earthquake

EARTHQUAKE

Introduction
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves.

CAUSE OF EARTHQUAKE

Earthquakes are caused by the movement of the earth's tectonic plates. Earthquakes occur where the earth's plates meet along plate boundaries (see plate tectonics page for more information on this).For example as two plates move towards each other, one can be pushed down under the other one into the mantle. If this plate gets stuck it causes a lot of pressure on surrounding rocks. When this pressure is released it produces shock waves. These are called seismic waves. This is an earthquake. The waves spread out from the point where the earthquake started - the focus. More damage is done near the focus. The point on the earth's surface directly above the focus is the epicentre.

EFFECTS OF EARTHQUAKE
Shaking and ground rupture
Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude, the distance from the epicenter, and the local geological and geomorphological conditions, which may amplify or reduce wave propagation.The ground-shaking is measured by ground acceleration.

Landslides
Earthquakes, along with severe storms, volcanic activity, coastal wave attack, and wildfires, can produce slope instability leading to landslides, a major geological hazard. Landslide danger may persist while emergency personnel are attempting rescue.

Fires
Earthquakes can cause fires by damaging electrical power or gas lines.

Tsunami
Large waves produced by an earthquake or a submarine landslide can overrun nearby coastal areas in a matter of minutes. Tsunamis can also travel thousands of kilometers across open ocean and wreak destruction on far shores hours after the earthquake that generated them.

Human Impacts
An earthquake may cause injury and loss of life, road and bridge damage, general property damage (which may or may not be covered by earthquake insurance), and collapse or destabilization (potentially leading to future collapse) of buildings.

Before an Earthquake
Make sure you have a fire extinguisher, first aid kit, a battery-powered radio, a flashlight, and extra batteries at home.
Learn first aid.
Learn how to turn off the gas, water, and electricity.
Make up a plan of where to meet your family after an earthquake.
Don't leave heavy objects on shelves (they'll fall during an earthquake).
Anchor heavy furniture, cupboards, and appliances to the walls or floor.
Learn the earthquake plan at your school or workplace.

During an Earthquake
Stay calm! If you're indoors, stay inside. If you're outside, stay outside.
If you're indoors, stand against a wall near the center of the building, stand in a doorway, or crawl under heavy furniture (a desk or table). Stay away from windows and outside doors.
If you're outdoors, stay in the open away from power lines or anything that might fall. Stay away from buildings (stuff might fall off the building or the building could fall on you).
Don't use matches, candles, or any flame. Broken gas lines and fire don't mix.
If you're in a car, stop the car and stay inside the car until the earthquake stops.
Don't use elevators (they'll probably get stuck anyway).

After an Earthquake
Check yourself and others for injuries. Provide first aid for anyone who needs it.
Check water, gas, and electric lines for damage. If any are damaged, shut off the valves. Check for the smell of gas. If you smell it, open all the windows and doors, leave immediately, and report it to the authorities (use someone else's phone).
Turn on the radio. Don't use the phone unless it's an emergency.
Stay out of damaged buildings.
Be careful around broken glass and debris. Wear boots or sturdy shoes to keep from cutting your feet.
Be careful of chimneys (they may fall on you).
Stay away from beaches. Tsunamis and seiches sometimes hit after the ground has stopped shaking.
Stay away from damaged areas.
If you're at school or work, follow the emergency plan or the instructions of the person in charge.
Expect aftershocks.