Separation, imaging, and velocity analysis of seismic diffractions using migrated dip‐angle gathers

2008 ◽  
Author(s):  
Evgeny Landa ◽  
Sergey Fomel ◽  
Moshe Reshef
Keyword(s):  
Velocity Analysis ◽  
Dip Angle

Post-stack velocity analysis in the dip-angle domain using diffractions

2009 ◽  
Vol 57 (5) ◽  
pp. 811-821 ◽  
Author(s):  
Moshe Reshef ◽  
Evgeny Landa
Keyword(s):  
Velocity Analysis ◽  
Dip Angle

Interval velocity analysis in the dip-angle domain

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. VE353-VE360 ◽  
Author(s):  
Moshe Reshef
Keyword(s):  
Real Data ◽  
Velocity Model ◽  
Velocity Analysis ◽  
Standard Analysis ◽  
Scattering Angle ◽  
Angle Measure ◽  
Interval Velocity ◽  
Resultant Velocity ◽  
Dip Angle ◽  
Higher Sensitivity

When interval velocity analysis is conducted over complex geologic regions, scattering-angle gathers may cause significant inaccuracies. These inaccuracies are related to the loss of structural dip information when generating common-image gathers (CIGs). In this study, the idea of performing interval velocity analysis in the dip-angle domain was examined and demonstrated with synthetic and real data examples. The effects of migration velocity errors and their identification in this domain were analyzed in detail. Carrying the analysis directly on dip-angle gathers is practically impossible. The ability to perform a standard analysis based on flattening the events in the CIGs is achieved by replacing the dip-angle measure with an equivalent offset measure. This equivalent offset provides higher sensitivity to velocity errors and may improve the accuracy of the resultant velocity model.

Multidip tomography formulation for migration velocity analysis

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. U1-U12 ◽  
Author(s):  
Raanan Dafni ◽  
Moshe Reshef
Keyword(s):  
Imaging System ◽  
Real Data ◽  
Velocity Model ◽  
Equation System ◽  
Migration Velocity ◽  
Opening Angle ◽  
Velocity Analysis ◽  
Migration Velocity Analysis ◽  
Seismic Image ◽  
Dip Angle

We have developed a new approach for migration velocity analysis by ray-based reflection tomography, formulated according to more than a single dip direction. It is suggested to use a summation-free subsurface imaging system in the angle domain for generating multiparameter common image gathers through depth migration. Each gather associated with this system comprised dip-dependent opening-angle images contributed from the prestack data. Independent moveout information, coming from either a specular or nonspecular dip direction, was extracted inside these gathers to allow the entire scattered field to be involved in the velocity model optimization. By obeying the linear tomographic principle, a multidip tomography system was set to include imaging errors from specular and nonspecular directions. The updated velocity model was reconstructed by a least-squares inverse solution of the multidip tomographic equation system. Providing additional moveout from the migration’s dip, other than the specular one, was believed to be essential because the seismic data were misplaced in the image space while applying depth imaging by an erroneous velocity model. It might make the determination of a clear specular orientation, usually from the seismic image itself, misleading or ambiguous. The conversion of depth moveout into traveltime error along nonspecular rays was done according to an analytic mechanism, derived in the angle domain. The proposed analysis of migration errors by a multiple dip-angle orientation is demonstrated via the multidip tomography formulation by 2D synthetic and real data examples. It seems to be more efficient, as accurate and reliable as the conventional analysis, and to be better able to determine the ill-posed conditioning of the tomographic inversion.

Failure Analysis Of Buried Gas Pipelines Crossing Seismic Faults

2020 ◽  
Vol 3 (2) ◽  
pp. 781-790
Author(s):  
M. Rizwan Akram ◽  
Ali Yesilyurt ◽  
A.Can. Zulfikar ◽  
F. Göktepe
Keyword(s):  
Ground Deformation ◽  
Warning System ◽  
Strike Slip ◽  
Gas Pipelines ◽  
Steel Pipes ◽  
Seismic Fault ◽  
Fault Parameters ◽  
Dip Angle ◽  
Permanent Ground Deformation ◽  
Recent Earthquakes

Research on buried gas pipelines (BGPs) has taken an important consideration due to their failures in recent earthquakes. In permanent ground deformation (PGD) hazards, seismic faults are considered as one of the major causes of BGPs failure due to accumulation of impermissible tensile strains. In current research, four steel pipes such as X-42, X-52, X-60, and X-70 grades crossing through strike-slip, normal and reverse seismic faults have been investigated. Firstly, failure of BGPs due to change in soil-pipe parameters have been analyzed. Later, effects of seismic fault parameters such as change in dip angle and angle between pipe and fault plane are evaluated. Additionally, effects due to changing pipe class levels are also examined. The results of current study reveal that BGPs can resist until earthquake moment magnitude of 7.0 but fails above this limit under the assumed geotechnical properties of current study. In addition, strike-slip fault can trigger early damage in BGPs than normal and reverse faults. In the last stage, an early warning system is proposed based on the current procedure. 

scholarly journals Dip angles of active faults from the surface to the seismogenic zone inferred from a 2D numerical analysis of visco-elasto-plastic models: a case study for the Osaka Plain

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hayami Nishiwaki ◽  
Takamoto Okudaira ◽  
Kazuhiko Ishii ◽  
Muneki Mitamura
Keyword(s):  
Urban Areas ◽  
Active Faults ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Earthquake Ground Motion ◽  
Convex Curve ◽  
Seismic Reflection Profile ◽  
Geological Structures ◽  
Dimensional Distribution ◽  
Dip Angle

AbstractThe geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are the most important factors used to evaluate earthquake ground motion, which is crucial for seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~ 12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone are not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. As a result, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~ 0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~ 30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone, but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, which is lower than that estimated in the previous studies. If the active fault has a low angle, the width of the fault plane is long, and thus the estimated seismic moment will be large.

Settling Velocity Analysis for Stormwater Solids in Urban Drainage BMPs

2009 ◽  
Vol 2009 (9) ◽  
pp. 6402-6413
Author(s):  
G. Ying ◽  
C. Berretta ◽  
I. Gnecco ◽  
G. Becciu ◽  
J. Sansalone
Keyword(s):  
Settling Velocity ◽  
Urban Drainage ◽  
Velocity Analysis
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