祁连山托来南山6号冰川雷达测厚与冰储量分析

冰川厚度测量是冰储量估算的关键。基于2019年7月利用探地雷达在托来南山6号冰川主冰川的测厚结果,通过普通克里格法绘制了主冰川的冰厚分布图,计算出主冰川的平均厚度为（39.61±5.32） m,冰厚空间分布呈自边缘向中间逐渐增厚的特征,最大冰厚［（100.78±1.78） m］位于纵剖面海拔4 770 m附近的凹陷盆地,结合半物理公式估算出整条冰川的冰储量为（0.0504±0.0082） km³。冰床为典型槽谷地形,谷槽横剖面呈U形,且随海拔的升高谷槽宽度逐渐变小。现有的面积-体积公式并不适用于单条冰川的冰储量估算,但分类型拟合公式具有降低估算结果误差的潜力。     

沥青心墙压实度的探地雷达探测研究

沥青心墙是水利水电工程的一种重要的防渗形式,其质量直接关系到工程的安全.压实度是评价其质量的重要指标,常采用取芯后实验室来测定,虽然探测结果可靠,但破坏性大、周期性长以及连续性差.我们采用探地雷达方法来评价沥青心墙的压实度.为消除沥青心墙的侧壁和两侧的堆石对探测结果的影响,本文模拟了雷达波在沥青心墙中传播,得出没有侧壁和堆石反射波影响的有效探测深度.并利用实测数据提取沥青心墙的雷达波属性如振幅、主频以及瞬态谱等,结合采样获得的孔隙度和密度,得出其与属性参数间的关系.研究表明,这种方法可以直观、快速、连续的反映心墙压实度变化,为工程质量的检测提供很好的依据.     

Time-lapse borehole radar monitoring of an infiltration experiment in the vadose zone

Ground-penetrating radar (GPR) is an effective tool for imaging the spatial distribution of water content. An artificial groundwater recharge test was conducted in Nagaoka City in Japan, and time-lapse crosshole GPR data were collected to monitor the infiltration process in the vadose zone. Since electromagnetic wave velocities in the vadose zone are largely controlled by variations in water content, an increase in traveltime is interpreted as an increase in saturation. In the test zone, the infiltrated water penetrated downward with an average velocity of about 2.7 m/h. A finite-difference time-domain method using two-dimensional cylindrical coordinates is applied to simulate radargrams associated with the advancing wetting front and to quantify the effects of critical refraction. Standard zero-offset profiling for which all first-arrivals are assumed to be direct waves results in an underestimation of water content in the transition zone above the wetting front. As a result, correct velocity analysis requires identification of first-arriving critically refracted waves from the traveltime profile to accurately determine a water content profile.     

面波的质点运动轨迹在小爆破识别与判据研究中的应用

本项工作主要研究宽频带数字地震记录中小当量爆破(即矿山爆破)与小震级地震事件的识别问题。以前我们利用北京遥测地震台网的短周期模拟记录资料和DAPS(台网中心数字化)系统(郑秀芬等,2000;王凤霞,2000)产出的资料作过一些研究(郑秀芬等,2006),取得了一定的进展。在此基础上,利用宽频带数字地震记录资料,进行了小当量爆破与小震级地震事件在近场源短周期面波质点运动轨迹方面的识别研究,并给出了一定的判据。     

GPR velocity determination by image-wave remigration

We have studied in detail the theoretical and numerical properties of a finite-difference algorithm for image-wave time-remigration. For a number of synthetic models, numerical experiments have been performed. For these examples, we obtained perfect agreement between the theoretical predictions and numerical results. The examples also prove the computational efficiency of the algorithm. An application to ground-penetrating-radar (GPR) data demonstrates that image-wave remigration can be used to estimate models with laterally varying velocities. The quality of the latter is confirmed by a final zero-offset time migration.     

