Earthquakes
Sara alqahtani
Farja alkurbei
Jwaher almarri
Thousands of small earthquakes occur almost all the time; however, most of these
occurrences are too weak to be felt by humans. On average, a major earthquake occurs once
per year. A major earthquake is one of the most devastating natural disasters; it can level
cities within seconds and can even cause great tsunamis if it occurs under the ocean.
Although earthquakes are generally destructive to humans, it is a natural process that our
.planet has to undergo in order to release pressures that build up beneath its surface
An earthquake is a shaking of the ground caused by the sudden breaking and
movement of large sections (tectonic plates) of the earth's rocky outermost
crust. The edges of the tectonic plates are marked by faults (or fractures).
Most earthquakes occur along the fault lines when the plates slide past each
other or collide against each other.
The shifting masses send out shock waves that may be powerful enough to

alter the surface of the Earth, thrusting up cliffs and opening
great cracks in the ground and

cause great damage ... collapse of buildings and other manmade structures, broken power and gas lines (and the
consequent fire), landslides, snow avalanches, tsunamis (giant
sea waves) and volcanic eruptions.
Mouseover to experience earthquake
Fault or fault plane = the surface where when two blocks of the
earth suddenly slip past one another
Hypocenter = the location below the earth’s surface where the
earthquake starts
Epicenter = the location on the surface of the earth directly above
the hypocenter
Image source: U.S. Geological Survey
http://www.vtaide.com/png/George/earthquake.htm
The short answer is that earthquakes are caused by faulting, a sudden lateral or vertical
movement of rock along a rupture (break) surface
Here's the longer answer: The surface of the Earth is in continuous slow motion. This is plata
tectonics--the motion of immense rigid plates at the surface of the Earth in response to flow
of rock within the Earth. The plates cover the entire surface of the globe. Since they are all
moving they rub against each other in some places (like the San Andreas Fault in California),
sink beneath each other in others (like the Peru-Chile Trench along the western border of
South America), or spread apart from each other (like the Mid-Atlantic Ridge). At such places
the motion isn't smooth--the plates are stuck together at the edges but the rest of each
plate is continuing to move, so the rocks along the edges are distorted (what we call
"strain"). As the motion continues, the strain builds up to the point where the rock cannot
withstand any more bending. With a lurch, the rock breaks and the two sides move. An
.earthquake is the shaking that radiates out from the breaking rock
People have known about earthquakes for thousands of years, of course, but they didn't
know what caused them. In particular, people believed that the breaks in the Earth's
surface--faults--which appear after earthquakes, were caused *by* the earthquakes rather
than the cause *of* them. It was Bunjiro Koto, a geologist in Japan studying a 60-mile long
fault whose two sides shifted about 15 feet in the great Japanese earthquake of 1871, who
first suggested that earthquakes were caused by faults. Henry Reid, studying the great San
Francisco earthquake of 1906, took the idea further. He said that an earthquake is the huge
amount of energy released when accumulated strain causes a fault to rupture. He explained
that rock twisted further and further out of shape by continuing forces over the centuries
eventually yields in a wrenching snap as the two sides of the fault slip to a new position to
relieve the strain. This is the idea of "elastic rebound" which is now central to all studies of
.fault rupture
Dr. Gerard Fryer
Earthquakes occur all the time all over the world, both along plate edges and along faults.
Along Plate Edges
Most earthquakes occur along the edge of the oceanic and continental plates. The earth's crust (the outer layer of the planet) is
made up of several pieces, called plates. The plates under the oceans are called oceanic plates and the rest 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. These plates
are always bumping into each other, pulling away from each other, or past each other. The plates usually move 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.
FIGURE 1 - AN IMAGE OF THE WORLD'S PLATES AND THEIR BOUNDARIES. NOTICE THAT MANY PLATE BOUNDARIES DO NOT COINCIDE WITH COASTLINES.
Along Faults
Earthquakes can also occur far from the edges of plates, along faults. Faults are cracks in the earth where sections of a plate (or
two plates) are moving in different directions. Faults are caused by all that bumping and sliding the plates do. They are more
common near the edges of the plates.
Types of Faults
Normal faults are the cracks where one block of rock is sliding downward and away from another block of rock. These faults
usually occur in areas where a plate is very slowly splitting apart or where two plates are pulling away from each other. A
normal fault is defined by the hanging wall moving down relative to the footwall, which is moving up.
FIGURE 2 - A NORMAL FAULT. THE 'FOOTWALL' IS ON THE 'UPTHROWN' SIDE OF THE FAULT, MOVING UPWARDS. THE 'HANGING WALL' IS ON THE
'DOWNTHROWN' SIDE OF THE FAULT, MOVING DOWNWARDS.
Reverse faults are cracks formed where one plate is pushing into another plate. They also occur where a plate is folding up
because it's being compressed by another plate pushing against it. At these faults, one block of rock is sliding underneath
another block or one block is being pushed up over the other. A reverse fault is defined by the hanging wall moving up
relative to the footwall, which is moving down.
FIGURE 3 - A REVERSE FAULT. THIS TIME, THE 'FOOTWALL' IS ON THE 'DOWNTHROWN' SIDE OF THE FAULT, MOVING DOWNWARDS, AND THE 'HANGING WALL'
IS ON THE 'UPTHROWN' SIDE OF THE FAULT, MOVING UPWARDS. WHEN THE HANGING WALL IS ON THE UPTHROWN SIDE, IT 'HANGS' OVER THE FOOTWALL.
Strike-slip faults are the cracks between two plates that are sliding past each other. You can find these kinds of faults in
California. The San Andreas fault is a strike-slip fault. It's the most famous California fault and has caused a lot of powerful
earthquakes.
FIGURE 4 - TWO STRIKE-SLIP FAULTS. (LEFT), A LEFT-LATERAL STRIKE-SLIP FAULT. NO MATTER WHICH SIDE OF
THE FAULT YOU ARE ON, THE OTHER SIDE IS MOVING TO THE LEFT. (RIGHT), A RIGHT-LATERAL STRIKE-SLIP
FAULT. NO MATTER WHICH SIDE OF THE FAULT YOU ARE ON, THE OTHER SIDE IS MOVING
http://www.geo.mtu.edu/UPSeis/where.html
Table earthquakes sequence from smallest to largest depending on the strength of the earthquake and the impact near the
epicenter of the earthquake and Statistics occurring annually
Recipe earthquake
The power of the
earthquake (Richter scale)
Near the epicenter of the
earthquake impact
Statistics occurring annually
Very small
<2.0
Generally imperceptible, but
is recorded
600,000
2.0 - 2.9
Possible realization is
difficult
300,000
Small
3.0 - 3.9
Felt by some people
49,000
Light
4.0 - 4.9
Felt by most people
6,200
Average
5.0 - 5.9
With devastating effect
800
5.0 - 5.9
With devastating effect
800
Strong
6.0 - 6.9
266
Clear destruction in
populated areas
Great
7.0 - 7.9
Strong earthquake leaves
havoc
18
Huge
≥ 8.0
A massive earthquake
succeed comprehensive
destruction
1.4
The pros and cons of earthquakes:
Negative -- Devastation to Manmade Structures

