潮汕坳陷多次波组合压制技术研究

潮汕坳陷中生界发育,是我国海上重要的油气勘探后备区。但该区多次波非常发育,多次波识别和压制一直是该区地震资料处理的关键和难点。合理地选取有效的多次波压制方法是获得高品质地震剖面的关键所在。针对原始资料中多次波异常发育的情况,文章分析了该区多种类型多次波的特点,尝试了零偏移距截距时间-射线参数(τ-p)域预测反褶积、自由界面多次波衰减法(Surface-Related Multiple Elimination,SRME)和双曲线Radon变换,对多次波进行组合压制,克服了仅依靠一种手段难以压制多种类型多次波的局限。从资料处理效果看,τ-p域预测反褶积方法对短周期的鸣震和微曲多次波的压制效果较好,SRME有效地压制自由表面多次波,且在近炮检距范围内压制多次波效果很好,而双曲线Radon变换是衰减长周期的层间多次波和未被充分压制的自由表面多次波很好的选择。组合压制多次波后的剖面质量明显得到改善。     

长江口北支倒灌影响区盐度预测经验模型

为预测不同径流过程影响下的盐水入侵强度,以长江口南支上段为研究对象,采用实测资料和理论分析相结合,建立了以大通流量和农历日期快速估算氯度值的经验模型。首先,以徐六泾实测潮位资料结合调和分析理论,在考虑11个主要分潮情况下证明日均潮差为半月周期函数,提出了用农历日期估算日均潮差的方法;其次,采用东风西沙实测氯度资料,选用不同函数形式,分析了以支汊盐水倒灌为主的情况下日均氯度对径流、潮差的量化响应关系;最后,提出了指数函数形式的氯度预测经验模型,模型计算值与实测值之间的决定系数在0.8以上。提出的经验模型可由大通流量快速估算特定位置的盐度,为相关的工程和规划研究提供了便捷途径。     

中国萤石矿预测评价模型与资源潜力分析

中国萤石矿资源较丰富,探明资源量居世界前列。我国的萤石矿研究工作主要围绕大中型萤石矿床的地质特征、物质来源、成因、区域成矿规律和少数省级萤石矿成矿远景区划、区域萤石矿资源潜力评价展开。为摸清萤石矿资源家底,制定科学合理的经济产业政策,亟需开展系统的、全国性的萤石矿成矿规律和资源潜力评价。依据中国萤石矿资源潜力评价报告数据和成果,文章分析了中国萤石矿矿床类型、矿床地质特征和时空分布特征,划分了成矿区带;在各省区建立的典型矿床预测模型和区域预测模型基础上,以成矿系列理论为指导,突出总结萤石矿成矿要素和预测要素,归纳、汇总、提出了热液充填型和沉积改造型萤石矿矿床预测评价模型;以各省区圈定的最小预测区、归并的2级预测区和估算的资源量为基础,依据预测要素和区域预测模型,归并、圈定了198个3级预测区,汇总估算了全国萤石矿预测资源量,提出了中国萤石矿预测远景区。中国萤石矿资源丰富,找矿潜力大,预测资源量（CaF2）约9.5亿t,其中单一萤石矿预测资源量约4.3亿t,以热液充填型预测资源量为主。预测远景区主要分布于中国东部,四子王旗、冀北-辽西、豫南、皖南-浙西、浙中、闽北-粤东等地区成矿条件好,资源潜力大,是萤石矿预测资源量较大的地区。     

国内外单体建筑物震害预测方法研究述评

国内外单体建筑物的震害预测方法包括历史震害统计法、专家评估法、模糊类比法、半经验半理论法、结构理论计算方法和动态分析法。本文首先对国内外单体建筑物震害的预测方法进行了研究评述 ,然后探讨了各种方法的优缺点     

Conductivity as a predictor of a total cations and salinity in Ethiopian lakes and rivers: revisiting earlier models

We used regression analyses of water samples from 18 lakes, nine rivers, and one spring in Ethiopia to (a) test the hypothesis that water bodies of relatively higher salinity (K₂₅>1000 μS cm⁻¹) have a different conductivity to salinity relationship than waters of lower salinity (K₂₅ < 1000 μS cm⁻¹), and (b) develop models to predict total cations and salinity from conductivity that can be used for Ethiopian waters and other African aquatic systems of similar chemical composition. We found no statistical difference in the bilogarithmic relationships (total cations vs. conductivity; salinity vs. conductivity) for waters of higher salinity (K₂₅ > 1000 μS cm⁻¹) and waters of lower salinity (K₂₅ < 1000 μS cm⁻¹). However, comparison among our models and models from the literature suggests that developing separate equations for low and high salinity water bodies has some merit. We believe that the equations developed in this study can be used for Ethiopian waters and other African waters within the range of conductivity in this study.     

