SplitRacer:用于远震剪切波分裂半自动分析和解释的MATLAB代码和图形用户界面

我们给出了MATLAB环境下的一个图形用户界面,用于远震剪切波分裂分析。鉴于越来越大型的地震学实验,设计SplitRacer来快速处理大型数据集,因为它集成了自动和用户主导步骤,这使得可根据用户自己的质量标准来进行直观的分析。SplitRacer提供了一系列用来确保精确测量以及用户友好的特征。可以从数字地震台网网络服务国际联合会成员的所有数据中心直接下载数据。将现有数据分割成1个小时的三分量地震波形后就很容易被使用。起初是自动数据检查,然后是对有问题的震相的目视评估。我们通过分析台站记录事件的质点运动并和理论反方位角进行比较来估计传感器的可能偏差。剪切波分裂分析是基于最小(切向)能量法(Silver and Chan,1991),这约束了快波偏振方向和延迟时间。可以对一系列时间窗进行重复测量来做统计误差分析。SplitRacer提供了每个台站单个震相分裂测量的概况,这可用于检测方位依赖性。为了推断台站下方的各向异性,SplitRacer为用一个或两个各向异性层模型,或平滑变化的各向异性模型来拟合观测数据提供了可能。此外,SplitRacer还提供了一个和两个假想层的多震相联合分裂分析,其中同时使用给定台站的所有事件来约束各向异性模型。这显著降低了噪声的影响,并使测量更稳健。作为示例,我们将应用SplitRacer来约束伯克利数字地震台网的固定台站BKS下方的地震各向异性。     

Transient oceanic and tidal contributions to water exchange and residence times in a coastal upwelling system in the NE Atlantic: the Pontevedra Ria, Galicia

An analysis of the intra-annual variability of hydrographic residence times, tau, is presented for the Pontevedra Ria--a large coastal system in NW Spain with a deep, unobstructed connection with the Atlantic Ocean. Ria-offshore water exchange and tau were quantified with an iterative approach to the fraction of freshwater method using 23 quasi-steady state water-salt budgets. Excluding prolonged flushing due to downwelling events at the end of the upwelling season, mean was 6 +/- 2 day in the central ria and 2 +/- 1 day in the internal ria. The tidal contribution, equal to 10-25% of total water renewal, was quantified for the first time for a Galician ria with the hydrodynamic model estuarine contaminant simulator (ECoS). The relationship between tau and residual freshwater input, Qz, was atypical, since Qz played a minor role in water exchange in comparison to periodic upwelling of East North Atlantic Central Water (ENACW) from the continental shelf mainly during spring and summer. During positive upwelling stress, the intrusion of ENACW into the ria produced enhanced flushing and tau < 4 day in the central ria and < 2 days in the internal ria. Under downwelling favourable conditions, water was retained and tau prolonged to >8 and >5 days, respectively. A quantitative parameterisation of tau with upwelling and Qz was weakly significant, due to the short-term variability in ria salinity. This paper elucidates problems associated with the use of water budgets to transient coastal systems such as the Pontevedra Ria.     

Surface flow boundary conditions in modeling land subsidence due to fluid withdrawal

Land subsidence due to subsurface fluid (water, gas, oil) withdrawal is often predicted by either finite element or finite difference numerical models based on coupled poroelastic theory, where the soil is represented as a semi-infinite medium bounded by the traction-free (ground) surface. One of the variables playing a most important role on the final outcome is the flow condition used on the traction-free boundary, which may be assumed as either permeable or impermeable. Although occasionally justified, the assumption of no-flow surface seems to be in general rather unrealistic. A permeable boundary where the fluid pressure is fixed to the external atmospheric pressure appears to be more appropriate. This paper addresses the response, in terms of land subsidence, obtained with a coupled poroelastic finite element model that simulates a distributed pumping from a horizontal aquifer confined between two relatively impervious layers, and takes either a permeable boundary surface, i.e., constant hydraulic potential, or an impermeable boundary, i.e., a zero Neumann flow condition. The analysis reveals that land subsidence is rather sensitive to the flow condition implemented on the traction-free boundary. In general, the no-flow condition leads to an overestimate of the predicted ground surface settlement, which could even be 1 order of magnitude larger than that obtained with the permeable boundary.     

