一种优化地震前兆观测点布设的方法

使用基于主成分分析的优化地震前兆观测点方法, 用1998年数据对上海地区的9个水氡观测台站进行优化。 结果表明, 可以撤消3个信息量较小的台站观测, 剩下的6个台所含信息量占全部9个台站信息量的比例为93.0%。 表明在地震前兆观测中, 如果局部地区的地震前兆观测台站数据具有一定的相关性, 那么即使大量增加前兆观测台站的数量, 也并不意味着所获取的信息量会同步增多。 文中所用的优化方法对于指导地震前兆观测台站的优化具有一定意义。     

一种新地震定位方法研究

提高地震定位精度一直是地震学应用研究的重要课题之一,目前已经发展了多种方法用于台网定位。这些方法的共同弱点是应对复杂情况的能力差、震后处理时间过长、不能根据地震信息的增加自动修改速度模型而提高下一次地震定位的精度。开发地震台网资源,使之实现地震预警的功能,必须解决地震快速定位问题。为此,本文提出了一种基于地震台网资料的网格化地震定位方法。震前建立每个区间网格到台站的理论走时数据库,震时仅通过优化搜索,以每两个台站的到时差与理论走时差之间的方差最小的网格位置为震源,并得到发震时刻。通过在黑龙江省地震台网的实际应用说明方法可靠,精度较高。     

A modified multiple tension upward infiltration method to estimate the soil hydraulic properties

Determination of saturated hydraulic conductivity, K_s, and the shape parameters α and n of the water retention curve, θ(h), is of paramount importance to characterize the water flow in the vadose zone. This work presents a modified upward infiltration method to estimate K_s, α and n from numerical inverse analysis of the measured cumulative upward infiltration (CUI) at multiple constant tension lower boundary conditions. Using the HYDRUS‐2D software, a theoretical analysis on a synthetic loam soil under different soil tensions (0, 0–10, 0–50 and 0–100 cm), with and without an overpressure step of 10 cm high from the top boundary condition at the end of the upward infiltration process, was performed to check the uniqueness and the accuracy of the solutions. Using a tension sorptivimeter device, the method was validated in a laboratory experiment on five different soils: a coarse and a fine sand, and a 1‐mm sieved loam, clay loam and silt‐gypseous soils. The estimated α and n parameters were compared to the corresponding values measured with the TDR‐pressure cell method. The theoretical analysis demonstrates that K_s and θ(h) can be simultaneously estimated from measured upward cumulative infiltration when high (>50 cm) soil tensions are initially applied at the lower boundary. Alternatively, satisfactory results can be also obtained when medium tensions (<50 cm) and the K_s calculated from the overpressure step at the end of the experiment are considered. A consistent relationship was found between the α (R² = 0.86, p < 0.02) and n (R² = 0.97, p < 0.001) values measured with the TDR‐pressure cell and the corresponding values estimated with the tension sorptivimeter. The error between the α (in logarithm scale) and n values estimated with the inverse analysis and the corresponding values measured with pressure chamber were 3.1 and 6.1%, respectively. Copyright © 2016 John Wiley & Sons, Ltd.     

MSDP单纯型和HYP2000定位方法对比分析

采用MSDP单纯型方法和HYP2000定位方法,对宁夏地区2008-2010年发生的232次ML≥2.0地震和83个爆破资料,从地震震中、震源深度、残差分布3方面进行对比分析.结果显示,采用HYP2000定位方法,震源距断裂带更近,小震群更为集中;震源深度的分布更为符合实际;残差分布明显小于MSDP单纯型定位法.由此建...     

A rapid method for simulating three-dimensional fluvial terrain

A rapid, computer-based method of simulating ‘geomorphologically-sensible’ three-dimensional terrain data by modelling landform morphology is presented. For some engineering applications such an approach, even in a simple form, is preferable to the synthesis of terrain data by purely stochastic methods, and additionally can be useful where real data sets are difficult to obtain. The approach adopted utilizes a computer program which models landscape evolution by establishing a stream network on a tilted surface, with accompanying fluvial downcutting and slope adjustment. This is achieved by an iterative mechanism that combines deterministic and stochastic processes with geomorphological theory. The end-product is a matrix of high-resolution altitude data that has been used as the terrain model for a vehicle simulation exercise.     

