成都地磁台的观测与评估

通过对成都地磁台的仪器配置、误差来源、资料质量等方面进行综合分析，结果表明．成都地磁台的观测质量稳定，资料连续可靠。成都地磁台的观测能够正确反映成都地区地磁场的变化特征。     

NO_3~-对硼同位素测定的干扰及其消除

在石墨存在下测定Cs2BO2+离子是硼同位素测定的最佳方法，但NO3-却存在严重的干扰，本文对这种干扰进行了详细的研究。为了避免NO3-的干扰，本文改进了硼的分离提取方法，完全避免了NO3-的引入，取得了满意的测定结果。     

Uncertainty analysis and the relative contributions of geological factors for the Qingshankou source rocks in the North Songliao Basin, northeastern China

Source rock evaluation is a critical factor in resource assessment of oil and gas. Models for evaluating source rocks are dependent on established geomathematical principles, the calculation of source-rock parameters, and geological data. The sensitivities and uncertainties associated with these models are a matter of concern. In this paper, the effects and relative contributions of 13 major geological factors, as well as their variations and distribution probabilities, have been analyzed for the source rocks in the North Songliao Basin in northeastern China. The geological factors include the time of formation of the regional caprock, composition of the regional caprock, the phases of hydrocarbons in migration, and those factors associated with the generation, retention, and expulsion of hydrocarbons and their effects on source-rock efficiency. Of the 13 factors analyzed, the most important are the source-rock depth, sedimentation rate, total organic content, and kerogen-type index; the relative contributions to the uncertainty of efficient gas/oil migration amounts for the most important factors are 37, 25, 19, and 1% for oil and 32, 17, 20, and 15% for gas, respectively. These most reflect the changes that have occurred in the Qingshankou source rocks.     

Conditional simulation as a tool for measuring uncertainties in petroleum exploration

A fundamental task for petroleum exploration decision-making is to evaluate the uncertainty of well outcomes. The recent development of geostatistical simulation techniques provides an effective means to the generation of a full uncertainty model for any random variable. Sequential indicator simulation has been used as a tool to generate alternate, equal-probable stochastic models, from which various representations of uncertainties can be created. These results can be used as input for the quantification of various risks associated with a wildcat drilling program or the estimation of petroleum resources. A simple case study is given to demonstrate the use of sequential indicator simulation. The data involves a set of wildcat wells in a gas play. The multiple simulated stochastic models are then post-processed to characterize various uncertainties associated with drilling outcomes.     

Information, uncertainty and decision making in site investigation for rock engineering

Although there is general awareness that uncertainty, information and decision making are key elements of site investigation, there has previously been little comprehensive attempt to formalize these factors in the site investigation process. In modern design, rock engineering is considered as a system and it is necessary to establish the key variables and interactions between the variables within the system as a precursor to design. Then, questions concerning (i) the information required to characterize the system, (ii) the uncertainty associated with this information, and (iii) the influence that this has on decision making, naturally arise and need to be addressed. We consider the application of information theory to geotechnical engineering through interpretation of informatic concepts in a rock mechanics context. Examples are then given, concentrating on the ideas of information received in sequential phases of site investigation, the information content of rock-mass classification systems, and the information content of scalar and vector quantities using discontinuity frequency as an example. In the concluding section, there are recommendations for making improvements to site investigation using information theory.     

Tunable diode laser measurements of trace gases during the 1988 Polarstern cruise and intercomparisons with other methods

Measurements of NO₂, HCHO, and H₂O₂ were made by the highly specific method of mid infra-red absorption spectroscopy using tunable diode lasers (TDLAS) during the 1988 Polarstern expedition. The TDLAS data are compared to those obtained during the cruise using less direct methods. Southern Hemisphere NO₂ levels suggest nett photochemical destruction of O₃ in the boundary layer. Northern Hemisphere HCHO averaged 0.47±0.2 ppbv; the HCHO measurements are used in a simple calculation to estimate OH noontime maxima of 3–6×10⁶ cm^-3.     

澜沧—耿马地震前后的地温异常变化

本文初次用近几年来站定点探测到的恒温层以下不同深度的地热随时间的变化资料,揭示澜沧—耿马7.6级大震前后地热的短、临异常特征,并对异常机制进行初步探讨。     

Bayes estimate of the probability of exceedance of annual floods

In this paper Lindley's Bayesian approximation procedure is used to obtain the Bayes estimate of the probability of exceedence of a flood discharge. The Bayes estimates of the probability of exceedence has been shown by S.K. Sinha to be equivalent to the estimate of the probability of exceedence from the predictive or Bayesian disribution, of a future flood discharge. The evaluation of complex ratios of multiple integrals common in a Bayesian analysis is not necessary using Lindley's procedure. The Bayes estimates are compared to those obtained by the method of maximum likelihood and the method of moments. The results show that Bayes estimates of the probability of exceedence are larger as expected, but have smaller posterior standard deviations.     

On the optimal risk based design of highway drainage structures

For a proposed highway bridge or culvert, the total cost to the public during its expected service life includes capital investment on the structures, regular operation and maintenance costs, and various flood related costs. The flood related damage costs include items such as replacement and repair costs of the highway bridge or culvert, flood plain property damage costs, users costs from traffic interruptions and detours, and others. As the design discharge increases, the required capital investment increases but the corresponding flood related damage costs decrease. Hydraulic design of a bridge or culvert using a riskbased approach is to choose among the alternatives the one associated with the least total expected cost.In this paper, the risk-based design procedure is applied to pipe culvert design. The effect of the hydrologic uncertainties such as sample size and type of flood distribution model on the optimal culvert design parameters including design return period and total expected cost are examined in this paper.