Magnitude
Description of effect
Usually felt by only a few people near the
less than 3.4
epicentre.
Felt by people who are indoors and some
3.5 - 4.2
outdoors; vibrations similar to a passing truck.
Felt by many people; windows rattle, dishes
4.3 - 4.8
disturbed, standing cars rock.
Felt by everyone; dishes break and doors swing,
4.9 - 5.4
unstable objects overturn.
Some damage to buildings; plaster cracks,
5.5 - 6.1
bricks fall, chimneys damaged.
Much building damage; houses move on their
6.2 - 6.9
foundations, chimneys fall, furniture moves.
Serious damage to buildings; bridges twist,
walls fracture, many masonry
7.0 - 7.3
buildings collapse.
Causes great damage; most buildings collapse.
7.4 - 7.9
Causes extensive damage; waves seen on the
ground surface, objects thrown into the air.
greater than
8.0
http://www.ga.gov.au/hazards/earthquakes/earthquake-basics/causes.html
Earth's outer layer or crust is broken into pieces called tectonic plates which are constantly
moving towards, away from or past each other. Because continents are part of these plates,
they also move. An earthquake occurs when the rocks break and move as a result of stresses
caused by plate movements.
Most earthquakes occur on the edge of plates, especially where one plate is forced under
another .
The epicentre is the point on the Earth's surface directly above the source of the earthquake.
The source, also known as the focus, can be as deep as 700 kilometres. Smaller earthquakes
occur much more frequently than large ones and most cause little or no damage. A very large
earthquake can be followed by a series of smaller events called aftershocks during a period of
adjustment which may last for several months.
Earthquakes also can cause a tsunami, or a series of waves which can cross an ocean and
cause extensive damage to coastal regions. In areas where there are steep slopes, vibrations
resulting from earthquakes may cause landslides.
Interesting fact: Earthquake vibrations travel very fast, up to 14 kilometres per second. The
fastest seismic waves take less than 20 minutes to reach the other side of the earth, a distance
of almost 13 000 kilometres!
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Tectionic plates are pieces which make up the earths crust. The tectionic plates are always
moving either towards, away from or past each other.
Earthquakes occur due to the stress built up from the constant movement of the tectionic
plates. (which then create seismic waves.)
Earthquakes can result in other horrific disaters such as tsunamis, landslides and sometimes
volcanic activity.
As contients are located on the plates the also move with them.
http://www.vtaide.com/png/George/earthquake.htm
Wikipedia
An earthquake 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. 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.
Seismic waves are waves of energy that travel through the earth, for example as a result of an
earthquake
http://www.nationalgeographic.com/forcesofnature/intera
ctive/index.html
http://www.weatherwizkids.com/weather-earthquake.htm
What is an earthquake?
Earthquakes are the shaking, rolling or sudden shock of the earth’s surface. They are the
Earth's natural means of releasing stress. More than a million earthquakes rattle the world
each year. The West Coast is most at risk of having an earthquake, but earthquakes can
happen in the Midwest and along the East Coast. Earthquakes can be felt over large areas
although they usually last less than one minute.
What is a fault?
A fault is an area of stress in the earth where broken rocks slide past each other, causing a
crack in the Earth's surface. There are the major types of faults: dip-slip normal, dip-slip
reverse, strike-slip, and oblique-slip.
What causes an earthquake?
There are about 20 plates along the surface of the earth that move continuously and slowly
past each other. When the plates squeeze or stretch, huge rocks form at their edges and the
rocks shift with great force, causing an earthquake. 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.
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Earthquakes are the natural way for the earth to release stress
The world experiences more than a million earthquakes a year
When the plates push, pull or rub against each other large rocks form at their
boundries and then the rocks move with vast strength which then causes the
earthquake.
http://earthquake.usgs.gov/learn/kids/eqscience.php
What is an earthquake?
An earthquake is what happens when two blocks of the earth suddenly slip past one another.
The surface where they slip is called the fault or fault plane. The location below the earth’s
surface where the earthquake starts is called the hypocenter, and the location directly above it
on the surface of the earth is called the epicenter.
