Some Common Myths about Earthquakes

Can animals predict earthquakes?

The earliest reference we have to unusual animal behavior prior to a significant earthquake is from Greece in 373 BC. Rates, weasels, snakes, and centipedes reportedly left their homes and headed for safety several days before a destructive earthquake. Anecdotal evidence abounds of animals, fish, birds, reptiles, and insects exhibiting strange behavior anywhere from weeks to seconds before an earthquake. However, consistent and reliable behavior prior to seismic events, and a mechanism explaining how it could work, still eludes us. Most, but not all, scientists pursuing this mystery are in China or Japan.

Can some people sense that an earthquake is about to happen? (Earthquake sensitive)?

There is no scientific explanation for the symptoms some people claim to have preceding an earthquake, and more often than not there is no earthquake following the symptoms.

Is there earthquake weather?

In the 4th Century B.C., Aristotle proposed that earthquakes were caused by winds trapped in subterranean caves. Small tremors were thought to have been caused by air pushing on the cavern roofs, and large ones by the air breaking the surface. This theory lead to a belief in earthquake weather, that because a large amount of air was trapped underground, the weather would be hot and calm before an earthquake.
However, there is no connection between weather and earthquakes. They are the result of geologic processes within the earth and can happen in any weather and at any time during the year. Earthquakes originate miles underground. Wind, precipitation, temperature, and barometric pressure changes affect only the surface and shallow subsurface of the Earth. Earthquakes are focused at depths well out of the reach of weather, and the forces that cause earthquakes are much larger than the weather forces. Earthquakes occur in all types of weather, in all climate zones, in all seasons of the year, and at any time of day. Sometimes, we are asked: "Do earthquakes change the weather in any way? Earthquakes themselves do not cause weather to change. Earthquakes, however, are a part of global tectonics, a process that often changes the elevation of the land and its morphology. Tectonics can cause inland areas to become coastal or vice versa. Changes significant to alter the climate occur over millions of years, however, and after many earthquakes.

Earthquake Facts

1. The largest recorded earthquake in the world was a magnitude 9।5 (Mw) in Chile on May 22, 1960।
2. Before electronics allowed recordings of large earthquakes, scientists built large spring-pendulum seismometers in an attempt to record the long-period motion produced by such quakes। The largest one weighed about 15 tons. There is a medium-sized one three stories high in Mexico City that is still in operation.
3. Before electronics allowed recordings of large earthquakes, scientists built large spring-pendulum seismometers in an attempt to record the long-period motion produced by such quakes। The largest one weighed about 15 tons. There is a medium-sized one three stories high in Mexico City that is still in operation.
4. The East African Rift System is a 50-60 km (31-37 miles) wide zone of active volcanics and faulting that extends north-south in eastern Africa for more than 3000 km (1864 miles) from Ethiopia in the north to Zambezi in the south। It is a rare example of an active continental rift zone, where a continental plate is attempting to split into two plates which are moving away from one another.
5. The first "pendulum seismoscope" to measure the shaking of the ground during an earthquake was developed in 1751, and it wasn't until 1855 that faults were recognized as the source of earthquakes।
6. Moonquakes ("earthquakes" on the moon) do occur, but they happen less frequently and have smaller magnitudes than earthquakes on the Earth। It appears they are related to the tidal stresses associated with the varying distance between the Earth and Moon. They also occur at great depth, about halfway between the surface and the center of the moon.
7. Although both are sea waves, a tsunami and a tidal wave are two different unrelated phenomenona। A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth. A tsunami is a sea wave caused by an underwater earthquake or landslide (usually triggered by an earthquake) displacing the ocean water.
8. The greatest mountain range is the Mid-Ocean Ridge, extending 64,374 km (40,000 mi) from the Arctic Ocean to the Atlantic Ocean, around Africa, Asia, and Australia, and under the Pacific Ocean to the west coast of North America। It has a greatest height of 4207 m (13,800 ft) above the base ocean depth.
9. The world's greatest land mountain range is the Himalaya-Karakoram। It countains 96 of the world's 109 peaks of over 7317 m (24,000 ft). The longest range is the Andes of South America which is 7564 km (4700 mi) in length. Both were created bythe movement of tectonic plates.
10. It is estimated that there are 500,000 detectable earthquakes in the world each year। 100,000 of those can be felt, and 100 of them cause damage.
11. It is thought that more damage was done by the resulting fire after the 1906 San Francisco earthquake than by the earthquake itself.

Can we cause earthquakes? Is there any way to prevent earthquakes?

Earthquakes induced by human activity have been documented in a few locations in the United States, Japan, and Canada। The cause was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies. Most of these earthquakes were minor. The largest and most widely known resulted from fluid injection at the Rocky Mountain Arsenal near Denver, Colorado. In 1967, an earthquake of magnitude 5.5 followed a series of smaller earthquakes. Injection had been discontinued at the site in the previous year once the link between the fluid injection and the earlier series of earthquakes was established. (Nicholson, Craig and Wesson, R.L., 1990, Earthquake Hazard Associated with Deep Well Injection--A Report to the U.S. Environmental Protection Agency: U.S. Geological Survey Bulletin 1951, 74 p.)

Other human activities, even nuclear detonations, have not been linked to earthquake activity. Energy from nuclear blasts dissipates quickly along the Earth's surface. Earthquakes are part of a global tectonic process that generally occurs well beyond the influence or control of humans. The focus (point of origin) of earthquakes is typically tens to hundreds of miles underground. The scale and force necessary to produce earthquakes are well beyond our daily lives. We cannot prevent earthquakes; however, we can significantly mitigate their effects by identifying hazards, building safer structures, and providing education on earthquake safety.

