What Cause the Earth Quake

Natural calamities are predictable, but inevitable. One of them is earthquake! So what is an earthquake? In simple terms, one can call it as shaking and vibration of the earth. And what causes an earthquake to happen? Frequent volcanic activities and constant movement of tectonic plates underground are palpable causes of earthquakes. So now that we know a little bit on what causes an earthquake, let's understand the different types and reasons for earthquakes.

Causes of Earthquakes

Before understanding types of earthquakes, it is important to know what causes earthquakes. So here you go! Basically, the earth crust is constituted of a solid core, molten magma mantle and the tectonic plates that constitute the crust. These plates are in constant motion due to the convection currents of the magma and hence are either sliding against each other or moving away from each other. Although there is constant motion under the grounds, none of these are felt by us.

So, due to this constant motion over the years, mountains and valleys are formed, with the former being formed when plates converge, causing one plate to go below the other. However if the plates move in different direction, sliding against each other, due to the friction generated, some sections of these plates lock together, causing a lot of kinetic energy to build up. The line of intersection which contains the point of friction between these plates, is often known as the earthquake fault line. These earthquake fault lines are often called fractures in the earth's crust. So when the plates start moving, the stored energy is released from the point of intersection (also known as the hypocenter), in the form of an earthquake. Hope, this answers your query, what causes an earthquake.

How Earth-Quake Happen

In the past two months the world has encountered a series of earthquakes of high magnitudes. With the devastating 7.0 earthquake hitting Haiti in January which took away more than 200,000 precious lives, the world saw three other earthquakes following in close succession. The 7.0 magnitude earthquake near Japan, the massive 8.8 earthquake near Chile on Saturday, and a 6.4 near Taiwan after that, all make us shudder. The Chile quake was so massive that NASA says it slightly tilted the earth's axis and shortened the day. Wow! What an impact! Moreover, the destruction caused by these quakes are simply mind boggling! The oodles of destruction with respect to lives and material destruction leaves the land hit by one, completely shattered. Geographical surveys state that several million earthquakes shake the earth every year. The only reason why these four earthquakes have been in the news so much is because the quakes hit highly populated regions of the world. As we see the destruction, death, pain and sorrow associated with earthquakes, it often makes us wonder why and how earthquakes happen? Read more on largest earthquake ever recorded.

Types of Earthquakes

When an earthquake occurs, it always comes out in three waves, the primary (P-Waves: high frequency short-wavelength longitudinal waves), secondary waves (S-Waves: high frequency, short-wavelength, transverse waves) and surface waves (L-Waves: low frequency, long-wavelength, transverse waves). Now that the question, how earthquakes happen, is clear, let's study the four types of earthquakes:

Tectonic Earthquake

This earthquake is triggered when there is a lot of strain and stress exerted on the tectonic plates. For instance, if you take a twig and try to bend it, you can feel energy building up through the twig, until it snaps. Once snapped, the twig vibrates, releasing energy. The same is what happens in a tectonic earthquake. Here, let me explain with the example of San Andreas Fault in California, where two plates, the Pacific plate and the North American plate were involved. Both these plates were moving in northwesterly direction, with one moving faster, due to which the tension created due to the friction of the plates caused an earthquake. Tectonic earthquakes are most common and keep happening all the time under the earth's crust, in both land and the ocean.

Volcanic Earthquake

Volcanic eruptions can also cause earthquakes. Many a time, the acidic lava that is vented out cools down as soon as it comes in touch with the atmosphere outside. This cooling blocks the volcanic vent and the pressure built inside gets trapped. But the pressure needs to be released in some way or the other and so chooses the weakest of the volcanic plates to escape through. This eventually causes massive and powerful earthquakes that can also give rise to tsunamis, pertaining to the ripples it has created. A significant example of this type is the explosion of Krakatoa (of Indonesia), whose repercussion was a massive earthquake that ratted Java and Sumatra islands. However, volcanoes that vent out basic lava do not cause earthquakes.

Collapse Earthquake

Small ripples that occur in mines and underground caverns, are known as collapse earthquakes. These earthquakes are also factored by massive landslides, or a mine burst which could happen due to intense stress on the rocks constituting the mines, causing large masses of rocks to displace. This eventually leads to collapsing of a mine, and hence is known as a collapse earthquake.

Explosion Earthquake

Detonation of nuclear devices can also set of earthquakes, more commonly known as explosion earthquakes. This occurs, when enormous energy nuclear energy is released during underground nuclear explosions, which when bottled within, increases a thousand times more than the atmospheric pressure, in intensity. Surrounding rocks get vaporized, leaving behind a mammoth cavity which is many meters in diameter.

