Exploration Geophysics Exploration Geophysics Society
Journal of the Australian Society of Exploration Geophysicists

Exploration Geophysics

Exploration Geophysics

Exploration Geophysics presents case histories, advances in data interpretation, and theoretical developments in applied geophysics. Read more about the journalMore

Managing Editor: Mark Lackie

Current Issue

Exploration Geophysics

Volume 49 Number 1 2018

Special Section: Marine Geophysics

EG16142Seismic imaging for an ocean drilling site survey and its verification in the Izu rear arc

Mikiya Yamashita, Narumi Takahashi, Yoshihiko Tamura, Seiichi Miura and Shuichi Kodaira
pp. 1-10

To evaluate the crustal structure of a site proposed for ocean drilling, high-resolution dense seismic surveys were carried out in the Izu rear arc, Japan. Our results suggest that use of a dense grid configuration is important in volcanic rear-arc situations, in order to recognise heterogeneous crustal structure, such as sediments from different origins.

We quantified effective VP, VS and the ratio of VP to VS of the 3D digital rock models with different crack-filling minerals. By comparing the elastic properties derived from the digital rock models with the seismic velocities around the Nankai seismogenic fault, we characterised the evolution process of the seismogenic fault.

EG17139Robust data processing of noisy marine controlled-source electromagnetic data using independent component analysis

Naoto Imamura, Tada-nori Goto, Takafumi Kasaya and Hideaki Machiyama
pp. 21-29

We have developed a new controlled-source electromagnetic (CSEM) data processing scheme that uses a robust method based on independent component analysis to extract interpretable datasets from noisy marine CSEM data. The results show that the coherent and environment noise is reduced sufficiently. It makes interpretation of the resulting data possible.

This study uses ultrasonic physical modelling to verify that Fermat’s minimum-time principle is better than the anisotropic non-hyperbolic moveout and conversion-point (CP) equations for calculating the traveltime and CP position of a P-SV wave reflected from a strong vertical transversely isotropic medium.

The outliers-out (OlO) stack is a novel seismic data stacking technique that is based on excluding a specific number of outliers from each time sample before stacking. The OlO stacking parameters are automatically obtained from the data according to the statistical distribution of amplitudes. The superiority of the OlO stack has been verified by experiments.

Sparse Gaussian beam decomposition and reconstruction is an ill-posed inverse problem. We construct a zero-norm constrained minimisation model, develop a dip-angle scanning strategy and adopt a quasi-Newton method to find the solution. This method can recover full wave field data and can be used for sparse Gaussian beam migration.

EG16105An efficient interpolation approach for insufficient 3D field data

Bona Kim, Soocheol Jeong, Joongmoo Byun and Young Kim
pp. 58-67

We have developed a new interpolation process for insufficient 3D field data that applies 2D curvelet transform-based projection onto convex sets (POCS) to the kx-ky transformed data of each time slice of 3D data. Additionally, to acquire accurate interpolation results, we have designed the preparation process to render the input data irregularly distributed with small-sized gaps.

We implement full waveform inversion in an auxiliary coordinate system to improve inversion quality of near-surface regions with strong elevation and velocity variation. Furthermore, a time-domain multi-scale decomposition method and an optimised encoding strategy are introduced to the inversion frame to promote the practical application of our method.

EG16011Effect of ground undulation and mounted vehicle velocity variation on stepped frequency continuous wave GPR data

Smitha Nage Gowda, Deverakonda R. Ullas Bharadwaj, Sridhara Abilash, Saligrama N. Sridhara and Vipula Singh
pp. 81-88

This paper describes a method to generate dataset on stepped frequency continuous wave ground penetrating radar for land mine detection. A novel ground undulation and ground bounce removal filter has been proposed which mitigates the effects of vehicle velocity variations. Kirchhoff and F-K migration algorithms are applied to the filtered output.

Airborne multi-wavelength, multi-polarimetric and interferometric radar data (NASA’s AIRSAR/TOPSAR) was processed and applied for geological mapping within densely forested north-western Tasmania. The results successfully compared with geophysical, topographic and vegetation classification information and showed the potential of such data to assist in the upgrading of existing published geological mapping.

