嘉峪关地磁台墩差测量与仪器比测

墩差测量和仪器比测是地磁观测中最基本的工作，直接影响到观测资料的质量和使用价值。近年的研究结果表明，震磁异常通常为几nT至几十nT。因此，提高观测数据的准确性对地磁预报地震具有深远意义。对嘉峪关地磁台仪器比测和墩差测量的方法及结果作了简要总结，供兄弟台站借鉴（文中所用的比测数据和墩差测量数据是北京台传递的标准结果）。     

地面伽玛能谱在仁差盆地找矿中的应用

在充分研究测区的地质及地球物理特征的基础上。,采用地面伽玛能谱进行勘查,查明了工作区的放射性特征,并划分了三个成矿远景片,充分体现了地面伽玛能谱测量比总量测量的优越性。     

多因素形变异常诊断方法及其动力学来源分析

气温的升降会造成介质的热胀冷缩,含水量的补充蒸发会导致介质的膨胀收缩,在将这两种因素同时考虑的情况下,提出了基于跨断层短基线测量的形变异常诊断方法,并将其实践于唐山地震台4个测段的短基线观测。研究结果表明,基于短基线观测的形变响应比序列在保持总体趋势稳定变化的同时,在不同的时间出现了显著的幅度变化。经过进一步分析,观察到:① 对于同一测段,形变响应比变化与温度-降雨的变换系数γ有关,当γ过小或者过大时,序列会保持稳定,失去观测分析价值;② 形变响应比幅度变化的动力学来源可能是台站周边的地震,而且是台站东北方向50 km以内的M≥4.0地震。对于不同测段,形变响应比幅值变化与地震的相关性有所差异,其中垂直于断层测量方向的两个测段得到的形变相应比与地震的相关性最好,与断层斜交但近乎平行断层走向的测段次之,与断层斜交的测段相关性最差。      

三维地质模型的CSAMT模拟研究

应用CSAMT方法进行标量测量时,一般要求测线沿垂直构造走向的方向布测.在实际测量的时候由于地表条件复杂经常出现无法判断地下构造走向的情况,例如,在长白山地区进行CSAMT测量,由于表面覆盖有玄武岩无法判断地下构造走向,对得到的标量数据进行一维、二维反演处理时无法判断哪种反演方式的结果更准确.鉴于此,建立三维地质模型,应用CSAMT三维正演程序进行数值模拟.研究测线与构造走向平行,呈45°及垂直三种情况下的一维、二维反演,对结果做比较分析.实验结果表明,测线平行构造走向时,一维、二维反演结果近似;测线与构造走向呈45°或垂直时,二维反演结果比一维反演结果对异常体的形状,大小,埋深及电性参数反演的更准确.     

张家口渤海地震带P2000与RAD7型测氡仪野外观测对比实验

针对P2000与RAD7型测氡仪相同测量条件下氡浓度测值存在差异的现象,在张家口渤海地震带野外进行断层气体氡测量对比实验。实验结果表明,钍射气是造成两台测氡仪观测值差异的主要原因。根据钍射气及其子体衰变期,先使用气袋采集断层气体,静置5～10 min后再进行测量,较好的解决了氡浓度测值差异较大的现象。通过断层气体氡的野外测量方法,为两种仪器观测值直接对比提供了可能,也为地震监测技术方法改进提供参考。     

山西定襄七岩泉新旧测氡仪水氡测值稳定性及映震分析

2014年山西定襄七岩泉新增BHC-336智能定标器,对新、旧2套测氡仪的水氡测值,就稳定性、数据一致性、内在质量等进行对比分析,结果显示,因存在系统误差,2台测氡仪水氡测值稳定性均值存在差异,测量精度和性能具有一致性;与新测氡仪相比,旧测氡仪水氡测值相对偏差和均值标准误差更小,精度更高,数据相关程度较高,数据稳定性更好。定襄水氡对华北5级以上地震具有较好的映震能力,新测氡仪对2016年4月7日原平4.6级地震映震效能比旧测氡仪灵敏。     

大连地磁台天文方位角测量

论述大连地磁台天文方位角的测量原理、方法及观测结果,在地磁观测室未封顶的条件下,能在观测墩直接观测北极星,避免比测墩转角换算等因素增加的观测误差,观测精度提高.     

用旋转式磁化率仪和卡帕桥对岩样磁组构的比测

磁化率各向异性(AMS)是岩石的普遍特性,它反映岩石磁性矿物的择优取向,即磁组构(Magnetic fabric).近三十年来,磁组构技术逐渐应用于地质和地球物理学,显示广阔的研究前景.测量磁组构的仪器有多种,原理不一,故有必要用同一样品在不同原理的仪器上进行比测,以便确认数据的一致性和可靠性.用黄土、变质岩、玄武岩及掺有铁粉的断层泥制成正方体或圆柱体样品,在卡帕桥(KLY-1和KLY-2)和旋转式磁化率仪(Minisep)上进行比测发现:(1)前者的精度(即重复性)在多数情况下优于后者;2)用旋转式磁化率仪测量之前,必须先测得样品z轴的体磁化率,其标定值取决于厂家在标准样品上标示的数值及被测样品与标准样品的相对体积.就旋转样品测量AMS而言,其标定值应为z轴体磁化率测量标定值的一半.      

航空重力测量数据的滤波与处理

我国首套航空重力测量系统(CHAGS)于2002年研制成功.本文设计了CHAGS观测数据的滤波处理流程,着重讨论了比力及各项改正的滤波计算方法,提出了'两步滤波法'.基于某航空重力测量实测数据,对测线重力异常的计算精度作了比较和分析,重复测线计算结果表明,CHAGS确定测线重力异常的内符合精度优于±3mGal,相应的波长分辨率为8km;与地面实测数据向上延拓数值比较表明,对于同样的波长分辨率,外部符合精度优于±4mGal.     

流动地磁测量资料的误差分析

用核子旋进式磁力仪在野外进行地磁场总强度测量的流动地磁测量工作已在地震部门许多单位开展多年,取得了不少经验。为获得高精度的测量数据,制定了有关规范,对仪器的标定、比测、野外观测以及资料通化等重要环节作了一系列具体规定,但还存在一些问题,特别对野外测量资料误差的来源、性质、量级等问     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.