提高地震定位精度新方法的研究

根据现有台网的分布密度、仪器配置的状况和目前震相判读精度提出了一些新的措施来提高地震定位的效率和精度。主要思想有采用“全局搜索和单纯形综和求解法”求解方程的极值，计算中考虑地球曲率，并做椭球校正。采用“翻台法”来改善目标函数、实现“目标函数拉伸”的思想、控制解域和自行调整发震时刻提高求解的稳定性和精度。采用“模拟退火法”的物理性质来控制试错解的跨越长度，提高求解效率和解的分辨精度。采用区域走时表加台站校正值的思想来减小速度模型的复杂性。采用ＰＴＤ方法和ｓＰｎ－Ｐｎ方法来求震源深度。在地震定位过程中显示地图经纬度，同步演示定位过程及结果。同时还在屏幕上显示传统的交切结果以帮助分析人员判定定位结果的可靠性。区域走时表采用地壳曲面模型，允许模型带有低速层，各层具有梯度，且不限层数，自动使用台站校正值并给出定位误差。根据上述思想和不同的需要分别编制了地方、区域台网定位程序，全国、全球地震定位程序，极远震定位程序用于速报和专门用于研究的地震定位程序。这些程序还带有求震源深度和震级的功能。对于专门进行地震定位研究的工作，还提供了绘制地震定位误差二维等值线图和三维误差分布图的功能。     

A rapid field method for detecting oil in sediments

A rapid thin-layer chromatographic technique for estimating the relative concentration of crude oil in sediments has been developed. The limit of detection on the chromatogram is 2 μg of Empire Mix or Saudi Arabian crude oil. The technique has been tested on 335 sediment samples collected from 67 stations in the Gulf of Mexico and has been utilized in assessing the location of oil entering the sediments from the Argo Merchant spill incident.     

A rapid method for hydraulic profiling in unconsolidated formations

Information on vertical variations in hydraulic conductivity ( K ) can often shed much light on how a contaminant will move in the subsurface. The direct-push injection logger has been developed to rapidly obtain such information in shallow unconsolidated settings. This small-diameter tool consists of a short screen located just behind a drive point. The tool is advanced into the subsurface while water is injected through the screen to keep it clear. Upon reaching a depth at which information about K is desired, advancement ceases and the injection rate and pressure are measured on the land surface. The rate and pressure values are used in a ratio that serves as a proxy for K . A vertical profile of this ratio can be transformed into a K profile through regressions with K estimates determined using other techniques. The viability of the approach was assessed at an extensively studied field site in eastern Germany. The assessment demonstrated that this tool can rapidly identify zones that may serve as conduits for or barriers to contaminant movement.     

随机方法在地震烈度速报中的应用

我国地震监测台网间距大,很难实现大震发生时地震烈度分布图的快速编制.基于随机方法,利用历史小震数据反演地震动估计模型的参数,参考地震发生时获取的少量强震动数据,选取合适的震源参数,正演地震动场的分布.根据地震烈度与地震动参数的经验关系,实现地震烈度速报.本方法可以模拟大震的近断层地震动特征,对高烈度区的判断较目前常用的烈度速报方法更为合理.研究成果既可以用于首张烈度分布图的发布,还能够用于地震烈度的动态修正.     

A simple and rapid method to relate land cover and river flow rate to river nutrient concentration

The quantification of diffuse input loads of nutrients to rivers is a challenge due to limited observed data. This study aimed to develop a simple model that can relate in-stream nutrient concentrations due to diffuse sources with land cover categories within a catchment affecting a river reach. A previously developed point-diffuse model was used to distinguish the diffuse nutrient signature within South African Department of Water Affairs historical monitoring flow and water quality data for selected river gauges. The diffuse signature was related to land cover categories within respective catchments using Principal Component Analysis (PCA), and influential land cover categories were used to construct land cover models relating land cover categories with in-stream nutrient concentrations. Generally, the land cover categories affecting diffuse signatures of nutrients as indicated by PCA were expected. Using land cover information, the developed land cover models performed well in re-creating the diffuse in-stream nutrient signature as determined by the point-diffuse model.     

