What is an Earthquake?

Question

All about Earthquake in the Philippines

Answer 1

It all comes down to stress and strain. It is not 'the plates rubbing together' as many people say; or at least that's a very simplistic view.

Plate tectonics causes stress on the continents and oceans, all over the surface of the earth. In some places, the stress is very small (usually within the plates). Elsewhere, the stress is high, usually where the plates meet each other. Since each plate moves, when two come in contact, the stress each other. They can push on each other and cause compressional stress, they can pull with extensional stress, and they can slide past or shear each other with tensional stress.

Faulting, causing earthquakes, comes from the fact that this stress is building up all the time, but rocks and continents are strong materials. Just like hitting a rock with a small hammer, you do put stress on it, but a small amount. It would take a sledgehammer to put enough strain (effects and accumulation of stress) to build up and cause breakage. In the earth, the area around an active fault builds up strain from the stress of plate tectonics. Most faults become locked, because of this strength, and thus can not release their strain. Away from the fault, the stress produces very small and slow movement of the rock masses as a whole. Eventually, the strain is too much and the rest of the plate has moved too far and the fault releases the strain build-up all at once in a big stress release called an earthquake. This is called the elastic rebound theory, and it explains most (but not all) movements.

This is why an earthquake's size is relative to the fault size. The bigger the fault, the bigger the strain build up, and the bigger the release in an earthquake. Subduction zones and collision zones, where large portions of plates actually can rub together as a whole, have the really big earthquakes, like the 2004 Sumatra earthquake. In other plate boundaries, the entire plate boundary does not act together, so the faults become spread out and many faults take up the strain from the tectonic stress, like with the San Andreas Fault in California (it only takes up ~3/4 of the stress between the plates).

Earthquakes are really tricky things; there is still so much we need to learn. As of now, there is no way to predict them, but we can say where the danger is highest and about how long between events.

Answer 2

Earthquakes are the Earth's natural means of releasing stress. Humans do by screaming, exercising or listning to music, well the earth does it by rocking and rolling (you like that joke, i spent hours thinking that one up :). When the Earth's plates move against each other, stress is put on the lithosphere which is made up of the crust and the upper mantle.

As the plates move they put forces on themselves and each other. When the force is large enough, the crust is forced to break. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which we feel and call an earthquake.

The earth is made of around 7 major plates. These plates are part of the earths crust and are floating of top of an area of the earth known as the mantle. This is the driving mechanism for the plates. Most Earthquakes are caused by Plate Tectonics. The earth's crust consists of a number of sections or plates that float on the molten rock of the mantle. These plates move on convection currents caused by heat rising from the center of the earth. The hot magma rises and spreads out on the surface, creating new crust.

The crust spreads out forming a new plate until it meets another plate. One of the plates will be pushed down into the interior of the earth and reabsorbed into the mantle. Plates can also be compressed to push up mountains when they collide or move sideways along what are known as transform faults. the other 2 faults are known as divergent faults which is when 2 paltes slowly move away from each other and converegent faults which is when 2 plates push against each other.

The plates are the Earth's crust that float on the molten rock in the center of the Earth. Most of the inside of the Earth is so hot that the rock just simply melts away. The molten rock, which is also known as magma, bubbles up very slowly in great currents under the surface of the Earth. The crust that floats on the magma moves with it. The Plates are just pieces of the crust. Just like a giant jigsaw puzzle. The part that makes it hard to understand is that it all moves extremely slowly. Just a few cm a year, roughly at the same rate a your finger nails are growing.

Answer 3

The world is like a jigsaw puzzle. The earth's crust is broken into various plates, different sizes and shapes. These plates float on on a body of magma (mantle) and can shift and move.

An earthquake occurs when the plates rub against eachother, slide under eachother or slide over eachother. There is an initial friction that holds the plates from moving, but eventually, the hold breaks and a sudden movement occurs. Those sudden jolts creates seismic waves that ripple throughout the crust.

It just so happens that the Phillippines are near one of those points (called faults) where two plates meet.

Please look for info on the Theory of Platetechtonics for more info.

Answer 4

As mentioned before, the Earth's crust is made up of plates. Because of convection of the mantle and magma (right below the crust), these plates are constanting moving and not all in the same way. Some crash into one another while others just slide past.

The borders between plates are known as boundaries. There are three types: subduction, convergence, and transform. In subduction, two or more plates are pushed together and one plate (the more dense one) slides beneath the other. In convergence, both plates get crunched up and form mountains. Transform boundaries are also known as faults. When two plates slide past eachother, they create friction. Pressure can build up for a long time between these two plates until the elasticity can't take any more. The elastic rebound theory explains how when the elasticity breaks, one or both plates are thrust suddenly.

This movement is what causes earthquakes.

I hope this helps!

Answer 5

An earthquake happens when Earth's tectonic plates shift. The Earth is like a house with a cracked foundation. These cracks in the Earth are called faults; and sometimes, those faults will 'settle' like the old house. When there is a collision or collapse of some sort, it might rattle the 'house', or the upper part of the house, around. Since the faults and tectonic plates are so massive, this happens very violently.

