The death toll from the March 11, 2011 Sendai earthquakes and tsunami continued to climb weeks after the initial destruction due to the amount of damage.

The National Police Agency of Japan reported in a September 2012 report with a total of 15,870 deaths,6,114 injured, and 2,814 people missing. The USGS reports 20,896 fatalities for this disaster. This surpasses the death toll for the 1995 Great Hanshin Earthquake.

The largest number of deaths was in the Miyagi, Iwate, and Fukushima districts. Over 92% of reported deaths were due to drowning.

Earthquakes are tremors or vibrations in the Earth's crust that are caused by the build up or accumulation of pressure (more correctly termed stress).

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The Earth's crust, or lithosphere (hard outer surface) is made up of "tectonic plates", or large plates. There are about 7 major plates and many smaller plates, around 100 km thick, which sit upon a lower soft layer (the asthenosphere). The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.

This accumulation of stress causes the rocks that make up the crust to deform elastically. This is very similar to what happens when you squash or stretch a spring and causes a form of energy to be stored in the rocks of the crust - technically described as elastic potential energy.

When this stress gets too large, it exceeds the strength of the rocks in the crust and causes a brittle failure. Brittle failures are failures where fractures form through the material. As these have been happening for a long time, the earth's lithosphere is already fractured. These fractures are known as faults and as these represent zones of weakness within the lithosphere, it is along faults where the majority of earthquake occur when they slip suddenly.

This sudden brittle failure causes all of the elastic potential energy to be released at one time in the form of seismic waves, just as if a spring or elastic band that was being stretched suddenly snapped.

These seismic waves cause the tremors that people feel on the surface and which can cause damage to buildings and other structures.

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The Earth's crust, or lithosphere (hard outer surface) is made up of "tectonic plates", or large plates. There are about 7 major plates and many smaller plates, around 100 km thick, which sit upon a lower soft layer (the asthenosphere).

When these plates move against each other along plate boundaries (where two plates meet) or along faults (a rift), an earthquake occurs. This may be through a variety of movements: sideways, up and down or apart. This causes anything upon the upper surface, above the earthquake, to also shift, whether they be buildings, roads, bridges, railways, etc.

What you actually feel when you feel the shaking of an earthquake are the seismic waves.

There are three types of seismic waves and they are determined by the properties of the rock through which they travel:

P-waves (compressional waves) or primary waves are the first waves: they travel the fastest and can travel through everything.

Then the S-waves (shear waves) or secondary waves come: they move slower and cannot travel through liquids.

At last the Surface-waves come. They are the slowest and they cause the biggest damage. Often it is when the surface-waves come that the buildings collapse.

An earthquake describes when the earth moves the ground under your feet. It can slide it from side to side or move it a few feet in one direction. It can lift it up in one place and make it sink in another. The results of this are quite visible in and near Anchorage, Alaska. One street in that town shows where an earthquake make the ground fell. Driving south, dead trees stick up out of a lake where the ground fell below sea level. Earthquakes are caused when faults or cracks in the earth's shell suddenly slip past each other. When they jerk, they move a lot of land with them. That makes the earth tremble. Sometimes it damages buildings.

The official definition for the word earthquake is "a sudden and violent shaking of the ground, sometimes causing great destruction, as a result of movements within the earth's crust or volcanic action." knowing these earthquakes happen almost everywhere they do most take place in the U.S

in the state of California just a (FYI)
tectonic plates- move in 3 ways

1. collide w/ eachother

2.seperate from eachother

3. slide against eachother

when plates are moved to the breaking point it causes an eartquake

an earthquake is a seismic wave

A brief summary of this long answer can be found by viewing the related question. For more information please read on!

This is a complex question and is a subject of continuing ongoing scientific research. A summary of some of the hypothesised causal mechanisms of plate movement (based on scientists current understanding of the process) is given below:

The primary source of energy for the motion of the lithospheric plates is dissipation of energy from the earth in the form of heat transfer. This heat transfer causes convection within the mantle and this convecting mantle material is hypothesised to exert a drag force on the base of the lithosphere. This is known as Basal Drag and was thought to be an important driver of tectonic plate motion until recently when advances in geophysical imaging techniques (specifically 3D seismic tomography) allowed geophysicists to form a more detailed model of the structure of the mantle but were unable to locate the necessary large scale convections structures. Further to this, geophysicists no longer believe that the asthenosphere has the necessary stiffness or rigidity to cause sufficient friction on the base of the lithosphere to be a significant driver of plate motion.