Sometimes an earthquake has foreshocks. These are smaller earthquakes that happen in the
same place as the larger earthquake that follows. Scientists can’t tell that an earthquake is a
foreshock until the larger earthquake happens. The largest, main earthquake is called the
mainshock. Mainshocks always have aftershocks that follow. These are smaller earthquakes
that occur afterwards in the same place as the mainshock. Depending on the size of the
mainshock, aftershocks can continue for weeks, months, and even years after the mainshock!
What causes earthquakes and where do they happen?
The earth has four major layers: the inner core, outer core, mantle and crust. The crust and
the top of the mantle make up a thin skin on the surface of our planet. But this skin is not all
in one piece – it is made up of many pieces like a puzzle covering the surface of the earth.
Not only that, but these puzzle pieces keep slowly moving around, sliding past one another
and bumping into each other. We call these puzzle pieces tectonic plates, and the edges of the
plates are called the plate boundaries. The plate boundaries are made up of many faults, and
most of the earthquakes around the world occur on these faults. Since the edges of the plates
are rough, they get stuck while the rest of the plate keeps moving. Finally, when the plate has
moved far enough, the edges unstick on one of the faults and there is an earthquake.
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When the earth pushes away and opens up its surface is called the fault.
The edge of the tectonic plates are called plate boundaries and they are made up of
faults.
http://www.pitara.com/discover/5wh/online.asp?story=120
An earthquake is caused by a sudden rupture in a fault. A fault is the fracture within the rocky
mass inside the earth's crust. The depth and length of faults vary greatly.
Stress in the earth's outer layer cause a pushing effect against the sides of the fault. Due to
this motion, rocks slip or collide against each other releasing energy. This released energy
travels in waves through the earth's crust and causes the shaking that we feel during an
earthquake.
Faults are divided into three main groups. Reverse fault - when two plates collide and one
side of the fracture moves on top of another; normal fault -when two plates are moving apart;
and strike-slip or lateral - when two plates slide past each other.
Under the surface of the earth, the two sides of a fault are constantly moving, relative to one
another. This movement is known as a fault slip. The movement of these two sides is not
smooth and is accompanied by a gradual build-up of elastic strain energy within the rocks
along the fault. The rocks store this strain like a giant spring being slowly wound up.
Eventually, the strain along the fault becomes too much and the rocks can no longer bear the
tension. The fault then ruptures with a sudden movement releasing all the energy built up
over the years. This energy is released in the form of vibrations called 'seismic waves'.
These waves travel along the surface and through the earth at varying speeds depending on
the material through which they move. It is actually these seismic waves that cause most of
the destructive effects, which we associate with earthquakes.
The location on a fault where the slip first occurs is called the hypocentre, whereas the
position directly above it on the ground surface is called the epicentre.
Sometimes new land mass are also formed.
It is estimated that there are 5,000,000 detectable earthquakes in the world each year. Of
these only 1,000,000 are felt, and only 100 of them cause actual damage.
Though there are certain parts of the earth where earthquakes are frequent, the majority of
earthquakes occur along the earth's plate boundaries, which carry the continents and the
ocean floor. They occur most between the Pacific plate and the North American plate
http://earthquake.usgs.gov/learn/kids/
DEFINITION OF AN EARTHQUAKE
An Earthquake is a sudden and sometimes vicious shaking of the ground. This can cause
immense damage and leed to many losses of life. Quakes are the result of tectonic plates
pushing, pulling or rubbing against each other. This movement causes large rocks to form at
the plate boundries which are made up of faults. The rocks later move with vast strength
which causes the quake. Earthquakes are the natural way for the earth to remove stress from
the constant movement of the plates which is another reason why earthquakes occur.
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The edge of the tectonic plates are called plate boundaries and they are made up of
faults
Earthquakes are the natural way for the earth to release stress
When the plates push, pull or rub against each other large rocks form at their
boundries and then the rocks move with vast strength which then causes the
earthquake
Tectionic plates are pieces which make up the earths crust. The tectionic plates are
always moving either towards, away from or past each other.
Earthquakes occur due to the stress built up from the constant movement of the
tectionic plates.
Earthquakes can result in other horrific disaters such as tsunamis, landslides and
sometimes volcanic activity.
As contients are located on the plates the also move with them.
http://www.earthquakecountry.info/roots/basics.html