任意各向异性介质相(群)速度的计算

反映弹性波在各向异性介质中传播特性的两个基础的物理量是相速度和群速度.本文在总结前人工作的基础上,提出任意各向异性介质相(群)速度的计算方案:首先推导各自计算公式,其次考虑剪切波奇点的特殊性,再次令其遵循相应约束条件,最后,采用三个计算实例检验该方案的正确性和有效性.通过对计算结果的分析以及各向异性理论预测可以加深对各向异性特有性质(如剪切波奇点、群速度多值性)的理解,有助于增强我们对任意各向异性理论的基本认识.     

Field measurements of normal and shear fracture compliance

Field estimates of the normal and shear compliance of water saturated fractures were obtained from a seismic experiment carried out on a wave‐cut platform of Upper Caithness Flagstone on the North coast of Scotland. The rocks are cut by two orthogonal sets of vertical fractures. Vertical geophones were glued to the rock surface and seismic waves were generated by striking the surface with a sledge hammer. First arrival traveltimes were obtained for source‐receiver distances up to 30 m. Differences of compressional velocity with direction across the platform were interpreted as resulting from the compliance of the fractures intersected by the transmitted waves. The average normal compliance for fractures at this site is 4.0 × 10^?12± 1.0 × 10^?12 m/Pa. There is much less certainty about the precise value of shear compliance. However, the normal/shear compliance ratio is determined to be ≤0.1.     

天津滨海地区浅层剪切波速与基底构造关系研究

Shear wave velocity is one of the important dynamic characteristics of soil layers and applied widely in aseismic engineering. In this paper, 500 drill logging data are used to make a linear interpolation based on 0.01°×0.01°×1m grid. A shallow 3-D shear wave velocity structure of Tianjin coastal area is obtained. According to the data and geological background, we selected two typical velocity profiles to try to introduce and explain its relationship to basement structure. The results show that the shear wave velocity structure clearly presents the characteristic of stratification and lateral inhomogeneity. Furthermore, the difference of the shear wave structure between tectonic elements is clear and the velocity structure between the two sides of the local or border fault in the Quaternary is disturbed or affected significantly. It intuitively shows that the basement structure and fault activity of this region had good control of sedimentation development and strata formation in the Quaternary period which would have an important effect on engineering seismic and geological condition evaluation.     

2011年安庆4.8级地震序列S波分裂研究

采用互相关系数法, 计算了2011年安庆M_S4.8地震的余震S波分裂参数。 结果表明, 余震序列的S波分裂现象明显, 快S波平均偏振方向在近NNW向, 与区域最大水平主压应力方向基本一致。 通过分析延迟时间随时间的变化趋势, 可以看出M_S4.8地震后有明显的应力释放现象。 在几次较大余震前, 观测到延迟时间呈现增加的特征, 并且其中一次余震在发生之前的短时间内还出现延迟时间减小的现象, 这一现象符合震前应力长时间积累和短时间应力释放的结论, 时间延迟在强震前会出现下降具有重要的地震短临预测意义。 研究认为 S 波分裂参数可以反映区域应力场的动态变化信息, 可以为安徽南部地区应力场研究与地震预测提供有用的信息。     

临汾地震台摆式倾斜仪的监测能力

我国境内几次中强震及山西地区6次有感地震前,临汾地震台两种摆式倾斜仪存在有不同反映,探讨不同摆式倾斜仪对同一地震监测能力的差异性和同一仪器对不同地震的异常反映能力,结果表明：①摆式倾斜仪监测震兆信息的距离范围由仪器自身的监测能力（综合噪声水平及观测精度）和未来震级的大小所决定;②对于不同地震,两摆式倾斜仪所表现出的异常形态不同,即便在同一观测仪器上表现出来的异常形态也存在差异;同一地震两摆式倾斜仪所反映的异常并非呈相关一致性,而且同一仪器的不同方向对异常信息的捕捉能力也存在明显差异。     

利用交会图法识别国外M油田岩性与流体类型的研究

利用测井曲线进行岩性与流体类型的识别是测井解释的重要内容之一,可为油田油气藏的综合评价提供重要的基础依据.基于交会图法和岩心资料,本文分析研究了国外M油田的常规测井曲线特征与岩性和流体类型的关系.首先以岩心资料为基础,选取对岩性和孔隙流体敏感的物理量进行交会图分析识别,在现有测井资料的前提下,综合这些物理量建立了GR-BK、GR-NGR、NGR-BK、PHIE-SW交会图版,然后利用这些图版进行了岩性和流体的识别.其中:岩性主要依据自然伽马、中子伽马、电阻率交会图版来识别,流体类型主要依据饱和度和电阻率交会图版进行识别.在上面工作的基础上确定了该油田不同类型的岩性和流体的识别标准值范围:1)碳酸岩识别标准为GR<70API,NGR>2.5CU,BK<5Ω.m;砂岩识别标准为,70API162API.2)油气层有效孔隙度PHIE>20%,SW<55%,BK>2Ω.m;水层的有效孔隙度PHIE>20%,但是SW>55%,BK<2Ω.m.从上面的结果可看出,在该研究区域,该方法不仅可以区分砂岩和泥岩这样不太复杂的岩性,甚至可以区分砂岩、石灰岩和白云岩这样易混淆的岩性.最后,通过待测试数据对建立的交会图版进行检验,岩性和流体识别的准确率达到了94%和100%.本文的研究结果对中亚地区油田的岩性识别和储层预测具有重要的应用价值.     

