An earthquake is a sudden and brief period of intense group shaking. Two different scales of are used to measure the strength of earthquakes.
The Global Distribution of Earthquakes
The Richter Scale
The Richter scale measures an earthquake’s strength according to the amount of energy that is released.
A Seismograph doesn’t measure like the Richter scale but just the amount of movement of a Surface
The Mercalli Scale
The Mercalli scale is based on what people experience and the amount of damage done.
Focus And Epicentre
Energy is released from the focus and spreads from the epicentre. The amount of damage caused depends on the focus and the type of rock. The worst damage is occurs where the focus is closest to the surface and where rocks are soft. Shock waves `liquefy` soft rocks so that they behaved like a liquid.
Preparation For An Earthquake
Mitigation (or adjustment) – involves taking action before, during and after an earthquake event to reduce its consequences.
Risk Assessment – Determining whether an earthquake event is probable or not and the damage it might cause.
Prediction – Monitor earthquakes areas to allow a prediction to give an early warning system. Scientists and Geologists can now predict when and where an earthquake will strike – along the active plate margins. Experts find it much more difficult to predict when earthquakes will happen than volcanoes, before some earthquakes the land may be seen to rise or tilt. Some times water in wells is seen to fall. If local people notice these changes they can alert everyone to reach places of safety, well away from buildings. If these signs are not seen there isn’t much chance of it being predicted at all therefore prepared for and therefore the could be a high chance of overall damage. Money is needed to set up the science to detect an earthquake. Earthquakes may be the most difficult hazards to predict, but at least they are a hazard that allows preparation.
Preparation (adjustment) – Finding ways to reduce deaths, injures and damage that will be caused. I.E. educating people with hat to do-having a plan.
Earthquake Event – The actual event it’s self happens.
Recovery – first emergency aid then repairing the damage.
Case Study: Japan, Kobe (MEDC/HIC)
Early in the morning on Tuesday, 17th January 1995 an earthquake struck with huge shock waves – measuring a 7.2 on the Richter scale killing thousands, destroying almost all buildings making the masses homeless. To make matters worse there were over 300 fires braking out because of ruptured gas lines and snapping of electricity lines this effected wooden houses especially, this overall caused almost all transport to go down and even causing damage to the famous built train. The overall predicted cost of this event was estimated at $200,000,000.
The epicentre was around near were Awaji island. The greatest destruction happened where there were more building and that buildings closer together. Earthquakes aren’t uncommon to Japan they can experience on average up to 1000 earthquakes a year but often minor and around 3-5 on the Richter scale. Japan takes earthquake threats and other natural disasters they bring very seriously they have to in such a densely populated country, most building are earthquake resistant now and there is a tsunami wall built and regular drills are carried out to protect Japan and reduce the dead, the destruction, the injured and the trapped, that unfortunately proved unsuccessful when this earthquake brought a tsunami.
I think that Japan was well prepared it was unfortunate that the event lead to what it did but in the future I believe that buildings will be built stronger, tsunami gates built higher and stronger along with other further protections.
Case Study: 2008 Iceland (LEDC/LIC)
This magnitude 6 – 6.5 was one of the larger earthquakes that Iceland constantly have but no one was killed, this is because there is little for the earthquake to destroy as there are no large buildings and with a small amount of people only 30 had minor injured and a few sheep died coincidently.