Joint research project

Spatiotemporal seismicity patterns and earthquake precursors at Aswan, Egypt. Contribution to earthquake hazard assessment.

Project leaders
Luciano Telesca, Amin Mohamed Abuo El-ela
Agreement
EGITTO - ASRT - Academy of Scientific Research and Technology
Call
CNR/ASRT 2011-2012
Department
Earth and Environment
Thematic area
Earth system science and environmental technologies
Status of the project
New

Research proposal

 Induced seismicity is the dynamic response of rock mass to human technological activity that changes the equilibrium of the medium. Increasing needs for energy and minerals, and the growing complexity of technological processes, result in the appearance of seismicity in previously aseismic areas. It can result from stress or pore pressure changes, from a volume change, from loading or unloading in the rockmass and from combinations of such causes. Induced seismic events accompany underground and open-cast mining, exploitation of oil and gas, geothermal energy production,  underground storage of liquids and gases. Strong seismic events caused by human activity are comparable to locally moderate earthquakes and are dangerous for people, technical devices, and various infrastructure objects.
Another important cause of induced seismicity is the filling of water reservoirs. Reservoir-induced seismicity is observed worldwide. For example, in Nurek Reservoir, Tadjikistan (Simpson and Negmatullaev 1981), in the reservoirs LG3 and Manic 3, Quebec, Canada (Anglin and Buchbinder 1985; Leblanc and Anglin 1978), in Govind Ballav Pant reservoir, India (Gahalaut et al. 2007), and especially in Koyna-Warna, India (Gupta et al. 1969). Reservoir-triggered earthquakes have characteristics (e. g. higher b-value, larger magnitude ratio  of the largest aftershock to the mainshock, increase of seismicity rate with the increase of water level) that discriminate them from normal seismic events (Gupta et al. 1972). Ground water plays an important role in reservoir-induced earthquake activity. Water pore pressure reduces the normal stress within a rock while not changing the shear stress. Under any circumstances, an increase in water pore pressure means that a failure is more likely. The critical value of shearing stress may be made arbitrarily low by increasing the pore pressure. Pore pressure can increase due to the decrease in pore volume caused by compaction under the weight of the reservoir and/or due to diffusion of reservoir water through permeable rock under the reservoir. The rate of flow depends on the permeability of the rock, so this effect is not instantaneous. The increase in pore pressure takes more time depending on the distance from the reservoir. It may take years for the pore pressure to increase at depths of kilometers beneath a reservoir.
Aswan area (Egypt) is known to be seismically active since the occurrence of November 1981 Aswan earthquake (Mw=5.8). Detailed geological and geophysical surveys in the area confirm the existence of few active faults to the southwest of the Aswan High Dam (e.g. Kalabsha, Khor El-Ramla and Kurkur faults). The seismic activity in this area might be related to both tectonic activities along these active faults and/or reservoir induced seismicity due to the Aswan Lake construction. The Aswan High Dam hydropower project was constructed in 1970. It is the most important project in Egypt from the social, agricultural and electrical energy production points of view. The importance of this dam comes from the fact that it is a unique case in the world where one single dam controls almost whole nation in its downstream. Protection of this structure from all kinds of hazard, particularly earthquakes, is actually a conservation of Egypt in the present and the future. In fact, a regional seismological network was established since 1982 around the northern part of the Naser Lake to monitor all earthquake activity. And recently on 2007, the National Research Institute of Astronomy and Geophysics (NRIAG) have started the upgrading of this network by using broad band stations that send data on real time to the main data center at Aswan using satellite communication.
Within this context, the project intends to perform a detailed study of the spatial and temporal distribution of seismicity at Aswan Lake and give a contribution to the problem of estimation and prediction of the hazards implied by reservoir-induced seismicity, which has not found fully satisfactory solutions yet. Therefore, spatial and temporal pattern of seismicity, stress field and modeling of the pore pressure diffusion due to seasonal variations of the water level in Aswan Lake will be studied.
To perform such activities the available resources for the project are: 1) Detailed geological setting based on the detailed studies performed by Woodward Clyde Consultants (WCC, 1985); 2) Detailed crustal structure provided from passive and active seismic studies previously performed by NRIAG researchers; 3) Previous geophysical studies performed by NRIAG researchers; 4) Revised regional and local earthquakes catalogue for Egypt from 1900-2010 and for Aswan area from 1981-2010, respectively; 5) Water level data from 1964-2010; 6) Digital waveform data of all significant events relevant to focal mechanism and moment tensor analysis.
The Egyptian and Italian groups will share their experience and competence in seismic data analysis, seismic measurements, seismological network design and installation; and they will carry out the project in terms of knowledge transfer, data and methodologies  sharing for a better understanding of seismic processes, acquisition of co-operation procedures and sharing of human resources, to be exploited for a future continuation of joint research/education activities.
 

Research goals

1) To analyze the space-time relationship of the induced seismicity at Aswan area with water level, the local stress field and the geological settings. 2) To study similarities and differences between natural and reservoir-induced seismicity in Aswan area. 3) To develop a hydrological model for the Aswan area and to estimate the vertical hydraulic diffusivity of the area.  4) To investigate and understand the geomechanics and processes involved in the induced seismicity.  5) To provide an assessment of the seismic hazard of the area on the base of the results obtained through the analysis of the geophysical parameters measured in the area. 6) To disseminate preliminary and final results of the project in international conferences, publications, and in a project-oriented internet website.

Last update: 29/03/2024