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 48 Number 3 2017

Under certain geological conditions, low induction number electromagnetic instruments are known to produce negative apparent conductivity responses. This is particularly the case when the subsurface is characterised by highly conductive bodies. We present 3D numerical modelling results of dacite dike intrusions in Sugisawa, Akita Prefecture, Japan.

Based on the Hilbert-Huang transform, a time-frequency analysis method is proposed to obtain stable estimates of the magnetotelluric response function. The response function estimation is performed in the time-frequency domain using instantaneous spectra rather than in the frequency domain, which allows for imaging the response parameter content as a function of time and frequency.

Polarity reversals and cross-talk noises, which degrade the converted wave images (P-S, S-P, and S-S images) of elastic reverse time migration (ERTM), are addressed. To overcome these problems, we derive a new P-S converted wave imaging condition for ERTM based on wavefield separation techniques.

EG15100Obtaining high-resolution velocity spectra using weighted semblance

Saleh Ebrahimi, Amin Roshandel Kahoo, Milton J. Porsani and Ali Nejati Kalateh
pp. 210-218

Accuracy and resolution of velocity spectra are very important in seismic data processing, as they have considerable impact on the quality of the final seismic section. We improve the accuracy and resolution of velocity spectra by introducing two weighting functions to the traditional semblance velocity analysis.

We introduce an efficient waveform inversion algorithm using common mid-point gathers. Since we perform both modelling and inversion in the wavenumber-space-time domain, it recovers only a one-dimensional velocity model. However, we can build a two-dimensional velocity model with moderate dips by assuming that reflectors are locally flat.

EG15065An experimental study of Rayleigh waves based on seismoelectric measurements

Ziying Xiong, Zhengping Liu and Kai Zhang
pp. 226-236

Rayleigh wave experiments were performed in homogeneous and lateral inhomogeneous models using acoustic and seismoelectric measurements, respectively. The experimental results suggest a potential application of the seismoelectric conversion effect to improve spatial resolution and meet the requirement of dispersion measurement in the laboratory acoustic experiments involving Rayleigh waves.

An analysis of three approaches for estimating 3D PS statics is presented. These include a surface-consistent inversion algorithm, PPS refraction statics, and a robust statistical method. This analysis is achieved through the use of synthetic models, and a coal-scale 3D-3C survey acquired in the Bowen Basin.

EG16036Microtremor exploration for shallow S-wave velocity profiles at stations in local strong motion network in Bursa, Yalova, and Kocaeli in north-western Turkey

Özgür Tuna Özmen, Hiroaki Yamanaka, Kosuke Chimoto, Ulubey Çeken, Mehmet Akif Alkan, Kudret Tekin and Erkan Ateş
pp. 255-263

We conducted microtremor array surveys for shallow Vs profiles at strong motion stations in Bursa, Yalova and Kocaeli provinces in Turkey. The Vs profiles to a depth of 100 m were deduced from Rayleigh wave phase velocities in frequencies from 1 to 30 Hz. Site amplification factors were discussed with the profiles.

This study applied a method that uses the H/V spectral ratio of ground motions to analyse site amplification characteristics. Its application was extended to S-waves, coda waves, and background noise. Analysis of data at seismic stations in Korea suggested consistent site amplification characteristics among the three types of seismic energies despite a logarithmic difference in the Fourier transform values.

New comprehensive seismic noise models and 3D seismic noise variation are constructed for Morocco, North Africa, using 23 broadband stations. The results bring a new perception to noise models and can be considered as a significant contribution. This study supplements the Peterson models and allows future permanent stations to be sited in Morocco.

We describe a new fast gravity inversion method to recover a 3D density model from gravity data. This gravity inversion method introduces a stabiliser model norm with a depth weighting function to produce smooth models and uses a new symmetric successive over-relaxation (SSOR) iterative conjugate gradient (CG) algorithm.

In this paper, we describe the utilisation of numerical models to simulate the downhole application of gravity gradiometry in order to benchmark the impact of a density contrast at depth, with specific application to monitor a density contrast consistent with the sequestration of CO2 displacing brine water in an abandoned oil reservoir.

Gravity, ground magnetics, DC resistivity and TDEM measurements are used to delineate the near-surface extent of the Okauia Low Temperature Geothermal System, New Zealand. Potential permeable pathways mapped by the geophysical surveys are consistent with the geological environment.

EG16035Three-dimensional inversion of in-line resistivity data for monitoring a groundwater recharge experiment in a pyroclastic plateau

Keisuke Inoue, Hiroomi Nakazato, Tomijiro Kubota, Mutsuo Takeuchi, Yoshihiro Sugimoto, Hee Joon Kim and Koji Furue
pp. 332-343

An artificial groundwater recharge experiment was conducted in a pyroclastic plateau in Kagoshima Prefecture in Japan, and time-efficient in-line resistivity surveys were performed along four intersecting lines. The zones of decreased resistivity shifted with time, indicating non-uniform penetration of water from the recharge areas and a horizontal flow of the recharged water.

