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Paper Number: 62
Seismic
hazard Analysis for Aswan High Dam Reservoir (Egypt)
Awad Hassoup
National
Research Institute of Astronomy and Geophysics
Helwan, Cairo, Egypt
_____________________________________________________________________
Earthquake activity and seismic hazard analysis are important
components of the seismic aspects for very essential structures such as
major dams. The Aswan High Dam (AHD) created the second man-made
reservoir in the world (Lake Nasser) and is constructed near
urban areas pose a high-risk potential for downstream life and property.
The Dam area is one of the seismically active regions in Egypt and is
occupied with several cross faults, which are dominant in the east–west
and north–south. Epicenters were found to cluster around active faults
in the northern part of Lake and AHD location. The space-time
distribution and the relation of the seismicity with the lake water
level fluctuations were studied. The Aswan seismicity separates into
shallow and deep seismic zones, between 0 and 14 and 14 and 30 km,
respectively. These two seismic zones behave differently over time, as
indicated by the seismicity rate, lateral extent, b-value, and
spatial clustering. It is characterized by earthquake swarm sequences
showing activation of the clustering-events over time and space. The
effect of the North African drought (1982 to present) is clearly seen in
the reservoir water level. As it decreased and left the most active
fault segments uncovered, the shallow activity was found to be more
sensitive to rapid discharging than to the filling. This study indicates
that geology, topography, lineations in seismicity, offsets in the
faults, changes in fault trends and focal mechanisms are closely
related. No relation was found between earthquake activity and
both-ground water table fluctuations and water temperatures measured in
wells located around the Kalabsha area. The peak ground acceleration is
estimated in the dam site based on strong ground motion simulation. This
seismic hazard analyses have indicated that AHD is stable with the
present seismicity. The earthquake epicenters have recently took place
approximately 5 km west of the AHD structure. This suggests that AHD dam
must be analyzed with high priority and redesigned to increase the
safety of the embankments and their appurtenant structures, if
necessary.
peak ground acceleration changes within a wide range (0.011 g and
0.564 g) for the dam sites of the basin. A seismic hazard map showing
the equivalent PGA (peak ground acceleration) values was developed so as
to use for the preliminary analysis of dam structures, which will be
designed in the basin. The total risk analyses depending on the seismic
hazard rating of dam site and risk rating of the structure have
concluded that fifteen large dams have high-risk class in the basin.
These dams must be analyzed with high priority and redesigned to
increase the safety of the embankments and their appurtenant structures,
if necessary.
Keywords
Dam; Earthquake; Euphrates basin; Potential risk; Seismic hazard