatomy of an Earthquake

An earthquake has two main points that give its location and identity: the hypocenter and the epicenter. The point under the Earth’s surface where the earthquake originated is called the focus or the hypocenter. The point directly above the hypocenter and on the Earth’s, surface is called the epicenter.

Magnitude and Intensity are two methods of measuring the strength of an earthquake. Magnitude is the measurement calculated and recorded through an instrument called seismograph. It is proportional to the energy that was released by an earthquake at the focus. It is represented by numbers (3.5, 6.1). On the other hand, intensity is a numerical rating based on the assessment of the effect of earthquake on the environment or the location of where the earthquake happens such as on people, objects, and structures. The closer the location to the epicenter, the higher the intensity is. Magnitude is measured by the Mercalli scale whilst intensity is measured by the Richter scale.

https://clatsopauxcomm.org/images/e-prep/ModifiedMercalli-Richter.jpg

Types of Earthquakes

a) Tectonic Earthquakes

This is the most common type of earthquake. It is a natural-occurring that is produced by the sudden movement of rock masses along fault lines and plate boundaries.

b) Volcanic Earthquakes

This is another natural type of earthquake that occurs when lava or magma beneath an active volcano erupts or when a volcanic eruption happens. It produces a sudden release of energy in the ground which causes a movement of shaking or an earthquake.

c) Man-Made Earthquakes

This is an artificially induced type of earthquake as it is from human activities such as fluid injection into the deep wells, the detonation of large underground nuclear explosions, excavation of deep mines, and filling of large reservoirs.

To see an updated list of earthquakes that are currently happening in the Philippines

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References

https://www.britannica.com/science/earthquake-geology

https://www.phivolcs.dost.gov.ph/index.php/earthquake/introduction-to-earthquake