Parallelism in seismic computing     

M. Kindelan  P. Sguazzero  A. Kamel 《Surveys in Geophysics》1989,10(2-4):377-388

This paper describes a vectorized and parallelized implementation of a two-dimensional pseudo-spectralseismic elastic model and of a (frequency-domain)seismic migration algorithm on the (tightly-coupled) vector multiprocessor IBM 3090 VF. Performance data of alternative parallel implementations on an LCAP (loosely coupled system of array processors FPS 164) are also given.The paper reports additionally performance data of a vector/parallel implementation on the IBM 3090 of some characteristicseismic velocity estimation algorithms. The three problems chosen are representative of a wide class of geophysical computations and the results summarized in this paper show their suitability to efficient implementation on the IBM 3090 vector multiprocessor: combined vector/parallel speedups in the range 15–30 are in fact observed.  相似文献   

Effect of temperature on the physical precursors of rock block failure     

Kamel Baddari  Anatoly D. Frolov  Victor Tourtchine  Said Makdeche  Fayçal Rahmoune 《Acta Geophysica》2012,60(4):1007-1029

The influence of temperature (25–400 °C) on the variations of mechanical, acoustic, electric and electromagnetic precursors of rock failure has been shown experimentally. The most significant variations were detected in the principal parameters of the acoustic and electromagnetic emissions whose impulse energy underwent a fast growth. However, the general character of hierarchical evolution stages of micro and macrofailure was practically unchanged. This has been confirmed by the so-called concentration parameter of rupture, which is theoretically calculated and checked in experiments; its space-time variations preceding the occurrence and progression of macrofailure are slightly depending on the rock temperature effect. This has been shown through the convolution of some physical precursors in a complex parameter whose variation showed an approaching of macrofailure, which remains slightly influenced by changes in temperature. Our results are interpreted in relation to physics of superficial earthquakes and precursors.  相似文献   

Incorporation of a Non-linear Image Filtering Technique for Noise Reduction in Seismic Data     

Jalal Ferahtia  Kamel Baddari  Nouredine Djarfour  Abdel Kader Kassouri 《Pure and Applied Geophysics》2010,167(11):1389-1404

Seismic noise is a fundamental part of seismic data which cannot be avoided when conducting any seismic survey. It consists of coherent and random noise. Noise removal or filtering is one of the major concerns in the field of seismic processing. In this paper, we introduce an image filtering technique based on a detection-estimation algorithm for Gaussian and random noise removal in seismic data, namely the trilateral filter, based on a statistic called rank-ordered absolute differences. The non-linear and adaptive behaviour of this filter makes it very robust in the presence of random and coherent noise, in addition to its computational simplicity and its ability to automatically identify noise in data. We have modified the strategy of trilateral filtering by adapting the rank-ordered absolute differences formula in order to extract the signal component. We have successfully used this filter for the removal of surface waves and random spiky noise from synthetic and field data. Results are very encouraging and show the superiority of this filter compared with other filters, particularly when used recursively.  相似文献   

Some Probabilistic and Statistical Properties of the Seismic Regime of Zemmouri (Algeria) Seismoactive Zone   总被引：1，自引：1，他引：0  

Kamel Baddari  Fouzi Bellalem  Ibtihel Baddari  Said Makdeche 《Acta Geophysica》2016,64(5):1275-1310

Statistical tests have been used to adjust the Zemmouri seismic data using a distribution function. The Pareto law has been used and the probabilities of various expected earthquakes were computed. A mathematical expression giving the quantiles was established. The extreme values limiting law confirmed the accuracy of the adjustment method. Using the moment magnitude scale, a probabilistic model was made to predict the occurrences of strong earthquakes. The seismic structure has been characterized by the slope of the recurrence plot γ, fractal dimension D, concentration parameter K_sr, Hurst exponents H_r and H_t. The values of D, γ, K_sr, H_r, and H_t diminished many months before the principal seismic shock (M = 6.9) of the studied seismoactive zone has occurred. Three stages of the deformation of the geophysical medium are manifested in the variation of the coefficient G% of the clustering of minor seismic events.  相似文献   

An elimination of the critical terms of a first-order Uranus-Neptune theory by Hori's method     

