Deep reflection seismic imaging of iron-oxide deposits in the Ludvika mining area of central Sweden     

Magdalena Markovic  Georgiana Maries  Alireza Malehmir  Julius von Ketelhodt  Emma Bäckström  Monica Schön  Paul Marsden 《Geophysical Prospecting》2020,68(1):7-23

Reflection seismic data were acquired within two field campaigns in the Blötberget, Ludvika mining area of central Sweden, for deep imaging of iron-oxide mineralization that were known to extend down to 800–850 m depth. The two surveys conducted in years 2015 and 2016, one employing a seismic landstreamer and geophones connected to wireless recorders, and another one using cabled geophones and wireless recorders, aimed to delineate the geometry and depth extent of the iron-oxide mineralization for when mining commences in the area. Even with minimal and conventional processing approaches, the merged datasets provide encouraging information about the depth continuation of the mineralized horizons and the geological setting of the study area. Multiple sets of strong reflections represent a possible continuation of the known deposits that extend approximately 300 m further down-dip than the known 850 m depth obtained from historical drilling. They show excellent correlation in shape and strength with those of the Blötberget deposits. Furthermore, several reflections in the footwall of the known mineralization can potentially be additional resources underlying the known ones. The results from these seismic surveys are encouraging for mineral exploration purposes given the good quality of the final section and fast seismic surveys employing a simple cost-effective and easily available impact-type seismic source.  相似文献   

A method for classifying pre‐stack seismic data based on amplitude–frequency attributes and self‐organizing maps          下载免费PDF全文

Erik Molino‐Minero‐Re  Ernesto Rubio‐Acosta  Héctor Benítez‐Pérez  Juan Marcos Brandi‐Purata  Nora Isabel Pérez‐Quezadas  Demetrio Fabián García‐Nocetti 《Geophysical Prospecting》2018,66(4):673-687

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时频方向谱分析在海洋电磁数据处理中的应用          下载免费PDF全文

徐震寰  李予国 《地球物理学报》2019,62(12):4874-4885

海底采集到的电磁数据按照其主要包含的信息及研究目的大致可分为海洋可控源电磁场(CSEM)信号、天然场源大地电磁场(MT)信号、海洋环境电磁场信号以及其他随机干扰信号.常常通过计算功率谱密度、时频分析和极化分析的方法研究海洋电磁场特征.本文介绍一种新方法——时频方向谱分析法及其在实测海洋电磁数据处理中的应用,该方法能够在一定的时间-频率尺度上有效分辨场源信号的运动方向.对于海洋CSEM数据,利用该方法可以估算发射源的运动方向,进而在发射源或采集站方位信息缺失情况下,实现海洋CSEM数据的旋转电性轴处理.对于海洋电磁数据,利用该方法可以详细分析海水运动感应电磁场的信号特征.  相似文献   

Stretch-free generalized normal moveout correction     

Jorge H. Faccipieri  Tiago A. Coimbra  Rodrigo Bloot 《Geophysical Prospecting》2019,67(1):52-68

The effective application of normal moveout correction processes mainly depends on four factors: the chosen traveltime approximation, the stretching associated with the given traveltime, crossing events and phase changes, the last two being inherent to the seismic data. In this context, we conduct a quantitative analysis on stretching considering a general traveltime expression depending on half-offset and midpoint coordinates. Through this analysis, we propose a mathematically proven procedure to eliminate stretching, which can be applied to any traveltime approximation. The proposed method is applied to synthetic and real data sets, considering different traveltime approximations and achieved complete elimination of stretching.  相似文献   

Heli-borne gravity gradiometry in rugged terrain     

Mark H. Dransfield  Tianyou Chen 《Geophysical Prospecting》2019,67(6):1626-1636

For airborne gravity gradiometry in rugged terrain, helicopters offer a significant advantage over fixed-wing aircraft: their ability to maintain much lower ground clearances. Crucially, this provides both better signal-to-noise and better spatial resolution than is possible with a fixed-wing survey in the same terrain. Comparing surveys over gentle terrain at Margaret Lake, Canada, and over rugged terrain at Mount Aso, Japan, demonstrates that there is some loss of spatial resolution in the more rugged terrain. The slightly higher altitudes forced by rugged terrain make the requirements for terrain correction easier than for gentle terrain. Transforming the curvature gradients measured by the Falcon gravity gradiometer into gravity and the complete set of tensor components is done by a Fourier method over gentle terrain and an equivalent source method for rugged terrain. The Fourier method is perfectly stable and uses iterative padding to improve the accuracy of the longer wavelengths. The equivalent source method relies on a smooth model inversion, and the source distribution must be designed to suit the survey design.  相似文献   

Designing and testing a network of passive seismic surveying and monitoring in Dehdasht (South Western Iran)     

Victor Salinas  Arantza Ugalde  Ahmad Kamayestani  Mehrab Jokar  Mojtaba Moradi Gharibvand  Antonio Villaseñor  Ghasem Heidari 《Geophysical Prospecting》2019,67(6):1652-1663

From August 2016 to July 2017, a passive seismic survey was conducted in South Western Iran as a part of a pilot project aimed to improve the imaging in geologically complex areas. Passive seismic methods have shown to be a useful tool to infer the physical properties of the underground geological structures where traditional hydrocarbon exploration methods are challenging. For this purpose, a dense passive seismic network consisting of 119 three-component borehole seismic stations was deployed over an area of 400 km² around the city of Dehdasht. This paper focuses on the details of the network design, which was devoted to high-resolution seismological applications, including local earthquake tomography and seismic attenuation imaging. In this regard, we describe the instrument types and the station installation procedures used to obtain high-quality data that were used to retrieve three-dimensional models of P- and S-wave velocity and P-wave attenuation in the area using tomographic inversion techniques. We also assess the network performance in terms of the seismic ambient noise levels recorded at each station site, and we revise the horizontal orientation of the sensors using surface waves from teleseismic earthquakes.  相似文献   