The Tertiary magmatic belts host the porphyry copper deposits in Iran. The combination of upward continuation and edge enhancement filters were used to find and predict the pattern of distribution of these deposits. The results prove that the deposits locate on regional magnetic lithologies and structures.

EG16076New constraints on the neotectonic stress pattern of the Flinders and Mount Lofty Ranges, South Australia

Mojtaba Rajabi, Mark Tingay, Oliver Heidbach, David Belton, Natalie Balfour and Betina Bendall
pp. 111-124

The results of this study suggest a regional E–W orientation of the maximum horizontal stress in the Flinders and Mount Lofty Ranges. Focal mechanism solutions of earthquakes suggest that the majority of events occur in a thrust faulting stress regime. However, our data also indicate the presence of strike-slip and normal faulting stress regimes in the region, which has not been suggested extensively before this study.

Online Early

The peer-reviewed and edited version of record published online before inclusion in an issue

Published online 22 February 2018

EG17072Analysis of reservoir heterogeneities and depositional environments: a new method

Cyril D. Boateng and Li-Yun Fu

A new methodology for quantifying reservoir heterogeneities based on a Monte Carlo parameter estimation technique using fractal parameters derived from the von Karman autocorrelation function is proposed. The reservoir heterogeneity parameters computed from sonic logs in an oilfield show that these parameters can be discriminants for depositional environments.

Published online 12 February 2018

EG17058Sensitivity evaluation of a seismic interpolation algorithm

Doan Huy Hien, Seonghuyng Jang, Ta Quang Minh, Bui Viet Dung and Nguyen Thanh Tung

To maintain the initial resolution of the seismic image from seismic sparse acquisition, we propose several ways to sample data irregularly but periodically. At every processing step, we quantified the effect of interpolation by comparing the results with those from the fully sampled data. The result shows that using 60% of the available data is feasible.

The projection onto convex sets (POCS) method is deduced using the iterative hard thresholding (IHT) algorithm and a projection operator with more detailed physical illustrations. The interpolation performances on noise-free and noisy data are explained in detail and the reasons behind these performances are fully discussed, which provide clues to further improve interpolation accuracy.

Published online 15 January 2018

EG17171Multiple-point geostatistical simulation for mine evaluation with aeromagnetic data

Jinpyo Hong, Seokhoon Oh and Seong-Jun Cho

Multiple-point geostatistical simulation (MPS) was applied to develop 3D ore models matched to surrounding geological information accompanying aeromagnetic data using training image. The present study proposes a method for reducing the uncertainty of the 3D ore model, applying MPS to create probabilistic ore models and analysing the correlation between the models and geophysical data.

Published online 04 January 2018

EG17128A high expansion implicit finite-element prestack reverse time migration method

Limin Liu, Yun Wang, Yong Wang, Jing Chen and Yanqiu Liu

Building on the concepts of cohesion degree and local relaxation, we propose an integrated hierarchical equilibrium parallel finite-element reverse time migration (HEP-FE-RTM) algorithm, which has the distinct advantage in that parallel efficiency does not decrease as the number of processors increases.

Published online 22 December 2017

EG17014Amplification characteristics at Iedang Reservoir dam sites determined using H/V spectral ratio with background noise, S-wave and coda wave energy

Jun Kyoung Kim, Soung Hoon Wee, Seong Hwa Yoo and Kwang Hee Kim

Amplification characteristics are critical in evaluating the reliability in seismic design for engineering and seismic source and crustal attenuation characteristics for seismology. Horizontal-to-vertical spectral ratios were analysed using six seismograms observed at four sites near Iedang Reservoir in Korea. Amplification characteristics were compared using the S-wave, coda wave and background noise of each seismogram.

A fast non-smooth regularisation method is proposed to solve the difficulties involved in the classical least-squares Kirchhoff migration. It not only accounts for the irregular and incomplete data sampling, but also compensates for the anomalous ray coverage and multipathing problem. Numerical experiments show that the method works well.

