Two-dimensional physical-based inversion of confined and unconfined aquifers under unknown boundary conditions

An inverse method is developed to simultaneously estimate multiple hydraulic conductivities, source/sink strengths, and boundary conditions, for two-dimensional confined and unconfined aquifers under non-pumping or pumping conditions. The method incorporates noisy observed data (hydraulic heads, groundwater fluxes, or well rates) at measurement locations. With a set of hybrid formulations, given sufficient measurement data, the method yields well-posed systems of equations that can be solved efficiently via nonlinear optimization. The solution is stable when measurement errors are increased. The method is successfully tested on problems with regular and irregular geometries, different heterogeneity patterns and variances (maximum K_max/K_min tested is 10,000), and error magnitudes. Under non-pumping conditions, when error-free observed data are used, the estimated conductivities and recharge rates are accurate within 8% of the true values. When data contain increasing errors, the estimated parameters become less accurate, as expected. For problems where the underlying parameter variation is unknown, equivalent conductivities and average recharge rates can be estimated. Under pumping (and/or injection) conditions, a hybrid formulation is developed to address these local source/sink effects, while different types of boundary conditions can also exert significant influences on drawdowns. Local grid refinement near wells is not needed to obtain accurate results, thus inversion is successful with coarse inverse grids, leading to high computation efficiency. Furthermore, flux measurements are not needed for the inversion to succeed; data requirement of the method is thus not much different from that of interpreting classic well tests. Finally, inversion accuracy is not sensitive to the degree of nonlinearity of the flow equations. Performance of the inverse method for confined and unconfined aquifer problems is similar in terms of the accuracy of the estimated parameters, the recovered head fields, and the solver speed.     

高采样率四分量钻孔应变同震响应分析

In this paper, we adopt the observation data of two 10Hz YRY 4-component borehole strainmeters and one 100Hz FBS-3B broadband seismometer to study the responses of their observations to the April 11, 2012 Mw 8.6 earthquake off the west coast of northern Sumatra, and compare the response characteristics during the coseismic stage after preprocessing of the data. We analyze the spectrum＇s dynamic process during the coseismic stage with the S transformation method, and discuss the spectrum＇s details in different seismic phases. The S transformation results of the data of seismometer and borehole strainmeter at the same station show that the coseismic spectrum evolution of the two kinds of observation are similar to each other and can be cross-referenced in indentifying the wave signals, which proves that the borehole strainmeter measurements at high frequencies are reliable.     

四川前兆钻孔应变观测数据质量影响因素分析

钻孔应变观测的目的是为地震预测及地震科学研究提供高质量的观测数据,台站钻孔应变观测受到不同外界因素干扰时,观测数据的完整率和观测数据内精度也会不同程度地受到影响,对各种干扰因素的认识、分析、排除,是提高观测数据质量最好、也是最有效的途径。     

太阳能供电系统在天津测震台站的应用

利用太阳能供电系统解决天津市部分台站无法接入交流供电的问题,对部分台供电系统进行改造,采用复合式供电模式,避免农忙或雷雨季节停电问题,以提升台网整体数据传输连续率。     

Influence of confining pressure and impact loading on mechanical properties of amphibolite and sericite-quartz schist

In order to investigate the dynamic mechanical properties of amphibolite and sericite-quartz schist under confi ning pressure, two rocks are subjected to impact loadings with different strain rates and confi ning pressures by using split Hopkinson pressure bar equipment with a confi ning pressure device. Based on the experimental results, the stress-strain curves are analyzed and the effects of confi ning pressure and strain rates on the dynamic compressive strength, peak strain and failure mode are summarized. The results show that:(1) The characteristics of two rocks in the ascent stage of the stressstrain curve are basically the same, but in the descent stage, the rocks gradually show plastic deformation characteristics as the confi ning pressure increases.(2) The dynamic compressive strength and peak strain of two rocks increase as the strain rate increases and the confi ning pressure effects are obvious.(3) Due to the effect of confi ning pressure, the normal stress on the damage surface of the rock increases correspondingly, the bearing capacity of the crack friction exceeds the material cohesion and the slippage of the fractured rock is controlled, which all lead to the compression and shear failure mode of rock. The theoretical analysis and experimental methods to study the dynamic failure mode and other related characteristics of rock are useful in developing standards for engineering practice.     

