SOME FEATURES OF EARTHQUAKES DISTRIBUTION AROUND PEKING AND CRUSTAL BUCKLING

The large spatial distribution of the activity of strong earthquakes is a characteristic feature. And it seems that the World-wide seismic zones are somehow arranged in several regularly directions on the spherical surface. We suppose that the cause of earthquakes might be related to the movements of the whole earth.A feature relating to earthquakes activity in blocks, the boundaries of which usually make 45° with the latitude or longitude was found. The same situation happened before strong earthquakes occurred in recent years. A stripe making an angle of 45° with the latitude or longitude has been delineated. Strong earthquakes occurred in recent years are located essentially along the two boundary lines of this stripe, and obviously distribute themselves at equal distance span, which means that the distance span between the strong earthquakes resembles equal wave length during the folding of geological strata. We have studied all of the M≥8 earthquakes occurred in China during history. We found that before or after each earthquake (M≥8), another earthquake (M≥7.5) generally occurred at a definite distance away. The distance span has two predominant distributions, one at a shorter distance of 480—550km, the other at a longer distance of about 1100km (the latter distance is about twice the former).We take for a preliminary discussion the buckling process of a simple cylindrical shell under compression in the axial direction. From analysis we know that, whenthe cylindrical shell buckles, the buckling wave length (1/2λ≈1.72 \sqrtRh ) was de-termined only by the radius of the cylinder and the thickness of the shell. Now if we substitute R=6000 km; h=15 km, the halfwave length will be 530km. It agrees with the distance span for strong earthquake distribution.So we have the tentative opinion that the character of earthquakes distribution is controlled by crustal buckling.