Subsurface structures using a new integrated geophysical analysis, South Aswan, Egypt
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ORIGINAL PAPER
Subsurface structures using a new integrated geophysical analysis, South Aswan, Egypt Maha Abdel Azeem & Mahmoud Mekkawi & Mohamed Gobashy
Received: 2 April 2013 / Accepted: 26 September 2013 # Saudi Society for Geosciences 2013
Abstract The Aswan High Dam located at the north of Nasser Lake in Aswan, Egypt, has a vital role because it is a multipurpose project for sustainable irrigation development, hydropower, and navigation improvement. In this work, we aim to detect the hazardous subsurface structures that control the South Aswan area and their causative source depths, through the application of both normalized standard deviation filters and deconvolution procedures. These computational approaches utilize a three-dimensional Euler homogeneity equation with unprescribed structural indices that is based on the properties of the differential similarity transformation on the available Bouguer gravity data. Hence, without any bias to a definite structural element (structural index), an automatic identification of the effective structural indices in the area is given. Moreover, possible vertical magnetic contacts are estimated from the reduced to pole magnetic anomaly map through an application of the tilt-depth technique. The mean focal depth of the earthquakes changes over time and migrates to shallower depths. The number of shallow events is increasing dramatically, whereas the corresponding magnitudes are decreasing. The integration of potential field data analysis with
M. A. Azeem (*) : M. Mekkawi National Research Institute of Astronomy and Geophysics (NRIAG), Helwan 11421, Cairo, Egypt e-mail: [email protected] M. Mekkawi e-mail: [email protected] M. Gobashy Department of Geophysics, Faculty of Science, Cairo University, Giza, Egypt e-mail: [email protected] M. Gobashy Department of Geophysics, Faculty of earth sciences, King Abdulaziz University, P.O. Box 80206, Jeddah 21589, Saudi Arabia
the new seismological and water level catalog (for the duration of 30 years) shows that the area began a hazardous cycle of activity (MI>4) that could continue over the next few years. Keywords Seismicity . Geo-hazard . Artificial lake hazard . Nasser Lake . Magnetic field . Gravity field . 3-D Euler . Aswan
Introduction Following the High Dam construction early in 1964, Nasser Lake (Aswan Lake) started to fill and form the second largest man-made reservoir in the world. This reservoir extends over 360 km along the Nile River in Egypt, and its height is approximately 111 m above the river bed. Its storage capacity is 162 km3, and its hydropower station capacity is 109 kWh/ year (Abu-Zeid and El-Shibini 1997). On November 14, 1981, a moderate sized earthquake (Ml=5.4) occurred in the northern area of Aswan Lake on the Kalabsha fault, at (latitude 23.55° and longitude 32.50°), which is approximately 60 km southwest of the Aswan High Dam (AHD) and 20 km deep. As a consequence of this earthquake, a local seismic network (Fig. 1) was installed around the epicentral area [supervised by the National Res
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