历史时期中国重大自然灾害时空分异特征(英文)

Based on historical documents and records this paper analyzes the characteristics of frequency and distribution of major disasters that took place in the history of China. The findings show that occurrences of different types of disasters varied and spatial pattern at provincial level are significantly different as well. The results also indicate that there is a strong relationship between type of disasters and spatial distribution and that the spatial pattern of losses was not the same as that of the frequency. The reasons are: (1) the hazard-formative environments which, to a large extent, determine the spatial pattern of the disasters are significantly different; (2) the losses caused by natural disasters were closely related to the concentration of economy and population. Number of deaths was usually large in areas where agriculture, culture and business were relatively developed. The spatial pattern of disaster losses is an evitable result of uneven economic development in the history of China.     

On the timing of the East Asian summer monsoon maximum during the Holocene—Does the speleothem oxygen isotope record reflect monsoon rainfall variability?

The evolution of the East Asian summer monsoon(EASM) during the Holocene has long been of significant interest.Knowledge of past EASM variability not only increases our understanding of monsoon dynamics on a long timescale,but it also provides an environmental and climatic background for research into Chinese cultural development.However,the timing of the EASM maximum remains controversial.The popular concept of an "early Holocene maximum" is mainly based on speleothemδ~(18)O(δ~(18)O_c) records from caves in southern China;however,the interpretation of δ~(18)O_C as a reliable proxy for EASM intensity is being increasingly challenged.The present paper is a critical review of the climatic significance of the δ~(18)O_C record from China.Firstly,we suggest that precipitation in northern China is an appropriate index of EASM intensity,the variation of which clearly indicates a mid-Holocene monsoon maximum.Secondly,an interregional comparison demonstrates that the precipitation record in northern China is quite different from that in southern China on a range of timescales,and is inconsistent with the spatial similarity exhibited by speleothem oxygen isotope records.Furthermore,both modeling and observational data show that the δ~(18)O_C records from southern China indeed reflect changes in precipitation δ~(18)O(δ~(18)O_P) rather than precipitation amount,and therefore that their use as an EASM proxy is inappropriate.Finally,we address several significant monsoon-related issues-including the driving mechanism of the EASM on an orbital timescale,the climatic significance of speleothem oxygen isotopes,and the relationship between atmospheric circulation and precipitation in monsoonal regions.     

Evaluation of site effects on ground motions based on equivalent linear site response analysis and liquefaction potential in Chennai,south India

We study local site effects with detailed geotechnical and geophysical site characterization to evaluate the site-specific seismic hazard for the seismic microzonation of the Chennai city in South India. A Maximum Credible Earthquake (MCE) of magnitude 6.0 is considered based on the available seismotectonic and geological information of the study area. We synthesized strong ground motion records for this target event using stochastic finite-fault technique, based on a dynamic corner frequency approach, at different sites in the city, with the model parameters for the source, site, and path (attenuation) most appropriately selected for this region. We tested the influence of several model parameters on the characteristics of ground motion through simulations and found that stress drop largely influences both the amplitude and frequency of ground motion. To minimize its influence, we estimated stress drop after finite bandwidth correction, as expected from an M6 earthquake in Indian peninsula shield for accurately predicting the level of ground motion. Estimates of shear wave velocity averaged over the top 30 m of soil (V_S30) are obtained from multichannel analysis of surface wave (MASW) at 210 sites at depths of 30 to 60 m below the ground surface. Using these V_S30 values, along with the available geotechnical information and synthetic ground motion database obtained, equivalent linear one-dimensional site response analysis that approximates the nonlinear soil behavior within the linear analysis framework was performed using the computer program SHAKE2000. Fundamental natural frequency, Peak Ground Acceleration (PGA) at surface and rock levels, response spectrum at surface level for different damping coefficients, and amplification factors are presented at different sites of the city. Liquefaction study was done based on the V_S30 and PGA values obtained. The major findings suggest show that the northeast part of the city is characterized by (i) low V_S30 values (<?200 m/s) associated with alluvial deposits, (ii) relatively high PGA value, at the surface, of about 0.24 g, and (iii) factor of safety and liquefaction below unity at three sites (no. 12, no. 37, and no. 70). Thus, this part of the city is expected to experience damage for the expected M6 target event.     

