正倾滑活动断裂垂直位移定量研究中相关问题的讨论

当探槽开挖长度未跨过断层变形带时，得到的断层垂直位移将偏离断层活动的真实情况，在缺少依据帮助确定断层陡坎原始下坡角的具体位置时，通过断层陡坎高度获得的断层垂直位移也将与实际情况有较大的偏离，文中对此进行了讨论。并讨论了应用断层两侧近水平地层累积变位量的分解确定古地震事件期次的方法，以及探槽剖面中断层两侧同层地层厚度差异是断层活动事件的反映等问题。引用了内蒙古大青山山前断裂和狼山山前断裂、北京平原夏垫断裂和南口－孙河断裂及日本丹那断层探槽开挖的实例。     

俯冲带库仑楔形体力学

楔形体理论研究楔形体在底部摩擦力、重力和边界外力共同作用下内部的应力状态,有助于我们定量分析断层强度和岩石性质与楔形体稳定状态之间的关系.本文首先简要介绍基于不同楔形体材料而得出的应力解析解.然后介绍基于理想弹塑性材料的俯冲带库仑楔应力解析解.最后介绍基于该解析解而提出的动态库仑楔形体理论.俯冲带地震反射剖面数据表明,...     

跨祁连山-海原断裂带综合观测剖面资料分析

通过对跨祁连山-海原断裂带的民乐、华藏寺和沙沟河等3个剖面2005～2009年GPS、水准及重力观测资料的分析,得到各观测量在每个时间段的变化特征,对剖面所跨主要断裂的活动特征有所了解。发现跨不同剖面的昌马-俄博断裂、毛毛山断裂、庄浪河断裂和海原断裂附近点位的位移和重力变化都较大,表明这些断层活动性较强;通过分析各剖面垂直位移与重力变化的关系,可知重力变化主要由于物质的迁移引起。GPS资料分析表明,2006～2007年水平运动基本沿断层走向,而2007～2008年水平位移偏离断层走向,以东向位移增大为主;通过进一步对剖面周围的中国地壳运动网络连续观测站坐标时间序列的去线性分析,得知2007～2008年的观测结果与汶川地震的影响有关。用2008～2009年的重力变化同重力布格异常背景相比,可知民乐剖面附近处于调整恢复阶段,而华藏寺和沙沟河剖面附近的异常仍没有完全解除。     

南天山低角度逆断层古地震破裂变形模式

近年来逆冲型破坏性地震频发,这对于逆冲型破裂的古地震研究方法提出了新的要求。由于逆断层角度的变化,在地震中可能表现出截然不同的破裂样式。通过对南天山大量古地震探槽开挖和古地震事件分析研究中发现,低角度逆断层的古地震具有一些常见的破裂类型。本文中挑选了位于南天山三个重要山前逆断裂褶皱带:西段柯坪推覆系、中段库车坳陷的秋里塔格褶皱带和东段焉耆盆地北缘和静逆断裂褶皱带的7个典型探槽剖面,对这类低角度逆断层的古地震进行变形模式、事件识别和位移量计算的总结归纳。低角度逆断层古地震破裂具有以下几种样式并具有各自识别古地震事件和计算位移量的方法:1一条断面对应一次事件的破裂形式,利用断面上断点位置识别古地震事件并判断事件的先后顺序。每个断面各自的位移量正好代表一次事件的位移量。2单条断面多次破裂的样式可以通过上下不同地层的位错量差异判断古地震事件,各个相邻地层之间的位错量差值代表古地震事件的位移量。3多条断面同时破裂的情况表现为多条断面被相同一套地层覆盖,事件位移量为多条断面的位错量之和。4挠曲变形和"推土机"作用是低角度逆断层古地震破裂常见的变形方式,这部分变形量不能忽略,可以通过线平衡和面平衡方法获得断层水平缩短量。     

凹凸体位错非均匀性对断层引起地表位移的影响

在已有的凹凸体震源模型基础上考虑凹凸体位错非均匀性,提出改进的凹凸体位错模式.新的位错模式随机设置凹凸体上各子断层位错量,同时在凹凸体与背景区交界处设置位错平缓变化的区域.以1989年美国 LomaPrieta地震为例,计算不同断层位错模式下引起的地表位移,并与反演得到真实情况下地表的位移作对比,验证改进凹凸体位错模式的可靠性.结果显示,使用改进的渐变凹凸体非均匀位错模式计算时,与真实情况下竖向地表位移差大于8cm 的区域面积为 43km2,相较凹凸体均匀位错模式缩减25%;水平地表位移差大于8cm 区域面积为117km2,相较凹凸体均匀位错模式缩减达31%.利用改进的渐变凹凸体非均匀位错模式,计算1679年三河—平谷大地震在北京地区形成的地表位移场.北京市外,最大竖向地表位移大于4．8m,最大水平地表位移大于2．6m,均出现在三河附近;北京市内,通州区至平谷区一带地表位移最大,最大水平地表位移大于 2．6m,最大竖向地表位移大于1m.研究结果可为今后北京地区的抗震设防提供参考.     