Shape factors of cylindrical piezometers in uniform soil

This article presents the analytical solution of Laplace equation for the steady flow around open-ended cylindrical piezometers located in an infinite, isotropic, and incompressible saturated soil. Shape factors are obtained for piezometers with varying length-to-diameter ratios. Comparisons are made with published factors obtained by means of approximate analytical solutions, numerical approaches, and measurements in electric analog models. It is shown that some expressions that are currently used in practice are inadequate and should be abandoned.     

Restoration of wadi aquifers by artificial recharge with treated waste water

Fresh water resources within the Kingdom of Saudi Arabia are a rare and precious commodity that must be managed within a context of integrated water management. Wadi aquifers contain a high percentage of the naturally occurring fresh groundwater in the Kingdom. This resource is currently overused and has become depleted or contaminated at many locations. One resource that could be used to restore or enhance the fresh water resources within wadi aquifers is treated municipal waste water (reclaimed water). Each year about 80 percent of the country's treated municipal waste water is discharged to waste without any beneficial use. These discharges not only represent a lost water resource, but also create a number of adverse environmental impacts, such as damage to sensitive nearshore marine environments and creation of high-salinity interior surface water areas. An investigation of the hydrogeology of wadi aquifers in Saudi Arabia revealed that these aquifers can be used to develop aquifer recharge and recovery (ARR) systems that will be able to treat the impaired-quality water, store it until needed, and allow recovery of the water for transmittal to areas in demand. Full-engineered ARR systems can be designed at high capacities within wadi aquifer systems that can operate in concert with the natural role of wadis, while providing the required functions of additional treatment, storage and recovery of reclaimed water, while reducing the need to develop additional, energy-intensive desalination to meet new water supply demands.     

西西里岛东部地震预警参数评估

地震预警系统正在成为适用于实时地震风险管理的一个工具。事实上,由于地震预警系统是在短时间内减轻地震风险的有效方法,因此在全球许多国家已经实施或正在进行试验。地震预警系统是以利用震后地震信号初始部分测量的一些参数之间的关系为基础的。本文我们介绍了在西西里岛东部为实施地震预警系统的初步探索,该地区遭受了几次破坏性地震的袭击。使用意大利国家地球物理和火山研究所的宽频带台站记录的M_L≥2.8的地震数据,我们估算了P波和S波的初至波的峰值地动位移Pd,地面运动周期τ_c和峰值地动速度(PGV)。我们发现P_d与地震的大小有关,可以用来为该地区的地震预警系统估算震级。我们还推导了τ_c和ML之间以及P_d和PGV之间的关系,这些关系可以用于给定台站周围的现场预警,并评估潜在的破坏性影响,这些关系可能对未来在该地区实施地震预警系统有实际的参考意义。     

A Giant Gold System, Geita Greenstone Belt, Tanzania

Please refer to the attachment(s) for more details.     

2009年拉奎拉地震后柔层机制的初步分析

对2009年4月6日阿布鲁佐地震造成的破坏观察表明,填充墙和钢筋混凝土结构之间局部的相互作用会产生柔层机制和脆性破坏。目前的实例研究成果是基于对佩蒂诺地区地震破坏观察的基础上进行的。建立了以模拟设计程序为基础的分析模型,并采用时程分析验证了由观察破坏所凸现出的结构倒塌的原因。通过考虑地面运动的所有分量,对这种破坏机制进行了研究。注意了砖砌块填充墙的非线性性能,考虑了填充墙力学性能的两个参数的假定,给出了表现这些非结构构件典型特征的不确定性。用三支撑杆宏观模型对填充墙进行非线性模拟,以考虑钢筋混凝土框架和填充墙之间局部和整体的相互作用。地震波输入是所研究结构附近在主震期间记录的真实信号。在评估中,选用了不同的抗剪承载力模型。分析结果似乎非常近似地证实了破坏观察所发现的主要类似倒塌情景;柱子缺乏合适的细部设计使得填充墙和钢筋混凝土柱之间的局部相互作用和地面运动的强烈垂直分量是造成脆性破坏的主要原因。