Published online 21 December 2017

EG17068Geophysical strata rating (GSR) as an aid in carbonate reservoir characterisation: an example from the South Pars gas field, Persian Gulf Basin

Mohammad Ali Faraji, Ali Kadkhodaie, Hossain Rahimpour-Bonab and Peter Hatherly

In this study, the geophysical strata rating (GSR), which is an empirical measure of rock competency, is calculated from petrophysical data. The GSR is then extended to the whole South Pars gas field in the framework of 3D seismic data through an acoustic impedance poststack seismic inversion.

Published online 07 December 2017

EG17093The Marine Vibrator Joint Industry Project: four years on

Andrew Feltham, Marc Girard, Mike Jenkerson, Vladimir Nechayuk, Shari Griswold, Nick Henderson and Graham Johnson

The Marine Vibrator Joint Industry Project (MVJIP), sponsored by Shell, Total and ExxonMobil, has been ongoing for four years. This paper discusses the history, motivation, technology and latest developments from the project.

Published online 01 December 2017

EG17077Estimation of reservoir properties from seismic data through a Markov Chain Monte Carlo-AVA inversion algorithm

Mattia Aleardi, Fabio Ciabarri and Alfredo Mazzotti

We formulate the amplitude versus angle (AVA) inversion in terms of a Markov Chain Monte Carlo algorithm and apply it for reservoir characterisation and litho-fluid facies prediction in offshore Nile Delta. A blind test, based on available well log information, demonstrates the applicability of the proposed method and the reliability of the results.

Published online 30 November 2017

EG16135Sensitivity of shale anisotropic parameters to core cutting rotation error

Shiguang Guo, Sumit Verma, Qing Wang, Fei Pang, Kui Zhang, Haifu Sun and Xiansheng Zhang

In laboratories, core cannot always be cut exactly along the axis of symmetry (normal to the bedding plane), which leads to a minor core cutting rotation error. This paper investigates the sensitivity of Thomson’s anisotropic parameters, epsilon (ε), gamma (γ) and delta (δ), to the cutting error.

Published online 17 November 2017

EG17055A constrained spectral inversion method based on compressive sensing in order to distinguish high-quality shale

Hua Zhang, Zhenhua He, Yalin Li, Rui Li and Guangming He

Distinguishing high-quality shale effectively is a difficult exploration problem. We propose a constrained spectral inversion method based on compressive sensing to handle this challenge. This method can help us improve the resolution and continuity of the profiles and enhance our ability to discover high-quality shale.

Published online 14 November 2017

EG17048Seismic facies-controlled prestack simultaneous inversion of elastic and petrophysical parameters for favourable reservoir prediction

Sheng Zhang, Handong Huang, Baoheng Zhu, Huijie Li and Lihua Zhang

This paper describes the development of a deterministic prestack inversion for estimating elastic and petrophysical parameters. The Gassmann equation is used to construct the relationship between the seismic data and petrophysical parameters. Seismic facies constraints were introduced to improve the accuracy. The very fast-simulated annealing method is used to quickly find the optimal solutions.

Published online 13 November 2017

EG17057Channel edge detection using 2D complex shearlet transform: a case study from the South Caspian Sea

Haleh Karbalaali, Abdolrahim Javaherian, Stephan Dahlke and Siyavash Torabi

Channel detection plays a significant role in seismic interpretation. Shearlet transform as a multi-scale and multi-directional transformation is capable of detecting anisotropic singularities. We applied complex-valued shearlet edge measure to synthetic and real seismic time-slices from the South Caspian Sea. The proposed algorithm outperformed both Sobel and Canny edge detectors.

Published online 09 November 2017

EG17049Synthetic modelling and analysis of CSEM full-field apparent resistivity response combining EM induction and IP effect for 1D medium

Weiqiang Liu, Pinrong Lin, Qingtian Lü, Yong Li and Jianhua Li

Full-field apparent resistivity response combining EM induction and IP effect for layered earth were modelled using the Cole–Cole model. The influence of chargeability is greater than that of the other two parameters, time constant and frequency dependent coefficient. The layered model was distorted seriously by using the inversion algorithm ignoring IP effect.

Published online 06 November 2017

EG17094Quantifying the differences between gravity reduction techniques

Philip Heath

This paper demonstrates the magnitude of change that results when different information (relating to calibration factors, time zones and time changes, height, geodetic datums and gravity datums) is introduced at various stages of the gravity reduction process. The differences range from below 0.01 mGal to over 16.0 mGal.

