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 47 Number 3 2016

ASEG-PESA 24th International Geophysical Conference and Exhibition: Special Issue on Case Studies

EG15088Helicopter AFMAG (ZTEM) EM and magnetic results over sedimentary exhalative (SEDEX) lead-zinc deposits at Howard’s Pass in Selwyn Basin, Yukon

Jean M. Legault, Ali Latrous, Shengkai Zhao, Nasreddine Bournas, Geoffrey C. Plastow and Gabriel Guang Xue
pp. 170-178

In 2008, a ZTEM natural field EM and magnetic survey was flown over the world-class, >250 Mt SEDEX deposits at Howard’s Pass in the Selwyn Basin, Yukon. The AEM data provide insights into regional structures and intrusions. They also reveal a correlation between enhanced conductivity along strike and the clustering of deposits at Howard’s Pass.

EG15080VTEM airborne EM, aeromagnetic and gamma-ray spectrometric data over the Cerro Quema high sulphidation epithermal gold deposits, Panama

Karl Kwan, Alexander Prikhodko, Jean M. Legault, Geoffrey C. Plastow, John Kapetas and Michael Druecker
pp. 179-190

In March 2012, a helicopter-borne VTEM survey was flown over the Cerro Quema high sulphidation (HS) epithermal gold deposits. The geophysical data obtained were analysed for geophysical signatures characteristic of HS epithermal gold deposits. The success of this survey points to the applicability of EM-Mag-Spec surveys for the exploration of similar deposits.

EG15089Passive airborne EM and ground IP\resistivity results over the Romero intermediate sulphidation epithermal gold deposits, Dominican Republic

Jean M. Legault, Jeremy Niemi, Jeremy S. Brett, Shengkai Zhao, Zihao Han and Geoffrey C. Plastow
pp. 191-200

The Romero gold-copper-zinc-silver deposits in the Dominican Republic are of the intermediate sulphidation epithermal type. Ground IP\resistivity results are compared to ZTEM passive airborne electromagnetics over the deposit region. The ZTEM results show good correlation with ground IP\resistivity results and identify a previously unknown deep (>500 m) continuity between the Romero deposits.

Data from the Far South project were acquired using a sub-audio magnetic (SAM) survey, set up in galvanic configuration. The galvanic source electromagnetic (GSEM) data were used to identify conductive responses. Modelling of the GSEM responses was attempted with some success, showing this method to be an effective reconnaissance tool.

EG15090New insights into the North Taranaki Basin from New Zealand’s first broadband 3D survey

Marjosbet Uzcategui, Malcolm Francis, Wai Tin Vincent Kong, Richard Patenall, Dominic Fell, Andrea Paxton and Tristan Allen
pp. 210-218

The North Taranaki Basin contains widespread (2D) seismic coverage and numerous wells. The basin hydrocarbon potential remains unproven. An active petroleum system is confirmed by hydrocarbon shows and non-commercial oil and gas discoveries (Karewa-1 and Kora-1). 3D seismic interpretation and amplitude-versus-offset (AVO) analysis support the renewed potential of the basin.

EG15075Airborne gravity gradiometer surveying of petroleum systems under Lake Tanganyika, Tanzania

Doug Roberts, Priyanka Roy Chowdhury, Sharon Jenny Lowe and Asbjorn Norlund Christensen
pp. 228-236

An airborne gravity gradiometry and high-resolution aeromagnetic survey conducted in Lake Tanganyika within the East African Rift System has been interpreted to demonstrate sedimentary sequences and structures prospective for petroleum. Numerous play types analogous to the Lake Albert oil discoveries further north in Uganda are revealed by further surveys.

We provide detailed geophysical characterisation of porphyry style Cu-Au mineralisation of the Atlántida project, located under 25–80 m post-mineral gravels of the Atacama Desert, Northern Chile. Clear geological controls on the geophysical signatures of the deposit are resolved via the use of petrophysical studies and incorporation of drill testing results.

The Eureka massive sulphide lens forms part of the Stockman Project in north-east Victoria. Eureka was discovered in early 2013, combining the interpretation of two subtle downhole electromagnetic anomalies with a robust geological model, with additional support from short-wave infrared and structural modelling.

