一种地下瞬变电磁法场值曲线的解释方法

均匀大地表面上大回线源在地下形成的瞬变电磁场解析计算式很复杂,无法用常规方法定义其视电阻率,而场值曲线本身分辨率低,进行分层解释困难。对大回线源在地下形成的瞬变电磁场场值,用由第一层介质充满半无限大地时的场值进行归一化的方法进行解释,经理论计算表明,与地面装置条件下的电阻率曲线进行解释有异曲同工之妙     

A new magnetic map of the Weddell Sea and the Antarctic Peninsula

As part of the Antarctic Digital Magnetic Mapping Project (ADMAP) workers from VNIIOkeangeologia (Russia), the British Antarctic Survey (UK) and the Naval Research Laboratory (USA) have brought together almost all of the available magnetic data in the area 0–120°W, 60–90°S. The final map covers the whole Weddell Sea and adjacent land areas, the Antarctic Peninsula and the seas to the west, an area comparable in size with that of the USA. This paper describes the methods used during the compilation of the map and reviews briefly some of the main features shown on it. Distinct magnetic provinces are associated with Precambrian rocks of the East Antarctic craton, highly extended continental crust in the Weddell Sea embayment, the arc batholith of the Antarctic Peninsula, and oceanic crust of the northern Weddell Sea, which was created as a direct consequence of South America–Antarctica plate motion and oceanic crust generated at the Pacific–Antarctic ridge. The magnetic anomaly map thus provides an overview of the fragmentation of south-western Gondwana and the tectonic development of the Weddell Sea sector of Antarctica.     

应用多波段合成图像圈定地热异常的初步探索

本文根据地热异常引起的植被效应模式,确定了多波段合成图像地热异常的解译标志,并进行了地面波谱测试及红外辐射测温工作,从遥感基本原理上论证了解译标志的可靠性。圈定的地热遥感异常,已得到证实,应用这一解译标志指导关中地区寻找地热取得了一定的效果     

惠安埔塘—青山断裂的活动特征

本文从构造，地貌和第四纪沉积学等研究了福建惠安埔－青山断裂活动特征，结果表明，该断裂的断层面具有新鲜擦痕，破劈理，有未固结的断层泥，角砾岩，断层两侧地貌面差异变形，有断层陡崖，三角面和跌水与瀑布；第四纪沉积层受构造扰动，发生拖曳和变形，经＾１４Ｃ年代测定认为，该断裂最新活动年代介于４２０００－２４０００ａ，Ｂ．Ｐ．间，断裂活动性质为兼具右旋水平错动的正断层（张扭性），平均垂直活动速率为２．１ｍｍ／     

Interpretation of landslide distribution triggered by the 2005 Northern Pakistan earthquake using SPOT 5 imagery

The 2005 northern Pakistan earthquake (magnitude 7.6) of 8 October 2005 occurred in the northwestern part of the Himalayas. We interpreted landslides triggered by the earthquake using black-and-white 2.5-m-resolution System Pour l’Observation de la Terre 5 (SPOT 5) stereo images. As a result, the counts of 2,424 landslides were identified in the study area of 55 by 51 km. About 79% or 1,925 of the landslides were small (less than 0.5 ha in area), whereas 207 of the landslides (about 9%) were large (1 ha and more in area). Judging from our field survey, most of the small landslides are shallow rock falls and slides. However, the resolution and whitish image in the photos prevented interpreting the movement type and geomorphologic features of the landslide sites in detail. It is known that this earthquake took place along preexisting active reverse faults. The landslide distribution was mapped and superimposed on the crustal deformation detected by the environmental satellite/synthetic aperture radar (SAR) data, active faults map, geological map, and shuttle radar topography mission data. The landslide distribution showed the following characteristics: (1) Most of the landslides occurred on the hanging-wall side of the Balakot–Garhi fault; (2) greater than one third of the landslides occurred within 1 km from the active fault; (3) the greatest number of landslides (1,147 counts), landslide density (3.2 counts/km²), and landslide area ratio (2.3 ha/km²) was found within Miocene sandstone and siltstone, Precambrian schist and quartzite, and Eocene and Paleocene limestone and shale, respectively; (4) there was a slight trend that large landslides occurred on vertically convex slopes rather than on concave slopes; furthermore, large landslides occurred on steeper (30° and more) slopes than on gentler slopes; (5) many large landslides occurred on slopes facing S and SW directions, which is consistent with SAR-detected horizontal dominant direction of crustal deformation on the hanging wall.     