Published online 01 November 2017

EG16156Estimation of elastic anisotropy from three-component ultrasonic measurements using laser Doppler interferometry

Andrej Bóna, Maxim Lebedev, Roman Pevzner, Boris Gurevich and Mahyar Madadi

Laser Doppler interferometers were previously employed to detect ultrasonic waves propagating in different directions and to estimate elastic anisotropy from these measurements. Our numerical simulations and laboratory measurements show that the recorded wavefield contains converted PS-waves, which need to be taken into consideration to obtain robust estimates of anisotropy.

Measurements of natural time-fluctuating magnetic and electric fields at the surface of Earth produce magnetotelluric data, most of which can be expressed as quantities invariant to the directions of field measurement. Such invariants give information on geological structure.

The ancient Roman city of Sagalassos (Turkey) is covered by layers of eroded soil that have preserved many secrets waiting to be revealed. A geophysical campaign was planned to highlight the buried structure. Geophysics revealed evidence of a clay quarry, a number of tombs related to the Byzantine period and defensive walls.

This paper shows that a method used to identify a peak of horizontal-to-vertical spectral ratios (HVSRs) of microtremors, which was proposed in 2001, is unreliable, and clarifies the reason for the unreliability. Because of the resemblance between the distribution of normalised HVSRs and the F distribution, we frequently fail to detect the deviation between them.

Published online 04 October 2017

EG16123A new method to enhance the characterisation of seismically thin beds based on the generalised S transform maximum modulus

Mingfei Fan, Shenghe Wu, Guangyi Hu, Jingjing Qu and Jiajia Zhang

Thin beds are common in underground hydrocarbon reservoirs, but rarely detected and characterised. In this work, we propose a new method to improve characterisation of thin beds and we are able to find and characterise more thin beds accurately. This new method will enhance our ability to discover more oil and gas.

Published online 27 September 2017

EG16124Correction and compensation of an airborne fluxgate magnetic tensor gradiometer

Yangyi Sui, Hongsong Miao, Zhijian Zhou, Hui Luan and Yanzhang Wang

In this paper, the correction coefficients of a fluxgate magnetic tensor gradiometer and the magnetic properties of an aircraft are determined. A recursive method is used to combine the magnetic interference model and the error model into a unified calibration model. The method is significant as there will be a greater use of airborne magnetic tensor gradiometers using a wide range of aircraft.

Published online 26 September 2017

EG16134Velocity analysis of CMP gathers acquired by an array GPR system ‘Yakumo’: results from field application to tsunami deposits

Honghua Wang, Hai Liu, Jie Cui, Xiangyun Hu and Motoyuki Sato

Velocity analysis is applied to explore the capability of a multi-static ground penetrating radar (GPR) system to estimate a vertical profile of dielectric constants of stratified tsunami layers. Both laboratory and field experiments demonstrate that multi-static GPR can accurately delineate the layered geological structures.

Published online 21 September 2017

EG17015Modifications to the Kozeny–Carman model to enhance petrophysical relationships

Amir Maher Sayed Lala

In this study, the deficiency of the Kozeny–Carman assumption is investigated and alternative derived equations for the Kozeny–Carman equation are suggested, including equations where the grain size is replaced with the pore size and with varying tortuosity. Relationships for the permeability of shaly sand reservoir are introduced.

Published online 18 September 2017

EG17104A simple inversion algorithm to estimate a linearly increasing velocity model for microseismic monitoring

Woochang Choi, Wonsik Kim and Sukjoon Pyun

In this study, we suggest a simple algorithm to estimate 1D velocity gradient for microseismic monitoring. The proposed algorithm is based on the analytically-derived ray formulas for a linearly increasing velocity model and the Gauss–Newton method. Numerical examples show that the proposed algorithm is robust to picking errors and initial guess.

Published online 15 September 2017

EG16158An elastic full-waveform inversion based on wave-mode separation

Yingming Qu, Jinli Li, Zhenchun Li and Jianping Huang

We propose an elastic full-waveform inversion method based on P- and S-wave mode separation to mitigate the crosstalk artefacts between P- and S-wave modes by deriving the gradient formulas with respect to various wave modes using a P- and S-wave mode separated first-order velocity-stress wave equation.

