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Estimation of frequency dependent coda wave attenuation structure at the vicinity of Cairo Metropolitan Area

El-Haidy S., Adel M., Adel M., Adel M., Abu-El-Ata A., Sayed M.

Acta Geophysica

2006

Vol. 54, no. 2

177-186

Estimation of seismic wave attenuation in the shallow crust in terms of coda wave Q structure previously investigated in the vicinity of Cairo Metropolitan Area was improved using seismograms of local earthquakes recorded by the Egyptian National Seismic Network. The seismic wave attenuation was measured from the time decay of coda wave amplitudes on narrow bandpass filtered seismograms based on the single scattering theory. The frequency bands of interest are from 1.5 to 18 Hz. In general, the values obtained for various events recorded at El-Fayoum and Wadi Hagul stations are very similar for all frequency bands. A regional attenuation law Qc = 85.66 f 0.79 was obtained.

Computer-aided variable wavelength Fourier transform polarizing microscopy of birefringent fibers.

Litwin D., Adel M.

Optica Applicata

1998

Vol. 28, nr 2

139-153

As automatic fringe analysis is used to measure the spectral dispersion of birefringence of cylindrical textile fibers. The approach presented is based on the optical Fourier transform microscopy of birefringent fibers. The pattern of the optical Fourier transform observed in a polarizing microscope is processed automatically to measure the radius of interference dark fringes as a function of light wavelength. This method allows us not only to calculate the interference orders and the spectral dispersion of birefringence of fibers but also to detect their optical and geometrical microdefects. The image is processed with a computer-controlled automatic analysis system. Examples of applying this method to highly fibers are given.