Sedimentary
rocks and natural hazards-incidences in Egypt.
Ahmed F. Kamel
Nuclear Materials Authority, Cairo, Egypt |
The intensively developed parts of Egypt were
subjected to some damage resulting from natural hazards. Historical records show that the
northern part of Egypt has been affected by earthquakes with high intensity. The S-W part
of Egypt is the least hazardous, as a result of low density of population. Most of the
larger earthquakes recorded in Egypt have their source of origin in regions outside its
borders except for a few local earthquake centers such as the earthquakes of ElFayum
(1847), Abu Dabbab (1955),El Gilf El Kebir (1978), Kalabsha (1981) and Dahshour (1992).
Earthquake intensity is less than IV in the Mesozoic sediments, ranging between V and VI
in the Tertiary, and increases in the Quaternary sediments to reach VI. The rock type
plays an important role in the earthquake intensity. It is very low in the Nubian
sandstones and shales, moderate in the limestone rocks and high in unconsolidated
materials and soft rocks.
Earthquake intensity correlates fairly well to rock fall which is also an integral part of
urbanization and regional planning. Damage caused by rock fall, slope failure and debris
flows depends on rock mechanics. The poor mechanical properties of the sedimentary rocks
constitute major factor in rock fall susceptibility. High clay content explains the
instability of the rock foundations. Fracture density in the limestones influences damage
caused by natural hazards. This shows the importance of minimizing natural hazard risks,
and particular attention must be paid to the developed parts of the country and their
sedimentary rocks.
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