Published online 14 September 2017

EG16084Separation of different order multiples based on focal transform and SRME

Zhina Li, Zhenchun Li, Peng Wang and Yueming Ye

Considering that the focal transform can flexibly perform order reduction or elevation of multiples and surface-related multiple elimination (SRME) can effectively separate primaries and multiples, a practical and novel method based on both the focal transform and SRME is proposed to separate different order multiples in this paper.

We propose a simple method for analysing gravity data to define 3D subsurface structures based on automatic separation of gravity anomalies into residual gravity and trend surfaces. This is achieved by assuming that the gravity anomaly trend surface is extremely smooth prior to analysis. The new method was applied to an area around Iwaki City, Fukushima Prefecture, Japan, and the results evaluated using a boot-strap simulation.

Published online 12 September 2017

EG17032Improving bitumen detection in resistivity surveys by using induced polarisation data

Seyyed Reza Mashhadi, Kamran Mostafaei and Hamidreza Ramazi

A hydrogeophysically and geologically complex bitumen deposit in western Iran was investigated by means of resistivity and induced polarisation (IP) methods. The results show the high potential of IP data to improve bitumen detection. It was also proven that saline water can sometimes be useful in target identification in mineral explorations.

Published online 04 September 2017

EG16148Revised potential field model of the Gilmore Fault Zone

Deepika Venkataramani, Robert J. Musgrave, David A. Boutelier, Alistair C. Hack and William J. Collins

The Gilmore Fault Zone marks a distinct geophysical and complex geological boundary. This work improves on existing models of this fault zone and presents a revised potential field model. These models of the subsurface morphology of this major thrust and/or strike-slip fault system are being used to refine tectonic models for the evolution of the Eastern Lachlan Orogen.

Published online 01 September 2017

EG16157Forward modelling formulas for least-squares reverse-time migration

Gang Yao, Nuno V. da Silva and Di Wu

We derive two formulas of forward modelling for least-squares reverse-time migration based on Born and Kirchhoff approximations. Analysis unveils an iω difference exists between the two formulas. Consequently, their seismic images have different shape/phase: the Born approximation produces anti-symmetric images while the Kirchhoff approximation gives symmetric images. Numerical examples demonstrate these features between the two formulas.

Published online 01 September 2017

EG16028Compensation for aircraft effects of magnetic gradient tensor measurements in a towed bird

Chunxiao Xiu, Xiaohong Meng, Lianghui Guo, Sheng Zhang and Xingdong Zhang

We present a compensation model of aircraft effects for full magnetic gradient tensor data acquired in a towed bird. Training flight tests were designed so that aircraft compensation parameters could be estimated. The feasibility of the compensation method was verified by modelling and by a flight simulation test.

This paper describes a semiquantitative, 3D-modelling based methodology that has been developed to remove topographic effects on magnetic data. Through synthetic and real cases in the Andes, we show that airborne magnetic surveys over rugged topography generate magnetic signatures that could be of similar amplitude with the signal of geological interest.

Flexible computational domains with irregular absorbing boundaries can improve the efficiency of seismic modelling. We propose a hybrid absorbing boundary condition for piecewise smooth curved boundary in mesh-free discretisation based on radial-basis-function-generated finite difference modelling. Modelling examples in both homogeneous and heterogeneous media with flexibly shaped computational domain demonstrate the effectiveness of our proposed method.

Published online 18 August 2017

EG17039Modified imaging condition for reverse time migration based on reduction of modelling time

Hadi Mahdavi Basir, Abdolrahim Javaherian, Zaher Hossein Shomali, Roohollah Dehghani Firouz-Abadi and Shaban Ali Gholamy

We propose a modification of the reverse time migration imaging condition by reducing the modelling time to about half of the recording time. Results showed that the proposed modification has no significant effect on the illumination of reflectors, while increasing the CPU and memory allocation performances by about 25% and 50%, respectively.

