Study on the feature selection and classifica－tion effect of precursory data of ground tilt

Using the view point of nonlinear science and the method of selecting numerical features of pattern recognition for reference, the physical and numerical features of precursory ground tilt data are synthetically employed. The dynamic changes of data series are described with the numerical features in multi dimensional space and their distributive relations instead of an unique factor. The relationship between the ground tilt data and earthquake is examined through recognition and classification.

Rotational motions of the Ms7.0 Jiuzhaigou earthquake with ground tilt data

Observation and research of rotational motions induced by earthquake has been ignored in the past decades due to the lack of understanding of important ground rotational motions and practical difficulty involved in directly measuring the rotational components. Currently, there is a paucity of methods to directly measure rotational motions in China. The present study attempts to discuss the possibility of obtaining seismic rotation from ground tilt data. The rotational motions generated by shear dislocation source are derived based on the displacement formula of elastic wavefields in the homogenous space. The characteristics of the three components of translational and rotational motions in near, intermediate, and far fields are compared and analyzed. Based on the corresponding relationship between the rotation and ground tilt on free surface boundary, a method to indirectly construct the rotational motions in the layered half space is obtained. Finally, the theoretical rotational motions generated by the Ms7.0 earthquake in Jiuzhaigou, Sichuan Province, on August 8, 2017 are calculated. The results indicate that the rotational motions generated by the Jiuzhaigou earthquake are concentrated in the vicinity of the epicenter(approximately150 km) and mainly distributed in the area perpendicular to the fault strike. The existence of free surface boundary attenuates the total energy of the rotational field and especially in the direction of the dominant energy. The ground tilt data is compared with rotational motions in the layered half space, and the results indicate that theoretical rotations and actual ground tilt data are essentially consistent, especially in the far field region. Thus, it is possible to obtain horizontal components of rotation from ground tilt data, and this provides more information for a complete description of the motion characteristics of an underground medium.

A Study on the Characteristics for the Ground Vibration Due to the Travelling Tilting Train

The development of the tilting train can contribute to solve the economic burden and enhance the transportation means of areas that did not share the benefits of the high speed railway. But the dynamic behavior caused by the interaction between the train and the track as well as the environmental vibrations along the railway should be evaluated to secure the safety of the train and riding comfort. In this paper a study on the characteristics for ground vibration due to the tilting train travelling in the conventional line are carried out. The transmitted load into the ground is computed through a study on the interrelation between the tilting car and the line. This load is applied into the numerical model which is one for the analysis of ground vibration due to the travelling tilting car. The far fields on the numerical model are formed by the absorbing boundary using dashpot, one of the most widely used absorbing boundary in finite element analysis. Using this numerical model, the analysis of the ground vibration characteristics caused by travelling tilting car is performed. From the analysis, it is shown that the transferred load due to the tilting train is larger than that of the conventional train.

A Study on the Characteristics and the Effective Reduction Methods for the Ground Vibration Due to the Travelling Tilting Train

In this paper, a study on the characteristics and the reduction methods of ground vibration due to the tilting train travelling in the conventional line is carried out. The load transmitted into the ground is computed considering the interaction between the tilting car and the line. This load is then applied in the numerical model for the analysis of ground vibration due to the travelling tilting car. The far-fields of the numerical model are modeled using the dashpot, as one of the most widely used absorbing boundaries in finite element analysis. Using this numerical model, the analysis of the ground vibration characteristics caused by the travelling tilting car and the analysis of the blocking effect of the ground vibration by wave barriers are performed. From the numerical analysis, it is shown that the blocking effect of the trench and the barrier filled with soft material is more effective than that of the barrier filled with hard material.

