Earthquakes

How earthquakes happen:  An earthquake happen when two plates rub together. The plates travel in different directions and different speeds. If one plate is slowly forced underneath the other, pressure builds up until the plates rip apart. This process causes groud to move. It is an earthquake.

Earthquakes are the shaking of the earth’s surface caused by the earth’s rocky outer layer. Earthquakes occur because of the energy stored within the earth. It is usually due to the strain within the rocks that is suddenly released. The study of earthquakes and the waves they create is called seismology (From the Greek seismos to shake) The damage an earthquake causes depends on where it is and the time it is happening. The size will vary from small to large. Earthquakes can deform the ground, make buildings and other structures collapse, and creates tsunamis (which means large sea waves.)  Every year there are several million small earthquakes.  Large earthquakes such as the 1964 Alaskan quake that measured 9.2 on the Richter Scale, cause millions of dollars in damages. In the last 500 years, millions of people have been killed by earthquakes around the world -  including 240,000 in the 1976 Tang Shan China earthquake.

Locations Scientists use the Plate tectonics theory to explain the movement of the earth plates and how this movement causes Earthquakes. The theory of plate tectonics arose from previous geologic theories and discoveries.   It is clear that big Earthquakes happen most in areas.

These are the main damage  causing events that happen during an Earthquake. Ground rumbling which leads to landslides and other soil movements.  Ground Shaking and Landslides Effect of earthquake Earthquake waves make the ground rumble, shakes buildings and structures, and causes poorly designed or weak structures to collapse.  During an Earthquake, water saturated sandy soil becomes like liquid mud, an effect called liquefaction.  Liquefaction causes damage as the foundation soil beneath structures and buildings weakens.

How earthquakes can cause damage.       Earthquakes can damage buildings, bridges and other structures, as well as many natural features.  Near a fault, both the shifting of large blocks of the earth's crust, called fault slippage, and shaking of the ground due to seismic waves cause destruction.

Emergency Preparedness Plans Earthquake education and preparedness plans can help reduce death and injury that are caused by earthquakes.  Maintaining an earthquake survival plan in the home and at the office is an important part of being prepared. In the home, earthquake preparedness includes maintaining an earthquake kit and making sure that the house is structurally stable.  The local chapter of the American Red Cross is a good source of information on how to assemble an earthquake kit. During an earthquake, people indoors should protect themselves from falling and flying glass by taking refuge under a heavy table. They should also listen for emergency bulletins on the radio, stay out of damaged buildings, and avoid coastal areas in case of a tsunami.

Can earthquakes be predicted?

Earthquake Precursors

Ø  changes in elevation or tilting of land surface, fluctuations in groundwater levels, magnetic field, electrical resistance of the ground

Ø  seismic dilatancy model

Ø  seismic gaps

Earthquake Prediction Programs

Ø  include laboratory and field studies of rocks before, during, and after earthquakes

Ø  monitor activity along major faults

Ø  produce risk assessments