Published online 17 August 2017

EG17013Prestack depth imaging in complex structures using VTI fast marching traveltimes

Seyed Yaser Moussavi Alashloo and Deva P. Ghosh

A fast marching eikonal solver is employed in the isotropic and VTI concepts. Instead of using a linear eikonal equation, we consider a nonlinear approximation because it is more realistic and accurate than the former. Overall, anisotropic approach is stable, fast and generates high-quality images with accurate details in deep structures.

Published online 11 August 2017

EG17004Seismic signal denoising using thresholded variational mode decomposition

Fangyu Li, Bo Zhang, Sumit Verma and Kurt J. Marfurt

In this paper, we propose an adaptive denoising method based on data-driven signal mode decomposition, where the noise is represented by the residual/last mode. The proposed approach adaptively extracts the noise component depending on the data statistics rather than defining a fixed priori threshold.

Published online 10 August 2017

EG17081Imaging the crustal structure along the KCRT-2008 profile in the Southern Korean Peninsula using regularisation

Jihyun Choi, Sangmin Lee, Joongmoo Byun, Ki Young Kim and Jung Mo Lee

In this study, high-resolution subsurface structures of the southern Korean Peninsula were delineated. To acquire images, we applied seismic data processing tools that are commonly used in oil exploration to irregularly sampled data after regularisation by matching pursuit interpolation.

This paper describes an improved and efficient workflow that refines the art of structural interpretation from 3D seismic data. The research aims to streamline the interpretation workflow using better data conditioning scheme and defining a meta-attribute (fault probability cube) using an artificial neural network. A robust pathway is provided for delineating structural details of complex geological terrain.

Published online 01 August 2017

EG16163Predicting lightning sourced electromagnetic fields

Lachlan Hennessy and James Macnae

Global lightning networks catalogue the time and location of up to four million lightning strikes per day. We use lightning network data to predict sferic arrival times, vertical electric field amplitudes and arrival azimuths at an audio-frequency magnetotelluric sounding near Heathcote, Victoria.

The low-frequency information and correct starting velocity are important for full waveform inversion (FWI). However, obtaining low-frequency information and accurate starting velocity from the field seismic exploration is difficult. This paper suggests a 4-phase FWI to invert the correct velocity model when a dataset lacks low-frequency information and accurate starting velocity.

Published online 30 June 2017

EG17054Estimating high hydraulic conductivity locations through a 3D simulation of water flow in soil and a resistivity survey

Keisuke Inoue, Hiroomi Nakazato, Tomijiro Kubota, Koji Furue, Hiroshi Yoshisako, Michiaki Konno and Daisuke Shoda

We propose a simple method for estimating high hydraulic conductivity locations. The proposed method uses the 3D simulations of soil water flow and resistivity survey during a groundwater recharge experiment. Results of numerical and field experiments indicate that the proposed method estimates the high hydraulic conductivity locations more precisely compared with 3D inversion of in-line data.

Published online 13 June 2017

EG16144Acoustic wave propagation simulation by reduced order modelling

Hadi Mahdavi Basir, Abdolrahim Javaherian, Zaher Hossein Shomali, Roohollah Dehghani Firouz-Abadi and Shaban Ali Gholamy

A reduced order modelling method is introduced for wave propagation modelling by using the mode shapes of the model. The numerical accuracy, computational performance and boundary conditions of the proposed method were investigated. According to the results, the proposed method substantially improves the computational efficiency of the reverse time migration.

We present a singular spectrum analysis (SSA)-based algorithm for regional and residual gravity anomaly separation. Initially, we tested the method on synthetic data and applied gravity profiles from the Umred coalfield, Nagpur, Maharashtra, India. Final 2D crustal models obtained from the filtered regional anomaly agree well with regional geology and borehole information.

Published online 07 June 2017

EG17029A novel approach to comparing AEM inversion results with borehole conductivity logs

Niels B. Christensen and Kenneth C. Lawrie

Two consistent methods of comparing borehole induction logs with models from inversion of AEM data have been developed: one in model space and one in data space. The two methods are applied to the Broken Hill Managed Aquifer Recharge project conducted by Geoscience Australia on AEM data from the SkyTEM system.

In this paper, we examine the characteristics of Scholte wave dispersion curves and their modal energy distribution by combining analytical solutions of the dispersion equation with numerical modelling. The modelling results showed that our approach can facilitate Scholte wave exploration in water-covered areas.

