第二届国际地球岩石圈活动的地球物理监测研讨会在俄罗斯举行

简要介绍第二届国际地球岩石圈活动的地球物理监测研讨会的情况。会议于2005年9月12～16日在俄罗斯新西伯利亚市鄂毕河畔的科学城举行,来自6个国家的90多名代表参加了此次国际会议。会议的报告丰富多彩,科学家就地球岩石圈的地球物理活动监测研究进行了多方面的讨论,出版了6个专题的89篇研究论文。俄罗斯、中国、蒙古和哈萨克四国交界区的代表还就研究2003年9月27日发生的7．9级地震草拟了国际合作协议。     

地面扰动重力垂直梯度的确定

鉴于扰动重力垂直梯度在大地测量和物探中有重要作用,在未直接测量的情况下,对如何由地面重力异常及地形数据求取扰动垂直梯度进行了研究和分析,认为在被研点附近要求重力点分布密集,且精度不低于1×10-6ms-2;对中央区域积分奇异性问题也作了讨论;此外,扰动重力垂直梯度如何在大地测量和地球物理中进一步得到应用,以及为何用扰动重力垂直梯度代替重力异常垂直梯度也给予了简明的论述.     

Deep Structure and Dynamics of Passive Continental Margin from Shelf to Ocean of the Northern South China Sea

To study the deep dynamic mechanism leading to the difference in rifting pattern and basin structure from shelf to oceanic basin in passive continental margin,we constructed long geological sections across the shelf,slope and oceanic basin using new seismic data.Integrated gravity-magnetic inversion and interpretation of these sections were made with the advanced dissection method.Results show that the basement composition changes from intermediate-acid intrusive rocks in the sheff to intermediate-basic rocks in the slope.The Moho surface shoals gradually from 31 km in the sheff to 22.5 km in the uplift and then 19 km in the slope and finally to 13 km in the oceanic basin.The crust thickness also decreases gradually from 30 km in the northern fault belt to 9 km in the oceanic basin.The crustal stretching factor increases from the shelf toward the oceanic basin,with the strongest extension under the sags and the oceanic basin.The intensity of mantle upwelling controlled the style of basin structures from sheff to oceanic basin.In the Zhu 1 depression on the shelf,the crust is nearly normal,the brittle and cold upper crust mainly controlled the fault development;so the combinative grabens with single symmetric graben are characteristic.In the slope,the crust thinned with a large stretching factor,affected by the mantle upwelling.The ductile deformation controlled the faults,so there developed an asymmetric complex graben in the Baiyun (白云) sag.     

一种基于神经网络的探地雷达信号解释研究

运用人工神经网络理论和方法,建立了用于隧道衬砌厚度探地雷达探测信号解释的BP神经网络模型,对某公路隧道衬砌检测厚度进行了分析应用,并与钻孔取芯结果进行比较,实践证明,该方法可提高探地雷达信号解释精度和工作效率．     

如何开展老矿山后备资源的寻找与定位预测--工作程序与实例分析

在老矿山的深部与外围寻找新的可用资源,要求勘探者具备新的找矿思路、行之有效的深部探测手段与合理的工作程序、新的找矿思路来自于研究者的相关知识储备和创新能力,使其不墨守成规,用新的视角重新认识矿化规律和控矿要素。进而在老矿区优选出潜在的有利成矿区段．行之有效的深部探测手段以其高分辨的数字图像,不仅可以客观地反映深部地质结构的各种变化及矿化信息,以验证地质推测的可靠性,而且借助属地化的解释模型对矿区深部和外围开展真正意义的矿体定位预测、同时还可以大大降低工程验证的盲目性和巨大浪费．根据我们目前拥有的先进地球物理深部探测手段和大量老矿山找矿的经验与教训,逐渐形成了一套实用的工作程序。     

基于MATLAB的工程物探软件快速开发

针对当前国内工程物探软件开发滞缓的现状,提出基于MATLAB语言快速开发工程软件．分析讨论了其必要性和可行性,详细介绍了MATLAB开发应用程序的基本思路,并给出了工程实例和经验总结．     

浅层地震探测的可控震源信号设计

在工程与环境物探中,浅层地震探测是一种常用的高分辨率物探方法,但是这种方法使用的炸药震源和枪击震源破坏力大,对人和建筑物都有危害,因而被禁止在人口稠密的地区使用．因此,无公害的电磁驱动可控震源技术得到了发展和应用．利用扫描信号压缩技术,小能量弹性波Chirp信号可持续向地下发送,不损害地面和建筑物,对人群也没有影响,是一种较理想的城市浅层地震震源．本文介绍了电磁驱动可控震源的信号设计方法,并简要介绍了具有波束定向能力的相控震源的设计思想．     

