Amplitude-compensated Laplacian filtering of reverse time migration and its application

Reverse time migration is an advanced seismic migration imaging method. When the source wavefield and the receiver wavefield are cross-correlated, the cross-correlations of direct arrivals, backscattered waves and overturned waves will produce a lot of low-frequency noise, which will mask the final imaging results. Laplacian filtering, as a common method to suppress low-frequency noise, can adapt to any complex media, just adding a little computational cost. However, simple direct Laplacian filtering will destroy the characteristics of the useful signals. Therefore, the amplitude needs to be compensated before filtering when using the Laplacian filtering method. Zhang and Sun proposed an improved Laplacian filtering method and gave a simple calculation formula and explanation. This method can effectively suppress the low-frequency noise in reverse time migration while retaining the useful signal characteristics, but lacks detailed and strict mathematical derivation. Therefore, this paper gives a detailed and rigorous mathematical derivation of the amplitude-compensated Laplace filtering method from the point of view of amplitude-preserved filtering. The source wavelet is used instead of the source wavefield to compensate amplitude, just adding a little calculation cost. Finally, the amplitude-compensated Laplace filtering method is verified by two theoretical models and compared with the direct Laplacian filtering method.     

Using Standardized Groundwater Index and Standardized Precipitation Index to Assess Drought Characteristics of the Kaoping River Basin,Taiwan

Water Resources - In the present study, long-term monitoring data were collected from the study area of the Kaoping River Basin, Taiwan. Specifically, data from six selected groundwater level...     

差不嘎蒿在科尔沁沙地草场植被中的作用

差不嘎蒿是科尔沁沙地草场退化过程中的一个重要缓冲种。在草场退化过程中能够迅速占领退出植物种遗留下来的空间, 生物量由81.6g/m²增加到285g/m²; 但从半固定沙丘草场到半流动沙丘草场, 其生物量减少到了190g/m², 占总生物量的77.2%。差不嘎蒿在半流动沙丘草场中的繁殖力最高, 当年生幼苗数和果实生物量分别为59株/m²和17.6g/m²。差不嘎蒿以无性繁殖为主, 但是, 在流动沙丘草场则以种子繁殖为主。     

Spatial–temporal changes in potential evaporation patterns based on the Cloud model and their possible causes

It is of importance to comprehensively investigate the spatial–temporal changes in potential evaporation patterns, which helps guide the long-term water resource allocation and irrigation managements. In this study, the Cloud model was adopted to quantify the average, uniformity, and stability of the annual potential evaporation in the Wei River Basin (WRB), a typical arid and semi-arid region in China, with the purpose of objectively and comprehensively characterizing its changing patterns. The cross wavelet analysis was then applied to explore the correlations between annual potential evaporation and Arctic Oscillation (AO)/El Niño Southern Oscillation (ENSO) with an aim to determine the possible causes of annual potential evaporation variations. Results indicated that: (1) the average of annual potential evaporation in the WRB first declined and then increased, and its stability also showed the same change characteristics, whilst its dispersion degree exhibited a decreasing trend, implying that potential evaporation has a smaller inter-annual variation; (2) the average of annual potential evaporation in the western basin was obviously smaller than that in the other areas, while its uniformity and stability in the Guanzhong plain and the Loess Plateau areas are larger than those in other areas, especially in the western basin where the uniformity and stability are the smallest; (3) both AO and ENSO exhibited strong correlations with annual potential evaporation variations, indicating that both AO and ENSO have played an important role in the annual potential evaporation variations in the WRB.     

无人机遥感技术在新疆皮山地震灾情获取中的应用

2015年07月03日,新疆维吾尔自治区和田地区皮山县（37.6°N,78.2°E）发生M_S6.5级地震,震源深度10km。本文利用高性能无人机数据采集平台获取灾区高分辨率影像数据,结合地震现场震害调查建立建筑物震害遥感解译特征,采用人工目视解译完成了灾区6个0.01°×0.01°格网评估区房屋类型及损毁程度应急遥感调查,获取测区地震灾情信息。结果表明:测区内房屋结构类型主要包括土木、砖木、砖混结构;倒塌房屋主要为土木结构及个别老旧砖木结构房屋,倒塌和局部倒塌的土木结构房屋占评估区土木结构房屋总数的68%,倒塌和局部倒塌的砖木结构房屋占评估区砖木结构房屋总数的12%;测区砖混结构房屋局部倒塌1间,未倒塌228间,砖混结构显示出良好的抗震性能,对避免人员伤亡和减少经济损失起到重要作用。     