Experimental study of headcut erosion in cohesive soils under different consolidation types and hydraulic parameters

Headcut is a change in stream channel elevation, where there is concentrated flow. Most of the past studies focus on non-cohesive soils, although many problems on the streams occur because of cohesive beds and banks. In this study, eight samples of cohesive soils, with a different composition of silt and clay, for different waterfall heights and flow velocity under long- and short-term natural consolidation conditions were tested. In one of the tests, a sand layer was settled on the headcut bed to investigate its impact on headcut erosion. By increasing clay content, the headcut will remain vertical as it moves backward. Result showed that the effect of clay content reduction was more noticeable under the long-term consolidation condition. In general, the effect of clay percentage variation on the measured parameters is much higher than the effects of waterfall height or flow velocity, and the effect of consolidation type and adding a sand layer on the measured values is much higher than the effect of clay percentage variation on the waterfall height and flow velocity.     

蔚县盆地中更新世哺乳动物化石新发现

1 研究目的(Objective) 蔚县盆地为典型的冀西北山间盆地,与阳原盆地仅一山之隔,二者共同组成了广义的"泥河湾盆地",盆地内广泛出露中更新统郝家台组(Qp2h)河-湖相沉积物.相比阳原盆地,蔚县盆地古生物化石研究程度较低.20世纪80年代,盆地北部(大南沟一带)出土具有上新世—早更新世面貌的小型哺乳动物化石,近...     

新疆阿尔泰塔拉特铁铅锌矿床流体包裹体研究及矿床成因

塔拉特铁铅锌矿位于新疆阿尔泰造山带南缘的阿巴宫多金属成矿带,矿体赋存于克兰盆地下泥盆统康布铁堡组中,为一套海相中酸性火山岩-火山碎屑岩、陆源碎屑沉积岩-碳酸盐岩建造,脉状矿体受阿巴宫大断裂次级断裂控制.根据矿物组合和脉体穿插关系,塔拉特铁铅锌矿可分为4个成矿阶段:矽卡岩,氧化物,硫化物和碳酸盐阶段,后3个阶段均有石英共生.其中,硫化物(方铅矿-闪锌矿±磁黄铁矿±黄铜矿)阶段是铅锌成矿的主要阶段.不同阶段石英中广泛发育流体包裹体,可分为水溶液包裹体(W型)、纯CO2包裹体(PC型)、CO2-NaCl-H2O包裹体(C型)及含子矿物多相包裹体(S型)4类.冷热台显微测温和激光拉曼分析表明,氧化物阶段石英含有4种类型的包裹体,以W型为主,C型和S型包裹体次之,包裹体均一温度介于271～ 426℃,W型和C型盐度范围0.5％～22.4％ NaCleqv,S型包裹体盐度30.5％ ～40.6％ NaCleqv;硫化物阶段的石英流体包裹体为W型、C型和PC型,均一温度为204 ～ 269℃,盐度介于0.2％～15.6％ NaCleqv之间;碳酸盐阶段的矿物只含W型包裹体,均一温度集中在175～211℃之间,盐度为1.1％ ～9.9％ NaCleqv.利用C型包裹体对硫化物阶段成矿压力估算,得到107 ～ 171MPa,对应深度为4～6km.塔拉特铁铅锌矿初始成矿流体具有高温、高盐度、富CO2的特征,但碳酸盐阶段低盐度、贫CO2,流体不混溶和混合作用导致了成矿物质的沉淀.塔拉特铁铅锌矿的地质和成矿流体特征显示其为碰撞造山体制形成的矽卡岩型成矿系统.     

