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Environmental Geology
Publisher date : July 2008
Chapter title : Earthquake
Data title : Prediction and risk decline

Prediction and risk decline:

Today's, given we know that the earthquakes are occurred at a fault areas and an impact place between previous or current plates, the maps of risk regions have been prepared that also this case has been performed in Iran. For doing this, it is a necessary the field geology on large basic scale and very carefully, and it is a necessary the geological study of regions that have a history of seismicity. As a result, we can prepare maps that determine a risk of earthquake at each region, and determine a magnitude of earthquake possibility at each region. Even with regard to a smaller earthquakes focus located on one region, we can draw the maps of earthquake intensity before.

Today's, geologists in many countries, particularly, seismic countries such as Japan , China, America, and Russia, search a solution for anticipating earthquakes, but they have not so far had a special success, and today, we can not say that it is possible the anticipation of earthquakes, but only seismic regions have been determined.

So far, in some of the world points the anticipation of earthquake has been performed, it has been based on their foreshock that of course, such anticipation of predictions are a correct rarely.

The expansion assumption, one was that at first it was a promising for the prediction of earthquakes very much, but finally, it didn't seem as a clear and suitable solution, because it doesn't apply to at mast of regions. According to the expansion assumption, that it's base is the different experiments related to stones reaction to the applied stresses and pressures, it is occurred a cracks and fractures in the stones resulting from the applied stress and is caused a multiple joints in them, that as a result, their volume increases and of course, the wares passing speed in them changes. On the other words. The earthquake waves speed stones decreases and the electric conduction increases.

These laboratory observations namely expansion assumption, it has derived a suitable anticipations at some of regions, and at other areas, it has no provided a correct answer.

Fore an occurrence of earthquake, the existing Radon gas at minerals having uranium become a free a given the existence of radioactive material at one region, that this subject was proved by Russian people.

The research on the waves speed P and S showed that before an accordance of earthquake, the waves speed P and S ratio changes considerably. This method of earthquake prediction is said VS-VP method, that it was anticipated given those two earthquakes. This has a disadvantage for a large earthquakes that it doesn't provide a correct answer.

Chinese predicated the earthquake dated on Hayching using a simple seismographs and domestic and wild animals movements, like chicken, cow, snack, rabbit, lions inside zoo and a red fishes and underground water surface change, that it was caused that a human fatalities approached to a minimum, because a city had been discharged before an earthquake.

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