Published online 24 May 2017

EG160583D seismic attributes for structural mapping and enhancement of deep gold mining: a case study from the West Wits Line goldfields, South Africa

Nomqhele Z. Nkosi, Musa S. D. Manzi, Oleg Brovko and Raymond J. Durrheim

In this study, we use sophisticated seismic attributes to interpret the 3D reflection seismic data to: (1) assess and mitigate the risks posed by deep mining activities and (2) improve the resource evaluation of the gold-bearing quartz pebble conglomerate horizons (reefs) in the world’s deepest gold mines (South Africa).

Published online 23 May 2017

EG16067Three-dimensional inversion of CSAMT data in the presence of topography

Changhong Lin, Handong Tan, Wangwang Wang, Tuo Tong, Miao Peng, Mao Wang and Weihua Zeng

In this paper, we present a scheme to incorporate 3D controlled-source audio frequency magnetotelluric (CSAMT) topographic distortions into the 3D inversion instead of correcting them. This approach has been verified by comparison with 2D FEM CSAMT solutions and synthetic inversion examples. The field example also illustrates the effectiveness of our approach.

Published online 19 May 2017

EG16079Three-dimensional tensor controlled-source audio-frequency magnetotelluric inversion using LBFGS

Kunpeng Wang, Handong Tan, Changhong Lin, Jianlong Yuan, Cong Wang and Jing Tang

We have shown in this paper that directly using a magnetotelluric method to invert the data of the tensor controlled-source audio-frequency magnetotelluric (CSAMT) will obtain an incorrect result, the inversion result of tensor CSAMT is more reliable than that of the traditional CSAMT, and the limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) method is more efficient than the nonlinear conjugate gradient (NLCG) method for tensor CSAMT.

We have constructed an anisotropic rock physics model at the seismic scale for shales, and applied it to the Longmaxi Shale in the Sichuan Basin, south-west China. The simplified reflectivity method is proposed to calculate seismic responses for amplitude variation with offset and azimuth (AVAz) analysis.

Magnetotelluric measurements were carried out in the southern Great Khingan Range, Inner Mongolia, China, from 2012 to 2014. After 2D inversion, the Paleozoic Hunnitu and Gadasu depressions were discovered and inferred to possibly contain Linxi strata. The Mesozoic Xiretu depression was also discovered, which possibly contains Cretaceous hydrocarbon-bearing strata.

Published online 21 March 2017

EG16100Regularisation parameter adaptive selection and its application in the prestack AVO inversion

Guangtan Huang, Jingye Li, Cong Luo and Xiaohong Chen

In this paper, based on L-curve criterion, we propose an improved method for the adaptive acquisition of regularisation parameters for arbitrary norm condition. A detailed derivation of the proposed method is described. Numerical experiments confirm that the proposed method is more accurate and robust than its main competitor, generalised cross-validation.

Published online 21 March 2017

EG17017A robust surface-consistent residual phase correction method based on migrated gathers

Jincheng Xu, Hao Zhang and Jianfeng Zhang

We present a novel approach for surface-consistent residual phase corrections based on migrated gathers to improve the SNR and resolution of migrated images. This method includes the following new aspects: the residual statics and phase are estimated by dual parameter cross-correlation, and determined after migration.

Published online 17 March 2017

EG17019Investigation of the line arrangement of 2D resistivity surveys for 3D inversion

Keisuke Inoue, Hiroomi Nakazato, Mutsuo Takeuchi, Yoshihiro Sugimoto, Hee Joon Kim, Hiroshi Yoshisako, Michiaki Konno and Daisuke Shoda

We have conducted numerical and field experiments to investigate the applicability of electrode configurations and line layouts commonly used for 2D resistivity surveys to 3D inversion. We propose that parallel lines are useful to highlight areas of particular interest where further detailed work with an intersecting line could be carried out.

Published online 17 March 2017

EG16046Noise reduction of grounded electrical source airborne transient electromagnetic data using an exponential fitting-adaptive Kalman filter

Yanju Ji, Qiong Wu, Yuan Wang, Jun Lin, Dongsheng Li, Shangyu Du, Shengbao Yu and Shanshan Guan

GREATEM field data usually includes a mixed variety of noises, which makes the exponential decaying signal too difficult to identify. This paper presents an exponential fitting-adaptive Kalman filter (EF-AKF) to remove mixed electromagnetic noises, while preserving the signal characteristics. As a new method, the EF-AKF can be used for denoising exponential decaying signals.

