大风天气老哈河下游迎风侧谷坡的风速脉动特征

基于春季大风天气野外实地风速观测数据,从平均风速、风速脉动、风速脉动强度3个方面对老哈河下游迎风侧谷坡坡脚和坡顶的风速脉动特征进行了分析.结果表明:(1)在距地表0.50 m高度以上,坡脚和坡顶风速在时间序列上波动各自具有均一性;(2)风速脉动幅度随着距地表高度的增加而逐渐加大,其最大值超过4.00 m·s^-1.坡脚和坡顶的风速脉动频率各自具有一致性,但脉动频率不稳定;(3)风速脉动强度基本一致,随高度增加而逐渐增大.在0.50 m高度以上,风速脉动相对值(阵性度)基本稳定,但坡顶的阵性因谷坡的干扰而相对减弱.     

电渗的二维固结理论

在Esrig一维固结理论的基础上,采用分块处理的办法,就阴极排水,阳极不排水;阴极不排水,阳极排水;阴极排水,阳极排水三种情况进行了二维固结理论的解析,证明了电渗最终产生的超孔隙压力可正、可负,其极值决定于两极所加电压大小,其分布与电压的分布和边界条件有关,和初始条件无关。     

一种新的节理裂隙岩体弹塑性模型

提出一种节理裂隙岩体弹塑性模型,将结构划分为块体单元和缝单元,其中缝单元可以是实际节理裂隙,也可以是人为缝单元。以块体单元形心的刚体位移和块体的平均应变作为基本未知量。该模型能充分考虑节理裂隙材料和块体材料的本构关系,计算量不大,是一种位移不协调单元。该模型特别适合节理裂隙岩体的数值分析。     

桩土作用对隔震梁桥地震易损性及震后通行能力影响

为确定桩土作用对一座位于Ⅲ类场地上的110m三跨连续梁桥地震易损性曲线和震后通行能力的影响,首先建立墩底固结和考虑桩土作用2种有限元模型,选取50条实测的、符合工程场地条件的不同强度地震波作为输入,分别以桥墩墩顶和支座最大位移为目标响应,计算得到转角延性比和支座剪应变值,进而构建桥墩和支座的易损性曲线;然后通过宽界限法建立桥梁系统的地震易损性曲线,提出新的平均损伤水平值计算公式并结合易损性曲线评估该连续梁桥的震后通行能力。分析结果表明,同一地震强度下考虑桩土作用时的桥墩位移峰值比墩底固结情况大,更符合实际情况;对于桥梁构件易损性曲线而言,考虑桩土作用时支座破坏超越概率最大,但与墩底固结情况相比相差不大;采用桥梁系统地震易损性曲线评价桥梁交通流量变化更加合理,固结模型的震后交通流量评估Ⅲ类场地情况时不可忽略桩土作用对桥梁地震易损性的影响。     

数字高程模型DEM精度研究

用不同地貌类型地区的实验数据对数字高程模型(规则格网DEM)的格网间距与中误差(RMSE)、平均高程、剖面曲率的关系进行研究,采用比较分析的方法,得到格网间距与中误差的数学模型,可以用通式:Y=A BX CX2表示,并且把地形因子(平均高程、剖面曲率)作为自变量,进一步分析通式中3个系数与地形因子的关系,发现两个地形因子与系数函数关系比较相似,并得到Y=A BX CX2 DX3的数学模型。由验证结果表明,所得模型效果良好。     

延安市冰雹云初始回波识别

根据隰县1961年-2007年的气温资料,利用线性回归分析,结合年平均气温的五年滑动平均值变化趋势和平均气温年际变化趋势,分析了隰县年、季平均气温的变化特征,表明47年来隰县年平均气温有明显升高趋势;各季均以增温为主,春季增温尤其显著。通过Mann—Kendall突变分析对年平均气温进行突变检验,表明年平均气温于1985年发,毛突变,突变前后温差1．2℃,突变显著。     

随机森林算法在机载LiDAR数据林分平均树高 估算中的应用研究

采用机载LiDAR数据估算森林结构参数是当前林业遥感中的研究热点。本文以福建省长汀县朱溪河流域为示范区,探讨了随机森林算法（RF）在机载LiDAR数据林分平均树高估测中的适用性。首先,通过渐进三角网（TIN）算法进行点云滤波并获取相应林分样地的植被点云子集和高程归一化的植被点云;然后,从归一化后的植被点云提取出高度分位数变量以及点云统计特征值等24个变量参数;最后,根据提取的变量参数和野外实测林分均高数据建立研究区林分平均高随机森林回归估测模型。研究结果表明,模型估测的样地平均树高与实测值具有明显线性相关关系,线性回归系数为0.938,相关系数达到0.968。对样地的估测精度都在86%以上,总体平均精度达到了93.17%。研究认为,基于植被点云变量参数的随机森林模型估测林分平均树高具有较高的可靠性。     