Percolation theory as a tool for imitation of fracture process in rocks

The statistical models of earthquake focal processes covering topological, kinetic, energetic and scaling aspects of the phenomenon are considered on the basis of the percolation and reliability theories. It is shown that these models do not contradict the basic experimental data of physics of fracture and seismology. Some predictive signs are also considered.     

用模糊数学方法对“地震预报”进行评分的研究

本文进一步简化了评分方法。仿照地震观测中的走时表给出了实用的时、空、强三要素的便查表,该表系用计算机对各参数和待定系数进行多方案选择制成,颇为简便,可供地震系统对地震预报意见进行评分时试用。     

Predicting Lahar-Inundation Zones: Case Study in West Mount Pinatubo, Philippines

This paper demonstrates techniques for pre-eruption prediction of lahar-inundation zones in areas where a volcano has not erupted within living memory and/or where baseline geological information about past lahars could be scarce or investigations to delimit past lahars might be incomplete. A lahar source (or proximal lahar-inundation) zone is predicted based on ratio of vertical descent to horizontal run-out of eruptive deposits that spawn lahars. Immediate post-eruption distal lahar-inundation zones are predicted based on “pre-eruption” distal lahar-inundation zones and on spatial factors derived from a digital elevation model. Susceptibility to distal lahar-inundation is estimated by weights-of-evidence, by logistic regression and by evidential belief functions. Predictive techniques are applied using a geographic information system and are tested in western part of Pinatubo volcano (Philippines). Predictive maps are compared with a forecast volcanic-hazard map through validation against a field-based volcanic-hazard map. The predictive model of proximal lahar-inundation zone has “true positive” prediction accuracy, “true negative” prediction accuracy, “false positive” prediction error and “false negative” prediction error that are similar to those of the forecast volcanic-hazard map. The predictive models of distal lahar inundation zones have higher “true positive” prediction accuracy and lower “false negative” prediction error than the forecast volcanic-hazard map, although the latter has higher “true negative” prediction accuracy and lower “false positive” prediction error than the former. The results illustrate utility of proposed predictive techniques in providing geo-information could be used, howbeit with caution, for planning to mitigate potential lahar hazards well ahead of an eruption that could generate substantial source materials for lahar formation.     

山东沭河上游流域考古遗址预测模型

以山东莒县沭河上游流域地区为研究案例,通过对大汶口、龙山和岳石文化时期遗址空间结构及其与环境特征的关系分析,建立了基于GIS的沭河上游考古遗址预测逻辑斯蒂回归模型,较为精确地分析得出遗址分布与地形高度、河流分布等因子间的定量关系。研究结果表明,山东莒县沭河上游流域地区遗址点分布在高程较低和坡度低于3°的地方,说明遗址点多选择在较为适宜农业活动的地方;在遗址选择朝向上,整个研究区域的朝向分布比较均衡,但以西、西南、东和东南为主;史前人类的居住地主要沿支流分布,而远离干流,以避免洪水灾害的危害;随着时间的推进,遗址点所处位置的高程和坡度逐渐增高增大,距离河流的各种距离总体上也呈增加的趋势,这与人类克服环境限制能力的提高有关系。     

Direct use of PGV for estimating peak nonlinear oscillator displacements

A predictive model is presented for estimating the peak inelastic oscillator displacements (S_d,ie) from peak ground velocity (PGV). The proposed model accounts for the variation of S_d,ie for bilinear hysteretic behavior under constant ductility (µ) and normalized lateral strength ratio (R) associated with postyield stiffness ratios of α=0 and 5%. The regression coefficients are based on a ground‐motion database that contains dense‐to‐stiff soil site recordings at distances of up to 30 km from the causative fault. The moment magnitude ( M ) range of the database is 5.2? M ?7.6 and the ground motions do not exhibit pulse‐dominant signals. Confined to the limitations imposed by the ground‐motion database, the model can estimate S_d,ie by employing the PGV predictions obtained from the attenuation relationships (ground‐motion prediction equations). In this way, the influence of important seismological parameters can be incorporated to the variation of S_d,ie in a fairly rationale manner. This feature of the predictive model advocates its implementation in the probabilistic seismic hazard analysis that employs scalar ground‐motion intensity indices. Various case studies are presented to show the consistent estimations of S_d,ie by the proposed model. The error propagation in the S_d,ie estimations is also discussed when the proposed model is associated with attenuation relationships. Copyright © 2008 John Wiley & Sons, Ltd.