Some of the most earthquake prone regions are Japan, Indonesia, Java and Sumatra, New Zealand, Hawaiian islands and Andaman & Nicobar islands. One can observe, that islands and high mountain regions are most prone to earthquakes due to the active tectonic plate movement in such areas. So how are earthquakes measured? Intensity of earthquakes is measured on Richter magnitude scale, which is calculated by comparing the maximum heights of seismic waves over a distance of 1000 kilometers, from the point of origin of the earthquake on the earth surface (which is also known as epicenter). And can you imagine how much energy is released during an earthquake? A magnitude of 2, releases 30 times more energy than what would have been released for a magnitudes of 1. So if the magnitude of earthquake, as on Richter scale is 8.6, then an enormous amount of energy as much as that of 10,000 atomic bombs is released from the earth! So now, one must have figured out, what causes an earthquake and how much energy is released during each occurrence. One of the interesting earthquake facts is that, these earthquakes keep happening all the time under the oceanic crust, which is not felt on land until the ripples created are of high intensity.

Main Topic:Earth-Quake

An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time. Earthquakes are measured using observations from seismometers. The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe. The more numerous earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter scale. These two scales are numerically similar over their range of validity. Magnitude 3 or lower earthquakes are mostly almost imperceptible and magnitude 7 and over potentially cause serious damage over large areas, depending on their depth. The largest earthquakes in historic times have been of magnitude slightly over 9, although there is no limit to the possible magnitude. The most recent large earthquake of magnitude 9.0 or larger was a 9.0 magnitude earthquake in Japan in 2011 (as of March 2011), and it was the largest Japanese earthquake since records began. Intensity of shaking is measured on the modified Mercalli scale. The shallower an earthquake, the more damage to structures it causes, all else being equal.[1]

At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity.

In its most general sense, the word earthquake is used to describe any seismic event — whether natural or caused by humans — that generates seismic waves. Earthquakes are caused mostly by rupture of geological faults, but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. An earthquake's point of initial rupture is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter.

Types of Disaster

Earthquake

Earthquake is an unexpected and rapid shaking of earth due to the breakage and shifting of underneath layers of Earth. Earthquake strikes all of a sudden at any time of day or night and quite violently. It gives no prior warning. If it happens in a populated area, the earthquake can cause great loss to human life and property.

Tornado

Tornado is one of the most violent storms on earth. It seems like a rotating and funnel shape cloud. It expands from the thunderstorm to the ground in the form of whirl winds reaching around 300 miles per hour. The damage path could move on to one mile wide and around 50 miles long. These storms can strike quickly without any warning.

Flood

Flood is also one of the most common hazards in the United States and other parts of the world. The effects of a flood can be local to a neighborhood or community. It can cast a larger impact, the whole river basin and multiple states could get affected. Every state is at its risk due to this hazard.

Water Damage

Water damage has a huge effect on your home, its neighborhood and your city. It is very much necessary that you should prepare for water damage. You must know what should be done during and after water damage.

Hail

Hail comes into existence when updrafts in the thunder clouds take the raindrops up towards the extremely cold regions in the atmosphere. They freeze and combine forming lumps of ice. As these lumps can be very heavy and are not supported by the updraft, they fall off with the speeds of about 100 km per hour or more. A Hail is created in the form of an enormous cloud, commonly known as thunderheads.

Wildfire

Wild forest areas catching fire is a very big problem for the people who live around these areas. The dry conditions caused several times in the year in different parts of United States can increase the possibility for wildfires. If you are well prepared in advance and know how to protect the buildings in your area, you can reduce much of the damage caused by wildfire. It is everyone’s duty to protect their home and neighborhood from wildfire.

Hurricane

Hurricane also like the tornado is a wind storm, but it is a tropical cyclone. This is caused by a low pressure system that usually builds in the tropical. Huricanes comes with thunderstorms and a counterclockwise spread of winds near the surface of the earth.

Winter Freeze

Winter freeze storms are serious threats for people and their property. They include, snow, frozen rain, strong winds and extreme cold. Many precautions have to be taken in order to protect yourself, your family, home or property.

Lightning

Lightning is a much underestimated killer. Lightning is an abrupt electric expulsion which comes from cloud to cloud or from cloud to earth followed by an emission of light. Lightning is a common phenomenon after heavy rain and can also occur around 10 miles off from rainfall. Most lightning victims are people who are captivated outdoors in summer during the afternoon and evening.

Volcano

Volcano is a mountain that has an opening downwards to the reservoir of molten rock towards the surface of earth. Volcanoes are caused by the accrual of igneous products. As the pressure caused by gases in the molted rock becomes intense, the eruption takes place. The volcanic eruption can be of two kinds, quiet or volatile. The aftermaths of a volcano include flowing lava, flat landscapes, poisonous gases and fleeing ashes and rocks.Read on to know more on types of disasters.