日本地震预警系统日趋完善

日本是全球第一个建立地震预警系统的国家,在3·11日本9.0特大地震时发挥了作用.本文介绍了日本预警系统在3·11地震时,东京地区公众在地震S波最大震动之前收到地震报警信息,得以避险.介绍了日本地震预警系统技术和在全国实施的概况,指出地震预警工程是一个复杂社会工程.日本从预警技术到能够为公众服务,采用的方式和体制,是值...     

Increasing free-air 0°C isotherm height in Southwest China from 1960 to 2010

Based on the radiosonde data observed at 14 stations in Southwest China from 1960 to 2010, as well as the corresponding surface air temperature, the long-term change of free-air 0℃ isotherm height in Southwest China and the relationships between surface air temperature and 0℃ isotherm height are discussed. The results indicated that the spatial distribution of 0℃ isotherm height is generally related with latitude, but the huge massif or plateau may complicate the latitude pattern. The two main regimes influencing the spatial patterns of 0℃ isotherm height in Southwest China are latitude and huge massif. The annual 0℃ isotherm height has increased by 35 m per decade in the recent decades, which is statistically significant at the 0.001 level. Generally, the increasing trend can be examined for each seasonal series, especially in winter （53 m per decade）. The diversity of trend magnitudes for annual and seasonal series can also be detected at a spatial view, but generally 0℃ isotherm height correlated well with surface air temperature.     

以2008年汶川8.0级地震为例分析地震触发的静态库仑应力计算的不确定性

Static Coulomb stress change induced by earthquake slip is frequently used to explain earthquake activities and aftershock distribution.However,some parameters for the Coulomb stress calculation are unable to be well constrained from laboratory experiments and field observations.Different parameters may directly affect the pattern of static Coulomb stress.The static Coulomb stress changes induced by the Wenchuan earthquake calculated by six research groups are not consistent with each other.To investigate how the parameters affect the calculation results,we change the parameters in turn through modeling and compare the results of different calculation parameters.We find that gravity,position and strike of receiver faults have little influence on coseismic Coulomb stress calculations,but other parameters can change the value and sign of the results in various degrees especially around the earthquake rupture plane.Therefore the uncertainty analysis of static Coulomb stress change induced by earthquake should be taken into consideration in the earthquake hazard analysis.     

Ordovician backarc‐basin metadolerite and metabasalt of the South Kitakami Terrane,Northeast Japan

Basement rocks that occur along the northern margin of the South Kitakami Terrane in Japan consist of Ordovician ultramafic rocks (Hayachine ultramafic complex), gneissose amphibolite (Kuromoriyama amphibolite), and mafic rocks (Kagura igneous rocks, KIR). The KIR are composed of metagabbro, metadolerite, metabasalt, and minor felsic–intermediate dikes. Although the KIR contain green hornblende due to metamorphism of greenschist to epidote–amphibolite facies, they rarely retain primary brown hornblende. Approximately 30% of the metabasalt shows porphyritic textures, with phenocrysts of saussuritized plagioclase and/or altered mafic minerals. The geochemistry of the common metadolerite and metabasalt of the KIR shows a tholeiite trend, a low TiO₂ content, and high Th/Nb and Ti/V ratios. The KIR are therefore indicative of a supra‐subduction zone tectonic setting, which implies a backarc origin (as also indicated by discrimination diagrams). Trace element patterns of the KIR resemble those of the backarc‐basin basalt of the Japan and Yamato basins in the Japan Sea. We propose that the KIR formed during backarc spreading from the Ordovician to Early Silurian. This view is supported by the geochemical data, the tectonic setting of the Hayachine ultramafic rocks, and the provenance of clastics within Silurian sedimentary rocks.     

Analysis of oil lens removal by extraction through a seepage face

Removal of LNAPL (oil) from an aquifer is described using a multiphase flow model. At the well boundary seepage face conditions are imposed. These conditions are implemented in a numerical model and withdrawal in a twodimensional domain is simulated for two different geometries of the oil lens and for varied values of the physical parameters. Assuming vertical equilibrium, the oil flow equation is reduced by vertical integration. The well boundary condition is approximated by imposing zero oil lens thickness. Similarity solutions of the reduced equations for the two geometries show good agreement with the numerical results in most cases.     

天然沉积粉质黏土的应力路径试验研究

天然沉积土在沉积过程中产生了结构性和各向异性,使其受力变形特性与重塑土存在明显的差异。实际工程中的天然土体往往在受荷过程中会经历不同的应力路径,因此,需要开展考虑结构性和各向异性影响的应力路径试验。通过研究不同应力路径下土体的力学特性,为建立复杂应力路径下的合理的本构模型提供试验依据。采用大直径PVC管取样器获取张家港地区地下2.5 m深的粉质黏土不扰动土样,通过GDS三轴仪对土样进行了K0固结不同排水应力路径试验。结果表明,应力路径对不扰动土样的体积变形和剪切变形均有显著影响,且球应力和偏应力对土的体应变和剪应变存在交叉影响。无论以体积变形为主还是剪切变形为主的应力路径下,应力-应变曲线都有明显的屈服性状。通过描绘试验所得各应力路径下的屈服点,获得张家港不扰动土样的屈服轨迹大致呈倾斜的椭圆形状,采用Wheeler模型的屈服面与试验屈服点的吻合程度要优于Nakano模型。     

模糊分维及其在地震研究中的某些应用

在模糊集理论与分形理论的基础上,引进了模糊分维的概念;给出了模湖容量维D₀与模糊关联维D₂的定义与确定方法;讨论了模糊分维与常用的分维（清晰分维）的关系.给出了模糊分维在地震研究中的应用结果: 1.根据模糊容量维D₀随时间的上升趋势变化,可以划分出大地震活动的高潮期;由模糊容量维D₀与模糊关联维D₂随时间变化的曲线,可以分析识别大地震前的中长期前兆异常. 2.根据模糊容量维D₀随空间和时间的变化,可以划分出未来大震所在的地区,并可发现大震前数年D₀呈现增大或减小的趋势. 3.根据前兆数据的模糊时间分维D₀随时间的变化,可以发现大地震的短期前兆异常.     

