Aftershock forecast "three law"

Aftershock forecast "three law"

Aftershock brings human suffering in the main shock.

Main earthquake suddenly attacking, half-dozen things down to Earth; however, in later days, or even a few months, but let people aftershocks keep few ruined homeland, while waiting. Therefore, some seismologists said aftershocks as "ghost" after the earthquake. Existing technology means not enough to make the main shock, then credible forecast? aftershocks

If you want to know if and how aftershocks, must first understand earthquake sequence type.

Sometimes an earthquake just some, there is no advance team also did not say I told you so, this is referred to as the "solitary"; If a certain time, the same geological structures, energy through several magnitude similar to the earthquake is released, that is, "" earthquake swarm, 1966 xingtai is typical (in the same month, there have been more than 7 levels, seismic 1st 6 or above, 5 4 earthquake-earthquake of 13 above); and the Wenchuan earthquake Basic is defined as "the main shock-type", in this type of earthquakes, the main shock releases of around 90% of its energy, its maximum aftershocks are basically will occur within 20 days.

Aftershock in general smaller than the main earthquake intensity, energy attenuation level before the earthquake of time period has been a spate of aftershocks, individual or even several years later also harassed humanity, therefore, despite the strength is not big, but it might be due to repeated strikes and overlay.

Sometimes the main shock to collapse of the building, under the action of the aftershocks is also very dangerous.

However, the aftershocks of two characteristics make them elusive.

First: aftershock and not necessarily the main shock around a small region. This is because the fault rupture is dynamic. From a scientific perspective, the study of seismic characteristics for great value, scientists can occur throughthe aftershocks of the place marked out the location of the seismic faults. For example the Wenchuan earthquake, the main earthquake and aftershocks will basically follow the terrain trend line up more than 600 km of seismic belt, this is the Dragon Mountain fault zone. In addition, the rupture of the surface, due to the stresses of accumulation, may also trigger the aftershock. The second characteristic is: as time goes by, the frequency of aftershocks will become smaller and smaller, but its strength is not necessarily decrease, in the main shock last a long time, also occasionally very big aftershock occurred.

Although these properties have the head, but the good news is that the performance of aftershocks are to a great extent, it can be expected, scientists will be summed up as "earthquake" mathematics three law.

The first rule called "Gutenberg-Richter correlation," from "Leeb magnitude" defined by Gutenberg and summed up: Richter earthquake series each lower level, a number of aftershocks will increase 10 times. The second law as a "Bath": on average, a maximum of aftershocks, its magnitude than the main shock small 1.2 times. The last "Omori's law" tells of the aftershocks frequency attenuation, that is, the probability of occurrence of aftershocks over time basically is reduced, or the last curve quite fast. Of course, the aftershocks of the form isn't always strictly follow these rules, which are usually different geographical conditions with slightly different. However, scientists with the earthquake aftershocks reflected in the occurrence, analysis of the local terrain (e.g. pursuant to the above mentioned faults trend), how can "hindsight" to say: a region within a certain time period may occur on the probability of a certain intensity earthquakes. This is the aftershock forecast — it is not a lottery draw like Meng blind, but it is 100% will be established.

□ Liu Yang (United States doctoral)