Published online 27 February 2017

EG16022Subsurface attenuation estimation using a novel hybrid method based on FWE function and power spectrum

Jingnan Li, Shangxu Wang, Dengfeng Yang, Genyang Tang and Yangkang Chen

A new Q estimation approach, called improved frequency weighted exponential (IFWE), is presented by combining the advantage of the FWE method and the power spectrum. Tests of synthetic and field data show that the IFWE is more robust and the bandwidth selection for the IFWE is more tolerant than the FWE.

Published online 24 February 2017

EG16139Trans-dimensional Bayesian inversion of airborne electromagnetic data for 2D conductivity profiles

Rhys Hawkins, Ross C. Brodie and Malcolm Sambridge

We apply a novel trans-dimensional Bayesian approach using a wavelet parameterisation to airborne electromagnetic (AEM) inversions using data from the Broken Hill region. This approach allows exploration of a range of plausible subsurface conductivity models and provides more robust uncertainty estimates while accounting for potential non-uniqueness.

We propose a new finite difference (FD) scheme that is implicit in space (adopting the Taylor-expansion-based or least-square based FD coefficients) and has high-order accuracy in time (adopting a combination of rhombus and cross stencils). Dispersion analysis, stability analysis and modelling examples validate the superiority of our method.

Published online 05 January 2017

EG16116Modified interferometric imaging condition for reverse-time migration

Xue-Bao Guo, Hong Liu and Ying Shi

The artefacts caused by random fluctuations in the background velocity model will contaminate the final image, which makes the work of interpretation difficult to implement in reverse-time migration. The imaging condition proposed in this paper, which exploits the pseudo-Wigner distribution function, can reduce this noise, and also help improve the continuity of complex layers.

Published online 04 January 2017

EG16111Adaptive phase k-means algorithm for waveform classification

Chengyun Song, Zhining Liu, Yaojun Wang, Feng Xu, Xingming Li and Guangmin Hu

To alleviate the effect of phase in waveform classification, the adaptive phase k-means is introduced for unsupervised seismic facies analysis. This method improves the traditional k-means algorithm by using an adaptive phase distance for waveform similarity measure, and is thus robust to phase variations caused by horizon interpretation.

Published online 23 December 2016

EG16057Investigating subsurface structures of Gachsaran oil field in Iran using 2D inversion of magnetotelluric data

Mohamadhasan Mohamadian Sarvandani, Ali Nejati Kalateh, Reza Ghaedrahmati and Abbas Majidi

In 2012, the National Iranian Oil Company conducted an electromagnetic survey in the Gachsaran oil field. The Bahr’s skew and Mohr diagrams were used to perform the dimensionality analysis. Magnetotelluric data were modelled using the smoothness-constrained least-squares method. The resulting model revealed the main anticline and overthrust zone in the region.

Published online 15 December 2016

EG15072Noise removal for airborne time domain electromagnetic data based on minimum noise fraction

Yue Li, Yang Meng, Yiming Lu, Lingqun Wang, Bin Xie, Yuqi Cheng and Kaiguang Zhu

Residual noise remains in airborne time domain electromagnetic profiles after preprocessing the data, and this noise affects the exploration of targets. An approach to reduce this noise based on the minimum noise fraction has been proposed in this paper.

To determine the seismic site conditions and microzonation of Chuncheon, Wonju, and Gangneung in Korea, shear-wave velocities were derived at 313 sites by the ESPAC method. The proxy-based Vs30 indicated that these cities were mainly categorised into NEHRP classes B, C, and D, with a minor proportion of A.

This study introduces the multi-objective particle swarm optimisation (MOPSO) strategy as a new tool for joint inversion of Rayleigh wave dispersion curve and refraction traveltimes. The proposed algorithm was tested on two synthetic datasets and an experimental dataset. The results showed that the applied joint inversion technique can considerably reduce uncertainties of the inverted models.

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