由构造应力场研究汶川地震断层的分段性

采用构造应力场均匀性对断层或板块边界进行分段的方法, 利用ldquo;裁剪-粘贴rdquo;法给出的余震震源机制解资料, 进一步从应力场角度确定汶川地震发震断层南、 北段分界点位置及南、北段震后应力场. 研究结果表明, 发震断层南、北段分界点位于北川附近, 与先前的研究结果较为一致. 南、 北段震后应力场反演结果显示, 南、北段的最大主应力轴方位均呈北东东向, 且近水平. 南、北段应力场反演的平均拟合残差和置信区间均较大, 主要原因可能是因为南、北段内应力场不均匀性造成的. 因为本文仅由大余震给出了震源断层的一级分段, 南、北段内应做进一步的细分.      

Effects of rainfall on soil moisture and water movement in a subalpine dark coniferous forest in southwestern China

Water content and movement in soil profile and hydrogen isotope composition (δD) of soil water, rainwater, and groundwater were examined in a subalpine dark coniferous forest in the Wolong National Nature Reserve in Sichuan, China, following rainfall events in 2003–2004. Light rainfall increased water content in the litter and at soil depth of 0–80 cm, but the increased soil water was lost in several days. Heavy rainfall increased soil water content up to 85% at depths of 0–40 cm. Following the light rainfall in early spring, the δD of water from the litter, humus, illuvial, and material layers decreased first and then gradually reached the pre‐rainfall level. In summer, light rainfall reached the litter humus, and illuvial layer, but did not hit the material layer. Heavy rainfall affected δD of water in all layers. The δD of soil interflow slightly fluctuated with rainfall events. The δD of shallow groundwater did not differ significantly among all rainfall events. Light rainfall altered the shape of δD profile curve of water in the upper layer of soil, whereas heavy rainfall greatly affected the shape of δD profile curve of water in all soil layers. Following the heavy rainfall, preferential flow initially occurred through macropores, decayed plant roots, and rocks at different depths of soil profile. With continuing rainfall, the litter and surface soil were nearly saturated or fully saturated, and infiltration became homogeneous and plug‐like. Forest soil water, particularly in deeper soil profile, was slightly affected by rainfall and, thus, can be a source of water supply for regional needs, particularly during dry seasons. Copyright © 2011 John Wiley & Sons, Ltd.     

新疆精河M_W6.3地震产生的静态应力变化研究

利用精河M_W6.3地震有限断层破裂模型,计算了精河地震产生的位移场、应力场、周围主要断层上的静态库仑应力变化以及主震对余震的触发作用。结果表明:(1)精河地震产生的地表隆升最大值约为6.6cm,沉降最大值约为1.8cm;水平位移方向呈现震中南北侧向震中汇聚、震中东西侧向外"流出"的特点。(2)精河地震产生的水平面应力场展布南北侧物质主要受到指向震中的拉张力作用,东西两侧物质主要受到因震中过剩物质东西向排出而导致的东西向挤压力作用。(3)震中西侧距震中约20km的库松木契克山前断裂中段和震中东北部距震中约50km的四棵树-古尔图南断裂西段的库仑应力加载均大于0.01MPa,即2处为地震危险区。(4)在震源深度为8~12km的余震事件中,约有85.5%处于库仑应力加载区,即受到主震的的触发作用;在深度为4~8km的余震事件中,约有87%受到主震的应力触发作用。     

An analytical study on three‐dimensional versus two‐dimensional water table‐induced flow patterns in a Tóthian basin

Although it has been increasingly acknowledged that groundwater flow pattern is complicated in the three‐dimensional (3‐D) domain, two‐dimensional (2‐D) water table‐induced flow models are still widely used to delineate basin‐scale groundwater circulation. However, the validity of 2‐D cross‐sectional flow field induced by water table has been seldom examined. Here, we derive the analytical solution of 3‐D water table‐induced hydraulic head in a Tóthian basin and then examine the validity of 2‐D cross‐sectional models by comparing the flow fields of selected cross sections calculated by the 2‐D cross‐sectional model with those by the 3‐D model, which represents the “true” cases. For cross sections in the recharge or discharge area of the 3‐D basin, even if head difference is not significant, the 2‐D cross‐sectional models result in flow patterns absolutely different from the true ones. For the cross section following the principal direction of groundwater flow, although 2‐D cross‐sectional models would overestimate the penetrating depth of local flow systems and underestimate the recharge/discharge flux, the flow pattern from the cross‐sectional model is similar to the true one and could be close enough to the true one by adjusting the decay exponent and anisotropy ratio of permeability. Consequently, to determine whether a 2‐D cross‐sectional model is applicable, a comparison of hydraulic head difference between 2‐D and 3‐D solutions is not enough. Instead, the similarity of flow pattern should be considered to determine whether a cross‐sectional model is applicable. This study improves understanding of groundwater flow induced by more natural water table undulations in the 3‐D domain and the limitations of 2‐D models accounting for cross‐sectional water table undulation only.     

