激发极化法的“饱和效应”问题

西格尔（H.O.Seigel）从理论计算得到导电颗粒含量为25％的极化球体有最大异常,因此认为:激发极化法只宜于寻找中等浸染程度的矿体,对于含量很高的矿体或良导致密型矿体,激发极化法是不行的。据称这种“饱和效应”的理论得到野外结果的证实。 本文根据我国激发极化法在良导致密型矿体上大都能获得明显视极化率异常的事实,说明西格尔的“饱和效应”理论与事实不符。本文认为良导致密型极化体不存在“饱和效应”问题,激发极化法对它们的勘探也是有效的。可能由于西格尔把低含量理论公式,不计条件地推导到高含量、甚至良导矿体,因此他的结论是错误的。本文最后讨论了电阻率因素对浸染型球体视极化率强度的影响。     

岩石激发极化弛豫时间谱与孔隙结构、渗透率的关系

激发极化衰减曲线包含丰富的地层信息,且由多个指数衰减叠加而成.本文采用奇异值分解法对泥质砂岩的激发极化衰减谱进行多指数反演,得到光滑连续的激发极化弛豫时间谱,合适的弛豫时间分布点数为32～64.激发极化弛豫时间谱能够表征饱和NaCl溶液的岩石孔隙结构.结合孔隙度和弛豫时间几何平均值,能够显著提高渗透率的求取精度.     

地球科学

“大洋一号”环球科考发现16处海底热液区 据报道,我国“大洋一号”科考船圆满完成环球大洋科考,近日返回青岛。此次科考开展了海底多金属硫化物、深海生物基因等多项调查,共发现16处海底热液区,其中在南大西洋发现的一处热液区是目前南大西洋洋中脊发现的最南端热液区。     

海底三宝 未来可期

<正>海洋除了源源不断地为陆地输送水汽,调节着全球的气候,为我们提供大量的渔业资源和水产品外,还为我们提供各种矿产资源,其中就包括三种珍贵的金属矿产:锰结核(也称多金属结核)、富钻结壳和多金属热液硫化物。虽然它们没有很高的颜值,但是随着勘探开发技术的不断进步,这海底三宝会不断融入到人类的工业生产和日常生活中,是服务未来的海底宝藏。     

冲绳海槽现代活动热水区CO_2-烃类流体:流体包裹体证据

冲绳海槽是正在发生着海底热水喷流 (黑烟囱式 )和现代成矿过程的弧后扩张盆地 .JADE热水区热液补给带水 岩反应产物中的流体包裹体研究表明 ,海底深部热流体系极度富气 ,并存在两类相对独立、密切共生的CO2 烃类流体和盐水流体 .CO2 烃类流体包裹体成分总体上与天然气田的流体包裹体成分相当 .盐水流体包裹体以H2 O为主 ,CO2 和CH4呈过饱和状态 .盐水流体在海底呈黑烟囱流体喷射 ,CO2 流体在海底呈CO2 气泡排泄 ,并形成CO2 水合物 ,烃类气体或流体可能被局部封存 .CO2 CH4 H2 S气体或流体的大量存储及其与盐水流体的反应效应导致金属硫化物工业堆积 .     

太湖五里湖区表层沉积物中酸挥发性硫化物和同步提取金属

湖泊底泥中的酸溶硫化物易与二价金属生成难溶金属硫化物,从而制约沉积物中二价有毒金属的化学活性以及生物有效性,进而影响沉积物的环境质量.对沉积物中的酸溶硫化物(AVS)和同步提取金属(SEM)进行测定,依据SEM/AVS的比值可以判定重金属生物有效性.通过对太湖五里湖、梅梁湾表层沉积物夏季和秋季AVS与SEM的采样分析,结果表明:研究区域内AVS的含量夏季高于秋季,SEM受季节影响很小,SEM/AVS大于1,且秋季高于夏季,初步判断该湖区沉积物中重金属具有潜在的生物毒性.     

激发极化法在西刚果造山带尼阿里裂谷盆地铜多金属矿勘查中的应用

金属矿床通常品位较低,极少产生电阻率异常,但部分金属矿,尤其是金属硫化物矿床,会产生明显的极化率异常。利用已有露头和岩芯样本,对西刚果造山带尼阿里裂谷盆地铜多金属矿围岩、铜矿化岩石等进行极化率和电阻率测定,分析认为研究区铜矿石具有中阻高极化特征。利用在西刚果造山带尼阿里裂谷盆地进行的激化极化法中梯装置扫面工作,获得视极化率和视电阻率平面图,结合当地地质和钻探资料,对铜矿床成矿远景区进行推断解释。钻探结果显示,在Mankala区块T₅异常70—90 m深度发现了延伸长度400 m、宽度100 m的原生辉铜矿床,铜品位为3%—6%。     

