RHEOLOGICAL PROPERTIES OF VISCOUS DEBRIS FLOWS IN THE JIANGJIA RAVINE, YUNNAN, CHINA

RIIEOLOGICAL PROPERTmS OF V1SCOUS DEBmS FLOWS1N THE JIANGat RAVIN'E, YUNNAN, CmNA*fYuy WANG', Chyandeg JAN', Changzhi LI3 and WeIiliang HAN4Abstract:The rheological ProPethes of natural debris flow are studied using exPerimental data obtained froma formeter bullt by the aUthOrS. The Present study is aimed to addrss the rheological Propenies ofviscous debris flow at lOw shear od. It is found that oversboss effeet and shearbo-thinninPhenomenon chM the viscous …     

INVESTIGATION OF INFILTRATION CHARACTERISTICS AND DEBRIS FLOW INITIATION CONDITIONS IN DEBRIS FLOW SOURCE AREAS USING A RAINFALL SIMULATOR

Rainfall was simulated on unconfined plots on regolith in debris flow source areas using a portable simulator. In total, 351 simulations were carried out on steep slopes (27–54°) with rainfall intensities of 28–291 mm/h. From these rainfall simulations the infiltration parameters sorptivity (S) and steady-state infiltration capacity (K) of the regolith, and a threshold for the occurrence of micro-scale mass movements, were obtained. Two evaluation methods were used to obtain the infiltration parameters K and S. The ‘infiltration envelope’ method uses rainfall intensity and time to ponding from multiple tests and fits an infiltration envelope through the data from which K and S can be obtained. The ‘constant runoff’ method uses rainfall intensity and overland flow intensity to calculate K, after which S can be calculated in several ways by using time to ponding. The constant runoff method produced K values of 16.6–128 mm/h, which usually show a log-normal distribution. K values depend on the regolith parent material and rainfall intensity. Using this method, S values are 0.088–0.381 cm/min^1/2. The infiltration envelope method produced K values of 9.8–131 mm/h and S values of 0.14–0.32 cm/min^1/2. It can be argued that both methods overestimate K as well as S, but quantitative relations between measured/calculated and actual values of K and S have not yet been obtained. At high rainfall intensities, typically 100 mm/h or more, micro-scale mass movements sometimes occur. A lower threshold curve for the occurrence of these micro-scale mass movements has been constructed. It is a function of both slope angle and rainfall intensity. The micro-scale mass movements could play an important part in the initiation of debris flows in the study area, possibly by delivering sediment to overland flow. On the very steep slopes, the sediment-rich overland flow can easily mobilize coarse material.     

西双版纳州地震活动特点及与环境因子的关系

本文揭示了西双版纳州东、西两部分地震（以澜沧江为界）的交替活动性、强震的近似原地重复性以及与环境因子的关系，进而指出本世纪90年代中至21世纪初该州的强震危险区主要在勐海县周围。最后，为实现逐年跟踪逼近预测，又提出了一种根据大气降水对地壳的加卸载动态变化具体化判断发震年份的方法。     

THE DISTRIBUTION OF PREFERENTIAL PATHS AND ITS RELATION TO THE SOIL CHARACTERISTICS IN THE THREE GORGES AREA, CHINA

To study the characteristics of the distribution of the preferential paths and the affecting factors in the Three Gorges area, four soil profiles were dug to observe the distribution of preferential paths in the Quxi watershed in the Yangtze River basin. The Morisita exponential test method was used to examine the distribution type of preferential paths. The physical properties and infiltration characteristics of the soil were also measured to evaluate their relationship to preferential paths. The results showed that in this area, preferential paths clustered and mainly distributed in the 80-100 cm soil layer, and along the interface between the weathered layer and semi-weathered layer. There were more non-capillary pores in the 83-110 cm layer than in the other layers. It can be derived that most non-capillary pores in this layer were preferential paths caused by geological processes and rotten plant roots. The percentage of coarse soil particles increased with the depth of the soil layer. In the deeper soil layer, the coarse soil particles helped the formation of preferential paths. The fastest steady infiltration rate was observed in the of 83-110cm layer, which is inferred to be due to the greater number of preferential paths.     