Holocene slip rate and paleoearthquake records of the Salt Lake segment of the Northern Zhongtiaoshan Fault,Shanxi Province

The Northern Zhongtiaoshan Fault is a major deep fault at the southern margin of the Yuncheng Basin. There have been few studies on the fault, and the historical earthquakes are few and weak. However, the intensity of activity on the fault should never be underestimated. Through interpretations of aerial images, topography measurements and excavation of trenches, this paper studied the fault distribution, the surface deformation and the activity of the normal fault south of Salt Lake near the city of Yuncheng. By tracing faults in the three trenches, it was found that there had been at least three large paleoseismic events, at 1–3.5, 3.6–4.4 and 7.4–8.8 ka BP. Employing 14 C dating, we determined the same gravel layers in the uplifted side and downthrown side. Making differential Global Positioning System measurements of the vertical difference and topographic profile, we obtained the mean slip rate of the Northern Zhongtiaoshan Fault since 24.7 ka BP(0.75±0.05 mm/a). Using the results of relevant studies, we calculated the possible vertical fault displacement of one earthquake(2.35 m) and obtained the recurrence interval of characteristic earthquakes as 2940–3360 a after dividing the displacement by the mean slip rate.     

人工冻土围压SHPB试验与冲击压缩特性分析

利用分离式Hopkinson压杆（SHPB）,以铝质套筒作为围压装置,分别研究温度为-8、-12、-16 ℃在不同应变率下的人工冻结黏土围压状态变形特征和轴向动态应力-应变关系。研究结果表明：在围压状态下,冻土呈黏塑性破坏特征;当人工冻结黏土温度为-16 ℃、平均应变率分别为410、457、525、650、827 s-1时,其最大应力分别为10.76、12.18、14.27、20.24、23.34 MPa,最大应变分别为0.081 7、0.097 2、0.105 0、0.131 0和0.166 0,表现出较强应变率效应;-12 ℃和-16 ℃时在应变率为457 s-1下的最大应力分别为8.28 MPa和12.18 MPa;当应变率相同时,温度越低,最大应力越大,冻结黏土表现出较强的温度相关性。人工冻土的动力学特性为冻土开挖方法的研究提供依据。     

粤西-琼东北近海沉积物的运移和沉积

为了深入认识珠江现代入海物质在粤西陆架随海流迁移扩散的路径和沉积中心,利用Gao-Collins方法分析了粤西-琼东北近海1 515个站位的粒径趋势,并用²¹⁰Pb法测定了8支柱样的现代沉积速率。结果表明,在粤西沿岸流和南海暖流这两个相向海流的共同作用下,珠江口外珠江来源的泥质沉积物的主体被限制在-50 m等深线以浅的内陆架。现代珠江入海物质能维持粤西陆架泥质沉积区0.1 cm/a左右的现代沉积速率。在川山群岛至海陵岛一带和琼州海峡东侧泥质区,分别受岛屿阻挡和逆时针中尺度涡旋的影响,形成了现代沉积中心。在沉积物不同粒级的来源和搬运方式存在差异的地方,粒径趋势分析结果可能主要反映的是粗颗粒沉积物的运移趋势,而非细颗粒沉积物的运移方向。     

乌兰布和沙漠东北缘地表风沙流结构特征

在国家林业局磴口荒漠生态站长期监测的基础上,利用多种积沙仪,对乌兰布和沙漠东北缘流动沙丘、油蒿半固定沙丘、白刺半固定沙丘、油蒿固定沙丘、白刺固定沙丘5种典型下垫面近地面（0～100 cm）的风沙流输沙量进行了实地观测和对比分析。结果表明：（1） 输沙率（q）随高度（h）增加呈幂函数（q=ah^-b,R²≥0.8409）规律衰减,随风速（v）增大呈幂函数（q=av^b,R²≥0.9256）规律增加,42.8%～70.7%的输沙量分布在10 cm高度内,67.6%～90.0%的输沙量分布于30 cm高度内。当地表植被盖度达到40%以上时,输沙率下降至无植被覆盖地表输沙率的6.6%以下,可有效阻止地表风蚀。（2） 沙物质主要由粒径为50～250 μm的细沙和极细沙构成,各高度层风蚀物粒度组成服从单峰态分布,峰值在100～250 μm。随高度增加,风蚀物粒径范围趋于变窄,粒径趋于更细。（3） 起沙风多出现在WSW和NW方向,占全年起沙风的53.19%。风沙流中跃移输沙、蠕移输沙的空间分布在理论上应与风向频率分布基本一致,差异性主要由各方位风的强度和持续时间等因素导致。研究结果可为该区域防沙工程设计提供理论参考。