We demonstrate the usefulness of fuzzy clustering for semi-automated rock mass classification and the importance of data preconditioning prior to analysis. We also show the impact of choosing different subsets and combinations of the available data on the classification result.

Online Early

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

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.

Published online 25 October 2017

EG17129Study of the Nankai seismogenic fault using dynamic wave propagation modelling of digital rock from the Nobeoka Fault

Chandoeun Eng, Tatsunori Ikeda and Takeshi Tsuji

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.

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 09 January 2017

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

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.

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

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

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.

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.

Published online 24 November 2016

EG16037Multi-scale full waveform inversion for areas with irregular surface topography in an auxiliary coordinate system

Yingming Qu, Zhenchun Li, Jianping Huang and Jinli Li

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.

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.

Published online 28 October 2016

EG16042Regional magnetic lithologies and structures as controls on porphyry copper deposits: evidence from Iran

Hassan Kheyrollahi, Firouz Alinia and Abdolreza Ghods

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.

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.

Published online 19 October 2016

EG16105An efficient interpolation approach for insufficient 3D field data

Bona Kim, Soocheol Jeong, Joongmoo Byun and Young Kim

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.

Published online 19 October 2016

EG16010The research on the buried public monumental complexes of Lupiae (Lecce) by geophysical prospecting

Giovanni Leucci, Lara De Giorgi, Giacomo Di Giacomo, Imma Ditaranto, Ilaria Miccoli and Giuseppe Scardozzi

This paper presents a case study that involves a geophysical survey employing the surface 3D ground penetrating radar (GPR) techniques, in order to archaeologically characterise the areas located in the south-western sector of the historical centre of Lecce (Italy). GPR measurements significantly contributed to reconstruction of the complex subsurface properties in these modern urban areas.

Published online 18 October 2016

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

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.

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.

Published online 06 October 2016

EG16025Outliers-out stack: a new algorithm for processing seismic data

Mohamed Rashed

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.

Published online 29 September 2016

EG15021Radiogenic heat production in Rudeis Formation, Lower Miocene, Belayim marine oil field, Gulf of Suez, Egypt

Hassan Mohamed, Hideki Mizunaga, Nasser Mohamed Abou Ashour, Refaat Ahmed Elterb, Ibrahim Mostafa Elalfy and Ayman Shebel Elsayed

This study describes radiogenic heat production (RHP) estimated from two sets of well logging data recorded in Rudeis Formation, Belayim marine oil field. Cross-correlation of the estimated RHP (AR and ABR) yielded a moderate fit of 0.75. The three-dimensional (3D)-slicing of the reservoir shows that the northern and north-western parts of the study area have higher RHP compared to other parts.

Published online 09 September 2016

EG16098Multiple lapse time window analysis using solely single events in South Korea

Asep Nur Rachman, Tae Woong Chung and Kyung-Hoon Chung

Depth variation of scattering attenuation by applying single events to multiple lapse time window analysis (MLTWA) was recently shown; however, this application inevitably combined several events due to insufficient data. This study demonstrated that a flexible range window can be applied successfully to solely single events in MLTWA.

We have proposed a dip-oriented gradient energy entropy (DOGEE) coherence method to detect subtle faults and structural features. Theoretical synthetic datasets and a real dataset show that our proposed method is not only robust to noise, but also improves the clarity of small-scale discontinuities.

A crooked-line 2D seismic reflection dataset recorded in the northern part of the Eastern Pannonian Basin was processed to obtain a high-resolution seismic image for the area of interest. Refraction interferometry was used to enhance the first arrivals and to compute static corrections with good accuracy.

Published online 23 August 2016

EG16031Separation of prestack seismic diffractions using an improved sparse apex-shifted hyperbolic Radon transform

Xiangbo Gong, Chenxia Yu and Zhihui Wang

We have developed an improved sparse apex-shifted hyperbolic Radon transform with Fourier-kernel Stolt-based modelling and imaging operators to separate seismic diffractions from reflections. The time axis is stretched to overcome the limitation of the multi-velocity model and a sparsity-promoting inversion is implemented to enhance the resolution of the Radon panel.

We have studied the correlation between bulk mineralogy and induced polarisation (IP) responses in iron oxide-copper-gold (IOCG) and porphyry copper concealed mineralised systems in northern Chile. Data analyses show that bulk sulphide concentration is the first order factor that explains variation in the IP effect, even for the case of magnetite-related IOCG mineralisation.