RILL INITIATION AND EROSION ON HILLSLOPES IN THE HILLY LOESS REGION,WESTERN SHANXI PROVINCE

I. INTRODUCTIONSumming up recent research achievements, Huang (1993) pointed out that the capaciucs ordetachment and transport by rill now were much greater than tboso by rain drop impact and sheet now. soil erosion by water on upper slope area is frcquenhy discussed interms of interrill and rill erosional sub--processes. Compared with rill erosion, interrlll erosion contributes a very small proportion to the sediment transported downwards (Foster,1982). Field experiments conducted by Ca…     

云南定点倾斜异常与强震关系研究

采用速率合成和趋势合成两种方法对云南定点形变倾斜观测资料进行了处理，旨在提取形变准同步群体异常的信息，分析研究倾斜与强震关系。结果表明：云南强震前1—2年形变场的群体异常信息较为显著，对云南地区强震的中期预测有一定的效能，倾斜南北向的观测变化结果对强震的反映优于东西向。     

大华北浅源地震与日本海西部及我国东北深震的关系

分析了大华北浅源地震与日本海西部及我国东北深震的关系,认为本世纪来日本海西部—我国东北深震经历了5个相对活跃期,大华北各地震区相应经历这5个活跃期的影响期。根据大华北M≧6级浅源地震与深震活动的相关性,建立了太平洋板块楔形俯冲带端部重大深震事件导致大华北浅源M≧6级地震发生的板块俯冲模型,应变波传播速度约94km/年,地表视速度约100km/年。重大深震事件突出、模型稳定性强,预测实验表明模型公式可做大华北地震监测参考。用本模型可以解释浅源地震迁移、各地震区地震与深震活动相关等现象。     

云南腾冲全新世火山源区性质及其岩浆演化

在对腾冲火山区进行野外考察的基础上,重点对区内3座全新世火山(黑空山、打莺山和马鞍山)的岩石学及地球化学特征、岩浆源区性质及其演化进行研究。对主量元素和微量元素研究表明,这套岩石属于高钾钙碱性系列,包括粗面玄武岩、玄武粗安岩、粗面安山岩和英安岩,从基性岩到酸性岩都有分布。这套火山岩富集大离子亲石元素和轻稀土元素,亏损Nb-Ta-Ti不相容元素,具有岛弧火山岩特征。通过微量数据模拟认为,腾冲全新世火山岩为石榴石相地幔橄榄岩在低压条件下大比例部分熔融的产物。源区富钾矿物为金云母,不含角闪石。腾冲及其邻区新生代以来的火山喷发主要受盆地内断裂控制,不受板块俯冲或者火山弧作用的控制。其活动产物为板内火山岩,表现出的岛弧火山岩特征是由于地幔源区受到古洋壳的俯冲板片的富集作用,富集作用发生在部分熔融作用之前。富集地幔部分熔融形成的富钾岩浆沿断裂上升进入地壳形成岩浆房,在岩浆房阶段经历了分离结晶作用和地壳混染作用,有钛铁氧化物、磷灰石、橄榄石、单斜辉石和斜长石的结晶分离。     

云南剑川近场横波特征及其与构造的关系

通过对1982年7月3日云南剑川Ms5．4级地震的余震震群近场记录的研究,为该地区存在横波分裂现象及上部地壳存在裂隙各向异性提供了直接的证据．剑川地区地震记录波形复杂,纵、横波视周期差异较大．横波快波偏振主要集中在NE45°和NW55°两个方向．7月20日ML4．8级强余震前后横波快波偏振取向变化显著,各台横波偏振方向震前彼此相对独立;震后整体上趋于有序．前者反映了地震发生前由于震源区应力集中在附近空间形成的应力分布的差异;后者显示出地震发生后由于震源区集中应力的释放带来的上述应力差异在一定空间范围的解除．该结果表明震源附近地区地震横波分裂特征不仅携带着地震处于相对平静期应力场的静态信息,而且也携带着地震发生前后应力场时、空动态变化的重要信息．文中还讨论了剑川地区构造对S波分裂的影响．     

