Ruo Wang

Multi-geophysical Investigation of Geological Structures in a Pre-selected High-level Radioactive Waste Disposal Area in Northwestern China

A potential high-level radioactive waste (HLRW) disposal site in northwestern China was investigated to determine its suitability for such a use. The site is primarily covered with welldeveloped metamorphic granite rocks. The primary targets for geological repositories are three granite rock masses (I, II, and III). Only surface geological data were available from previous studies. The objective of this study was to evaluate the quality of the rock mass and identify any weak geological structures that could jeopardize this future underground repository. We used gravity and aeromagnetic data on a large scale to study the regional geological structures within and around the three rock masses. Subsequently, in 2009, a controlled source audio-frequency magnetotelluric (CSAMT) survey was conducted to study rock mass I in more detail. This paper introduces three-dimensional (3-D) tomography imaging of gravity and aeromagnetic data. 3-D tomography imaging was carried out on previously collected gravity and aeromagnetic data and, using the results of different depth slices, we evaluated the rock mass quality and interpreted the geology. The aeromagnetic depth slices show that at about 1-km deep in rock masses I and III there is a high magnetic susceptibility body, possibly caused

Geophysical exploration for a long deep tunnel to divert water from the Yangtze to the Yellow River, China

To identify problematic geological structures which would be encountered when driving tunnels in the high mountainous area of South West China, a joint geophysical and engineering geological study was made. The tunnels will form part of a project to divert water from the Yangtze to the Yellow Rivers. A controlled source audio-frequency magnetotelluric method (CSAMT) was carried out in 2004 between the Ma-ke and Jia-qu rivers in high, steep terrain. The paper discusses the method of data collection, processing, and analysis for the West route. The faults/fractures identified will need to be taken into account in the design and construction of the tunnel.RésuméAfin d’identifier des structures géologiques contraignantes qui pourraient être rencontrées lors du creusement de tunnels au travers des régions montagneuses de la Chine du sud-ouest, une étude couplée de géophysique et de géologie de l’ingénieur a été réalisée. Les tunnels feront partie du projet de détournement des eaux du bassin du Yangtze vers celui du Fleuve Jaune. Une méthode magnéto-tellurique (CSAMT) a été mise en œuvre en 2004 entre les rivières de Ma-ke et Jia-qu dans une région d’altitude présentant des pentes raides. L’article discute des méthodes de récupération, traitement et analyse des données pour l’itinéraire de l’Ouest. Les failles et fractures identifiées devront être prises en compte dans la conception et la construction du tunnel.

Removal of the airwave effect by main-part decomposition of the anomalous field of MCSEM data

The airwave effect greatly influences the observational data from controlledsource electromagnetic exploration in shallow seas, which obscures the abnormal effects generated by exploration targets and, hence, affects the accuracy of the late exploration data interpretation. In this study, we propose a method to separate the main part from the anomalous field of marine controlled-source electromagnetic method (MCSEM) data based on Stratton–Chu integral transforms to eliminate the airwave effect, which dominates observed electromagnetic (EM) response in shallow seawater. This method of separating the main part from the anomalous field is a type of finite impulse response filter based on a discrete data set. Theoretical analysis proved that the method is stable and able to effectively depress noise. A numerical test indicated that the method could successfully eliminate the airwave effect from the observed EM signals generated by an air–water interface and a seawater layer. This technique is applicable for seawater models with either flat or rough seabeds.

Time domain electromagnetic migration imaging

This article is about the study of time domain electromagnetic data migration imaging. First, based on the electromagnetic diffusion theory and the boundary conditions, we deduce the analytical formula of electromagnetic migration field. Then, we complete the calculation of electromagnetic migration field filter by electromagnetic migration field theory in frequency domain. The analytical electromagnetic migration filter is discretized to achieve electromagnetic numerical migration filter to make it able to be applied into practical discrete sampling. By analyzing the error caused by of discretization procedure according to the theory of electromagnetic migration filter, we deduce discretization error correction formula. Moreover, we study and realize the transform from time domain to frequency domain, and make it able to be used in time domain electromagnetic migration imaging. In order to test migration imaging technology, whole space 2D or 3D geoelectric models are built with the transmiter-receiver distance varying from near field to several thousand kilometers. Using the technology presented by this paper to the numeric data, the reasonable position of underground exploration body can be recovered. Finally, we deduce 2D migration field analytical formula in time domain and discretize it, then complete the numeric calculation in time domain directly. We analyze the kernel function of time domain electromagnetic migration filter and its influence factors, and test the effect of time domain migration field imaging by several simple geoelectric models.

CSAMT research survey for preventing water bursting disaster in mining

Control source audio-frequency magnettelluric method (CSAMT) exploration on 13 lines in a mine area of 440m * 300m was conducted in March 2001, using the multi-function instrument, V6 system (Phoenix, Canada). Karsts, Faults and water-bearing fracture belts in the limestone above ore body are shown clearly in CSAMT profiles. The results provide important information for preventing water bursting in this iron ore mine.