Online Early

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

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 03 October 2016

EG16099S-wave reflection and surface wave surveys in liquefaction affected areas: a case study of the Hinode area, Itako, Ibaraki, Japan

Toshiyuki Yokota, Motoharu Jinguuji, Yoshiaki Yamanaka and Kazunori Murata

We performed surface wave and S-wave reflection surveys to investigate the Hinode area of Itako, Ibaraki, Japan. This area suffered serious liquefaction damage during the Great Eastern Japan Earthquake of 2011. Using subsurface boundaries imaged by the reflection surveys and the Vs structures obtained by surface wave analyses, we delineated the layer in which liquefaction occurred.

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 22 September 2016

EG16016Towards a global network of gamma-ray detector calibration facilities

Marco Tijs, Ronald Koomans and Han Limburg

Gamma-ray tools are used heavily in borehole logging, both in oil and gas, as well as in mining applications. For proper functioning, these tools need to be calibrated against a source of known activity and geometry. In this paper, we present a holistic approach to tool calibration, aiming to interlink several calibration facilities around the world, allowing quantitative interpretation of data.

Published online 20 September 2016

EG15125A new noise reduction method for airborne gravity gradient data

Jirigalatu, Jörg Ebbing and Josef Sebera

A new noise reduction method that iteratively projects data to a lower height and upward continuing the data back to the survey height is described. This method can significantly improve the signal-to-noise ratio of noisy gravity gradient data, and has been successfully applied to both synthetic and real data.

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.

Published online 02 August 2016

EG16033Airborne EM for mine infrastructure planning

Chris Wijns

In environments of suitable conductivity contrast, airborne electromagnetic surveys can map variations in the depth to bedrock for mine infrastructure planning. A survey in northern Finland illustrates the success of this approach for guiding the placement of a mine crusher and related infrastructure.

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.

There has been evidence of the IP effect in TDEM data. This phenomenon is known to be responsible for incorrect inversion modelling of electrical resistivity, lower DOI and lost information about chargeability. In the current paper, we show the possibility of extracting IP information from VTEM data using Cole-Cole modelling.

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.

If the horizontal and vertical derivatives of the total field magnetic anomalies of thin dykes and contacts are put into an amplitude-phase form, then this can aid in their interpretation. In addition, the relationships between local wavenumber and source-distance semi-automatic interpretation methods are clarified.

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.

Published online 06 June 2016

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

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.

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

EG15039A Monte Carlo approach to constraining uncertainties in modelled downhole gravity gradiometry applications

Samuel J. Matthews, Craig O'Neill and Mark A. Lackie

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.

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, , 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 30 May 2016

EG16014Joint inversions of two VTEM surveys using quasi-3D TDEM and 3D magnetic inversion algorithms

Vlad Kaminski, Domenico Di Massa and Andrea Viezzoli

We present the results of a joint quasi-3D inversion of two VTEM datasets, flown over a VMS-Au prospect in northern Ontario, Canada, six years apart from one another. The TDEM data were inverted jointly using the spatially constrained inversion (SCI) approach and verified against known geology.

Published online 20 May 2016

EG15053New comprehensive standard seismic noise models and 3D seismic noise variation for Morocco territory, North Africa, obtained using seismic broadband stations

Younes El Fellah, Abd El-Aziz Khairy Abd El-Aal, Mimoun Harnafi and Antonio Villaseñor

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.

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.

Published online 10 May 2016

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

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.

Published online 05 May 2016

EG15065An experimental study of Rayleigh waves based on seismoelectric measurements

Ziying Xiong, Zhengping Liu and Kai Zhang

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.

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.

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.

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.

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.

An object program provides hands-on searching through magnetic survey data. The power spectrum is remapped on-screen so that any isolated compact body appears as a straight line in a spectrum of depths. Results are typically noisy, so facilities are provided to change parameters to track down an elusive depth signal.

Published online 01 April 2016

EG15115Statics correction methods for 3D converted-wave (PS) seismic reflection

Shaun Strong and Steve Hearn

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.