Identification and classification of transient pulses observed in magnetometer array data by time-domain principal component analysis filtering          下载免费PDF全文

Karl N. Kappler  Daniel D. Schneider  Laura S. MacLean  Thomas E. Bleier 《地震科学（英文版）》2017,30(4):193-207

A method for identification of pulsations in time series of magnetic field data which are simultaneously present in multiple channels of data at one or more sensor locations is described. Candidate pulsations of interest are first identified in geomagnetic time series by inspection.Time series of these ‘‘training events' ' are represented in matrix form and transpose-multiplied to generate timedomain covariance matrices. The ranked eigenvectors of this matrix are stored as a feature of the pulsation. In the second stage of the algorithm, a sliding window(approximately the width of the training event) is moved across the vector-valued time-series comprising the channels on which the training event was observed. At each window position, the data covariance matrix and associated eigenvectors are calculated. We compare the orientation of the dominant eigenvectors of the training data to those from the windowed data and flag windows where the dominant eigenvectors directions are similar. This was successful in automatically identifying pulses which share polarization and appear to be from the same source process. We apply the method to a case study of continuously sampled(50 Hz) data from six observatories, each equipped with threecomponent induction coil magnetometers. We examine a90-day interval of data associated with a cluster of four observatories located within 50 km of Napa, California,together with two remote reference stations-one 100 km to the north of the cluster and the other 350 km south. When the training data contains signals present in the remote reference observatories, we are reliably able to identify and extract global geomagnetic signals such as solar-generatednoise. When training data contains pulsations only observed in the cluster of local observatories, we identify several types of non-plane wave signals having similar polarization.  相似文献   

Feasibility of utilizing wavelet phase to map the CO2 plume at the Ketzin pilot site,Germany          下载免费PDF全文

Fei Huang  Christopher Juhlin  Li Han  Daniel Sopher  Monika Ivandic  Ben Norden  Wubing Deng  Fengjiao Zhang  Thomas Kempka  Stefan Lüth 《Geophysical Prospecting》2017,65(2):523-543

Spectral decomposition is a powerful tool that can provide geological details dependent upon discrete frequencies. Complex spectral decomposition using inversion strategies differs from conventional spectral decomposition methods in that it produces not only frequency information but also wavelet phase information. This method was applied to a time‐lapse three‐dimensional seismic dataset in order to test the feasibility of using wavelet phase changes to detect and map injected carbon dioxide within the reservoir at the Ketzin carbon dioxide storage site, Germany. Simplified zero‐offset forward modelling was used to help verify the effectiveness of this technique and to better understand the wavelet phase response from the highly heterogeneous storage reservoir and carbon dioxide plume. Ambient noise and signal‐to‐noise ratios were calculated from the raw data to determine the extracted wavelet phase. Strong noise caused by rainfall and the assumed spatial distribution of sandstone channels in the reservoir could be correlated with phase anomalies. Qualitative and quantitative results indicate that the wavelet phase extracted by the complex spectral decomposition technique has great potential as a practical and feasible tool for carbon dioxide detection at the Ketzin pilot site.  相似文献   

Seismic data interpolation using generalised velocity‐dependent seislet transform          下载免费PDF全文

Yang Liu  Peng Zhang  Cai Liu 《Geophysical Prospecting》2017,65(Z1):82-93

Data interpolation is an important step for seismic data analysis because many processing tasks, such as multiple attenuation and migration, are based on regularly sampled seismic data. Failed interpolations may introduce artifacts and eventually lead to inaccurate final processing results. In this paper, we generalised seismic data interpolation as a basis pursuit problem and proposed an iteration framework for recovering missing data. The method is based on non‐linear iteration and sparse transform. A modified Bregman iteration is used for solving the constrained minimisation problem based on compressed sensing. The new iterative strategy guarantees fast convergence by using a fixed threshold value. We also propose a generalised velocity‐dependent formulation of the seislet transform as an effective sparse transform, in which the non‐hyperbolic normal moveout equation serves as a bridge between local slope patterns and moveout parametres in the common‐midpoint domain. It can also be reduced to the traditional velocity‐dependent seislet if special heterogeneity parametre is selected. The generalised velocity‐dependent seislet transform predicts prestack reflection data in offset coordinates, which provides a high compression of reflection events. The method was applied to synthetic and field data examples, and the results show that the generalised velocity‐dependent seislet transform can reconstruct missing data with the help of the modified Bregman iteration even for non‐hyperbolic reflections under complex conditions, such as vertical transverse isotropic (VTI) media or aliasing.  相似文献   

Directional interpolation of multicomponent data          下载免费PDF全文

Fredrik Andersson  Adriana Citlali Ramírez  Torgeir Wiik  Viktor V. Nikitin 《Geophysical Prospecting》2017,65(5):1246-1263

A method for interpolation of multicomponent streamer data based on using the local directionality structure is presented. The derivative components are used to estimate a vector field that locally describes the direction with the least variability. Given this vector field, the interpolation can be phrased in terms of the solution of a partial differential equation that describes how energy is transported between regions of missing data. The approach can be efficiently implemented using readily available routines for computer graphics. The method is robust to noise in the measurements and particularly towards high levels of low‐frequent noise that is present in the derivative components of the multicomponent streamer data.  相似文献