基于气候变化和人类活动影响的土地利用分析——以新疆阿克苏河流域绿洲为例

以1990、 2000、 2010年3期Landsat TM影像为土地利用基础数据, 结合1990年以来的社会经济资料和反映气候变化的气温、 降水数据, 对1990年以来阿克苏河流域绿洲土地利用变化进行了分析. 结果表明: 1990-2010年期间, 耕地、 建设用地以单向转入为主, 耕地对绿洲"扩张"贡献最大, 前期(1990-2000年)的贡献率为129.1%, 后期(2001-2010年)的贡献率提高到142.5%; 草地、 水域以单向转出为主, 草地对绿洲"萎缩"贡献最大, 前期的贡献率是-39.8%, 后期是-34.8%; 其次是水域, 前期对绿洲的贡献率是-1%, 后期是-9.3%; 河漫滩、 林地、 湿地在前期对绿洲的"扩张"贡献率分别是7.5%、 0.3%和5.1%, 后期对绿洲的"萎缩"贡献率分别是-2.4%、 -0.02%和-0.4%. 近20 a来流域绿洲规模整体上持续扩张. 通过分析绿洲土地利用驱动力系统可以看出, 绿洲土地利用类型变化主要受人类活动影响, 气候变化起基础性作用.     

青藏高原多年冻土区高寒草甸植物种群物候学定量研究

采用青藏高原腹地北麓河多年冻土区高寒草甸14种代表性植物种群2009年和2010年两个生长季的物候观测资料, 进行植物种群物候学特征的定量分析, 划分物候类型并指出影响不同物候期的环境因子主次. 结果表明: 营养期和结实期的物候指数都较大, 分别为32.70和24.39, 其他物候期则相对较小; 整个生长期持续天数较短, 为155 d左右. 14种植物可划分为3种类型和6大类群. 在营养期和整个生长期, 与物候变化最为密切的环境因子为降水量, 其次为日照时数, 温度居第三; 而影响其他物候期的因子均以日照时数为主, 降水量和温度依次居后.     

南黄海盆地古潜山分类及构造特征

南黄海是下扬子的主体,奠基于晋宁期变质基底之上,构造演化历经南华纪—早、中三叠世海相地层发育期、晚白垩世—古近纪箕状断陷发育期和新近纪—第四纪坳陷发育期,为一典型地台-断陷-坳陷多层结构的复合盆地。盆地历经多次构造运动改造,古潜山发育,类型多样。在总结前人对古潜山研究的基础上,结合南黄海新近采集的二维地震剖面,对该地区古潜山类型进行了系统划分,并对典型古潜山的构造特征及生储盖匹配关系进行了初步描述。根据成因划分为剥蚀型潜山、拉张型潜山、挤压型潜山和复合型潜山四大类,每一类又可根据形态划分出剥蚀残丘型潜山、拉张翘倾断块型潜山、拉张断阶型潜山、拉张断垒型潜山、挤压褶皱型潜山、拱张褶皱型潜山和褶皱—断块复合型潜山等类型。南黄海盆地古潜山的发育具有分带性,按盆地中潜山的构造位置,分为凸起潜山带、陡坡潜山带、洼陷潜山带和缓坡潜山带,每一构造带发育了不同类型潜山。研究表明南黄海古生界和中生界古潜山数量众多,规模较大,是南黄海地区实现油气突破的一种重要油气藏类型。     

New Zealand estuary benthic health indicators summarised nationally and by estuary type

ABSTRACT

Ecological data are often collected at small geographic scales. However, analysing data collectively over wider scales can reveal results and patterns not shown in the smaller-scale data. We summarised data for intertidal benthic ecological (physico-chemical and biological) health indicators from New Zealand estuaries and compared the results against thresholds above which ecological impacts are expected to occur. Values for the sediment physico-chemical indicators mud and nutrients (nitrogen and phosphorus collectively) were above thresholds for at least 50% and at 31% of sites measured respectively. Sediment organic content and metal concentrations were generally low, with only maximum values exceeding the thresholds. Scores for biological indicators were within (or better than) the moderate health category for either at least 50%, or at least 75%, of sites. When compared across estuary types (based on a geomorphic classification system) we found statistically significant differences for thirteen of the sixteen indicators. Differences (among mean values) for highly significant results were relatively large compared to the range of values observed nationally for those indicators. However, the differences, except those for mud, were smaller than their respective ecological health threshold values. Our summary provides a reference for future comparisons of estuary indicators nationally and across estuary types.