Deadliest earthquakes on record

Rank	Name	Date	Location	Fatalities	Magnitude	Comments
1	"Shaanxi"	January 23, 1556	Shaanxi, China	830,000	8
2	"Tangshan"	July 28, 1976	Tangshan, China	255,000 (official)	7.5	Estimated death toll as high as 655,000.
3	"Aleppo"	August 9, 1138	Aleppo, Syria	230,000		Death toll disputed as first mention of 230,000 dead was in the 15th century.
	"Indian Ocean"	December 26, 2004	Off west coast northern Sumatra, Indonesia	230,000	9.3	Deaths from earthquake and tsunami.[3]
5	"Damghan"	December 22, 856	Damghan, Iran	200,000
	"Gansu"	December 16, 1920	Ningxia-Gansu, China	200,000	8.6	Major fractures, landslides.
	"Tsinghai"	May 22, 1927	Tsinghai, China	200,000	7.9	Large fractures.
8	"Ardabil"	March 23, 893+	Ardabil, Iran	150,000
9	"Great Kantō"	September 1, 1923	Kantō, Japan	143,000	7.9	Great Tokyo fire.
10	"Ashgabat"	October 6, 1948	Ashgabat, Turkmenistan	110,000	7.3
11	"Kashmir"	October 8, 2005	Kashmir & N.W.F.P, Pakistan	100,000 (estimated) , 80,000 (official)	7.6 or 7.8	3.5 million people homeless, 100,000 feared dead

Largest earthquakes by magnitude

Pos.	Date	Location	Magnitude
1	May 22, 1960	Valdivia, Chile (see: Great Chilean Earthquake)	9.5
2	December 26, 2004	Off west coast northern Sumatra, Indonesia (see: 2004 Indian Ocean earthquake)	9.31
3	October 16, 1737	Kamchatka, Russia (see: Kamchatka earthquakes)	9.3
4	March 27, 1964	Prince William Sound, Alaska, USA (see: Good Friday Earthquake)	9.2
5	March 9, 1957	Andreanof Islands, Alaska, USA	9.1
6	November 4, 1952	Kamchatka, Russia	9.0
7	January 26, 1700	Cascadia subduction zone (see: Cascadia earthquake)	9
8	January 31, 1906	Colombia-Ecuador	8.8
9	February 4, 1965	Rat Islands, Alaska, USA	8.7
10	November 25, 1833	Sumatra, Indonesia	8.7
11	November 1, 1755	Lisbon, Portugal (see: 1755 Lisbon earthquake)	8.7
12	March 28, 2005	Sumatra, Indonesia	8.5-8.7
13	December 16, 1920	Ningxia-Gansu, China	8.6
14	August 15, 1950	Assam-Tibet	8.6
15	December 16, 1575	Valdivia, Chile	8.5

Know the Terms

Familiarize yourself with these terms to help identify an earthquake hazard:

Earthquake: A sudden slipping or movement of a portion of the earth’s crust, accompanied and followed by a series of vibrations.

Aftershock :An earthquake of similar or lesser intensity that follows the main earthquake.

Fault: The fracture across which displacement has occurred during an earthquake. The slippage may range from less than an inch to more than 10 yards in a severe earthquake.

Epicenter: The place on the earth’s surface directly above the point on the fault where the earthquake rupture began. Once fault slippage begins, it expands along the fault during the earthquake and can extend hundreds of miles before stopping.

Seismic Waves: Vibrations that travel outward from the earthquake fault at speeds of several miles per second. Although fault slippage directly under a structure can cause considerable damage, the vibrations of seismic waves cause most of the destruction during earthquakes.

Magnitude: The amount of energy released during an earthquake, which is computed from the amplitude of the seismic waves. A magnitude of 7.0 on the Richter Scale indicates an extremely strong earthquake. Each whole number on the scale represents an increase of about 30 times more energy released than the previous whole number represents. Therefore, an earthquake measuring 6.0 is about 30 times more powerful than one measuring 5.0.

Earth Quake

An earthquake is the result of a sudden release of stored energy in the Earth’s crust that creates seismic waves. Earthquakes are accordingly measured with a seismometer, commonly known as a seismograph. The magnitude of an earthquake is conventionally reported using the Richter scale or a related Moment scale (with magnitude 3 or lower earthquakes being hard to notice and magnitude 7 causing serious damage over large areas)
At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground. Sometimes, they cause tsunamis, which may lead to loss of life and destruction of property. An earthquake is caused by tectonic plates getting stuck and putting a strain on the ground. The strain becomes so great that rocks give way by breaking and sliding along fault planes.
Earthquakes may occur naturally or as a result of human activities. Smaller earthquakes can also be caused by volcanic activity, landslides, mine blasts, and nuclear tests. 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.
An earthquake's point of initial ground rupture is called its focus or hypocenter. The term epicenter means the point at ground level directly above this.

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 release to space of the heat in the Earth's mantle and core. The heat causes the rock in the Earth to become flow on geological timescales, so that the plates move, slowly but surely. Plate boundaries lock as the plates move 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 process 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, or is released to friction. Therefore, earthquakes lower the Earth's available potential energy and raise its temperature, though these changes are negligible.
The majority of tectonic earthquakes originate at depths not exceeding tens of kilometers. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, Deep focus earthquake may occur at much greater depths (up to seven hundred kilometers). These seismically active areas of subduction are known as Wadati-Benioff zones. 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 there both by tectonic faults and by the movement of magma in volcanoes. Such earthquakes 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.