对强震地形变监测预报方法的思考

简要回顾了中国地形变用于强震监测预报领域的发展过程及现状。对几次强震前得到的比较突出的地形变异常进行了分析,收集了大面积形变异常与强震中长期预测、地震前兆分布存在时间有序和空间配套,强震前发现巨幅形变异常,InSAR给出强震前地面垂向形变,强震前地倾斜异常,慢地震和预滑移等方面的研究成果。综合分析认为,强震前震中区附近存在与孕震体尺度相当的巨幅快速地面异常隆升。及时有效地捕捉强震前巨幅快速地面异常隆升的时间有序和空间配套的异常信息,可望针对人口稠密区域未来发生的强震给出具有减灾实效的预测预报意见,值得尝试。基于本研究提出了针对人口稠密的地震重点监视防御区开展高密度、大量程、低精度地倾斜观测的设想,并初步给出了观测方案、基本原理和数据计算处理方法。

乌什M_(S)7.1地震前地倾斜、地应变加卸载响应比异常分析

基于岩石应力的本构关系,以2024年1月23日乌什M_(S)7.1地震前震中及周边500 km范围内地倾斜、地应变数据作为“响应量”,利用库伦应力触发模型的加卸载响应比方法进行计算,结果显示,乌什洞体应变等3个测项均出现震前LURR异常,这表明震源区介质存在明显的应力积累过程,同时也说明从倾斜、应变的潮汐频段中能够提取出地震预测的有效信息。

The Datong earthquake and its anomalous tilt Field

In this paper, the similarity and the meanings of anomalous pattern of entropy for tilt tide amplitude factor, the distribution of entropy and dimension for tilt velocity, the similarity and relationships for long-period tilt deformation and earthquake migration are demonstrated. The deformation wave and its meanings have also been explained. The authors explored the relationships between distribution of similar pattern and epicenter. The possibility of prediction for next earthquake epicenter has also been explored based on the combining tilt field and earthquake activity.

高地隙施药机自主作业杆臂辨识方法研究

为改善高地隙施药机自动导航系统的可靠性,减少作业过程中的伤苗率、重喷及漏喷等现象,基于RTK-GNSS与INS的相对位置关系推导了因定位杆臂产生的位置及速度误差,并根据杆臂误差模型及INS误差模型,提出了一种基于GNSS/INS组合导航滤波的杆臂辨识方法。通过仿真实验分析了影响杆臂辨识效果的因素,基于半物理试验平台对杆臂辨识效果进行验证。仿真结果表明:载体的直线运动对杆臂可观测度影响较小,但绕某一轴线的角运动可以增强角运动平面内的定位杆臂可观测度,且增大角速度可提高杆臂辨识的滤波收敛速度。仿真和半物理试验平台均表明:所提出的杆臂辨识方法可有效估计施药机子导航系统间的杆臂参数,设置仿真过程杆臂真值为[1m 2m 3m],辨识结果为[1.028m 2.047m 2.91m],辨识精度在95%以上;半物理试验平台卷尺测量的杆臂真值为[0.05m 0.2m 1m],辨识结果为[0.056m 0.18m 1.05m],辨识精度在88%以上,可靠性较高,能够替代工程应用中的手工测量,提高了导航系统定位精度。

Baseline correction for near-fault ground motion recordings of the 2008 Wenchuan Ms8.0 earthquake

In this study, both records of a digital accelerometer and a seismograph at a far-field station for the 2008 Ms8.0 Wenchuan earthquake were analyzed, and a pulsive noise model for acceleration record was found. By comparing with the result of a rotary-table tilt test, we concluded that the noises in the acceleration records were caused by ground tilt as a result of rotational ground motion. We analyzed the key noises that may cause baseline offset, and proposed a baseline-correction scheme for preserving the long-period ground motion in accordance with specific pulse positions. We then applied this correction method to some near-field strongmotion acceleration records. The result shows that this method can obtain near-field ground displacements, including permanent displacements, in agreement with GPS data, and that this method is more stable than other methods.