Gravity is also believed to play a role in the driving of plate motions, both at mid-ocean-ridges (MOR) and at subduction zones. Both these mechanisms are also linked to the dissipation of heat and convection in that they are reliant on variations in the buoyancy of the lithosphere as temperature changes occur as described below:

When hot (and so low density, buoyant) mantle material rises at an MOR, it is intruded into the pre-existing oceanic lithosphere as well as extruded at the upper surface. This newly intruded material is at a high temperature and cools relatively slowly. As such the newly formed oceanic lithosphere is buoyant and rises relative to the older cooler oceanic lithosphere further from the MOR. Even though this younger lithospheric crust is buoyant it is still significantly denser than the underlying upwelling hot mantle material and so "slides" down away from the crest in a process known as gravitational sliding. This is considered a secondary driving force as it only acts in close proximity to the ridge and does not transmit load into the surrounding lithosphere (it does not "push" the lithosphere away from the ridge, it is instead dragged - the tectonic regime is tensile, not compressive).

Another more significant gravitational driving force of plate motion is that caused by the old, cool and so low buoyancy oceanic crust that sinks back into the mantle at subduction zones and acts to drag the attached oceanic lithosphere towards the plate boundary. This is known as slab pull and is thought to be a significant driver of plate motions as it has been observed that tectonic plates with subduction boundaries tend to move with a higher velocity than those without. Subducting oceanic slabs also promote another driving force of plate motion known as trench or slab suction. This is a process where the movement of the downgoing slab promotes flow in the nearby mantle. This flowing mantle material is thought to exert a traction both on the downgoing slab and the overlying non subducting slab, pulling them both towards the subduction zone.

It should be noted that not all plates have significant subduction boundaries and yet still undergo plate movements so it is possible that a combination of all these mechanisms influences plate movement (as well as the possibility that there is some as yet undiscovered driving force that has a significant role).

The above is a simple summary of a complex topic and as has been stated the causal mechanisms that drive the motions of tectonic plates are not fully understood and as such the reader should remember that this is a current and active area of research in geophysics and so the hypotheses summarised above may be accepted, rejected or modified over time!

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Wild animals have evolved to respond to their natural environment, coping with seasonal flooding, wild fires, volcanoes and earthquakes. Most often loss of wildlife in the face of a catastrophic environmental event is a result of changes made to the ecosystem. Habitat fragmentation, in particular, prevents them from responding as they normally would.

It occurred in the afternoon (19:11 GMT, 14:11 local time) and its resulting tsunami affected southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia, and the Aleutian Islands in Alaska.

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Checking other sites, including the Institute of Geological & Nuclear Sciences of New Zealand and the Geophysics Program at the University of Washington. Every site we checked corroborated the first site's information.

Okay, we now know about the biggest quake in the world, but what about the biggest quake to hit the United States? Well, it was a 9.2 rocker that hit Prince William Sound, Alaska, on March 28, 1964. The destruction was massive, but, luckily, only 125 lives were lost as a result of the earthquake (15) and ensuing tsunami (110).
The strongest earthquake ever recorded is the 1960 Valdivia Earthquake that occurred in Chile. This had a magnitude of 9.5.

The Richter Magnitude Scale often shortened to Richter scale represents a number to quantify the energy released during an earthquake on a logarithmic scale.

• Earthquakes with magnitude less than 2.0 are generally not felt by people but only registered by sensitive machines.
• Earthquakes at the 9.0 and greater range cause severe damage or collapse to all buildings in the area.

Most earthquakes occur along the edge of the oceanic and continental plates. The earth's crust is made up of several pieces, called plates. The plates under the oceans are called oceanic plates and the rest which are under the land surface 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.

Earthquakes mostly occur in places where there is a Fault Line. Plates under the Earth's surface move and push against each other.

Some of these places are:

• South America
• North America
• Japan
• Australia
• Africa
• Philippines
• India
• Caribbean
• Haiti

Alaska is the most earthquake-prone state and one of the most seismically active regions in the world. Alaska experiences a magnitude 7 earthquake almost every year, and a magnitude 8 or greater earthquake on average every 14 years. or just this near subduction zones.