地球物理与中国的可持续发展

在20世纪中国的发展历程中,地球物理在资源探查、环境保护和减轻自然灾害服务等诸多方面发挥了举足轻重的作用。21世纪,中国走可持续发展之路已成为必然选择。随着可持续发展思想及内涵的逐渐丰富,地球物理必将为中国的可持续发展起到更大作用。     

JaTS: a fully portable seismic tomography software based on Fresnel wavepaths and a probabilistic reconstruction approach

JaTS, a Java 2D seismic tomography software, is presented. It implements original algorithms achieving optimal accuracy with reasonable computing costs. A second-order Fast Marching Method (FMM) is used for solving the eikonal equation, therefore enabling a fast and robust computation of seismic traveltimes between sources and receivers. The wavepaths are materialized by Fresnel volumes rather than by conventional rays. This approach accounts for complex velocity models and has the advantage of considering the effects of the wave frequency in the velocity model resolution. The model is computed by a Simultaneous Iterative Reconstruction Technique (SIRT) which has been reformulated to integrate Fresnel wavepaths by using a probabilistic approach. In addition, various utilities are implemented, such as a tapering filter, used to decrease artifact effects occurring in the vicinity of the sources and receivers. The software also offers the possibility of reconstructing the velocity field on a grid larger than the one used for the wave propagation computation. This contributes to stabilize the estimated values. All of the seismic processing tools have been integrated with a user-friendly graphical interface. JaTS represents a tightly integrated tool suite that supports the entire process of importing the SG2 field records, first-break picking, forward modeling and velocity-field computing across multiple platforms.     

Analytical ray tracing system: Introducing art, a C-library designed for seismic applications

Ray tracing technique is an important tool not only to forward but also for inverse problems in Geophysics, which most of the seismic processing steps depend on. However, implementing ray tracing codes can be very time consuming. This article presents a computer library to trace rays in 2.5D media composed by a stack of layers. The velocity profile inside each layer is such that the eikonal equation can be analytically solved. Therefore, the ray tracing within such profile is made fast and accurate. The great advantage of an analytical ray tracing library is the numerical precision of the quantities computed and the fast execution of the implemented codes. Even though ray tracing programs exist for a long time, for example the seis88 package by ?ervený, most of those programs use a numerical approach to compute the ray. Regardless of the fact that numerical methods can solve more general problems, the analytical ones could be part of a more sophisticated simulation process, where the ray tracing time is completely relevant. We demonstrate the feasibility of our codes using several examples (Miqueles et al., 2013)  [1]. The library can also be used for other applications besides seismic, e.g., optics and tomography.     

An interactive FORTRAN 77 program using GKS graphics for 2.5 D modeling of gravity and magnetic data

An interactive 2.5 D gravity and magnetics modeling program has been written for an ICL PERQ 2 workstation using FORTRAN 77 and GKS graphics. All of the available hardware and software input devices are utilized through GKS to produce an easy-to-use menu-driven program. A large number of functions are controlled by the software in order than the user can concentrate on the model. A range of options also are provided for manipulating the observed anomaly. The use of FORTRAN 77 and GKS should make the program easily portable to other computer systems and graphics devices. The modular form of the program should facilitate readily further development including optimization and real time modeling, given a more powerful computer with high-speed graphics.     

瑞利波超前探技术在瓦斯突出预测中的应用

介绍了瑞利波探测法在阳泉煤矿进行瓦斯突出预测预报中的应用,通过对现场采集数据的处理、总结分析,以及开采验证,认为瑞利波超前探测技术可以有效发现瓦斯聚集区,对煤矿安全生产具有指导作用.     

新疆那拉提成矿带铜金矿找矿前景分析

通过对那拉提成矿带野外实地资料综合对比研究,阐述了该区区域地质特征、区域地球物理特征、区域地球化学特征和与邻区的关系,得出那拉提成矿带与该构造带上已知铜、金矿床具有非常相似的大地构造环境、构造演化和掘铜（金）建造条件,认为那拉提成矿带仍具有进一步发掘铜（金）矿床的较大潜力。     

Exorcise—an algorithm for detection of spurious values and prediction of missing data

A FORTRAN program is presented which generates a statistical model of broadscale spatially coherent data, and from that model identifies and removes outlying data values. The algorithm also interpolates missing data values by making use of this model, as well as the assumption of broadscale coherence. Examples of the application of this technique to geomagnetic data are presented. A significant improvement in the statistical efficiency and consistency of subsequent estimators is seen to obtain from preprocessing data with this method.     

A review of the New Geophysics：a new understanding of pre-fracturing deformation in the crack-critical crust with implications for hydrocarbon production

The multi-factor recombination and processes superimposition model for hydrocarbon accumulation is put forward in view of the hydrocarbon geological characteristics of multiple episodes of structural evolution, multiple sets of source-reservoir-seal assemblage, multiple cycles of hydrocarbon accumulation and multiple episodes of readjustment and reconstruction in the complex superimposed basins in China. It is a system including theories and methods that can help to predict favorable exploration regions. According to this model, the basic discipline for hydrocarbon generation, evolution and distribution in the superimposed basins can be summarized in multi-factor recombination, processes superimposition, multiple stages of oil filling and latest stage preservation. With the Silurian of the Tarim basin as an example, based on the reconstruction of the evolution history of the four factors （paleo-anticline, source rock, regional cap rock and kinematic equilibrium belt） controlling hydrocarbon accumulation, this model was adopted to predict favorable hydrocarbon accumulation areas and favorable exploration regions following structural destruction in three stages of oil filling, to provide guidance for further exploration ofoil and gas in the Silurian of the Tarim basin.     

Engineering geological and geophysical investigation of the reclaimed Lekki Peninsula, Lagos, South West Nigeria

 It was hoped to develop an area of reclaimed land on the Lekki Peninsula of Lagos State. An investigation was therefore carried out in order to establish the subsurface geological/geo-electrical sequence; to identify the sand columns and determine their thickness and prepare a map of the geomorphological features of the original, pre-fill terrain. Vertical electrical resistivity soundings (VES) and penetrometer tests were carried out in a sand filled segment of the Lekki Peninsula. The information obtained showed a good correlation between the geomorphological features as interpreted from the aerial photographs and those identified from maps derived from the VES/penetrometer results. Received: 28 August 1998 · Accepted: 18 January 1999     

Transition of gap-graded soil fabric – shear wave measurements and dispersion relation

The dynamic response of gap-graded soils is complex; it requires massive experimental and theoretical investigation in order for a sound understanding to be developed. The complexity of the behaviour of such soils arises partially due to the presence of many influential parameters, such as the finer sand/silt content (F_s), size ratio (R_d), and void ratio (e). In this contribution, experiments are conducted on a series of gap-graded soil mixtures, where the coarser sand is mixed with four different finer sands or non-plastic silt with different sizes, namely various R_d, and one well-graded material is also tested. The S-wave velocity (V_s) and low-pass threshold frequency (f_lp) are measured in the isotropic stress state using a triaxial apparatus equipped with planar piezoelectric transducers. The experimental results reveal that, for a given e or relative density (D_r), both f_lp and V_s decrease at a low F_s, but increase at a high F_s. The slope of the linear regression between f_lp and V_s appears to capture this transitional behaviour, depending on F_s and R_d, which can then be used to correlate the physical state of the gap-graded soil fabric. The transitional behaviour is more noticeable at a larger R_d, which is in line with the existing literature. To understand the effect of the R_d on the shear wave propagation at a low F_s, the particle-scale dispersion relation for binary chains is newly introduced and correlated with accompanying experimental observations.