Answer 6

An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy in the crust that propagates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground and sometimes tsunamis, which may lead to loss of life and destruction of property.

Earthquakes may occur naturally or as a result of human activities. In its most generic sense, the word earthquake is used to describe any seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves.

You could get more information from the link below...

Answer 7

I'm a native born and raised S.F. Bay Area gal and not literally sure what a causes an earthquake. But, I think it is caused when certain heat factors within the earth heats up especially alot. When that increased heat occurs it causes certain 'rock' plates to shift, thus moving the rock plates, thus a felt earth shift and quake on the earth's surface. That must mean that certain places within the earth are more prone to more heat than others places in the world. California's placement on the earth more prone to increased heat deep within the earth? Not sure...but I think that is what it is.

Answer 8

An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy in the crust that propagates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground and sometimes tsunamis, which may lead to loss of life and destruction of property.

http://en.wikipedia.org/wiki/Earthquake

Answer 9

Philippines Earthquake Information

Historic Information
Learning from Earthquakes: Philippines
http://www.eeri.org/lfe/philippines.html
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Institutions
Philippine Institute of Volcanology and Seismology: PHIVOLCS
http://www.phivolcs.dost.gov.ph/
Seismological Observation and Earthquake Prediction Division: SOEPD
http://www.phivolcs.dost.gov.ph/soepd2/main.html
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Maps
Political Map of the Philippines
http://earthquake.usgs.gov/regional/world/philippines/map.php
Seismic Hazard Map
http://earthquake.usgs.gov/regional/world/philippines/gshap.php
Earthquake Density Map
http://earthquake.usgs.gov/regional/world/philippines/density.php
Seismicity Map of the Philippines
http://earthquake.usgs.gov/regional/world/philippines/seismicity.php

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Notable Earthquakes
Historical Earthquakes
http://www.phivolcs.dost.gov.ph/Maps/Misc/HistoricalEQ.gif
List of Destructive Earthquakes in the Philippines
http://www.phivolcs.dost.gov.ph/DestructiveEQ.htm
Historic Earthquakes in the Philippines
http://earthquake.usgs.gov/regional/world/historical_country.php#philippines

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Recent Earthquakes
Last Earthquake in the Philippines
from the NEIC Earthquake Bulletin
http://neic.usgs.gov/neis/last_event/world_philippines.html
Recent Local Earthquakes
http://www.phivolcs.dost.gov.ph/soepd2/index_bulletin.html
Latest Earthquake Information
http://www.phivolcs.dost.gov.ph/EQlatest.html
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Tectonic Information
Tectonics and Volcanoes of the Philippines
http://volcano.und.nodak.edu/vwdocs/volc_images/southeast_asia/philippines/tectonics.html

Answer 10

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An earthquake is a phenomenon that results from and is powered by the sudden release of stored energy in the crust that propagates seismic waves. At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground and sometimes tsunamis, which may lead to loss of life and destruction of property.

Earthquakes may occur naturally or as a result of human activities. In its most generic sense, the word earthquake is used to describe any seismic event—whether a natural phenomenon or an event caused by humans—that generates seismic waves.

Most naturally occurring earthquakes are related to the tectonic nature of the Earth. Such earthquakes are called tectonic earthquakes. The Earth's lithosphere is a patchwork of plates in slow but constant motion caused by the heat in the Earth's mantle and core. Plate boundaries grind past each other, creating frictional stress. When the frictional stress exceeds a critical value, called local strength, a sudden failure occurs. The boundary of tectonic plates along which failure occurs is called the fault plane. When the failure at the fault plane results in a violent displacement of the Earth's crust, the elastic strain energy is released and seismic waves are radiated, thus causing an earthquake. This processes of strain, stress, and failure is referred to as the Elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth and is converted into heat. Therefore, earthquakes lower the Earth's available potential energy, though these losses are negligible.

Earthquakes occurring at boundaries of tectonic plates are called interplate earthquakes, while the less frequent events that occur in the interior of the lithospheric plates are called intraplate earthquakes.

The majority of tectonic earthquakes originate at depths not exceeding a few tens of kilometers. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, earthquakes may occur at much greater depths (up to hundreds of kilometers). These seismically active areas of subduction are known as Wadati-Benioff zones. Deep focus earthquakes are another phenomenon associated with a subducting slab. These are earthquakes that occur at a depth at which the subducted lithosphere should no longer be brittle, due to the high temperature and pressure. A possible mechanism for the generation of deep focus earthquakes is faulting caused by olivine undergoing a phase transition into a spinel structure.

Earthquakes may also occur in volcanic regions and are caused by the movement of magma in volcanoes. Such quakes can be an early warning of volcanic eruptions.

A recently proposed theory suggests that some earthquakes may occur in a sort of earthquake storm, where one earthquake will trigger a series of earthquakes each triggered by the previous shifts on the fault lines, similar to aftershocks, but occurring years later, and with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th Century, the half dozen large earthquakes in New Madrid in 1811-1812, and has been inferred for older anomalous clusters of large earthquakes in the Middle East and in the Mojave Desert.