January 16. Kohat plateau in north-western Pakistan is a special geological structure that moves on the surface of another tectonic plate small, successive short steps — about the same as a caterpillar, say Indian and American geologists in an article published in the journal
Roger Bilham (Roger Bilham) from the University of Colorado at Boulder (USA) and his colleagues believe that "tracked" nature of the movement was the cause of the mysterious plateau earthquake May 20, 1992, the force of which reached 6 on the Richter scale. To date, this event is considered the most powerful earthquake for the time in which people live in the north-western boundaries of Pakistan.
The scientific team led by Bilham tried to find the causes of this earthquake by studying the structure of the tectonic plates in the region of the epicenter with special interferometric radar.
As the article notes, the district Kohat Plateau is interesting that in this region there are two large tectonic plates — the Eurasian and Indian. The eastern and northern boundaries between them are held throughout the length of the Himalayas and other mountain massifs where the clash between the plates causes the rare but extremely powerful earthquake.
On the other hand, the western part of the collision zone is different "quiet" character. In this area, the Indian plate slowly disappears under the rocks coming Eurasian plate by the airspace of soft rock on which the slide of its mass.
Scientists have "enlightened" this substrate using interferometric radar and found that there are several sites where they played harder than in other regions of the plateau of rock. Apparently, one of these points was the epicenter of the 1992 earthquake, as evidenced by the strong deformation of the material of the substrate itself and covering her Indian plate.
As explained by Bilham and his colleagues, volcanic ridges, and other hard rocks on the surface of the substrate significantly slow down the "flow" downstream rocks. As a result of this matter is the Indian tectonic plate gradually accumulate in the region of the lip, causing the pressure and stress at this point is gradually increased. After a while the stove burst, which was the cause of the earthquake.
After this plateau continued to fall under the Eurasian plate without major obstacles. Scientists compare this way of movement of the crust with the way a caterpillar crawling — it moves only one segment of the body and moves them one by one, from the head to the tail, resulting in a rise to specific wave-like motion.
The researchers suggest that "tracked" nature of the flow of rocks is the main cause of a small number of earthquakes in this part of Pakistan.
According to their calculations, the disaster in 1992 is the exception rather than the law — such events should occur no more frequently than once every 600 years. Following an earthquake is likely to occur in the southern part of the plateau, near the mountains Surgar adjacent to the Kohat Plateau. Maximum power cataclysm will not exceed 7 on the Richter scale.