الفهرس 
History of the Nuclear TestsOnly 14 pages are availabe for public view
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Abstract
In this thesis, several diagnostic techniques (complexity, spectral ratio, spectral displacement, amplitude ratio of P/S and mb body wave and Ms surface wave magnitudes are applied in five regions (China, India, Pakistan, North Korea, and USA) to discriminate between nuclear explosions and natural earthquakes. The waveform data were collected from different international sources for the period from 1990 to 2017 with a set of 35 seismic events; 19 events are nuclear explosions and 16 events are natural earthquakes with 4 ≤ mb ≤ 6.5. The broadband and long period stations at local, regional and teleseismic stations are used. In China region the data used are 7 earthquakes and 7 explosions. In India region the data used are one earthquake and one explosion. In Pakistan region the data used are one explosion and one earthquake. In North Korea region the data used are 6 explosions and 3 earthquakes and in USA region the data used are 4 explosions and 4 earthquakes.
The complexity and spectral ratio method are applied in each zone using the same vertical component of the broadband stations in the time domain and frequency domain to calculate complexity and spectral ratio parameters; respectively. Complexity parameters of earthquakes are higher than for nuclear explosions. This is due to explosions usually generate compressional wave signals which tend to be simple, consisting of a few cycles while earthquakes generate a shear wave along with the compressional wave which tend to be complex, consisting of a long series (known as the Coda) following the initial few P-wave cycles. On the other hand, spectral ratio parameters are larger for explosions than for earthquakes as the explosion seismogram have higher frequency content than for earthquakes.
Both P-wave and S-wave displacement spectra of explosions demonstrate, that the corner frequencies are higher than those obtained from earthquakes of the similar magnitudes while the P-wave and S-wave displacement spectra of Nevada Test Site (NTS) explosions demonstrate lower corner frequencies than earthquakes of the similar magnitudes. This is due to most explosion tests are detonated in saturated crystalline rocks with a high effective strength while, the Nevada test is detonated in weak, porous rocks.
For explosions, the corner frequency of P- waves ( P) in China is ranged from 0.95 to 1.8 Hz while for earthquakes it is ranged from 0.6 to 1.45 Hz, In India, P for explosions is 1.3 Hz while for earthquakes is 1 Hz, In Pakistan, P for explosions is 1 Hz while for earthquakes is 0.8 Hz, In North Korea, P for explosions is ranged from 1.8 to 2.4 Hz while for earthquakes it is ranged from 1.7 to 2 Hz and finally in USA, P for explosions is ranged from 0.8 to 1.8 Hz while for earthquakes it is ranged from 0.48 to 1.4 Hz.
On the other hand, for explosions, the corner frequency of S-waves ( S) in China is ranged from 0.8 to 1.5 Hz while for earthquakes it is ranged from 0.5 to 1.1 Hz, In India, S for explosions is 1.2 Hz while for earthquakes is 0.85 Hz, In Pakistan, S for explosions is 1.1 Hz while for earthquakes is 0.6 Hz, In North Korea, S for explosions is ranged from 0.98 to 1.98 Hz while for earthquakes it is ranged from 0.9 to 1.3 Hz and finally in USA, S for explosions is ranged from 0.6 to 1.4 Hz while for earthquakes it is ranged from 0.4 to 1 Hz.
The amplitude ratio of P/S for explosions is higher than for earthquakes and the spectral amplitudes of S waves are less for the explosions. As explosions release energy in a 3D symmetric volume and their waveforms are dominated by P-waves while earthquakes represent a line source with dimension several times larger than explosions and generate much larger S-waves. The surface waves are weaker for explosions compared to those to an earthquakes.
from Pn/Sn amplitude ratio, we have determined the best frequency band in discrimination in each region. In China, the best frequency band in discrimination is about (1- 7) Hz. In India, the best band is (1- 6) Hz. In Pakistan, the best bands are (1- 3) and (7.5- 10) Hz. In North Korea, the best band is (1- 5) Hz. Finally, In USA, the best frequency band in discrimination is (1- 6) Hz.
The mb - Ms relation method is applied in each studied zone using the same broadband and long period stations at tele seismic distances from to 50 o to calculate body wave and surface wave magnitude; respectively. This technique reveals a higher values of body wave magnitude (mb) for explosions compared to earthquakes. On the contrary, the surface wave magnitude (Ms) is larger for earthquakes compared to explosions.
Finally, the mean and standard deviation of all parameters used in discrimination were calculated and the output results are plotted to detect the percentage of each method in discrimination. Based on these results, the standard deviation values of complexity and spectral ratio parameters are ranging from 0 to 0.74 and the percentage of discrimination in this method is 70%. While the standard deviation values of corner frequency of P and S waves are ranging from 0 to 0.2 and the percentage of discrimination in this method is 78% and the standard deviation values of body wave magnitude and surface wave magnitude are ranging from 0 to 0.05 and the percentage of discrimination in this method is 84%. In conclusion, this study revealed that the amplitude ratio of P/S and mb-Ms techniques are the most effective seismic methods for identifying the nature of the seismic source.