Seismicity and 3D velocity structure in the Aswan Reservoir Lake area, Egypt

Haggag, Hamed Mohamed; Bhattacharya, Pankaj Mala; Kamal, S.; Kayal, J. R.

doi:10.1016/j.tecto.2009.07.015

Cited by 17 publications

(10 citation statements)

References 9 publications

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“…Kalabsha fault has a lateral extent of (∼300 km) which is the longest of all the faults present within the study area. The Aswan earthquake (M w 5.7) of 1981 (Awad 1994;Kebeasy et al 1981;Haggag et al 2009) occurred along it (Fig. 1).…”

Section: Geology and Tectonic Settingsmentioning

confidence: 97%

“…1 The tectonic features, earthquakes (black dots) which were used for the analysis and seismic stations (triangles) are shown. Reservoir-induced Aswan earthquake (1981) of magnitude 5.7 is shown by a star (after Haggag et al 2009) 3.2 Separation of Q i and Q s Most of the methods available for separation of Q sc and Q i are based on the assumption of isotropic distribution of scatterers and constant Q i in the same earth volume (e.g., Zeng et al 1991;Fehler et al 1992). This assumption may be unrealistic as it is generally accepted that heterogeneity decreases with increasing depth.…”

Section: Estimation Of Q Smentioning

confidence: 99%

“…In this study, the average S wave velocity is taken to be 3.5 km/s from the results of Haggag et al (2009). The results are discussed below.…”

Section: Estimation Of Q I and Q Scmentioning

confidence: 99%

“…1, Kebeasy et al 1981). Ever since, occurrences of earthquakes are reported from this place (Haggag et al 2009). This makes it a potential region for reservoir-induced earthquake damage, and it would be useful to study attenuation characteristics of this region for future use by other scientists who would be interested in hazard zonation/microzonation of this area.…”

Section: Introductionmentioning

confidence: 96%

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Estimation of attenuation characteristics of Aswan reservoir region, Egypt

2015

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The attenuation characteristics of Aswan reservoir region in Egypt was estimated using microearthquakes records. Frequency-dependent attenuation characteristic of S wave was estimated using coda normalization method. The evaluated quality factor (Q s ) shows strong frequency dependence with its value increasing with increasing frequency. For Aswan region, the average frequency-dependent relation is given by Q s =(34.2 ±2.9)f (1.023±0.107) . The low values of Q s lie within those observed for seismically active regions of the world, although the study area is seismically moderately active and known to be a region where reservoir-induced seismicity occurs. The low value of Q s would mean that the medium is highly heterogeneous. Separation of intrinsic and scattering Q was carried out using estimated Q s values and values of coda Q (Q c ) estimated earlier by other workers from the same data set. It is observed from this that S and coda wave attenuation is primarily controlled by intrinsic attenuation at 1-Hz frequency. At higher frequencies, intrinsic and scattering attenuations contribute almost equally as seismic albedo at 1-Hz frequency is 0.04, and at higher frequencies, it varies between 0.34 and 0.55. Extinction length varies between 16.4 and 23.6 km. The frequency-dependent relationship for scattering Q (Q sc ) and intrinsic Q (Q i ) are Q sc = (699.3 ± 334.5)f (0.13 ± 0.06) and Q i = (52.9 ± 5.6)f (1.09±0.03) .

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Section: Geology and Tectonic Settingsmentioning

confidence: 97%

Section: Estimation Of Q Smentioning

confidence: 99%

“…In this study, the average S wave velocity is taken to be 3.5 km/s from the results of Haggag et al (2009). The results are discussed below.…”

Section: Estimation Of Q I and Q Scmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Estimation of attenuation characteristics of Aswan reservoir region, Egypt

2015

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“…Resorting to the dynamic variations of 3-D V P and V P /V S , GUNASEKERA et al (2003) found water repletion of the Geysers geothermal reservoir area. HAGGAG et al (2009) used the local earthquake tomography method to image the 3-D velocity structure of Aswan reservoir lake which ever triggered the world's second largest reservoir earthquake, and they found that the upper shallow crustal earthquakes were mostly influenced by the fluid saturation. Therefore, studies of the 3-D Vp and Vp/Vs structure in reservoir areas can provide us fundamental knowledge for seismic risk assessment and earthquake fortification in the reservoir dam area.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional V P and V P /V S Structure in the Longtan Reservoir Area by Local Earthquake Tomography

Zhou

Zhao

Chen

et al. 2011

Pure Appl. Geophys.

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High-resolution three-dimensional V P and V P /V S images in the Longtan reservoir area were obtained from local earthquake data by using 3,178 events with total 24,153 P-wave and 23,987 S-wave arrivals collected from 23 seismic stations. The tomographic images show that significant V P heterogeneities can be seen at layers of different depth in the Longtan reservoir area. Low-V P anomalies both beneath and around the main rivers in the reservoir area may be related to the composition of rocks which are mainly deposit carbonate and arenaceous shale, which contributes to water saturation. We deduced that the high porosity rocks beneath the main rivers may be fully saturated with water. The phenomenon that V P is relatively high in the area which is 10-20 km away from the rivers indicates that horizontal saturation of water is limited within a small range of area that is about 10-20 km from the main rivers. The characteristic is significant that seismicity in the Longtan reservoir area is coincident with the distribution of the low-V P area. V P /V S tomographic images show that V P /V S ranges from 1.8 to 2.05 in shallow layers above 4 km depth beneath the Longtan reservoir, suggesting the properties of the rocks are limestone and shale. At the depth of 7 km, the distribution of V P /V S image varies quite remarkably, especially in the dam area. This demonstrates that the range of influence by the saturation of water in the media below the reservoir surface can reach 4-7 km depth in the dam area.

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