A genetic algorithm for filter design to enhance features in seismic images

We present a novel method to enhance seismic data for manual and automatic interpretation. We use a genetic algorithm to optimize a kernel that, when convolved with the seismic image, appears to enhance the internal characteristics of salt bodies and the sub‐salt stratigraphy. The performance of the genetic algorithm was validated by the use of test images prior to its application on the seismic data. We present the evolution of the resulting kernel and its convolved image. This image was analysed by a seismic interpreter, highlighting possible advantages over the original one. The effects of the kernel were also subject to an automatic interpretation technique based on principal component analysis. Statistical comparison of these results with those from the original image, by means of the Mann‐Whitney U‐test, proved the convolved image to be more appropriate for automatic interpretation.     

Avoidable Euler Errors – the use and abuse of Euler deconvolution applied to potential fields

Window‐based Euler deconvolution is commonly applied to magnetic and sometimes to gravity interpretation problems. For the deconvolution to be geologically meaningful, care must be taken to choose parameters properly. The following proposed process design rules are based partly on mathematical analysis and partly on experience.

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Relating electrical conduction of alluvial sediments to textural properties and pore‐fluid conductivity

Electrical conductivity of alluvial sediments depends on litho‐textural properties, fluid saturation and porewater conductivity. Therefore, for hydrostratigraphic applications of direct current resistivity methods in porous sedimentary aquifers, it can be useful to characterize the prevailing mechanisms of electrical conduction (electrolytic or shale conduction) according to the litho‐textural properties and to the porewater characteristics. An experimental device and a measurement protocol were developed and applied to collect data on eight samples of alluvial sediments from the Po plain (Northern Italy), characterized by different grain‐size distribution, and fully saturated with porewater of variable conductivity. The bulk electrical conductivities obtained with the laboratory tests were interpreted with a classical two‐component model, which requires the identification of the intrinsic conductivity of clay particles and the effective porosity for each sample, and with a three‐component model. The latter is based on the two endmember mechanisms, surface and electrolytic conduction, but takes into account also the interaction between dissolved ions in the pores and the fluid‐grain interface. The experimental data and their interpretation with the phenomenological models show that the volumetric ratio between coarse and fine grains is a simple but effective parameter to determine the electrical behaviour of clastic hydrofacies at the scale of the representative elementary volume.     

时移地震流动单元解释的分析与实现

时移地震又称四维地震,是近些年发展起来的前沿物探技术。本文分析了时移地震中用到的关键技术;给出了其流动单元的概念和具体定义流动单元的数据结构;重点阐述了在剖面或切片上解释流动单元时增加解释点的实现方法。通过一个具体的实例数据展示了处理效果。     

鄂尔多斯盆地黄土覆盖区TM图象的地层解译

在基岩裸露区进行地层解译是比较方便的,但在黄土高原区,尤其是当其还受到林木覆盖时,地层的解译就有一定的难度,问题在于所有基岩的直接解译标志都会被掩盖或受到干扰。在这种情况下,建立间接解译标志就显得十分重要。这些标志包括河道的宽窄变化,曲流强度,色彩差异以及纹形图案等。它们是由岩石成分结构所决定的物理性质、化学组成以及由此派生的波谱特征的外在表现,因而其解译结果是可靠的。