2D equivalent linear site effect simulation: example applications to two deep valleys

In the framework of the Sismovalp European project, an equivalent linear 2D code was developed to compute the response of a valley to SH waves, using the discrete wave-number method proposed by Aki and Larner (Aki K, Larner KL (1970) J Geophys Res 75:5). To overcome the frequency upper bound limitation, the Aki and Larner’s method is combined with a one-dimensional computation using a classical multi-layer method (Aki K, Richards PG (1980) Quantitative Seismology: Theory and Methods, vols. 1 & 2. W.H. Freeman & Co, San Francisco). The so-called “Aki–Larner extended method” is associated to an iterative algorithm, as proposed by Seed and Idriss (Seed HB, Idriss IM (1969) Report No. EERC 70–10, Earthquake Research Center, University of California, Berkeley, California) which accounts for the modulus and damping degradation using a linear visco-elastic model. A comparison of the results in the linear and the equivalent linear cases, for a magnitude 6.0 earthquake, shows that the account for the equivalent linear behaviour of the soil significantly reduces the amplification level, especially at frequencies higher than the fundamental resonance frequency of the site. In the case of site effects or microzonation studies devoted to produce design spectra for engineering structures, this can have a major impact on the associated results and costs, depending on the frequency of interest for the considered structure. As a first application of the developed technique, 2D equivalent linear Aki–Larner computations are used to perform the seismic microzonation study of the upper Rhone valley, in the Visp area (Switzerland), a typical 2D alpine valley. These investigations made it possible to determine site specific spectra, associated with different zones, to be used instead of the code spectra that do not take into account the local 2D amplification.     

PRINCIPES FONDAMENTAUX DE LA THEORIE DU MOUVEMENT DES EAUX SOUTERRAINES

ABSTRACT

In southeastern Arizona, almost all summer rainfall results from widely-scattered high-intensity afternoon or evening thunderstorms of limited areal extent. For eleven years of record on the Walnut Gulch Experimental Watershed, Tombstone, Arizona, about 70 percent of the annual rainfall of 11 1/2 inches and over 95 percent of the annual runoff occurred in July, August, and early September. In contrast, about 5 percent of the rainfall occurred in the previous 3 months, and about 25 percent in the remaining 6 1/2 months.

Therefore, summer rainfall, although highly variable, represented the most dependable source of water to the Walnut Gulch watershed. On the average, significant rainfall was recorded on some part of the watershed on 40 percent of the days in the critical July-August period. The maximum frequency was 3 out of every 4 days in 1955, and the minimum 3 out of every 10 days in 1960.

The wettest year was 1955, with a continuous rainy period of 47 days; whereas, the driest was 1960, with the longest rainy period lasting only 5 days. The longest summer drought during the period of record occurred in 1962, when no rain fell for 17 days in August, following a 14-day rainy period in late July.

As yet, there are not enough data to determine reliable expectancies for summer rainy or drought periods.     

简要介绍R2V的功能及其在数字化图件中的应用

许多物化探及地质成果资料以纸质图件保存,在资料的再利用时需对其进行数字化.这里简要介绍一种数字化功能强大的矢量化软件-R2V的功能,针对物化探图件的特点,探讨了R2V数字化的流程.     

鄂西黄陵隆起东缘鄂宜页2井五峰组—龙马溪组页岩气储层特征与含气性

鄂西地区五峰组-龙马溪组已成为中国南方页岩气勘探的热点领域。为深化该区页岩储层及含气性特征认识,本文以鄂宜页2井钻井及测试分析资料为基础,以笔石带为标尺,对五峰组-龙马溪组下部黑色富有机质页岩的岩石学特征、有机地化特征、储集空间类型及结构特征进行深入研究,分析总结了页岩储层含气性特征及影响因素,并对页岩储层开展了综合评价。结果表明：鄂宜页2井五峰组-龙马溪组下部黑色岩系缺失LM5-LM6笔石带,富有机质页岩上延至LM7笔石带,总厚度约16 m;岩性以硅质页岩夹少量硅质岩、混合质页岩和黏土质页岩为主,有机质类型为Ⅰ-Ⅱ1型,Ro为1.88%~2.03%,显示黑色页岩已过大量生气阶段;页岩储集空间主要为小于100 nm的有机质纳米孔、直径大于5 μm的微米孔和构造微裂缝,其中纳米孔占比超过50%,孔隙容积、比表面积与有机碳含量存在显著正相关性;现场解析总含气量为0.068~3.33 m³/t,平均1.13 m³/t,高含气量段集中于凯迪阶WF2-WF3与鲁丹阶LM2-LM4,含气量与TOC、脆性矿物含量之间具有明显的正相关性;根据TOC、含气性、脆性矿物含量以及页岩沉积环境等参数进行综合评价,Ⅰ类储层主要对应于凯迪阶WF2-WF3笔石带以及鲁丹阶LM2-LM4笔石带以深水环境下形成的硅质页岩和硅质岩层段,总厚度约9 m,是该区五峰-龙马溪组水平钻井的最佳甜点段。     

