San Francisco Earthquake example essay topic

Earthquakes occur throughout the world but the vast majority of them develop along narrow belts. These belts are tens to thousands of kilometres long and mark the boundaries on the Earth's surface. The belts are considered very active geological wise. Earthquakes occur when rocks rupture under the pressure created by continues movement and collision of thin jigsaw-like tectonic plates found under the Earth's surface. Seismic waves (vibrations) are then created and proceed outwards in all directions at up to 14 kilometres per second.

The fastest waves would only take up to 20 minutes to reach the other side of the Earth. The focus point is the section of Earth directly above the earthquake - also known as the epicentre. The focus point can be as deep as 700 kilometres deep. Faulting causes a release of energy because stored up stress is unexpectedly transformed to motion causing an earthquake.

The waves disfigure the rocks they pass through but once the waves have long gone the rocks return to their original shape. Earthquakes are most common along plate boundaries which is where the tectonic plates meet. Large earthquakes usually occur when two tectonic plates crash. About 80% of recorded earthquakes have developed at the circum-Pacific Seismic Belt which is the zone surrounding the Pacific Ocean and is characterised by frequent and strong earthquakes. It is also known as 'The Ring of Fire.

' No part of the Earth is safe from earthquakes. Depending on the vibrations being carried reflects the arrival of seismic waves. There are three types of waves: primary, secondary and surface. Primary waves arrive first and distort the rocks by changing their volume. This is quickly done by expanding and then compressing them. Secondary waves are received next and disfigure the rocks by modifying their shape.

Surface waves are received last but instead of passing through the Earth, they travel around. The epicentre is then established by comparing the arrival time of the P an S waves, this is done on a seismograph. The larger the time differences the further the seismogram is from the epicentre. Earthquakes are measured on the Richter Scale. This scale divides the size into categories called magnitudes.

The larger the number on the scale the more damage the earthquake will cause. The size of an earthquake is measured by comparing the maximum heights of the seismic plates recorded at a distance of 100 km from the epicentre. Predicting earthquakes is based on the lowering in groundwater levels, radon gas emission and changes in animal behaviour. Also tilts and budge in the Earth's surface and a change in the speed of P and S waves. The outcomes of earthquakes extend more significantly than the damage caused and the horror placed on the population. Society has come up with numerous methods to guard against the damage that is probable throughout earthquakes.

Warning systems Research and Advances in the engineering have done an incredible job in giving resources essential to surviving during earthquakes. The way that people perceive earthquakes has a great influence on the precautionary measures that can be taken to decrease the contingency of injury, property damage and loss of life. Many people are in denial about the importance of the precautions shown therefore some of the damage that would be caused could be prevented. There are federal warnings that there could be a possible earthquake which seems like a reasonable way to protect against the affects of the disaster. This warning system could have a great impact on the economy though. Economic affects include adverse changes especially in the area where it happened.

These changes include mortgage availability, property value, investment patterns and employment opportunities. The town at where the earthquake took place would notice a reduction in tax revenues for the local government which would then lead to a reduction in public services. Emotional affects include psychological affects on everyone involved in the earthquake and also of those involved. More girls than boys are affected by earthquakes. This is said to be because girls express their feelings more easily. The major earthquake that I chose was the San Francisco.

San Francisco lies along the San Andreas Fault which is 32 kilometres deep and is the length of California in the United States. The San Francisco earthquake started at 5: 12 a.m. On the 18th of April 1906. Towering office blocks swayed, masonry crashed to the ground and windows shattered.

In hotels and homes people were thrown from their beds. Buildings and bridges collapsed, tramlines like strips of licorice, water, gas mains burst and fires spread. The aftermath 8 km 2 of offices, shops and houses were flattened and charred. The death toll is not exactly know but was estimated at 700 and approximately 250,000 people were left homeless. The damage from the earthquake and fire following was assessed at 400 million. The fire started 2 minutes after the earthquake and lasted for three days and caused more havoc than the actual earthquake.

This was classed as a minor earthquake compared to others. Imagine the extent of the damage caused by larger earthquakes. Amid the flames, smoke and.