热动力条件对白云凹陷深水区珠海组砂岩成岩演化过程的影响

珠江口盆地白云凹陷位于中国南海北部,是目前我国深水油气勘探研究的重要区域.盆地现今大地热流值为24.2～121.0mW/m^2,单井现今地温梯度(Gra)最高可达6.64℃/100m,具"热盆"属性.白云凹陷裂后沉降阶段,特别是白云运动(23.8Ma)发生之后,盆地由断裂控盆转变为断裂、热作用共同控盆,热作用及热动力条件成为控制研究区储层成岩演化过程的重要因素,珠海组地层的镜质体反射率值、砂岩中次生流体包裹体均一温度、热液成因自生矿物等热流背景及岩石学记录为这一观点提供了有力证据.通过铸体薄片显微镜下观察与定量统计、电镜扫描观察、X-射线衍射分析等,发现白云凹陷北部中-低地温梯度(LGR,Gra≤4.5℃/100m)和南部高地温梯度(HGR,Gra>4.5℃/100m)两个地区珠海组砂岩的成岩作用特征、成岩演化过程存在以下差异:(1)中-低地温梯度地区珠海组砂岩的压实作用主要是静岩压实作用;高地温梯度地区珠海组砂岩的原生孔隙受静岩压实作用和热压实作用的共同控制,压实减孔速率高,等孔隙度埋深显著变浅;(2)地层升温速率的增大加快了储层中粘土矿物转化的速率,高地温梯度地区高岭石消失的埋深界限较中-低地温梯度地区浅,I/S(伊利石/蒙皂石混层)有序化进程较中-低地温梯度地区有所加快;(3)中-低地温梯度地区珠海组砂岩成岩演化过程属正常有序演变,高地温梯度地区受构造热事件的影响明显,深部流体参与了高地温梯度地区珠海组砂岩的成岩演化过程,地层孔隙水物质交换过程复杂,成岩演化进程加快,改变了碳酸盐矿物溶解-沉淀热平衡状态,各成岩作用过程活跃并出现一些典型的热液成因自生矿物组合.     

东北地区湿度梯度下的表土植硅体的空间分布规律

植硅体的现代过程研究是恢复古环境的基础,探讨表土植硅体分布及组合特征对环境因子的响应尤为重要。沿中国东北地区年均温为4 ℃等温线采集70块表土样品,研究了单一温度因素控制下表土植硅体的空间分布规律,以期获得不同类型植硅体对降水的响应。研究结果表明：所有表土样品中植硅体丰富且数量较多,主要有棒型、尖型、块状、扇型、扁平状、短鞍型、帽型、哑铃型、齿型、三棱柱型、导管型、硅质突起、硅化气孔、弓型和多面表皮植硅体;且主要以短细胞、棒型、尖型为主,其平均百分含量之和高达80.77%,块状、扁平状、扇型次之,其他类型的植硅体含量较少。方差分析结果表明：棒型、三棱柱型、硅质突起、哑铃型和扁平状在大兴安岭、松嫩平原和长白山之间存在显著性差异,且棒型、三棱柱型、硅质突起的百分含量与年降水量具有极显著的正相关性,哑铃型的百分含量与年降水量具有极显著的负相关性。总之,年均温为4 ℃等温线上70块表土样品中植硅体类型基本相同,但不同类型植硅体的百分含量存在差异,说明本研究区域内表土植硅体组合特征对降水的响应较为敏感。

     

GPS RTK技术用于滑坡动态实时变形监测的研究

为了研究GPS RTK技术用于滑坡动态变形监测的精度和可靠性,本文结合某类滑坡的大型物理模型试验,在滑坡体上布设了若干监测点,并用GPS RTK技术、全站仪三维测量技术和GPS单历元定位技术实时跟踪监测了该滑坡在自然状态下从稳定到产生破坏的全部过程。通过对监测数据的处理和分析,获得了RTK技术用于滑坡变形监测的可靠性和精度等技术参数,即在基准站和流动站同步观测到的卫星数在7颗以上且RTK系统的数据链能够正常工作的情况下,RTK测量的平面和高程精度就能分别控制在15mm和20mm以内。研究结果表明,RTK技术在一定条件下完全可用于滑坡灾害的动态实时变形监测。     

武汉城市区域水陆风环流的形成与转化特征研究

大气细颗粒物PM_2.5污染引起的雾霾天气既与本地污染物排放密切有关,也受局地特殊的风场影响.本文以武汉城市区域为研究对象,分别研究了长江沿岸的江陆风环流、东湖沿岸湖陆风环流的形成与转化特征,发现江风、湖风开始时间均为07：00-08：00,一年中最大风速均能达到2 m/s左右,而春夏季江风的持续时间高于秋冬季,夏季湖风的持续时间高于春季.同时发现区域附近温度和相对湿度之间有明显的相关性,湿度变化趋势大体上跟温度变化趋势相反,且温度对相对湿度的影响存在一定的滞后性,延迟时间大约为1 h.