Earthquake is Manmade Catastrophe Rather than a Natural Disaster: Turkey

摘要

Soil grounds are several billion times more susceptible to earthquake disaster than rocky grounds. The probability of any soil to be liquefied is several billion times greater than that of even an extremely weak rock in case of fully saturated. Any rock, ranging from extremely weak to strong rock, is not susceptible to liquefaction even at submerged state. Shear strength of a saturated soil under dynamic condition approaches zero whereas the reduction in strength of the saturated rock is practically negligible. In another saying, the ratio of shear strengths [τ = c+σ_n' tan |μ] of saturated rock over soil goes to infinite. Similarly, the ratio of modulus of elasticity [E, kPα] of saturated rock over soil tends to go infinite too. Turkey is a country over which many micro plates are moving relative to each other. The Nnrth Anatolian (NAF), East Anatolian (EAF), and Ecemis fault (EF) are the three major strike-slip faults that cause destructive earthquakes only in soil grounds. The fourth distinct one is the gravity fault (graben) system prevailing in the Aegean region, which is less destructive due to lower energy storage capacity. All of the active fault systems comprise fertile farm fields and extend their limits with time. Such soil grounds form lowlands rich in groundwater and mineral. However, such soil lands are exposed to earthquake catastrophe. Furthermore, the lowlands are not good human health. Most of the viruses and bacteria can grow up. That is the main reason why such lands have to be preserved for farming and should be closed to settlement. The strike slip faults are, in general, coincident with the former suture zones bearing numerous polished sub-vertical discontinuities. These planes have great potential to act as a strike slip fault plane. San Andreas Fault in USA, Kobe Fault in Japan, and Dead Sea Fault extending from Jordan to Turkey are the typical examples. The recurrences of earthquakes create fertile low lands with shallow groundwater table. Such medium favors liquefaction, plastic deformation, rupture, sand ridges and cones, and magnification of the amplitude. An earthquake becomes more destructive in the cases of shallower groundwater table (z < 20 m) and thicker soil mantle (t > 20 m). Hence, one may conclude that rocky grounds are favorable for construction whereas soil grounds should be reserved for agricultural activities.