宽城地震台地倾斜观测的气压响应分析及排除

将宽城地震台地倾斜观测和气压观测数据,通过小波变换分析提取气压对地倾斜观测的干扰时段,再对气压干扰时段观测数据进行线性拟合去趋势、别尔采夫滤波获得观测数据的日漂移信息,最终获得地倾斜观测和气压观测的相关系数,通过线性拟合进行气压干扰的排除研究。结果表明:宽城台地倾斜观测与气压观测具有正相关性,通过此方案对地倾斜观测受气压干扰的观测数据进行干扰排除,可以取得较好的效果,提高观测数据可靠程度。

地下水位线倾斜的地面塌陷演化过程试验研究

为探究地下水位线倾斜情况下岩溶地面塌陷的演化过程,设计一种模拟地下水位倾斜致塌的试验装置。首先,以砂土为试验材料,考虑地下水位线倾斜角度及岩溶水位高度变化等因素,开展室内物理模型试验。其次,通过监测试验过程中孔隙水压力、竖向土压力、地表沉降量及岩溶通道渗流总量等数据,测绘塌陷体的空间形态,分析地面塌陷的演化过程。试验结果表明:距离岩溶通道孔口越近,土中的孔隙水压力降幅及水力梯度越大,加速了孔口附近土体的变形和破坏。岩溶水位下降会在土体内部形成降落漏斗,引起地下水渗流量的非线性增长。以临界土洞为界,岩溶地面塌陷可分为内部塌陷和地表塌陷2个阶段。随着地下水位线倾角的增大,岩溶通道的渗流强度减弱,土体内部偏压特征逐渐显著,且偏压条件会增强对土拱效应的削弱作用。塌陷体中心线向高水位侧的偏斜角度与地下水位线倾角呈正相关,其空间形态由漏斗状转为牛角状。最后,参考渗水条件下深埋隧道松动土压力的计算方法,对渗流作用下岩溶土洞顶部松动土压力进行求解,所得结果与实际试验数值较为吻合,具有一定的合理性和参考意义。

光伏项目最佳倾角与间距的选择

对于固定式安装的大型地面光伏发电项目,如何选择好安装倾角和间距对项目的经济性有着显著的影响。介绍了基于特定项目的条件下如何优化系统的最佳倾角和间距选择,并与常规的方法进行了分析对比,在项目执行过程中可以根据项目特点进行选择实施,以达到降低项目度电成本的目的。

采用双面光伏组件的光伏电站在系统集成设计中应考虑的因素分析

采用双面光伏组件是一种能够有效提升光伏电站发电量的手段。基于双面光伏组件的特点,通过列举行业内常用的双面光伏组件辐照度数学模型,对影响双面光伏组件发电量的地面反射率、前后排光伏阵列间距、光伏组件最佳安装倾角和光伏组件离地高度这几个主要因素进行了研究,并通过PVsyst软件对这几个主要因素进行了逐一仿真验证,从实际应用角度提出了采用双面光伏组件的光伏电站在系统集成设计中应考虑的几个因素。研究结果表明:1)双面光伏组件的最佳安装倾角比单面光伏组件的最佳安装倾角大,根据地区、地面反射率的不同,二者的差值大致在2°~10°之间;2)提高光伏组件离地高度可以增加双面光伏组件的发电量,而发电量增益大小会因光伏组件所在地纬度的不同有所不同,实际光伏电站的系统集成设计中,可选择最具经济性的光伏组件离地高度;3)在光伏组件最佳安装倾角过低的地区,光伏组件的自遮挡效应严重,需要根据实际情况选择是否采用双面光伏组件。

无人机仿地倾斜摄影建模精度浅析

无人机倾斜摄影测量通过搭载多种传感器对地多视角拍摄扫描,快速获取基础测绘数据而被广泛应用。然而,传统恒高航摄像片因中心投影成像原理在地形高差明显的地区产生像点差异,严重影响了建模精度和模型纹理特征的表达和显示。随着测绘科学技术发展,无人机仿地飞行技术改善了大高差引起的位移差异,为精细化建模提供重要技术支撑。本文在贵州省毕节市某水利枢纽项目采用D2000无人机搭载5镜头的D-OP3000倾斜摄影模块仿地飞行,获取倾斜航摄数据,分析建模精度。实验结果表明,该方法符合精细化建模精度要求,为获得实景三维模型提供可靠的数据基础。

