板块剪式汇聚加地体拼贴——中特提斯消亡的新模式

中特提斯是中生代中晚期存在于南、北大陆之间的海洋。该海洋在晚白垩世消亡后,遗留长千余公里的班公湖－怒江板块结合带。在大量研究成果中,对中特提斯如何消亡这一重大问题至今分歧甚大。不少研究者持洋壳俯冲消亡（东太平洋模式）观点,但在俯冲方向上却有向南或向北之别。笔者则认为中特提斯是一个具有众多互不相通、时代早晚不同的狭窄洋盆的特殊海洋,綦肖亡过程中根本未发生过大规模的洋壳俯冲,帮提出剪式闭合加地体逐次拼     

BOUNDARY LAYER TRANSPORT OF METAL IONS IN FROZEN SOIL

Two series of freezing column tests with distilled water and municipal solid waste leachate were investigated, using illitic silty clay. Temperature distributions along the freezing column were recorded as a function of distance and time. Unfrozen moisture content and osmotic pressures as a function of temperature were calculated. It was shown that temperature distributions as a function of distance and time were similar in all tests, probably as a result of the limited amount of moisture intake. The amount of moisture intake was directly related to freezing time and temperature gradient in the freezing column. Unfrozen moisture contents, ion concentrations and temperature gradients were identified as the controlling parameters that contributed to the boundary layer transport (BLT) of metal ions in frozen specimens. Na⁺ concentration profiles were mostly dependent on water movement in the freezing column. The behaviour of Ca²⁺ and Mg²⁺ cations was similar to Na⁺; their concentrations in the soil solution decreased with freezing time due to ion exchange. Temperature, moisture content in an unfrozen boundary layer (UBL), and concentration gradient were taken into consideration in the development of a boundary layer transport model (BLTM). Based on the experimental results and Powell's optimization technique, the diffusivity parameters of various metal ions were calculated. Comparison of experimental and predicted results indicated that the BLTM can predict the migration of metal ions in UBL.     

Submerged forest off Nyuzen, Kurobegawa alluvial fan, Toyama Bay, Central Japan

Remnants of a submerged ancient forest have been found on the continental shelf of NW Japan off the Kurobe alluvial fan in Toyama Bay. The remains, standing tree stumps and roots, are located at depths between 20 and 40 m and ages of 8,000 years B.P. to 10,000 years B.P. have been determined by the ¹⁴C method. Alnus and Salix are the most commonly preserved genera and the trees grew on the now sub-merged seaward margin of the alluvial fan. Pollen analysis permits an estimate of palaeo-temperatures 2°C to 4°C lower than at present. Diatoms give some indication of salinity variations at the time of forest development and suggest brackish water, possible lagoonal conditions. The distribution of the stumps and roots suggests that there were probably two separate forests which were overwhelmed by rising sea-level and flash flood deposits. The present day submarine exposures may be due to recent submarine erosion related to the seaward movement of flood waters which passed from the fan into the upper reaches of the Toyama submarine canyon system.     

单轴压缩下干燥和饱水岩石中超声P波的衰减

根据脉冲传播和频谱比方法的基本原理建立了一套超声波衰减和波速测量系统。研究了单轴压缩下超声P波在干燥和饱水的小浪底砂岩和房山大理岩中的衰减和速度。常压下,水饱和样品的Q_P值低于干燥样品。初始加载时,在大多数情况下,Q_p值明显增加即衰减减小;当应力水平达破裂强度50-60％后,岩石开始膨胀,Q_p减小即衰减增加;临近破裂Q_p减至最小。Q_p的变化量达一个数量级。单轴压缩下,在干燥和饱水的砂岩、大理岩中,V_p分别增加为27％和28％,44％和11％。径向Q_p和V_p随单轴压力的变化比轴向小得多,呈现明显各向异性。在本实验条件下,波在裂纹表面的摩擦耗散是主要的衰减机制,水的作用主要是潮湿和润滑裂纹表面,促进滑动,增加衰减。     

拼合岩石样品破裂的初步研究

岩石的脆性、延性以及脆性-延性的转变的研究对于地球物理学和地质学都是非常重要的课题。考虑到在地壳中可能存在着岩石的脆性-延性交界面,我们设计了拚合样品的三轴实验来模拟这种情况。 拼合样品由房山大理岩、济南辉长岩和昌平花岗岩组成。每个拼合样品由两块或三块高度相同、直径50毫米的不同岩石圆柱拼合组成。拼合样品的总高度为110毫米,各岩     

An experimental study on fractural features of concrete samples containing hard inclusion

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1997—1998年El-Nio至La-Nia期间东海黑潮的变异

基于日本“长风号”调查船在 1 997与 1 998年 1 0个航次的CTD资料 ,采用改进逆方法及改进动力计算方法对东海黑潮的流速、流量进行计算 .1 997年 5月出现了El Ni no现象 ,东海黑潮流量在 1 997年夏季减少 ,1 997年东海黑潮的平均流量也减少 .在 1 997年 1月与 6— 7月 ,即El Ni no现象出现前后 ,东海环流的流态有些不同 .在 1 998年 4至 1 1月黑潮在PN断面出现多流核心的结构 ,特别在 1 0— 1 1月出现 3个流核心 ,黑潮主流核的位置秋季时东移 .1 995年与 1 998年都是东海黑潮异常年 ,这些异常现象可能与冲绳岛以南出现的反气旋涡的强度变化以及从El Ni no现象过渡到La Ni na现象有关     

1996年中国中西部地区高精度绝对重力观测结果

1996年,中国科学院测量与地球物理研究所利用目前国际上最先进的FGS／112型绝对重力仪,在我国中西部地区的湖北、四川、云南和广西省开展绝对重力测量．给出了15个绝对重力点的最新观测结果,并与其他类型仪器在一些点上的观测结果进行了比较．结果表明,FGS／112绝对重力仪在15个点的观测结果的精度优于2．78×10－8m／s2．该仪器具有较好的稳定性和重复性,并与其他类型仪器没有明显的系统误差．     

试用累积求和方法研究地震活动平静现象及大震概率预报

以表征区域地震活动强度背景的震级期望值作为单个地震事件的目标值,利用震级累积和C值随时间的变化分析地震活动相对平静现象,并给出其显著性检验. 文中还定量分析了平静异常与大震的关系,提出了利用核函数对大震发生时间进行概率外推的方法. 用上述方法对华北区的山西、张家口-渤海地震带的部分地区及新疆区域进行计算,显示该方法能够描述地震活动平静现象,并可合理地对未来大震发生时间进行概率外推估计.     

测定浅震震源参数的宏观方法

本文提出了利用等震线测定地震断层面的走向、倾向、倾角和破裂长度等震源参数的宏观方法。用这种方法测定了35个地震（1830年-1973年）的参数,其结果与用微观方法得到的结果进行了比较,二者基本一致。 关于破裂方式对等震线的影响问题,本文也进行了初步的讨论。