Published online 23 March 2016

EG15117Testing cluster analysis on combined petrophysical and geochemical data for rock mass classification

Maria C. Kitzig, Anton Kepic and Duy T. Kieu

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.

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.

Published online 16 February 2016

EG15041Fast inversion of gravity data using the symmetric successive over-relaxation (SSOR) preconditioned conjugate gradient algorithm

Zhaohai Meng, Fengting Li, Xuechun Xu, Danian Huang and Dailei Zhang

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.

Published online 12 February 2016

EG15127Gas hydrate saturation and distribution in the Kumano Forearc Basin of the Nankai Trough

Jihui Jia, Takeshi Tsuji and Toshifumi Matsuoka

The spatial distribution and characteristics of gas hydrates in the Kumano Forearc Basin of the Nankai Trough were investigated by using logging data and 3D seismic data. This study demonstrates that tectonic activity of the underlying accretionary prism at the plate convergent margin is responsible for hydrate formation.

Published online 05 February 2016

EG15100Obtaining high-resolution velocity spectra using weighted semblance

Saleh Ebrahimi, Amin Roshandel Kahoo, Milton J. Porsani and Ali Nejati Kalateh

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.

Published online 29 January 2016

EG15092Forward modelling of spectral depths using 3D Fourier convolution

Roger Clifton

3D Fourier convolution is a fast method for forward modelling irregular magnetic bodies. A kernel consisting of the field of a single dipole, convolved over a random distribution of dipoles, simulates the heterogeneity of bulk material. A demonstration studies the depth information collected by different survey parameters.

Published online 27 January 2016

EG16003Converted-wave guided imaging condition for elastic reverse time migration with wavefield separation

Hyungwook Choi, Soon Jee Seol and Joongmoo Byun

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.

Published online 20 January 2016

EG15121Electromagnetic exploration in high-salinity groundwater zones: case studies from volcanic and soft sedimentary sites in coastal Japan

Koichi Suzuki, Yukiko Kusano, Ryota Ochi, Nariaki Nishiyama, Tomochika Tokunaga and Kazuhiro Tanaka

In order to evaluate the freshwater–saltwater interface of three sample areas in the Chugoku-Shikoku region of western Japan, we conducted CSAMT surveys at locations with varying hydrogeological features, and performed laboratory tests to measure the electrical properties of rock core samples from each site.

Published online 20 January 2016

EG15120Fast first arrival picking algorithm for noisy microseismic data

Dowan Kim, Joongmoo Byun, Minho Lee, Jihoon Choi and Myungsun Kim

We have developed a new fast picking method, optimised for noisy microseismic data, using cross-correlation and stacking. In experiments with synthetic data and field data, this method produces reliable results and the computation time is dramatically reduced.

Published online 13 January 2016

EG150703D inversion of total magnetic intensity data for time-domain EM at the Lalor massive sulphide deposit

Dikun Yang and Douglas W. Oldenburg

3D voxel inversion of HeliSAM data at the Lalor massive sulphide deposit suffers from: (1) contamination of early-time data by the near-surface infrastructure and (2) creation of a mathematically acceptable but non-geologic model from inversion of late-time data. We propose a procedure that incorporates the infrastructure in our inversion, and a warm-start approach to overcome the non-uniqueness.

Published online 23 December 2015

EG15068Comparison of artificial absorbing boundaries for acoustic wave equation modelling

Yingjie Gao, Hanjie Song, Jinhai Zhang and Zhenxing Yao

We provide a thorough review of all typical absorbing boundary conditions and derive their equations in a uniform mathematical form. We examine their performance via numerical experiments and qualitatively show their advantages and disadvantages. Finally, we provide some suggestions on choosing different boundary conditions for practical applications.

Published online 23 December 2015

EG14120Automatic first-arrival picking based on extended super-virtual interferometry with quality control procedure

Shengpei An, Tianyue Hu, Yimou Liu, Gengxin Peng and Xianghao Liang

We have developed an automatic first-arrival picking method that combines extended super-virtual interferometry with quality control. The field data examples show that the proposed method yields stacked sections of similar quality to those obtained by laborious and costly manual picking.