华北地区MS≥6.5级地震震源断层参数的研究

本文根据地震和地震构造等资料，研究华北地区公元1300年以来MS≥6.5级地震的发震断裂的基本参数.利用1966年以来隆尧、海城、渤海和唐山等有仪器记录的地震的相关参数进行回归分析得出了地震烈度Ⅷ度区长轴长度与余震区长轴长度的回归关系式及震级与震源体破裂长度的回归关系式.用余震区长轴长度代替震源体的破裂长度，从而给出各次地震的震源断层破裂长度.利用地震测深的地壳结构构造剖面、地震序列的震源分布、壳内低速层和地壳上部的构造、盆地构造与居里面分布和已知地震震源分布等资料推断了震源破裂的上下界.基于一定的合理假定推导出了断层滑动角的估计方法，并应用于本研究区，得出了各次事件的断层滑动角.     

地电阻率变化与孕震过程研究

在分析唐山７．８级地震前后地电阻率异常变化特征的基础上，研究地电阻率异常量△ρ／ρ０与应变的关系，给出了地电阻率异常量△ρｓ／ρ０对应变ε的转换关系式；分析和研究地电阻率异常发展，演变特征与地震孕震，发生过程的联系及其前兆异常标志。     

多点输入反应谱中耦合系数的研究

首先利用虚拟激励法推导了仅考虑行波效应下多点输入反应谱表达式,重点对多点输入反应谱中动位移耦合系数ρijpq及拟静位移耦合系数ρSpq的计算方法及其特性进行了研究。为了避免繁琐的积分运算,提出了一种"拟合+插值"的耦合系数计算方法,不但精度高,而且大大提高了计算效率。研究表明,ρijpq相对于地震波到达支座点的时差Δt具有明显的三角函数的关系;从总体趋势上看,ρijpq绝对值基本随ωj/ωi的增大而减少,这一点与一致输入时的振型耦联系数ρij相同。在仅考虑行波效应的情况下,可以认为,各支座点的拟静力位移完全相关,即ρSpq=1,结构拟静力位移谱与地震动的位移谱相同。     

隐伏走滑断层破裂扩展特征的实验研究

通过模拟实验研究了基岩中走滑断层在上覆沉积层中的破裂扩展特征,利用白光数字散斑相关方法分析了沉积层表面变形场的演化过程,重点研究了基岩断层位移和沉积层厚度的影响。结果表明,在沉积层厚度一定的情况下,随基岩断层的滑动,沉积层中围绕断层投影线逐渐形成一个变形带以及由张性破裂和剪切破裂组成的破裂带,基岩断层的位移越大,沉积层中的变形带越宽、变形越强烈;但当基岩断层位移超过某一临界值后,变形带宽度将保持稳定,只是变形随断层位移增加而更集中。对于同样的基岩断层位移,沉积层厚度越大,受基岩断层控制的变形破裂带越宽,即基岩断层的影响范围越大;但当沉积层厚度超过某一临界值时,沉积层的变形发生了变化,沉积层表面并不存在与基岩断层走向一致的变形带,而是发育了较大尺度、与基岩断层走向斜交的张剪性破裂带。实验结果意味着,临界断层位移和临界沉积层厚度对于确定隐伏断层发震产生的地表变形和破坏具有重要意义     

独山子山前断层现今活动特征与形变异常研究

利用新疆独山子台跨断层形变观测资料,对独山子山前断层的活动速率、活动特征及区域应力场进行了分析,结合震源机制解的研究成果进行了对比验证,同时应用"速率累加"分析方法进行了异常提取.结果显示:①独山子一安集海断裂垂直位移年平均变化量为0.106 mm,沿基线方向的水平位移年平均变化量为0.189 mm,沿断层走向的水平走滑年平均变化量为-0.883 mm,断层活动以右旋走滑为主兼具逆冲分量;②1993～2007年独山子断层的最大水平主压应力方向在339.85°～346.78°之间,平均为344.23°;③乌苏5.1级地震前,独山子台的形变记录曲线有较明显的速率异常变化与同震形变波动.     

Ashes to ashes, dust to dust

An account of the RAS Presidential Address of 11 February 2000, given by David A Williams , Perren Professor of Astronomy, University College London.     