江西省大湖塘石门寺矿区超大型钨矿的发现及找矿意义

江西省武宁县大湖塘石门寺超大型钨矿的成功勘查是我国地质找矿工作的重大发现。矿化类型划分为细脉浸染型、隐爆角砾岩型和石英大脉型。前者占总储量的74％,该类型以晋宁晚期黑云母花岗闪长岩为容矿围岩,以燕山中期酸性深成至浅成花岗岩为成矿母岩。矿体厚大且产状平缓,大致平行于黑云母花岗闪长岩与似斑状黑云母花岗岩株顶部的接触面分布,以外接触带为主（I1矿体）,水平投影面积1．50km2,单工程最大厚度389．33m,平均厚度143．67m,平均品位0．193％,厚度变化系数63．7％,品位变化系数115．8％。工业矿物主要为白钨矿、黑钨矿、黄铜矿、辉钼矿。矿石组构类型主要有结晶结构、交代结构、细脉状构造、浸染状构造,常见近矿围岩蚀变为黑鳞云母化、云英岩化、绿泥石化,成因类型属岩浆期后高中温热液矿床,工业类型可划归为细脉浸染型白钨矿。石门寺矿区以黑云母花岗闪长岩为容矿围岩的细脉浸染状白钨的发现,改变了以往只专注评价石英大脉型黑钨矿的找矿思路,为矿区及九岭矿集区实现钨多金属找矿突破指明了新的方向。     

希尔伯特-黄变换在海底大地电磁测深数据处理中的应用

海水运动产生的电磁场,是海底大地电磁探测数据中的主要噪声之一,影响了数据处理与解释的精度.为提高海底MT探测的应用效果,本文在海底MT信号处理中引入HHT时频分析方法.结合海底MT噪声的特点与海底MT信号的特性,对南海实测数据进行分析,通过对比去噪前后信号的Hilbert时-频谱和边际谱,表明利用经验模态分解及其多尺度滤波特性,能够有效压制海水运动产生的电磁噪声.经HHT去噪后的测深曲线在一定程度上有所改善,仍存在"飞点"现象;再结合Robust估计,明显改善海底大地电磁探测数据质量,得到满意的观测结果.     

不含金属矿物的饱和多孔介质激发极化机理与模型综述

实验室研究发现不含金属矿物的饱和多孔介质激发极化参数受岩石物理特性影响,建立岩心尺度的低频(<10⁶ Hz)复电导率与孔隙结构参数、流体属性等因素之间的定量关系对解释激发极化数据具有重要指导意义.然而,产生激发极化效应的原因还未形成统一的物理/化学过程认识,现有理论未能完全解释激发极化数据,激电参数与多孔介质结构参数之间的定量关系缺少深入的机理研究.为此,本文首先阐述了双电层理论和用以解释激发极化效应的机理,包括Stern层极化、膜极化、Maxwell-Wagner极化和动电效应等;其次,总结了现有激发极化模型研究的最新进展,包括等效电路模型、Stern层极化模型、膜极化模型、等效介质模型等.综述表明：(1)低频激发极化效应的微观机理仍未达成统一认知,在特定条件下,膜极化模型与Stern层极化模型都能解释低频激发极化数据;(2)特征弛豫时间受孔径或粒径控制仍存在争议.     

基于解析时间波场外推与波场分解的逆时偏移方法研究

双程波方程逆时深度偏移是复杂介质高精度成像的有效技术,但其结果中通常包含成像方法引起的噪音和假象,一般的滤波方法会破坏成像剖面上的振幅,其中的假象也会给后续地质解释带来困扰.将波场进行方向分解然后实现入射波与反射波的相关成像能够有效地消除这类成像噪音,并提高逆时偏移成像质量.波传播方向的分解通常在频率波数域实现,它会占用大量的存储和计算资源,不便于在沿时间外推的逆时深度偏移中应用.本文提出解析时间波场外推方法,可以在时间外推的每个时间片上实现波传播方向的显式分解,逆时深度偏移中利用分解后的炮检波场进行对应的相关运算,实现成像噪音和成像信号的分离.在模型和实际数据上的测试表明,相比于常规互相关逆时偏移成像结果,本文方法能够有效地消除低频成像噪音和特殊地质构造导致的成像假象.     

Common-reflection-point time migration

Since the early days of seismic processing, time migration has proven to be a valuable tool for a number of imaging purposes. Main motivations for its widespread use include robustness with respect to velocity errors, as well as fast turnaround and low computation costs. In areas of complex geology, in which it has well-known limitations, time migration can still be of value by providing first images and also attributes, which can be of much help in further, more comprehensive depth migration. Time migration is a very close process to common-midpoint (CMP) stacking and, more recently, to zero-offset commonreflection- surface (CRS) stacking. In fact, Kirchhoff time migration operators can be readily formulated in terms of CRS parameters. In the nineties, several studies have shown advantages in the use of common-reflection-point (CRP) traveltimes to replace conventional CMP traveltimes for a number of stacking and migration purposes. In this paper, we follow that trend and introduce a Kirchhoff-type prestack time migration and velocity analysis algorithm, referred to as CRP time migration. The algorithm is based on a CRP operator together with optimal apertures, both computed with the help of CRS parameters. A field-data example indicates the potential of the proposed technique.     

