Numerical solution to the problem of ionoshperic filtration of ULF waves in thePc1 range. the total wave field inside the ionospheric transition layer

1991 ◽  
Vol 35 (2) ◽  
pp. 90-99 ◽  
Author(s):  
Karel Prikner ◽  
Vladimír Vagner
2021 ◽  
Author(s):  
R. Alay

In this abstract, a case study from offshore Indonesia is showcased with examples emphasizing integrated wave field separation methods with the objective of diffraction imaging towards refined karst feature and fault identification. For imaging optimally all diffraction energy, pre-migration and post-migration methods have been integrated. The dataset and examples in this abstract are in a complex geological setting in a very shallow water environment, with a subsurface that is characterized by large carbonate pinnacles containing large amount of karst features with thinning and thickening carbonate layers. For the purpose of refined imaging of diffraction energy only, the total wave field has been separated into specular reflections and diffractions prior to migration and these have been integrated with existing post-migration wave field separation methods. Both the pre-migration and post-migration wave field separation methods have their advantages and disadvantages and is discussed later in this abstract. Diffraction energy, in general is much lower in amplitude than the specular reflections and separately imaging these, unveils higher resolution small scale geological features such as karst features and faults complementing the total wave field PSDM data. With existing industry available methods applying wave field separation in either pre-migration or post-migration stage, limitations have been observed, and therefore we propose in this abstract to integrate both methods and take advantage of the improvements showcased with examples throughout the abstract.


Geophysics ◽  
1989 ◽  
Vol 54 (11) ◽  
pp. 1420-1429 ◽  
Author(s):  
S. G. Squires ◽  
C. D. Y. Kim ◽  
D. Y. Kim

Approximately 5 miles (8 km) of total wave‐field data were acquired by Production Geophysical Services (then Kim Tech., Inc.), using the OMNIPULSE® Multi‐mode Shear‐wave Generator source over the southern end of Lost Hills field, Kern County, California. The quality of the shear‐wave sections was excellent. They represent a significant improvement over conventional P‐wave sections from the area in that they provide better reflection continuity and imaging of the Lost Hills anticline. A multicomponent VSP, which was acquired close to the line, provided crucial P‐wave to S‐wave correlation, as well as fracture information. [Formula: see text] ratios computed from interval times ranged from 2.79 to 1.63. An anomalously low [Formula: see text] ratio of 1.65 in the zone of interest (Lower Reef Ridge to McDonald shale), confirmed by multicomponent VSP data, corresponds to the producing interval. Evidence of shear‐wave splitting due to azimuthal anisotropy was observed, so the SV‐wave and SH‐wave data sets were rotated into principal‐component axes of N45E for S1 and N45W for S2. The predominant fracture orientation changes from N45E at depth to N45W near the surface. This change in fracture orientation with depth was confirmed by multicomponent VSP data. Delay‐time ratios (used as a measure of fracture intensity) ranged from a maximum of 11.71 percent to a minimum of −5.48 percent across the structure. These ratios are interpreted to show changes in fracture intensity and orientation across the structure. Delay‐time ratios in the zone of interest were anomalously high (1.55–6.53 percent). Comparison of fracture intensity on the flanks of the structure with that on the crest indicates that the flanks have undergone greater deformation than the crest. The total wave‐field data set and associated analyses have provided significant structural and stratigraphic information on the Miocene Monterey formation over the Lost Hills field, highlighting the productive interval.


1988 ◽  
Author(s):  
Stewart G. Squires ◽  
Christopher D. Y. Kim ◽  
Daniel Y. Kim
Keyword(s):  

2014 ◽  
Vol 580-583 ◽  
pp. 3083-3088
Author(s):  
Li Ming Cai ◽  
Hui Qi ◽  
Xiang Nan Pan

The scattering of time harmonic SH waves by arbitrary positions of circular cylindrical cavity is studied in continuous, homogeneous, isotropic, elastic strip region. In this paper, the completely analytical expression of total wave field is explicitly presented and the dynamic stress distribution is symbolically visualized in the strip region. The total wave field is divided into four sub wave fields, incident wave field and scattering wave field by the upper bound, the lower bound and the cylindrical bound, on big arc supposition. Specific wave functions are employed for each wave field expansion in series, such as circular cylindrical functions, respectively. Corresponding infinite linear algebraic equations are constructed by means of solving coefficients of Fourier series expansion on each sub wave field. Coefficients of cylindrical function expansion of each sub wave field are determined by truncated equations, which are reduced number of coefficients on pre-given computational accuracy. Numerical results graphically describe the dynamic stress concentration factor around the circumference of the cavity and the normalized dynamic stress along the cross section directly above the cavity.


2020 ◽  
Vol 2 (1) ◽  
pp. 15-18
Author(s):  
Syabeela Syahali ◽  
Ewe Hong Tat ◽  
Gobi Vetharatnam ◽  
Li-Jun Jiang ◽  
Hamsalekha A Kumaresan

This paper analyses the backscattering cross section of a cylinder both using traditional method model and a new numerical solution model, namely Relaxed Hierarchical Equivalent Source Algorithm (RHESA). The purpose of this study is to investigate the prospect of incorporating numerical solution model into volume scattering calculation, to be applied into microwave remote sensing in vegetation area. Results show a good match, suggesting that RHESA may be suitable to be used to model the more complex nature of vegetation medium.


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