基于天地图高精度建筑物的四川宝兴县人口估算

为了提高震前灾害风险评估和震后灾情快速评估工作中人口空间分布估计的准确性,利用2016年四川宝兴县乡镇人口数据及天地图中的建筑物数据,运用居住建筑人口密度方法得到四川宝兴县各乡镇居住建筑物尺度的人口分布矢量数据,并利用实地调研获取的单体建筑物实际人口进行精度验证。实验结果表明:以居住建筑物体积作为人口空间分布指示因子建模,得到的拟合精度为0.9027,人口平均相对误差为15.23%,结果具有可靠性,可为震前灾害风险评估和震后灾情快速评估提供更为可靠的数据支撑。     

地磁低点时间与经度的相关性分析

地磁低点时间在空间分布上的主要特征是随着经度变化而变化。为了求出这种变化关系的解析式,首先使用国家地磁台网的数据计算甘肃省近三年13个地磁台站的低点时间序列和低点时间的期望,并绘制了低点时间序列的频次分布图和概率密度曲线;然后对低点时间与台站经度的关系做线性回归,并指出这个线性回归方程应无限趋近于“格林尼治时间-经度”关系式。文章第一次提出台站经度与地磁Z分量低点时间的关系式,并提出它的趋近方程。各台站低点时间的期望就是地磁低点时间的正常背景值,它是判定地磁低点时间异常与否的参考标准。本文的工作完善和发展了丁鉴海先生的地磁低点位移法。     

地震活动性总体参量Rt在北京及邻区地震预测中的应用

采用地震活动性总体参量R_t方法,研究北京及邻区R_t值在中等地震前随时间的变化特征,分析跟踪地震发生前研究区域地震活动状态,探讨中等地震孕震过程的异常信息的变化特征。结果显示:当R_t值大于阈值0.84时,研究区域地震活动状态比较稳定,发生中等地震的可能性较小;反之,表明地震活动处于不稳定状态,具有发生中等地震的危险。检验R_t值的地震预测效能,预测效果比较理想,利用地震活动状态参量R_t研究北京及邻区地震活动状态,判定中等地震发生的风险性,具有一定预测意义。     

CO2 saturation estimates at Sleipner (North Sea) from seismic tomography and rock physics inversion

CO₂ saturations are estimated at Sleipner using a two-step imaging workflow. The workflow combines seismic tomography (full-waveform inversion) and rock physics inversion and is applied to a two-dimensional seismic line located near the injection point at Sleipner. We use baseline data (1994 vintage, before CO₂ injection) and monitor data that was acquired after 12 years of CO₂ injection (2008 vintage). P-wave velocity models are generated using the Full waveform inversion technology and then, we invert selected rock physics parameters using an rock physics inversion methodology. Full waveform inversion provides high-resolution P-wave velocity models both for baseline and monitor data. The physical relations between rock physics properties and acoustic wave velocities in the Utsira unconsolidated sandstone (reservoir formation) are defined using a dynamic rock physics model based on well-known Biot–Gassmann theories. For data prior to injection, rock frame properties (porosity, bulk and shear dry moduli) are estimated using rock physics inversion that allows deriving physically consistent properties with related uncertainty. We show that the uncertainty related to limited input data (only P-wave velocity) is not an issue because the mean values of parameters are correct. These rock frame properties are then used as a priori constraint in the monitor case. For monitor data, the Full waveform inversion results show nicely resolved thin layers of CO₂–brine saturated sandstones under intra-reservoir shale layers. The CO₂ saturation estimation is carried out by plugging an effective fluid phase in the rock physics model. Calculating the effective fluid bulk modulus of the brine–CO₂ mixture (using Brie equation in our study) is shown to be the key factor to link P-wave velocity to CO₂ saturation. The inversion tests are done with several values of Brie/patchiness exponent and show that the CO₂ saturation estimates are varying between 0.30 and 0.90 depending on the rock physics model and the location in the reservoir. The uncertainty in CO₂ saturation estimation is usually lower than 0.20. When the patchiness exponent is considered as unknown, the inversion is less constrained and we end up with values of exponent varying between 5 and 20 and up to 33 in specific reservoir areas. These estimations tend to show that the CO₂–brine mixing is between uniform and patchy mixing and variable throughout the reservoir.     

主动震源在中国区域尺度及水库地震监测中的应用

综述精密可控震源与陆上气枪2种主动震源特性及在国内区域尺度上的应用,估算观测介质波速随时间变化的精度,探讨主动震源在构建水库地震观测介质波速随时间变化中的系统应用。     

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Use of sparse iterative methods for the resolution of three-dimensional soil/structure interaction problems

In this paper we present a study of the performance of sparse iterative solvers regarding the resolution of three-dimensional and non-linear problems encountered in soil/structure interaction. It is composed of two parts. In the first one, we present briefly iterative methods and preconditioners used in this study, then we analyse their performance on three soil/structure interaction problems: a shallow foundation under a vertical loading, a single pile subjected to a lateral loading and the construction of a lined tunnel in a soft soil. Tests are performed assuming an elastic–perfectly plastic constitutive law for the soil material with a non-associated Mohr–Coulomb flow rule. Copyright © 1999 John Wiley & Sons, Ltd.     

局地温度变化中各项因子的定量估算

基于安徽沿江地区高温、降水两类天气过程,利用逐时实测气温、NCAR/NCEP再分析资料提供的风、气温、垂直速度等资料,从天气学基本原理出发,由天气学原理和ω与w的换算关系式等估算局地气温的平流项、垂直项大小,并由实测气温经过计算获得非绝热项的估算值。结果表明,各项对于局地温度的升温作用为：平流项的变化相对比较复杂,就高温天气而言平流项的作用往往使得局地温度降低,但是两类天气平流项的作用非常弱;两类天气过程中的垂直项都导致局地温度升高,比例占1％～5％;可以说,安徽沿江地区局地温度的增温主要来自于非绝热项,增温比例常常超过95％,它对局地温度的升高具有举足轻重的作用。     

用气象卫星资料估算吉林省主要农作物产量

净第一性生产力（Npp）分析是全球变化研究中广为利用的方法,利用气象卫星资料获得年际植被指数（Iv）估算Npp建立不同作物的Npp与其产量的关系模型,即可实现对粮食总产和不同作物产量的估算。文中介绍了应用净第一性生产力遥感（NPP—RS）模型对吉林省粮食总产和主要作物产量进行估算的方法。采用NPP—RS模型,对1995～2000年吉林省的粮食总产及主要农作物玉米、水稻产量进行了动态估算。对粮食总产估产的平均相对误差为13．6％,玉米的平均相对误差为17．6％,水稻的平均相对误差为6．7％。要提高用此方法进行遥感估产的精度,还需要对当年的种植制度、种植结构的变化有所了解,注意当年的灾情,增加灾害影响系数。