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 1 2017

RESEARCH FRONT: Geophysical Surveys after the Great Eastern Japan Earthquake


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.

EG16113Shallow subsurface structure estimated from dense aftershock records and microtremor observations in Furukawa district, Miyagi, Japan

Hiroyuki Goto, Hitoshi Mitsunaga, Masayuki Inatani, Kahori Iiyama, Koji Hada, Takaaki Ikeda, Toshiyasu Takaya, Sayaka Kimura, Ryohei Akiyama, Sumio Sawada and Hitoshi Morikawa
pp. 16-27

Severe residential damage in the Furukawa district, Miyagi, Japan, occurred during the Great Eastern Japan Earthquake of 2011. We model the shallow subsurface structure based on aftershock records from a dense seismometer network and results of microtremor observations. Site amplifications estimated from the model explain the damage distribution well.


The Hinode area of Itako City in Ibaraki Prefecture, Japan, suffered severe liquefaction damage in the Great Eastern Japan Earthquake in 2011. The National Institute of Advanced Industrial Science and Technology (AIST) has carried out numerous investigations in the area. We have conducted risk analysis using cone penetration testing and electric resistivity data. The distribution of the risk estimated from both data sets is in agreement with the distribution of actual damage.


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.


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.


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.


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.

EG15068Comparison of artificial absorbing boundaries for acoustic wave equation modelling

Yingjie Gao, Hanjie Song, Jinhai Zhang and Zhenxing Yao
pp. 76-93

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.

Online Early

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

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.

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 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

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.

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