改善瀑布沟水库数字地震台网定位精度的办法

利用2006年12月至2007年2月共3个月瀑布沟水库数字地震遥测台网资料,与四川省地震台网的资料用同一定位方法(LOC91)进行对比;后又将四川省地震台网的一些子台资料加入水库台网中,再用LOC91进行定位。经过对比,四川区域台网资料和瀑布沟水库数字地震遥测台网的资料,对该网内地震的定位精度较高,而网缘外的地震若只用水库台网的资料定位则不尽然。瀑布沟水库数字台网一期工程各台的台间距小(台间距约5千米),对网外地震,在定位时张角就拉不开,有时仅有四分之一的张角(甚至更小),因此定位精度不高。若把四川省区域台网的一些子台加入水库台网地震观测资料中,台站基本上"包围"地震,则定位精度就可得到提高。     

利用煤体破裂电磁信号进行局部震源定位方法研究

准确预测煤岩破裂震源方位,确定采掘工作面重点灾害区域,可以使煤岩动力灾害防治措施更为有效.根据煤岩变形破裂电磁效应规律和电磁波基础理论,提出了一种利用电磁信号能量来确定局部震源方位的方法,并通过实验室定向接收实验和平煤十矿现场测试验证该方法的有效性.结果表明,电磁信号强度随着煤岩体应力状态变化而变化;两个正交天线接收的电磁信号能量分别与各自接收夹角余弦值的平方成正比,利用此比例关系可以确定震源的方位;电磁信号定位方法与静态指标法预测局部区域危险性具有较好的检验一致性.研究成果为煤岩动力灾害重点灾害区域的判定提供依据.     

A method for rapid evaluation of magnetic anomalies over thin sheets

A method for rapid evaluation of magnetic anomalies over thin sheets is presented. This method is based on characteristic distancesX _3/4,X _1/2,X _1/4 at which the anomaly falls off to 3/4, 1/2, and 1/4 of the total (peak to peak) amplitude, respectively. Simple mathematical relations using these characteristic distances are presented to estimate the death and dip of the sheet. This method is fast and does not require prior knowledge of the base level and the origin. A few field examples are included to show the applicability and efficacy of the method.     

Difference infiltrometer: a method to measure temporally variable infiltration rates during rainstorms

We developed a difference infiltrometer to measure time series of non‐steady infiltration rates during rainstorms at the point scale. The infiltrometer uses two, tipping bucket rain gages. One gage measures rainfall onto, and the other measures runoff from, a small circular plot about 0.5‐m in diameter. The small size allows the infiltration rate to be computed as the difference of the cumulative rainfall and cumulative runoff without having to route water through a large plot. Difference infiltrometers were deployed in an area burned by the 2010 Fourmile Canyon Fire near Boulder, Colorado, USA, and data were collected during the summer of 2011. The difference infiltrometer demonstrated the capability to capture different magnitudes of infiltration rates and temporal variability associated with convective (high intensity, short duration) and cyclonic (low intensity, long duration) rainstorms. Data from the difference infiltrometer were used to estimate saturated hydraulic conductivity of soil affected by the heat from a wildfire. The difference infiltrometer is portable and can be deployed in rugged, steep terrain and does not require the transport of water, as many rainfall simulators require, because it uses natural rainfall. It can be used to assess infiltration models, determine runoff coefficients, identify rainfall depth or rainfall intensity thresholds to initiate runoff, estimate parameters for infiltration models, and compare remediation treatments on disturbed landscapes. The difference infiltrometer can be linked with other types of soil monitoring equipment in long‐term studies for detecting temporal and spatial variability at multiple time scales and in nested designs where it can be linked to hillslope and basin‐scale runoff responses. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

中国地震观测台网地震速报定位偏差的分析

介绍并分析了中国地震速报台网目前地震速报定位的现状、存在的问题及原因,并利用1990～1997年的速报定位资料,统计分析了中国地震速报台网测定地震震中位置的偏差、产生偏差的原因,并提出了相应的改进意见。     

Comparison of infiltration models with regard to design of rectangular infiltration trenches

ABSTRACT

Guidelines for the design of infiltration trenches of rectangular cross-section are compared. Four concepts of infiltration into a native soil from linear soakaways of rectangular cross-section are discussed. The results of calculations using analytical equations are compared with numerical two-dimensional (2D) simulations using HYDRUS computer code and field measurements. Satisfactory agreement is achieved for Kozeny’s concept of infiltration and the free-surface approach, applied to a trench in a highly saturated sandy loam. Theoretical solutions, neglecting matric potential, suggest that the mean infiltration rate along the wetted perimeter of a rectangular trench varies in the range 1.0 to 1.5 of the value of saturated hydraulic conductivity.     