近2600年来黄河下游沉积量和上中游产沙量变化过程

主要基于华北平原上93个钻孔中沉积物详细观测和分析数据,结合182组14C测年和埋深数据、参考前人黄河下游河道历史变迁及其他相关研究成果,估算出2600年以来黄河下游在602BC～11A.D.,11～1034A.D.,1034～1128A.D.,1128～1855A.D.和1855～1997A.D.等5个历史时期的年平均沉积量分别是3.89×108t/a,2.24×108t/a,6.63×108t/a,6.78×108t/a和8.47×108t/a。通过建立黄河下游有无堤防和决溢频率与泥沙输移比的关系,计算出5个时期黄河上中游的平均年输沙量分别是6.2×108t/a,6.8×108t/a,8.3×108t/a,11.5×108t/a和15.3×108t/a。进而探讨了黄河输沙量变化的主要原因,以及历史上王景治河后出现的600年安流时期的原因。     

Increasing critical sensitivity of the Load/Unload Response Ratio before large earthquakes with identified stress accumulation pattern

The Load/Unload Response Ratio (LURR) method is proposed for short-to-intermediate-term earthquake prediction [Yin, X.C., Chen, X.Z., Song, Z.P., Yin, C., 1995. A New Approach to Earthquake Prediction — The Load/Unload Response Ratio (LURR) Theory, Pure Appl. Geophys., 145, 701–715]. This method is based on measuring the ratio between Benioff strains released during the time periods of loading and unloading, corresponding to the Coulomb Failure Stress change induced by Earth tides on optimally oriented faults. According to the method, the LURR time series usually climb to an anomalously high peak prior to occurrence of a large earthquake. Previous studies have indicated that the size of critical seismogenic region selected for LURR measurements has great influence on the evaluation of LURR. In this study, we replace the circular region usually adopted in LURR practice with an area within which the tectonic stress change would mostly affect the Coulomb stress on a potential seismogenic fault of a future event. The Coulomb stress change before a hypothetical earthquake is calculated based on a simple back-slip dislocation model of the event. This new algorithm, by combining the LURR method with our choice of identified area with increased Coulomb stress, is devised to improve the sensitivity of LURR to measure criticality of stress accumulation before a large earthquake. Retrospective tests of this algorithm on four large earthquakes occurred in California over the last two decades show remarkable enhancement of the LURR precursory anomalies. For some strong events of lesser magnitudes occurred in the same neighborhoods and during the same time periods, significant anomalies are found if circular areas are used, and are not found if increased Coulomb stress areas are used for LURR data selection. The unique feature of this algorithm may provide stronger constraints on forecasts of the size and location of future large events.     

Paleocollapse structure as a passageway for groundwater flow and contaminant transport

 Paleocollapse structure is a rock collapse, resulting from the failure in the geological history of the bedrock overlying karstified limestone. Depending on the present hydrogeological conditions within the area of paleocollapse and the internal properties of these structures, they can provide a means to facilitate groundwater flow and contaminant transport. Inactive paleocollapse structures can be reactivated by human activities such as dam construction, mining underground minerals, pumping groundwater, and development of landfills. They can also be reactivated by natural events such as earthquakes and neotectonic movements. In the mines of northern China, sudden inflow of karst water from Ordovician limestone into drifts and mining stopes through paleocollapse structures has caused significant economic loss. Water pumping tests and accompanied dye traces are effective approaches of locating water-conducting paleocollapse structures. Grouting is probably the best means of preventing them from becoming geohazards. Received: 26 November 1996 · Accepted: 17 June 1997     

Groundwater resources assessment using integrated geophysical techniques in the southwestern region of Peninsular Malaysia

Combined geophysical techniques such as multi-electrode resistivity, induced polarization, and borehole geophysical techniques were carried out on volcano-sedimentary rocks in the north of Gemas as part of the groundwater resource’s investigations. The result identifies four resistivity units: the tuffaceous mudstone, tuffaceous sandstone, the tuff bed, and the shale layer. Two types of aquifer systems in terms of storage were identified within the area: one within a fracture system (tuff), which is the leaky area through which vertical flow of groundwater occurs, and an intergranular property of the sandy material of the aquifer which includes sandstone and tuffaceous sandstone. The result also reveals that the aquifer occupies a surface area of about 3,250,555 m² with a mean depth of 43.71 m and a net volume of 9.798?×?10⁷?m³. From the approximate volume of the porous zone (28 %) and the total aquifer volume, a usable capacity of (274.339?±?30.177)?×?10⁷?m³ of water in the study area can be deduced. This study provides useful information that can be used to develop a much broader understanding of the nature of groundwater potential in the area and their relationship with the local geology.     

石器功能研究的现代模拟实验: 石刀表面残留物中淀粉粒来源分析

淀粉粒分析在国内外环境考古学研究中得到了大量应用,但是目前国内还没有关于淀粉粒分析、石器功能与植物利用关系的现代过程研究。本研究针对石刀这一新石器时代重要的生产和生活工具开展现代过程的模拟实验,尝试利用淀粉粒分析方法验证石刀功能及其加工的植物类型。我们利用打制的简易石片模拟石刀,对未成熟和成熟的小麦(Triticum aestivum L.)进行了共两次割穗操作,提取并观察石片割穗后不同部位表面残留物中的淀粉粒形态及其组合。实验结果表明,石片表面残留物中的淀粉粒主要来源于小麦秸秆; 小麦秸秆淀粉粒的A型和B型淀粉粒(未成熟和成熟小麦秸秆淀粉粒——A+B型淀粉粒,含量分别为90.91 ％ 和92.59 ％ )分别与其成熟籽粒的A型和B型淀粉粒形态、大小相似,具备形态鉴定的特征; 小麦秸秆中还发现了独特的多面体型淀粉粒(未成熟和成熟小麦秸秆多面体型淀粉粒含量分别为9.09 ％ 和7.41 ％ ),这是小麦种子中缺少的类型。根据本次现代实验模拟的结果,考古遗址出土石刀上提取到的淀粉粒很可能来自于植物收割(或切削)过程的残留物,结合淀粉粒分析、石刀形制和出土状况进行分析,可以获取出土石刀功能与古人类植物利用的信息。     

Geochemistry of Thermal－Mineral Waters in Siping＇an District， Shanxi Province， China

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