经验加速度补偿对HY-2A卫星精密定轨的影响

针对HY-2A卫星定轨中存在系统误差的问题,该文提出了加入经验加速度补偿系统误差。为了获得HY-2A卫星的高精度轨道,采用星载DORIS距离变率数据探索了经验加速度对定轨精度的影响。探讨了1d、3d和7d作为经验加速度周期的定轨精度差异,分析了3d作为经验加速度周期时在径向、法向和切向3个方向设置经验加速度对定轨精度的不同影响。研究结果表明:HY-2A卫星在径向和切向不存在系统误差,而在法向存在系统误差,因而在法向设置经验加速度进行力学模型补偿能够取得较好的定轨结果;3d作为经验加速度的补偿周期较为合适,不仅能够减少解算参数个数,缩短计算时间,而且径向定轨精度可达到1.00cm,满足HY-2A卫星精密定轨需求。     

The response of CO2 flux to rain pulses at a saline desert

As the substantial component of the ecosystem respiration, soil CO₂ flux is strongly influenced by infrequent and unpredictable precipitation in arid region. In the current study, we investigated the response of soil CO₂ flux to rain pulses at a saline desert in western China. Soil CO₂ flux was measured continuously during the whole growing season of 2009 at six sites. We found that there were remarkable changes in amplitude or diurnal patterns of soil CO₂ flux induced by rainfall events: from bimodal before rain to a single peak after that. Further analysis indicated that there is a significant linear relationship (P < 0.001) between soil CO₂ flux and soil temperature (T_soil). However, a hysteresis between the waveform of diurnal course of CO₂ flux and T_soil was observed: with soil CO₂ flux always peaked earlier than T_soil. Furthermore, a double exponential decay function was fitted to the soil CO₂ flux after rainfall, and total carbon (C) releases were estimated by numerical integration for rainfall events. The relative enhancement and total C release, in association with the rain pulses, was linearly related to the amount of precipitation. According to the size and frequency of rainfall events, the total amount of C release induced by rain pulses was computed as much as 7.88 g C·m^–2 in 2009, equivalent to 10.25% of gross primary production. These results indicated that rain pulses played a significant role in the carbon budget of this saline desert ecosystem, and the size of them was a good indicator of rain‐induced flux enhancement. Copyright © 2012 John Wiley & Sons, Ltd.     

江苏东海地区石英脉地质特征及找矿方向

区域变质作用、韧性剪切作用和超高压变质作用为SiO2富集创造条件,印支期-燕山期的构造活动为石英脉富集定位创造构造环境。东海群地层、韧性剪切带、超高压变质带为石英脉的形成提供了SiO2物质来源。     

南海北部水体叶绿素a浓度反演的生物光学模型

利用2003年至2005年秋季在南海多个航次的现场观测数据,研究了南海北部海区遥感反射率的变化,并分析了用于全球海洋叶绿素a浓度反演的OC2和OC4模型在本海区的适用性。结果表明,在南海北部海域,OC2和OC4模型高估了叶绿素a浓度,高估范围一般约在80%—200%之间,其中最高可达640%,即OC2和OC4模型并不适用于南海海域。在此基础上,根据现场实测的表观光学数据,利用遥感反射率比值(Rrs(433)/Rrs(555))与叶绿素a浓度的关系建立了两套能够精确反演南海北部海域叶绿素a浓度的本地化经验算法———算法1和算法2,并利用其对南海北部海域的叶绿素a浓度进行反演。结果表明,由本地化模型反演得到的叶绿素a浓度与实测的叶绿素a浓度具有较好的相关关系,其平均相对偏差分别为51%和53%,相关系数为0.75。     

Numerical Simulation of Residual Circulation due to Bottom Rouglmess Variability Under Tidal Flows in A Semi-Enclosed Bay

Nowadays there are some chronic serious environmental problems, such as eutrophication, blue tide and so on, in a complicated coastal zone or a semi-enclosed bay, because the water exchanges between an inner bay and an outer sea is weak compared with the supply of contaminant. Under this situation, a method to improve the water quality by 3-dimensional small unsymmetrical structures has been proposed by Komatsu et al. In this paper, several numerical simulations of the tidal current and concentration for various arrangements of bottom roughness in a semi-enclosed model bay are carfled out with a depth-averaged 2-D numerical model. The model is solved by the hybrid finite analytic method with nonstaggered grid. And the SIMPLES algorithm with Rhie and Chow＇ s momentum interpolation technique is used for the simulation. The effect of Komatsu＇ s method for water purification is examined by numerical simulation. The result of numerical experiment indicates that it is possible to generate a new tidal residual current and to activate a tidal exchange by bottom roughness arrangement only.