Earthquake prediction

Earthquake prediction and earthquake prediction is the totality of methods, means, and attempts to predict the occurrence of an earthquake of a certain strength at a precise time and at a precise location.

Because of the damage to the economy and potential victims ( mass panic or mass hysteria ) is an early warning of the population from a single earthquake only makes sense if the expected number of victims of the earthquake is estimated to be very large, or if the earthquake predicted very accurately in space and time can be. The temporally and spatially accurate, reliable earthquake prediction is not possible in the present state of science. There are at most warning systems that provide a lead time of a few seconds.

Probability of earthquakes

Basically, the triggering processes and the probabilities for the occurrence of earthquakes are understood scientifically in a given area. This is especially true for the overall probability of occurrence of earthquakes, because the vast majority are bound to plattentektonisch active regions. Therefore, the knowledge of the tectonic contexts allows for many areas of the world the compilation of earthquake maps which represent the probability of earthquakes for this area on the basis of statistical analysis already registered earthquakes. In well- known and intensely studied areas a more accurate earthquake prediction is possible. Here too, however, the uncertainty of the prediction is in the range of several months or years. When looking at individual events a complex interplay of a large number of parameters have to observe, so that the isolated observation of a single size for the successful prediction is not promising.

Precursor phenomena

There are a number of effects are known which can be observed from earthquake events in advance and often are referred to as precursor phenomena. Some of these are manifested in the change geophysically measurable parameters, such as seismic velocity, the slope of the ground or the electromagnetic properties of the rock. Other phenomena are based on statistical observations, such as the concept of seismic calm where in a potentially vulnerable region over a long period seismic background activity, ie the steady occurrence of smaller earthquakes, and decreases indicating an upcoming major event. Statistical methods based on a method which uses rapid changes of the probability density of the vertical component of the seismic recordings.

In the Radon method is measured, in what amounts the noble gas radon emerging from the ground. This method allows the previously reliable predictions. Indicator is the easily verifiable fact that before the quake to increase the amount of radon in water from wells at four times the usual amount. Following the adoption of seismologists are deep underground rock layers just before an earthquake suddenly permeable and cracked, they expand, thus radon is released, penetrates into the ground and tightly focused below the surface. The best-known example of such measurements, the holes along the San Andreas Fault (also known as the San Andreas Fault ), which are assessed weekly to extending their back to keep seismic changes on the horizon in this way.

Repeats have also been reported unusual behavior in animals shortly before larger earthquakes as with tsunamis. These reports are not statistically significant and can be used for earthquake prediction only in rare cases.

Both measurable and statistically recorded precursor phenomena each vary greatly in their time course (up to years ) as well as in magnitude. In many cases, one or more of these effects are also quite. In addition, would the instrumental complexity that would be required for a complete recording of these phenomena can not be implemented, so that the possibility of an exact prediction of earthquakes in the near future is not expected.

Previous predictions

Occasional reports of successful predictions show against the backdrop of the frequency of earthquakes in the region concerned generally have little statistical significance. So a magnitude 7 earthquake in Tokyo was predicted for example by a Japanese scientist on the basis of an electromagnetic precursor phenomenon for the period 14 to 19 September 2003. Although entered on 20 September 2003 in fact an earthquake in Tokyo, but the magnitude was lower by about 1.5 magnitudes, which is less than one hundredth of the predicted energy release. A much stronger earthquakes (magnitude 8), with two strong aftershocks ( Mag 5.8 and 7) a week later occurred, on 26 September, but the epicenter was located at some distance, about 80 km southeast off the coast of the main island Hokkaidō.

An example of a successful earthquake prediction is the earthquake of Liaoning in Manchuria on 4 February 1975 in the People's Republic of China. Authorities ordered the evacuation of millions of Haicheng City the day before the quake, after an increase was observed of smaller earthquakes that took place at the end of a months-long period of changes in the elevation of the land surface and the water table. In addition, strange behavior of animals was observed. It is estimated that without the evacuation, the number of victims would have been at about 150,000; However, it was 1300. however, showed, for example, the Tangshan earthquake of 27 July 1976, in which there were several hundred thousand dead, according to various reports, no such clear signs, so that short-term warning was not possible. However, the statement about the lack of animal anomalies is not true. Immediately after the Tangshan earthquake was working in the earthquake region an extensive Chinese Investigation Commission, which was attended by 16 scientific institutes. She delivered a 459 page comprehensive documentation ( in Chinese ), which also took in Chapter 12 to abnormal animal behavior before earthquakes detail position. In his 2202 cases of eye-catching animal behavior are documented, which began a day or two before the quake and tremble towards increased significantly. Among them there were very unusual, never before observed animal behavior (about 100 Wiesel run into a village center, 300 mice motionless on the ground, a 100 -foot-wide swarm of dragonflies, bees from all 100 hives of apiary flee from these, clenched a few hundred lines at a pond edge ). According to a participant in the investigation Commission responsible for the earthquake warning politicians from their posts were removed at the time of the earthquake. Therefore, the prediction may be denied on the basis of observations of nature.