大兴安岭原始森林覆盖区化探异常查证方法研究与实践

文章综述了原始森林覆盖区勘查技术方法研究历史、现状及意义.通过对区内某1:20万化探异常进行追踪、查证方法的实验性研究,初步确定适合原始森林覆盖区的物探方法和化探方法.对具有成矿远景的1:20万异常的查证方法、过程为:①1:5万网格法水系沉积物或1:5万土壤测量;②配合以适量的1:1万或1:2万剖面土壤测量,最终达到分解异常、缩小找矿靶区的目的;③1:1万～1:2万地质简测,结合地表工程确定是否为矿致异常,初步确定矿化类型;④选用高精度磁测、双频激电测量方法进行1:2.5万或1:1万的面积性物探测量;⑤运用槽探、坑探、浅井及钻探等探矿手段寻找工业矿体.对二根河、洛古河、阿南林场3个1:20万异常查证证明该方法是适宜森林覆盖景观区的快捷且行之有效的异常查证方法.     

Assessment of Dynamic Characteristics for Compaction Piles with Geophysical Logging in Soft Ground

In this paper, a case study was performed on a sand compaction pile (SCP) and a gravel compaction pile (GCP) to estimate the dynamic characteristics and the improvement effect of soft ground. The dynamic elastic modulus, shear modulus, bulk modulus, and Poisson's ratio were estimated and the dynamic characteristics were analyzed using the compression and shear wave velocity of the improved ground based on the results of suspension P- and S-wave (PS) logging. The results revealed that the dynamic properties were increased in the order of unimproved subsoil and improved subsoil using SCP and GCP. The increase in the effects of dynamic properties with each replacement ratio of SCP was not large, whereas a good increase in the effects was observed in the case of the improved subsoil with GCP. Consequently, it was presented that the resistance characteristics against the seismic loading of GCP are excellent. As a result of analyzing the density distribution of the improved subsoil through density field logging, the overall density distribution gradually exhibits increasing trends in the order of unimproved subsoil and improved subsoil with SCP and GCP. Thus, the improvement effect of GCP was relatively high in comparison with the same replacement ratio of SCP.     

Offshore sand sources for beach replenishment: Potential borrows on the continental shelf of the Eastern Gulf of Mexico

Erosion of sandy beaches is a worldwide problem that elicits innovative geoengineer‐ing techniques to reduce adverse impacts of shoreline retreat. Beach replenishment has emerged as the “soft”; shore‐stabilization technique of choice for mitigating beach erosion. This method of shore protection involves the addition of sand to the littoral sediment budget for sacrificial purposes. Because inland sand sources are often uneconomical or impractical to use, and known nearshore sources are limited, finding adequate quantities of suitable sand on the inner continental shelf is often vital to beach replenishment projects. The technical studies of survey and materials analysis that identify and delineate usable sand sources are sometimes almost as expensive as small‐project dredging, pumping, and placing the sand on the beach as fill. Inadequate quantity or substandard quality of shelf sand, as well as often‐prohibitive overhead expenses, thus compel shoreline managers to seek suitable sand sources offshore.

In the study area off the central‐west coast of Florida, offshore potential borrow areas (PBAs) were identified on the basis of studies conducted in reconnoitory and detailed phases. Sophisticated state‐of‐the‐art equipment used in this investigation provided more detailed subbottom mapping information than is normally obtained with conventional seismic equipment. An example of sand exploration studies was incorporated in a 215‐km² survey of offshore areas by conducting bathymetric surveys and subbottom seismic profiling, collecting jet probes, grab samples, and vibrocores, and analyzing sediment grading in subsamples from vibrocores. These combined analyses indicated that at least 8.8 ×10⁶ m³ of sand is available in potential borrow areas from 7.0 to 12 km offshore in water depths of 8.0 to 11.5 m. In the PBAs, mean grain size of sand falls into the range 0.13–0.53 mm, sorting averages 0.65–1.31ø, and the overall silt content varies from 3.9–8.5%. High silt contents (13–19%) mapped in some areas make these sedimentary deposits unsuitable as fill for artificial beach renourishment.