无人机倾斜摄影测量与地面三维激光扫描的精度对比

无人机倾斜摄影以及地面三维激光扫描等新型测绘技术近年来快速发展,在诸多领域得到了广泛应用。为此,文章以某科技园为例,对无人机倾斜摄影测量与地面三维激光扫描的精度进行对比。通过对精度结果进行分析得出:无人机航测地面点的精度优于房角点,但是三维激光扫描房角点的精度优于地面点;无人机航测与三维激光扫描的平面精度相当,但在高程精度方面,三维激光扫描精度显著高于无人机航测精度。实践证明,将无人机倾斜摄影测量和三维激光扫描技术相结合,能大大提高测量效率并降低劳动强度。

基于空地影像融合的实景三维建模研究

由于古建筑物形状窄而高、建筑结构复杂多样,导致基于单一数据的建模技术因数据采集的限制,无法构建完整的古建筑三维模型。本研究以倾斜影像数据为主,地面近景影像数据为辅的采集方法来克服以上问题。通过将空地影像同名区域的点云数据进行融合来实现多源坐标系的统一,并对融合后的模型进行精度评价。实践证明,该方法可以为古建筑物的建模提供新思路。

基于控制点蒙特卡罗检验的无人机地形建模精度影响因素研究

针对消费级无人机相机单一、镜头畸变大,地形建模精度受航线设计和控制测量的影响等问题,设计了不同的数据采集方案和控制点蒙特卡罗检验,分析了相机倾角、航高和控制点数量对地形建模精度的影响。在黄土高原3个典型小流域的实验结果表明:①在进行无人机摄影测量数据处理时,应先使用蒙特卡罗检验对控制点质量进行分析,排除控制点误差再进行数据处理。②相机倾角方面,在无地面控制点时,采用较大角度的倾斜摄影不仅有利于提高样区整体精度,还优化了误差的空间分布;这与相机畸变模型的优化有关。在有地面控制点时,相机倾角对高程精度的影响不大,但是影响控制点饱和数量;相对于垂直摄影,倾斜摄影需要略多的控制点才能达到最优精度。③航高方面,在有地面控制点时,使用倾斜摄影有利于降低高程精度对航高变化的敏感性。在有地面控制点时,航高在60~160 m范围内对高程精度的影响不明显,且航高变化不影响控制点饱和数量。

汶川地震前南北地震带中北段地形变变化特征的研究

2008年5月12日汶川8.0级地震是我国自建国以来灾难最为严重的一次强地震。文中讨论了汶川地震前震源附近与外围地区潮汐形变变化及龙门山地震带、鲜水河地震带和祁连山地震带断层活动的特点。分析结果表明:震前沿龙门山地震带分布的雅安、汶川及茂县观测台地倾斜测项在2006年初发生转折,由单向东倾或西倾转向平稳,临震前无明显变化;龙门山断裂带及附近地区有5个断层水准观测场地,除耿达场地观测到巨幅变化外,其他场地震前未观测到突出的前兆性变化。震源外围龙灯坝断层蠕变仪(Δ=220 km)震前观测到持续时间在3个月左右的突变性异常,但依据突变持续时间较难估计相应地震为8级。而离震中较远的祁连山地震带中西段,震前也有巨大的断层水准变化,其与汶川地震的关系值得讨论。

汶川地震近震源区地形变短期前兆现象的解析

2008年汶川8.0级地震是我国自建国以来灾难最为严重的一次强地震,有关震前该区域地壳变形情况引起许多学者的关注。本文给出了沿龙门山地震带地倾斜及跨龙门山断裂断层水准剖面临震前变化的特征:汶川地震前沿龙门山地震带分布的康定、汶川及茂县台地倾斜无明短期显变化;6个断层水准观测场地,除耿达场地观测到较大幅度变化有争议外,其他断层观测场震前均未观测到突出的短临前兆性异常变化。本文分析了汶川地震前大区域地震活动性资料及震前沿南北地震带显著形变异常点分布特点,探讨了汶川地震震中区域应变积累过程,认为近震源区域无显著短期前兆变化现象很可能与震中区域介质所具有的高应变、小变形性质有关。另外,也不排除地形变观测点所处的位置等有关因素。