Osman M. Kamel 《Earth, Moon, and Planets》1992,59(2):111-140

We eliminate the 1:2 critical terms — after a previous elimination of the short period terms — in the Hamiltonian of a first order U-N theory. We take into account terms of degree 0, 1, 2, 3, 4 in the eccentricity-inclination. We apply for this elimination the Hori-Lie technique through the Poincaré canonical variables and the Jacobi coordinates. The purely principal first order secular U-N Hamiltonian admits a complete solution. We obtained the U-N equations of motion generated by the principal first order long period U-N Hamiltonian which will be solved later. This part III is closely related to the two previous papers (Kamel, 1982, 1983).  相似文献   

East-west stationkeeping requirements of nearly synchronous satellites due to Earth's triaxiality and luni-solar effects     

Ahmed Kamel  Donald Ekman  Richard Tibbitts 《Celestial Mechanics and Dynamical Astronomy》1973,8(1):129-148

A closed form solution, for longitude and semimajor axis deviations in the neighborhood of a prespecified station, is obtained for nearly synchronous satellites. The model use includes the important terms in Earth's zonal and tesseral harmonics as well as the luni-solar perturbations. The initial semimajor axis for two-maneuver east-west stationkeeping is then deduced. Due to the luni-solar effects, it is found that the initial semimajor axis deviation from synchronous orbit value is highly dependent on the initial position of the satellite relative to the Moon and the Sun. Verifications of the results by means of numerical integrations are also included.  相似文献   

Some useful results on initial node locations for near-equatorial circular satellite orbits     

Ahmed Kamel  Richard Tibbitts 《Celestial Mechanics and Dynamical Astronomy》1973,8(1):45-73

Perturbation theory based on Lie transforms is used to obtain a second-order long period solution for inclination and right ascension of ascending node, of near-equatorial circular satellite orbits. The solution includes the average effects of the Earth's oblateness and the luni-solar perturbations. Three algorithms, useful in mission analysis, are then given. The first algorithm finds the initial node location that results in a decrease of inclination to zero and it also finds the corresponding time to arrive at this zero inclination. The second algorithm determines the initial nodal band that maintains the orbital inclination below a specified value for a given time interval. The third algorithm obtains the initial node location that maximizes the time in which the satellite can be maintained within a given inclination tolerance without the use of any active control and it also obtains the corresponding maximum time. The results of the first and the third algorithms are given for 24-h near-equatorial circular satellite orbits and are cast in simple closed forms.  相似文献   

The construction of a third order secular analytical J-S-U-N theory by Hori-Lie technique     

Abdel Aziz Bakry  Osman M. Kamel  Salwa M. Waziry 《Earth, Moon, and Planets》1994,64(1):59-93

The first and second order generating functions and the first second and third order new J-S-U-N Hamiltonians are calculated by the Hori-Lie procedure.  相似文献   

Elimination of the critical terms in a first-order general planetary theory     

Kamel  Osman M. 《Earth, Moon, and Planets》1981,24(2):137-155

We construct a first order canonical general planetary theory, assuming the solar system to be composed of 8 planets excluding Pluto, referring to common fixed plane and applying the Jacobi-Radau set of origins. We eliminated by von Zeipel's method the 2:5 and 1:2 critical terms of Jupiter-Saturn and Uranus-Neptune inequalities. Our variables are those of Poincaré, and we expanded up to power three in the eccentricities and sines of the inclinations.  相似文献   

Calpionellid zonation of the Jurassic–Cretaceous transition in North-Atlasic Tunisia. Updated Upper Jurassic stratigraphy of the ‘Tunisian trough’ and regional correlations     

Mabrouk Boughdiri  Houaïda Sallouhi  Kamel Malaoui  Mohamed Soussi  Fabrice Cordey 《Comptes Rendus Geoscience》2006,338(16):1250-1259

The analysis of calpionellid associations from jebels Amar and Jédidi sections in North-Atlasic Tunisia provides, for the first time, a precise biozonation of the Jurassic–Cretaceous transition succession. In the light of the new data obtained and considering recently published results, the age of Upper Jurassic formations is clarified, allowing correlations with the Tunisian ‘Dorsale’ and the North–South Axis successions. Within the Maghrebides' range, sections from the external zones correlated to the Tunisian successions are quite distinctive from their equivalent in the internal zones. Both have evolved in different palaeogeographic domains related to the early structuration of the northwestern and southwestern Tethys margins. To cite this article: M. Boughdiri et al., C. R. Geoscience 338 (2006).  相似文献