Published online 21 July 2016

EG16063Multi-parameter full waveform inversion using Poisson’s ratio for elastic media

Ju-Won Oh and Dong-Joo Min

A new parameterisation using P-wave velocity, Poisson’s ratio and density is proposed for multi-parameter full waveform inversion (FWI) for isotropic elastic media. By introducing Poisson’s ratio, the virtual source for the P-wave velocity generates additional S-waves in the partial derivative wavefields, which increases the spatial resolution of FWI.

Published online 14 July 2016

EG15095Short-offset grounded-wire TEM method for efficient detection of mined-out areas in vegetation-covered mountainous coalfields

Nannan Zhou, Guoqiang Xue, Dongyang Hou, Hai Li and Weiying Chen

The objective of this study was to overcome the limitations in using the loop-source TEM method and realise the efficient detection of mined-out areas using the short-offset grounded-wire TEM (SOTEM) method in vegetation-covered mountainous coalfields. The feasibility of SOTEM is verified by the drilling result in the field test.

Published online 07 July 2016

EG15124Effects of the symmetry axis orientation of a TI overburden on seismic images

Chih-Hsiung Chang, Young-Fo Chang and Cheng-Wei Tseng

Benefitting from the forward modelling studies, the phenomenon of spatial mispositioning in apparent reflections caused by the symmetry axis orientation of the TI overburden was demonstrated. Numerical manipulations show the imaging problems can be well described by the TERF method and properly handled by the RAKTM method.

Published online 23 June 2016

EG15112Improved reservoir characterisation using fuzzy logic platform: an integrated petrophysical, seismic structural and poststack inversion study

Muhammad Kamran Jafri, Aref Lashin, El-Khedr Hassan Ibrahim, Kamal A. Hassanein, Nassir Al Arifi and Muhammad Naeem

In this study, petrophysical properties, seismic structural and poststack seismic inversion results are integrated using the fuzzy logic AND operator to characterise the Tensleep Sandstone Formation at Powder River Basin, Wyoming, USA. The 3D seismic cube and logging datasets of 17 wells are used for enhancing the seismic and petrophysical evaluation.

This paper introduces a low redundancy curvelet transform which can reduce the redundancy to 10 for three dimensional data and simultaneously interpolate and denoise. Numerical experiments on synthetic and field data demonstrate that the low redundancy transform can provide reliable results while at the same time improving the computational efficiency.

Published online 08 June 2016

EG16004Adaptive mixed-norm seismic inversion for non-Gaussian errors

Zhiyong Li, Guangmin Hu and Jiashu Zhang

Subsurface-property estimation from remote geophysical measurements is subject to non-Gaussian errors. We propose to minimise the misfit with a robust error measure, which is based on a generalised Gaussian distribution. A suboptimal solution is proposed through a mixed-norm functional combination of the l1 and l2 norms.

Forward and inverse modelling are used to demonstrate that the resistivity method can detect alteration above the Midwest uranium deposit in Canada. The inverse section of the field data is similar to the inverse section of a synthetic model when alteration is present, but dissimilar when there is no alteration.

Published online 02 June 2016

EG15078Near-surface high resolution imaging of a metallogenic zone in the northern fringe of Dalma volcanics in eastern India using electrical resistivity tomography

P. K. Adhikari, P. K. Yadav, Shalivahan Srivastava, Ved P. Maurya, Shailendra Singh, Anurag Tripathi, Roshan K. Singh and Ashish K. Bage

An ERT survey was conducted over a defined conducting zone through a magnetotelluric survey in the Dalma volcanics, India. The resistivity models resolved four major zones and the results corroborate well with the geological succession. The resistivity values of less than 1 Ωm at a depth of ~25 m correspond to the deposit.

Published online 31 May 2016

EG16043Microtremor exploration for shallow S-wave velocity structure in Bandung Basin, Indonesia

Andi Muhamad Pramatadie, Hiroaki Yamanaka, Kosuke Chimoto, Afnimar, Kazuki Koketsu, Minoru Sakaue, Hiroe Miyake, I Wayan Sengara and Imam A. Sadisun

We obtained the shallow S-wave velocity profile distributions in the Bandung Basin, Indonesia, from the inversion of the observed Rayleigh wave phase velocity spectra using a microtremor survey. The profiles will be used for calculation of the average S-wave velocity of the upper 30 m and site amplification factors for seismic hazard evaluation in the area.

Published online 12 May 2016

EG15074Divergence correction schemes in finite difference method for 3D tensor CSAMT in axial anisotropic media

Kunpeng Wang, Handong Tan, Zhiyong Zhang, Zhiqiang Li and Meng Cao

This paper presents a study on divergence correction in the finite difference method for 3D tensor controlled-source audio-frequency magnetotellurics (CSAMT) in an axial anisotropic media. We show how divergence correction can be performed more efficiently and the study results can be used to help accelerate a whole 3D tensor CSAMT forward modelling and inversion.

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