A subregional-scale method to assess aquifer vulnerability to pesticides

A method to predict aquifer vulnerability to pesticide contamination at the subregional scale was developed. The assessment method was designed to incorporate relevant hydrologic and pesticide-transport information and to use generally available data. The method assumes steady-state advection of pesticides in the vadose zone, including sorption and biological decay. The solution is presented as a vulnerability index (VI) that increases as the aquifer vulnerability increases. The hydrologic input data for the VI model are obtained from the soil survey geographic database. Pesticides were grouped into three leachability classes using a leachability ratio (half-life divided by organic carbon partition coefficient). Pesticide transformation is assumed to occur in the surface layer. The influence of vertical transport in the remainder of the vadose zone has been incorporated by applying a multiplying factor to the VI that varies with depth to ground water. Hydraulic conductivity is used as a surrogate for soil-water velocity for practical purposes. The performance of the VI model is evaluated using ground water data from Weld County, Colorado. The model is demonstrated to be successful at predicting relative vulnerability, defined as the magnitude of pesticide concentration and percent of wells in a unit that exhibit a pesticide detection. Areas of low, medium, and high vulnerability are assigned. Results indicate that the vulnerability classifications are most dependent on the leachability ratio, hydraulic conductivity, and organic carbon content.     

1996～2003年全世界灾害地震统计分析

讨论了1996～2003年8年期间全世界灾害地震的空间分布特征和地震灾情与全球地震活动性、地震震级和地震发震时刻的关系。结果表明：这8年期间地震灾情与全球地震活动性及地震震级无明显的统计相关关系,似乎与发震的国度、地震的发震时刻有一定的关系。     

钢筋混凝土框架结构地震破坏的研究

本文对钢筋混凝土框架的地震破坏进行了计算机模拟试验研究，指出了破坏过程中结构瞬态动力特性的变化特征，研究了影响瞬态动力特性的若干因素，明晰了结构整体耗能能力的大小与结构周期的延长之间的关系。作者认为结构瞬态动力特性和地震动的特性是影响结构破坏过程的主要因素，指出结构地震破坏模拟具有广阔的应用前景。     

Multilevel samplers as microcosms to assess microbial response to biostimulation

Passive multilevel samplers (MLS) containing a solid matrix for microbial colonization were used as in situ microcosms in conjunction with a push-pull biostimulation experiment designed to promote biological U(VI) and Tc(VII) reduction. MLS were deployed at 24 elevations in the injection well and two downgradient wells to investigate the spatial variability in microbial community composition and growth prior to and following biostimulation. The microbial community was characterized by real-time quantitative polymerase chain reaction (Q-PCR) quantification of bacteria, NO(3)(-)-reducing bacteria (nirS and nirK), delta-proteobacteria, Geobacter sp., and methanogens (mcrA). Pretest cell densities were low overall but varied substantially with significantly greater bacterial populations detected at circumneutral pH (t-test, alpha= 0.05), suggesting carbon substrate and low pH limitations of microbial activity. Although pretest cell densities were low, denitrifying bacteria were dominant members of the microbial community. Biostimulation with an ethanol-amended ground water resulted in concurrent NO(3)(-) and Tc(VII) reduction, followed by U(VI) reduction. Q-PCR analysis of MLS revealed significant (1 to 2 orders of magnitude, Mann-Whitney U-test, alpha= 0.05) increases in cell densities of bacteria, denitrifiers, delta-proteobacteria, Geobacter sp., and methanogens in response to biostimulation. Traditionally, characterization of sediment samples has been used to investigate the microbial community response to biostimulation; however, collection of sediment samples is expensive and not conducive to deep aquifers or temporal studies. The results presented demonstrate that push-pull tests with passive MLS provide an inexpensive approach to determine the effect of biostimulation on contaminant concentrations, geochemical conditions, and the microbial community composition and function.     

Converting Radial Distortions Due to Geopotential Models to Geopotential Stokes Coefficients

A methodology for improving geopotential models has been developed. Theoretical relations have been derived converting coefficients in harmonic expansions for radial distortions due to geopotential models into geopotential Stokes coefficients. Terms of the order of 10 ^–10 in magnitude have been retained.     

Semigroup solutions to stochastic unsteady groundwater flow subject to random parameters

Two methods for the solution of partial differential equations (PDE) for the general case of random in time physical parameters are presented and their application to the solution of unsteady regional groundwater flow equations are illustrated. The first method is the semigroup approach which directly offers a solution without resorting to closure approximations (hierarchy techniques), perturbation techniques, or Montecarlo simulation techniques. The semigroup approach can also handle the general stochastic problem when randomness also appears as initial conditions, boundary conditions or forcing terms. The second method is an approximation scheme to obtain the semigroup solution in complex cases and permits the solution of equations with more than one random coefficient.