Published online 22 December 2015

EG150233D joint inversion of gravity-gradient and borehole gravity data

Meixia Geng, Qingjie Yang and Danian Huang

We perform 3D joint inversion of surface and borehole data using cokriging. The examples presented demonstrate that the method is remarkable in its ability to include the geological information and physical property. Also, both depth and horizontal resolution of the recovered model can be improved by joint inversion.

Published online 11 December 2015

EG14126Automatic detection of multiple UXO-like targets using magnetic anomaly inversion and self-adaptive fuzzy c-means clustering

Gang Yin, Yingtang Zhang, Hongbo Fan, Guoquan Ren and Zhining Li

A method for automatically detecting UXO-like targets based on magnetic anomaly inversion and self-adaptive fuzzy c-means clustering is proposed. Magnetic anomaly inversion methods are used to estimate the initial locations of targets. The self-adaptive fuzzy c-means clustering algorithm is then used to cluster these initial locations, giving the number and locations of magnetic targets.

By considering two constraints from the Sobolev penalty function and the difference operator, we have developed an optimised regularisation model for extracting seismic diffractions. An efficient iterative method based on projection onto a convex set has been developed to solve the minimisation problem. The proposed method has high-resolution capability for detecting small-scale discontinuities.

Published online 27 October 2015

EG15050Azimuthal AVO signatures of fractured poroelastic sandstone layers

Zhiqi Guo and Xiang-Yang Li

Frequency-dependent seismic responses from a fractured sandstone layer show complex azimuthal variations due to anisotropic propagation and attenuation of transmission waves associated with fluid flow. It would be practical to investigate wavetrains reflected from the fractured layers that are regarded as integrated units.

Published online 26 October 2015

EG15081Acquisition, processing and interpretation of high-resolution seismic data using a small-scale multi-channel system: an example from the Korea Strait inner shelf, south-east Korea

Dong-Geun Yoo, Nam-Hyung Koo, Ho-Young Lee, Byoung-Yeop Kim, Young-Jun Kim and Snons Cheong

The results of the present study show that a small-scale multi-channel seismic system is an effective way to improve the quality of seismic records and to document the evolution of shallow sediment deposits. The shelf deposits in the Korea Strait inner shelf consist of three distinct seismic units formed during the late Quaternary.

A fundamental step in reservoir characterisation and modelling is the preconditioning of the initial reservoir model to honour both the geological knowledge and seismic data. In this paper, we analyse the issues that have significant impact on the (mis)match of the reservoir model with well logs and inverted seismic data.

Published online 17 September 2015

EG14074Joint elastic and petrophysical inversion using prestack seismic and well log data

Zhiyong Li, Beibei Song, Jiashu Zhang and Guangmin Hu

We present a strategy for the joint estimation of elastic and petrophysical properties from prestack seismic data based on Gassmann equations with deterministic optimisation techniques. Given poor-quality prestack seismic data, two regularisation parameters are introduced to control the trade-off between fidelity to the data and the smoothness of the solution.

Published online 13 August 2015

EG14121An efficient hybrid scheme for fast and accurate inversion of airborne transient electromagnetic data

Anders Vest Christiansen, Esben Auken, Casper Kirkegaard, Cyril Schamper and Giulio Vignoli

We present a hybrid inversion scheme for airborne TEM data that introduces approximation only in the calculation of partial derivatives. The objective function is evaluated with a full nonlinear one-dimensional (1D) forward model.

We investigated the range of sensitivity of five tools for measuring the conductivity or resistivity in drillholes and on drill core. Each tool has a limited range of sensitivity, so one or more tools should be used to cover the range of values expected on a particular project.

Published online 22 July 2015

EG15012A simple method for depth determination from self-potential anomalies due to two superimposed structures

El-Sayed M. Abdelrahman, Eid R. Abo-Ezz, Tarek M. El-Araby and Khalid S. Essa

A method to determine the depth to two superimposed sources from a self-potential anomaly profile has been developed. The method uses a relationship between the depths to the two superimposed structures determined from a combination of observations at symmetric points with respect to the coordinate of the sources’ centre.

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