THIRTY FIVE YEARS INVESTIGATION OF THE RESERVOIR INDUCED SEISMICITY IN AND AROUND THE NORTHERN PART OF LAKE NASSER, EGYPT | ||||
| Journal of Egyptian Geophysical Society | ||||
| Volume 19, Issue 1, 2021, Page 23-36 PDF (7.22 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jegs.2021.385830 | ||||
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| Authors | ||||
| G.H. HASSIB; E.M. EL-AMIN | ||||
| National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt. | ||||
| Abstract | ||||
| The first instrumentally recorded earthquake at Aswan province occurred on November 14, 1981 on Kalabsha fault with magnitude of 5.3. Thirty five years of seismic monitoring in the northern part of Lake Nasser (the second largest reservoir in the world) has shown that the epicenters were clustered on the active fault segments near the eastern part of Kalabsha fault at the weakness area of the intersecting of Kalabsha fault with Khor El-Ramla fault beneath the Kalabsha bay (the largest bay of the Lake Nasser). Composite focal mechanisms have been determined for different earthquake clusters. In all cases, the composite focal mechanisms are characterized by strike-slip faulting and horizontal stress axes. A gradual increase in shallow seismicity at Kalabsha area started in 1995 associated with the gradual increase of the lake water level and relatively higher seismic activities have been observed within the time period from 2007 up to 2016. This activity is concentrated mainly on the two fault segments east of Gebel Marawa beneath the lake. The interesting phenomena shown at Khor El-Ramla seismic zone is outward migration of epicentres followed the growth of the reservoir upstream from 1982 to 1998. The epicentres are moved slightly from southwest to northeast as water level increased from 175.29m in 1982 to 181.3m in November 1998. The temporal distribution of the seismic activity east of Gebel Marawa and Khor El-Ramla area from 1982 to 2016 showed an alternating in seismic activity along these two seismic zones. The increasing seismicity at some places on the lake periphery following the seasonal increasing of the lake water level reveals that the pore pressure diffusion plays an important role in triggering earthquakes. The b-value is calculated for seismicity occurred at the most active zones from 1982 to 2016 using the cumulative frequency-magnitude of Gutenberg and Richter relation. The result shows that the b-values are ranged from 1.03 to 1.07. | ||||
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