A new baseflow separation method based on analytical solutions of the Horton infiltration capacity curve

The separation of baseflow is an important issue in hydrology. The objective of this paper is to develop a new baseflow separation method based on the Horton infiltration capacity curve. For this purpose, the mathematical expressions of three parameters for the Horton infiltration capacity curve were derived in terms of rainfall and runoff data, and the lag time of the effective rainfall in the unsaturated zone and the groundwater flow routing equation are also presented. With these equations, the baseflow hydrographs at the outlet of the basin can be separated. The flow chart of the proposed method for baseflow hydrograph separation is given. Three recent baseflow separation methods, i.e. digital filter, non‐linear reservoir and the Boussinesq equation, were chosen as parallel schemes to compare with the proposed method. Rainfall‐runoff data from four watersheds located in different climatic regions in China were selected and used as case studies. Test and application results indicate that the proposed baseflow hydrograph separation method is in accordance with the hydrological physical process. The proposed method is comparable with current available methods and reduces some of the subjective aspects for the rising limb of the baseflow hydrograph, and it is useful for unit hydrograph analysis and for the study of the rainfall‐runoff relationship. Copyright © 2006 John Wiley & Sons, Ltd.     

A rapid seismic safety assessment method for mid-rise reinforced concrete buildings

The majority of existing buildings are not safe against earthquakes in most of the developing countries. Existing building stocks should be assessed with a seismic safety assessment method before a devastating earthquake. Cheaper and quicker rapid seismic safety assessment methods can be used instead of code-based assessment methods to determine the seismic performance of existing buildings. In this study, an approach was introduced to determine the seismic performance of existing mid-rise reinforced concrete buildings with fewer parameters and process steps than code-based detailed assessment procedures. Calibration and regulation of the introduced method were conducted on the 39 collapsed buildings’ projects in 1999 Kocaeli, Turkey, earthquake. Finally, 55 existing buildings located in Eskisehir, Turkey, assessed with this calibrated method and the results were compared with the results of a code-based detailed assessment method; the results showed a very good agreement of about 83%. This study shows that the proposed method can be applied for the determination of the seismic performance of existing mid-rise reinforced concrete buildings quickly and without compromising reliability.     

Toxic cyanobacteria at Nakuru sewage oxidation ponds - A potential threat to wildlife

Phytoplankton composition and biomass, and microcystin content were determined on diverse dates between November 2001 and June 2006 in the final oxidation pond of the Nakuru town sewage treatment plant. The oxidation ponds as well as the rivulet that drains the same are important water sources for some wildlife in the park. The phytoplankton composition of the pond studied mostly comprised coccoid green alga species. However, occasionally cyanobacteria or euglenoids were dominant. Among the cyanobacteria, Microcystis sp. made periodic appearance in the phytoplankton, and was the dominant species on some occasions. Total phytoplankton biomass varied widely from 48 to 135 mg L⁻¹ (wet weight) while cyanobacteria biomass ranged from undetectable levels to 130 mg L⁻¹. Most phytoplankton biomass was due to one or a few species. Detectable cyanotoxin concentrations (sum of microcystins) of up to 551.08 μg mg⁻¹ dry weight (DW) of cyanobacteria biomass or 0.28 μg mg⁻¹ DW of total phytoplankton biomass were recorded in samples collected on different dates. Microcystin content did not appear to correspond to the biomass of cyanobacteria suggesting that toxin production is possibly triggered by environmental changes or changes in the proportion of toxic strains. An occasional presence of microcystins in the pond water suggests that the wildlife species, which regularly use the ponds as drinking water sources are potentially exposed to intoxication. A close monitoring of pond water phytoplankton composition is necessary to accurately quantify the potential impact of cyanotoxins on these wildlife species.     

国家地震速报备份系统定位结果评估

国家地震速报备份系统的自动实时处理系统能够在地震发生后几分钟之内自动确定出地震的3要素.分析2009年1月～2010年10月的自动定位结果后发现,282个4级以上地震的自动定位结果与中国地震台网中心(CENC)的人机交互速报结果(CC)匹配;70％的地震震级误差≤0.3;69％的国内及周边地区地震的震源水平位置定位误差≤20km,73％的国外地震的震源水平位置定位误差≤50km;国内及周边地区地震的平均速报时间为3.5min,国外地震平均为11.1min,该系统速报速度明显高于人机交互速报速度.全球6级以上地震中有284个的定位结果与欧洲-地中海地震学中心(EMSC)的实时定位结果匹配,其中49％的地震震级误差≤0.3;73％的地震水平误差不超过50km,68％的地震震源深度误差≤50km,对于震源深度大于300km的深源地震,90％的地震震源深度误差不超过50km.另对未匹配及误差较大的地震事件进行了进一步的分析.