LATE HOLOCENE AVERAGE RECURRENCE INTERVAL OF GREAT EARTHQUAKES OF SHANGZHI PART OF THE YILAN-YITONG FAULT ZONE,NE CHINA: CONSTRAINTS FROM PALEO-EARTHQUAKES AND HISTORICAL WRITTEN RECORDS

Although the kinematics and mechanics of the Yilan-Yitong fault zone (YYFZ) since the Mesozoic-early Cenozoic were studied very well in the past decades,few results about the average recurrence interval of great earthquakes in late Quaternary,which is the most important parameter for us to understand the active tectonics and potential seismic hazard of this crucial structure,were obtained because of its unfavorable work environments.Based on interpretations of high-resolution satellite images and detailed geologic and geomorphic mapping,we discovered that there exist linear fault scarp landforms and troughs in the Shangzhi part of YYFZ with a length of more than 25km.Synthesized results of trenches excavation and differential GPS measurements of terrace surfaces indicate two paleo-events EⅠ and EⅡ occurring in Shangzhi part during the late Holocene,which resulted in ca.(3.2±0.1) m accumulated vertical coseismic displacement with strike-slip motion accompanied by thrusting and shortening deformation.¹⁴C samples dating suggests that event EⅠ might occur at (440±30) and (180±30) a BP and event EⅡ might happen between (4 090±30) and (3 880±30) a BP,and the average recurrence interval of major earthquakes on the YYFZ is around (3 675±235) a.Historical written records discovered from Korea show that the event EⅠ may correspond to the earthquake occurring in AD 1810(Qing Dynasty in Chinese history) in Ningguta area with magnitude 7.0.     

research of source parameters and stress state in shandong segment of tanlu fault zone

In recent years, there have been few researches and analysis published on the seismic activity and stress state in Shandong segment of Tanlu fault zone using digital seismological methods such as seismic apparent stress, focal mechanism solution and so on. In this paper, source parameters such as focal mechanism solutions and apparent stress are calculated using the waveform data of M_L≥1 moderate-small earthquakes in Shandong segment of Tanlu fault zone recorded by Shandong digital seismic network since 2007. According to focal mechanism solutions, a statistical analysis is done on the focal dislocation types in the study area using triangle graphical method, and the results show that the faulting in this area is mainly of strike-slip mechanism, and there are less thrust and normal mechanism. Calculation with the mean stress tensor method illustrates that the direction of mean principle stress of Shandong segment of Tanlu fault zone is NEE-SWW, which is the result of the combined effect of the subduction of West Pacific plate and the extrusion of Indian plate to Eurasian plate; the small dip angle indicates that the mode of action of stress is nearly horizontal, and the direction of principal stress axis is nearly perpendicular to the Tanlu fault zone. Under the action of such compressive stress field, dislocation is not likely to occur and the stress accumulation is enhanced on both sides of the fault. The apparent stress is calculated using the source spectral parameters method. Apparent stress has positive correlation with the magnitude and increases with the increased magnitude. So we get apparent stress difference by subtracting the empirical fitting value from the apparent stress. By removing the impact of magnitude, and according to the temporal-spatial evolution image of apparent stress difference, we found that the apparent stress in Shandong segment of Tanlu fault zone generally has a trend of decrease starting from the Wenchuan earthquake in 2008, and the spatial distribution of apparent stress in the region is very uneven. Combined with the spatial distribution of b values, the result shows that high stress is mainly located in Anqiu segment and Tancheng-Juxian segment, especially in Anqiu segment where small magnitude earthquakes appeared accompanying with the high stress. Low b-value means high stress and low frequency means low stress release, which indicates that Anqiu segment might accumulate higher stress and is at the fault locking stage. The research will provide new data for better understanding the present active feature and stress state of the Shandong segment of the Tanlu fault zone.     

新疆测震台网常用地震定位方法对比

选取2009年新疆测震台网记录的49个ML≥3.0地震,选用相同地震台及相同震相到时数据,分别采用单纯形、Loc Sat和Hypo Sat定位方法重新定位,从定位残差和震中位置对各定位效果进行对比,结果表明:对地震台站包围好的浅源地震,3种定位方法均适合;对地震台站包围不好的浅源地震,Loc Sat定位方法效果较好;对深源地震,Hypo Sat定位方法效果较好。