中国数字地震台网的建设与发展

ldquo;十五rdquo;（2001——2005年）期间,中国地震观测系统得到了迅速的发展,中国地震局完成了ldquo;中国数字地震观测网络rdquo;项目建设,将所有模拟地震观测系统全部进行了数字化改造,并新建了一些数字化地震台站,标志着中国的地震观测已进入数字时代. 本文介绍了新一代国家数字地震台网、区域数字地震台网、火山数字地震台网和流动数字地震台网的规模、布局原则和主要功能.      

Construction and development of China digital seismological observation network

The seismological observation system in China has experienced rapid development over the Tenth Five-year Plan period. China Earthquake Administration (CEA) has completed the establishment of China digital seismological observation network. CEA has accomplished analog-to-digital conversion of the existing seismological observation systems and set up a number of new digital seismic stations. This indicates full digitization of seismological ob-servation in China. This paper presents an overview of the scale,layout principle and major functions of the up-dated national digital seismograph network,regional digital seismograph network,and digital seismograph net-work for volcano monitoring and mobile digital seismograph networks in China.     

“彩虹”台风对宽频带地震计记录的影响

201522号"彩虹"台风于2015年10月4日14时前后登陆广东湛江坡头区,对其登陆及前后1周时间内,相邻地震台站宽频带地震计记录的台基噪声速度幅值相关关系进行分析,结果显示:(1)随着台风发育和消亡,在台风登陆的8区域附近,地震台记录的速度幅值由逐渐增加变为逐渐减小,相邻地震台速度幅值线性相关系数达0.9以上;(2)滤波后1—10 s频段数据,相邻地震台速度幅值比趋于稳定。可见"彩虹"台风对1—10 s频段台基噪声影响明显,相邻地震台幅值比趋于稳定。     

基于激发振幅成像条件的探地雷达逆时偏移成像

针对基于互相关成像条件的探地雷达（GPR）逆时偏移计算效率低、存储量大及易产生低频假象的不足,本文将激发振幅成像条件应用于GPR逆时偏移成像中.通过在源点电磁波场正向传播过程计算每个网格点的能量密度,并保存最大能量密度的时刻和相应的电磁波场值;在接收点电磁波场逆向传播过程提取每个网格点最大能量密度时刻及对应的电磁波场值,并利用保存的最大能量源点电磁波场及走时做归一化,从而获得了依赖反射系数成像剖面,避免了源点正向传播电磁波场的存储和重建.此外,为了提高电磁波场的模拟精度,采用了基于三角形剖分的时间域有限单元法（FETD）计算电磁波正向和逆向传播过程.最后通过模型试算表明：激发振幅成像条件相比于归一化互相关成像条件,成像结果低频噪声更弱,空间分辨率更高,计算效率提高了近2倍.     

Regional variation of spectral parameters for seismic design from broadband probabilistic seismic hazard analysis

The characterisation of the seismic hazard input is a critical element of any seismic design code, not only in terms of the absolute levels of ground motion considered but also of the shape of the design spectrum. In the case of Europe, future revisions of the seismic design provisions, both at a national and a pan‐European level, may implement considerable modifications to the existing provisions in light of recent seismic hazard models, such as the 2013 European Seismic Hazard Model. Constraint of the shape of the long‐period design spectrum from seismic hazard estimates on such a scale has not been possible, however, owing to the limited spectral period range of existing ground motion models. Building upon recent developments in ground motion modelling, the 2013 European Seismic Hazard Model is adapted here with a new ground motion logic tree to provide a broadband Probabilistic Seismic Hazard Analysis for rock sites across a spectral period range from 0.05 seconds to 10.0 seconds. The resulting uniform hazard spectra (UHS) are compared against existing results for European and broadband Probabilistic Seismic Hazard Analysis and against a proposed formulation of a generalised design spectrum in which controlling parameters can be optimised to best fit the uniform hazard spectra in order to demonstrate their variability on a European scale. Significant variations in the controlling parameters of the design spectrum are seen both across and within stable and active regions. These trends can help guide recalibrations of the code spectra in future revisions to seismic design codes, particularly for the longer‐period displacement spectrum.