Manmade structures, such as buildings, get damaged heavily when hit by a strong
earthquake. Buildings and other structures sometimes even collapse, because the
foundation cannot handle the force of the shaking ground. Roads, electrical structures
and piping systems also tend to be victims of the earth's sudden forceful movements.
This destruction sometimes leads to fires, harmful chemical leaks and massive
damage to transportation infrastructures such as bridges.
Negative -- Tsunami and Flooding

Earthquakes can also cause tsunamis, which in turn cause massive flooding on
coastal areas. When a strong earthquake occurs underwater, it changes the level of
the seabed and causes the water level to either rise or fall. Whether it rises or falls, it
is a danger to coastal areas because of the creation of huge waves of water that
"inundates" on shore. Inundation happens when a large amount of water goes inland
in a short period of time, flooding coastal areas. It can destroy vegetation, human
structures and even whole coastal communities. An example of massive devastation
includes the tsunami from 2004 that occurred in the Far East, affecting massive areas
of Thailand and surrounding countries
Positive -- Natural Process of Earth's Cycle

Earthquakes happen because our planet needs to "adjust" itself in order to maintain its proper
equilibrium. Whether we like it or not, earthquakes are going to happen because tectonic plates
continuously adjust and release pressure. Aside from this regular "self-correction," earthquakes
also allow nutrients and minerals to cycle from the ocean to the earth's surface. Hugh Ross,
one of the astrophysicists in Royal Astronomical Society in Canada, said that "In the absence
of an earthquake or tectonic activity, the nutrients needed by living on the land would be
undermined from the continent and collected in the oceans."
Evacuation of one of the buildings in Doha after feeling the earthquake
9
April
2013
Doha Ibrahim Elewa and Mohamed Noman
Hit the Iranian city of Bushehr earthquake noon, Tuesday, felt by residents of the
Qatari capital of Doha, which hit some panic and fear, and they have to evacuate the
living buildings and went to the empty squares.
And soon echoed this tremor in some areas of Doha and felt more of both from the
dam area and Ben Mahmoud, Bin Omran, and sparked panic among residents of
these neighborhoods, and lasted for a few seconds.
And left a number of people outside the houses and homes and stayed away from
buildings tens of minutes after the entry into force of rumors about the occurrence of
the so-called aftershocks following the quake first.
For his part, said the observatory U.S. to earthquakes that an earthquake measuring
6.3 Richter scale hit the city of Bushehr, southern Iran, as pointed out initial reports to
the deaths of at least three people in Iran, but he did not specify the size of human
and material losses caused by the earthquake, which was felt by residents of Qatar,
Saudi Arabia and Bahrain .
Repeated exposure raises "Bushehr" of earthquakes on an ongoing basis, anxiety in
the hearts of locals and Gulf close to the city for fear of a repeat of the incident
Foucault Shima Japanese.
Earthquake phenomenon of phenomena that God created the universe and each Xi
God created him that what I was meaning I want to gain him of through My Project