营养状态指数在长江下游小型浅水湖泊富营养化水平评价中的局限及改进建议

基于多个环境变量、以等权或者加权平均法获得的综合营养状态指数（Carlson指数：TSIc;修正后的Carlson指数：TSImc;综合营养状态指数：TLIc;湖库营养状态指数：EIc）得分是当前评价湖泊营养水平的主要依据,其值计算时先要获得基于单个环境变量的营养状态指数分值。若基于总氮（TN）、总磷（TP）和透明度（SD）等的单个理化指标与基于叶绿素a(Chl.a)的营养状态指数得分间存在显著差异,表明依据理化指标的评估结果低估或者高估湖泊的实际营养水平。长江下游分布大量的小型浅水富营养化湖泊,但基于理化指标的评估结果是否会误判湖泊的实际富营养化水平的研究很少。本研究以长江下游的14个浅水富营养化湖泊为对象,于2019 2020年按照季度采集水样并测定水环境因子,分析基于理化指标和基于Chl.a的各营养状态指数（TSI、TSIm、TLI和EI）得分间的差异。结果表明,基于SD的TSI、TSIm、TLI和EI的年均得分均显著高于基于Chl.a的相应营养状态指数的年均值;除TSI(TP)vs.TSI(Chl.a)外,基于TP与基于Chl.a的其他营养指数的年均得分间均有显著性差异;仅TL...     

2017年8月9日精河6.6级地震灾害损失及灾后恢复重建经费评估

2017年8月9日新疆精河发生6.6级地震,地震造成36人受伤,各类房屋建筑、公共服务设施、基础设施等遭受不同程度的破坏。通过实地抽样调查,按照国家标准的原则和方法,评估出此次地震造成的直接经济损失为429964万元,灾后恢复重建经费约需538461万元。     

山西省4口井(泉)水化学特征与水氡映震效能研究

对山西4口水化学观测井（泉）及周边地表水进行水化学和氢氧同位素分析,利用Piper图、durov图、Na-K-Mg三角图等方法研究其水化学特征及成因,得出井（泉）水岩平衡程度、热储温度、地下水循环深度及地下水补给来源详情;分析了井（泉）水氡测项映震特征,应用水氡映震效果与水岩平衡程度、地下水循环深度表现出的特征,评价了地震监测效能。评价结果显示夏县井、奇村井优于临猗井,适于开展地震水化学观测;定襄泉应用该水化学方法评价尚存不足之处,需要探索适用于该类观测泉点的物理与化学相结合的评价方法。     

地震预警示范系统试运行月报产出软件设计

为提高河北省地震预警示范系统试运行月报产出质量,加快产出速度,减轻人员负担,基于JAVA技术,设计月报产出软件,通过对烈度计台站延迟数据和运行数据的分析,借助POI工具、MYSQL数据库和JFreeChart,实现月报产出、历史数据查询、数据可视化展示等功能,解决了月报产出周期长、历史数据查询不便、数据展示模式单一等问题,为地震预警示范系统试运行提供有力支持。     

山东乳山南东庄金矿床地质特征及找矿潜力分析

南东庄金矿位于胶东昆嵛山-乳山凸起西北部,牟(平)-乳(山)金成矿带北端。该文通过矿床地质特征、围岩蚀变、控矿构造等方面展开综合研究,划分了蚀变组合分带及成矿阶段,总结了矿体赋存规律。矿体严格受NNE或NE向断裂带控制,呈脉状、透镜状产出,具尖灭再现特点。围岩蚀变主要有绢英岩化、硅化、黄铁矿化、钾化、绿帘石化、绿泥石化等,并具明显蚀变组合分带。矿床的成矿阶段划分为5期,其中石英-黄铁矿阶段和多金属硫化物阶段是主要的金成矿阶段。通过区域及矿区两方面成矿地质条件分析,认为该区具良好的找矿前景。