How are storm time injections different from nonstorm time injections?

One of the key elements of storms and substorms is the injection of energetic particles into the region of near geosynchronous orbit, that is, the sudden flux enhancement in the energy range of tens to hundreds of keV. This paper reports the observational results on how such injection features during storm times are different from those of nonstorm times. We particularly focus on the difference between proton injections and electron injections. Based on a number of storm time injection events that meet our strict selection criteria, we find a notable difference between proton injections and electron injections in the energy-spectral dependence of the flux enhancement averaged over the first 30 min after the injection onset: The average flux enhancement of many protons injections tends to be bigger at higher energy channels than at lower energy channels, but electron injections exhibit the opposite tendency for the energy-spectral dependence of flux enhancement, i.e., average flux enhancement decreasing with increasing energy. We show that this feature is almost unique only for the injection events during the storm main and early recovery phase. It is suggested that any successful scenario intended to model storm time injections should be able to explain this difference between proton injections and electron injections.     

鄱阳湖换水周期与示踪剂传输时间特征的数值模拟

在复杂湖泊水动力环境作用下,换水周期和传输时间变化直接影响着污染物的迁移和转化.本文运用数值模拟方法,定量研究了季节水情动态下鄱阳湖换水周期和示踪剂传输时间的空间分布.结果表明,不同季节下鄱阳湖换水周期均具有较高的空间异质性,贯穿整个湖区的主河道换水周期约10 d,大多湖湾区的换水周期则长达300多天.尽管不同季节下换水周期空间分布格局几乎相似,但受鄱阳湖水动力场的季节变化影响,夏、秋季的换水周期要明显大于春、冬季.基于换水周期频率分布曲线的统计表明,80%的鄱阳湖区的换水周期约30 d,其余湖区换水周期为几十天至几百天,表明鄱阳湖应该更加确切地描述为一个快速换水和慢速换水同时共存的湖泊系统.鄱阳湖示踪剂传输时间介于4~32 d,夏、秋季的传输时间(11~32 d)约为春、冬季(4~8 d)的4倍,主要与鄱阳湖季节性水情特征及示踪剂的迁移路径有关.本文所获取的换水周期和示踪剂传输时间的时空分布信息可为今后鄱阳湖水质、水环境和生态系统管理和维护等方面提供重要科学参考.     

The arrow of time

Why does time apparently fly one way, when the laws of physics are actually time-symmetrical? Paul Davies proposes a quantum solution, in the Whitrow Lecture 2004, given on 8 October 2004.     

实时测量桥梁挠度

本文介绍了一种实时测量桥梁挠度的方法。大量的实验分析数据表明：采用QY型倾角仪测量得到的桥梁挠度时程曲线有很高的精度，从而为桥梁的安全性评价和工程验收提供了可靠的依据。该方法真正实现了桥梁挠度的动态测量，避免了传统静态测量方法必须采取的封桥措施，提高了检测效率，工程应用前景广阔。     

Streamflow drought time series forecasting

Drought is considered to be an extreme climatic event causing significant damage both in the natural environment and in human lives. Due to the important role of drought forecasting in water resources planning and management and the stochastic behavior of drought, a multiplicative seasonal autoregressive integrated moving average (SARIMA) model is applied to the monthly streamflow forecasting of the Zayandehrud River in western Isfahan province, Iran. After forecasting 12 leading month streamflow, four drought thresholds including streamflow mean, monthly streamflow mean, 2-, 5-, 10- and 20-year return period monthly drought and standardized streamflow index were chosen. Both observed and forecasted streamflow showed a drought period with different severity in the lead-time. This study also demonstrates the usefulness of SARIMA models in forecasting, water resources planning and management.     

日本地震学已到变革之时

罗伯特.盖勒(Robert J Geller)呼吁日本停止使用有缺陷的方法进行地震长期预测,并废弃试图预测"东海地震"的系统。在过去的20年左右时间,日本一些地震学家曾警告过地震和海啸对核电厂安全的危害,尤其是日本神户大学荣誉教授石桥克     

Errors in time delay measurements

Summary Simple delay and sum of sensors in a seismic array is an effective method for noise suppression. However, unless we have precise steering delays, much of the signal energy is lost during the beam forming process too. We have investigated possible error sources in time delay measurements, using a computerized cross-correlation procedure. Parameters perturbed are correlation window length and positioning, signal frequency content and signal to noise ratio (SNR). Our results indicate that relative low frequency waves and using the very first part of theP-signals give the most reliable and stable time delay values. High frequency bandpass filtering improves SNR, but signal correlation and the precision in beam steering corrections decrease. Significant loss of high frequency energy during beamforming seems to be unavoidable.