Journal of Geophysics and Engineering - Latest Papers

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Latest articles for Journal of Geophysics and Engineering
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First-arrival traveltime computation for quasi-P waves in 2D transversely isotropic media using Fermat’s principle-based fast marching

Tue, 11/07/2017 - 7:00pm
First-arrival traveltime computation for quasi-P waves in transversely isotropic (TI) media is the key component of tomography and depth migration. It is appealing to use the fast marching method in isotropic media as it efficiently computes traveltime along an expanding wavefront. It uses the finite difference method to solve the eikonal equation. However, applying the fast marching method in anisotropic media faces challenges because the anisotropy introduces additional nonlinearity in the eikonal equation and solving this nonlinear eikonal equation with the finite difference method is challenging. To address this problem, we present a Fermat’s principle-based fast marching method to compute traveltime in two-dimensional TI media. This method is applicable in both vertical and tilted TI (VTI and TTI) media. It computes traveltime along an expanding wavefront using Fermat’s principle instead of the eikonal equation. Thus, it does not suffer from the nonlinearity of the eikonal ...

Roof instability characteristics and pre-grouting of the roof caving zone in residual coal mining

Tue, 11/07/2017 - 7:00pm
Abandoned roadways and roof caving zones are commonly found in residual coal, and can destroy the integrity of the coal seam and roof. Resulting from mining-induced stress, continuous collapse and fracture instability in roof caving zones (RCZs) jeopardize the safety and efficiency of residual coal mining. Based on the engineering geology conditions of remining face 3101 in Shenghua Mine, the roof fracture and instability features of the RCZ were analyzed through physical simulation, theoretical analysis, and field measurements. In this case, influenced by the RCZ, the main roof across the RCZ fractured and rotated towards the goaf, greatly increasing the working resistance, and crushing the supports. The sudden instability of the coal pillars weakened its support of the main roof, thus resulting in long-key blocks across the RCZ and hinged roof structures, which significantly decreased the stability of the underlying immediate roof. This study establishes a mechanical model for...

Accurate and efficient seismic data interpolation in the principal frequency wavenumber domain

Tue, 11/07/2017 - 7:00pm
Seismic data irregularity caused by economic limitations, acquisition environmental constraints or bad trace elimination, can decrease the performance of the below multi-channel algorithms, such as surface-related multiple elimination (SRME), though some can overcome the irregularity defects. Therefore, accurate interpolation to provide the necessary complete data is a pre-requisite, but its wide applications are constrained because of its large computational burden for huge data volume, especially in 3D explorations. For accurate and efficient interpolation, the curvelet transform- (CT) based projection onto convex sets (POCS) method in the principal frequency wavenumber (PFK) domain is introduced. The complex-valued PF components can characterize their original signal with a high accuracy, but are at least half the size, which can help provide a reasonable efficiency improvement. The irregularity of the observed data is transformed into incoherent noise in the PFK domain, and ...

Density reconstruction in multiparameter elastic full-waveform inversion

Tue, 11/07/2017 - 7:00pm
Elastic full-waveform inversion (EFWI) is a quantitative data fitting procedure that recovers multiple subsurface parameters from multicomponent seismic data. As density is involved in addition to P - and S -wave velocities, the multiparameter EFWI suffers from more serious tradeoffs. In addition, compared with P - and S -wave velocities, the misfit function is less sensitive to density perturbation. Thus, a robust density reconstruction remains a difficult problem in multiparameter EFWI. In this paper, we develop an improved scattering-integral-based truncated Gauss–Newton method to simultaneously recover P - and S -wave velocities and density in EFWI. In this method, the inverse Gauss–Newton Hessian has been estimated by iteratively solving the Gauss–Newton equation with a matrix-free conjugate gradient algorithm. Therefore, it is able to properly handle the parameter tradeoffs. To give a detailed illustration of the tradeoffs between P

Amplitude inversion of the 2D analytic signal of magnetic anomalies through the differential evolution algorithm

Tue, 11/07/2017 - 7:00pm
In this work, analytic signal amplitude (ASA) inversion of total field magnetic anomalies has been achieved by differential evolution (DE) which is a population-based evolutionary metaheuristic algorithm. Using an elitist strategy, the applicability and effectiveness of the proposed inversion algorithm have been evaluated through the anomalies due to both hypothetical model bodies and real isolated geological structures. Some parameter tuning studies relying mainly on choosing the optimum control parameters of the algorithm have also been performed to enhance the performance of the proposed metaheuristic. Since ASAs of magnetic anomalies are independent of both ambient field direction and the direction of magnetization of the causative sources in a two-dimensional (2D) case, inversions of synthetic noise-free and noisy single model anomalies have produced satisfactory solutions showing the practical applicability of the algorithm. Moreover, hypothetical studies using multiple mo...