溢油物理化学性质灰色模式的研究

应用灰色系统理论对海面溢油物理化学性质(蒸发率、溶解率、表面张力、黏度和密度)在风化过程中的变化进行研究,建立了溢油物理化学性质在风化过程中的预测模式GM(1,1)和GM(0,m).结果表明,在风化过程中,溢油物理化学性质的GM(1,1)和GM(0,m)模式预测精度令人满意,皆符合统计学检验的要求;在风化过程中,溢油物理化学性质所具有的灰色相关性可用GM(0,m)模式的灰色辨识参数来表征;在风化过程中,溢油的蒸发率和溶解率可分别用表面张力、黏度和密度作为预报因子。     

Numerical model simulations of continental shelf flows off northern California

The three-dimensional circulation on the continental shelf off northern California in the wind events and shelf transport (WEST) experiment region during summer 2001 is studied using the primitive equation regional ocean modeling system (ROMS). The simulations are performed with realistic topography and initial stratification in a limited-area domain with a high-resolution grid. Forcing consists of measured wind-stress and heat flux values obtained from a WEST surface buoy. The general response shows a southward coastal upwelling jet of up to and a weakening or reversal of currents inshore of the jet when upwelling winds relax. Model results are compared to WEST moored velocity and temperature measurements at five locations, to CODAR surface current observations between Pt. Reyes and Bodega Bay, and to hydrographic measurements along shipboard survey lines. The model performs reasonably well, with the highest depth-averaged velocity correlation (0.81) at the inshore mooring (40 m water depth) and lowest correlation (0.68) at the mid-depth mooring (90 m depth). The model shows generally stronger velocities than those observed, especially at the inshore moorings, and a lack in complete reversal of southward velocities observed when upwelling winds relax. The comparison of surface velocities with CODAR measurements shows good agreement of the mean and the dominant mode of variability. The hydrography compares closely at the southern and northern edges of the survey region (correlation coefficients between 0.90 and 0.97), with weaker correlations at the three interior survey lines (correlation coefficients between 0.44 and 0.76). Mean model fields over the summer upwelling period show slight coastal jet separation off Pt. Arena and significant separation off Pt. Reyes. The cape regions also experience relatively strong bottom velocities and nonlinearity in the surface flow. Across-shelf velocity sections examined along the shelf reveal a double jet structure that appears just north of Bodega Bay and shows the offshore jet strengthening to the south. We examine the dynamics during an upwelling and subsequent relaxation event in May 2001 in which the WEST measurements show evidence of a strong flow response. The alongshelf variability in the upwelling and relaxation response introduced by Pt. Reyes is evident. Analysis of term balances from the depth-averaged momentum equations helps to clarify the event dynamics in different regions over the shelf. A clear pattern in the nonlinear advection term is due to the spatial acceleration of the southward jet around the capes of Pt. Arena and Pt. Reyes during upwelling. Results from a three-dimensional Lagrangian analysis of water parcel displacement show significant southward displacement in the coastal jet region, including a strong signal from the double jet. Alongshelf variability in parcel displacements and upwelling source waters due to the presence of Pt. Arena and Pt. Reyes is also apparent from the Lagrangian fields. A cyclonic eddy-like recirculation feature offshore of Pt. Arena prior to the upwelling event causes large patches of onshore-displaced parcels. Additionally, across-shelf variability in the response of water parcels along the D line includes decreased vertical displacement and increased alongshelf displacement in the offshore direction.     

中国西北地区近50年夏季0 ℃层高度及气温时空变化特征

采用1960-2009 年112 个地面观测站和21 个探空站气象资料,分析中国西北地区近50 年夏季0 ℃层高度和平均气温变化趋势。结果表明：西北地区近50 年来夏季0 ℃层高度平均值为4675.7 m,在1987 年以前表现为下降趋势,平均每年下降5.6 m,而1987 年以后表现为显著的上升趋势,平均每年上升2.6 m;夏季平均气温与0 ℃层高度变化趋势大致相同,西北气候显著转型前后表现出相反的变化趋势,且1987 年以来夏季平均气温增加急剧,平均每10 年上升0.53 ℃。1960 年以来夏季0 ℃层高度在北京时间08 时该区大部分地区表现出显著的上升趋势,而在20时大部分地区表现出相反的变化趋势,1987 年以来在08 时和20 时大部分地区夏季0 ℃层高度都为上升趋势;50 年来大部分地区夏季平均气温都表现为上升趋势,乌鲁木齐和秦巴山地则表现为显著的下降趋势。西北不同气候区的夏季0 ℃层高度和平均气温变化也有一定的差异。西北地区夏季0 ℃层高度和平均气温具有较好相关性,东部季风区相关性最差,青藏高寒区最好。