岩石圈流变强度与中国大陆构造运动关系的探讨

以GPS观测资料和地震学研究成果为约束，针对不同流变参数的中国大陆岩石圈模型，数值模拟了岩石粘度与中国大陆板块边界作用强度的关系，探讨了陆-陆碰撞对中国大陆分层岩石圈运动的驱动机制．给出了陆-陆碰撞驱动力、附加地形与山根浮力及热浮力对中国大陆构造运动的驱动特点．印度板块、太平洋板块和菲律宾板块对中国大陆驱动的边界作用强度之比约是4：1．25：1，所引起的水平主压应力主要集中在坚硬岩石层；而附加地形等垂直方向作用力在水平方向产生的最大主压应力则主要集中在软弱岩石层．这种垂直方向上的作用力在高原南部地区阻碍陆-陆碰撞向北的推挤运动，在高原东北部增加对其它块体的推挤作用。     

云南剑川近场横波特征及其与构造的关系

通过对1982年7月3日云南剑川Ms5．4级地震的余震震群近场记录的研究，为该地区存在横波分裂现象及上部地壳存在裂隙各向异性提供了直接的证据．剑川地区地震记录波形复杂，纵、横波视周期差异较大．横波快波偏振主要集中在NE45°和NW55°两个方向．7月20日ML4．8级强余震前后横波快波偏振取向变化显著，各台横波偏振方向震前彼此相对独立；震后整体上趋于有序．前者反映了地震发生前由于震源区应力集中在附近空间形成的应力分布的差异；后者显示出地震发生后由于震源区集中应力的释放带来的上述应力差异在一定空间范围的解除．该结果表明震源附近地区地震横波分裂特征不仅携带着地震处于相对平静期应力场的静态信息，而且也携带着地震发生前后应力场时、空动态变化的重要信息．文中还讨论了剑川地区构造对S波分裂的影响．     

滇西地区地壳上地幔电性结构与地壳构造活动的关系

本文根据滇西地区18个大地电磁测深点资料的数据处理和分析结果,对测区深部导电率在纵、横向上的变化特征进行了研究。结果表明:滇西地区深部电性为多层结构,大致可分四至五个电性结构层;深部电性结构横向变化大,明显受区域构造控制;该区上部地壳内普遍存在低阻层;上地幔高导层明显存在两个隆起区,一个以剑川—鹤庆为中心呈北北西向展布的隆起区,另一个以腾冲—潞西为轴呈南北向展布的隆起区。 本文还讨论了地壳上地幔电性结构与大地构造的关系,滇西北裂陷区盆地的形成,以及该区地震活动与深部构造的关系     

华北及邻近地区月相与地震关系研究

本文研究了１９４０－１９９０年间华北及邻地地区大于５．５有的地震与月相的对应关系。通过对本地区断裂带的分析，把地震划分为沿四个断层带发生，分断层带讨论与月相的关系。结果表明，有两个断层带的地震发生在朔望期的比率可达５７％－６０％。这个结果优于没有按断层带划分地震的结果。     

1995年云南孟连西7.3级地震前震序列特征及其与主震的关系

在分析１９９５年云南孟连西７．３级地震的前震序列时,发现跟踪最大前震６．２级的余震序列中,有一组较大震级的地震呈现出随时间的增长不断线性递增的特点,这种特点在云南其他震例中也曾多次出现过。利用修正的大森公式ｎ（ｔ）＝ｋ／（ｔ＋ｃ）＾ｐ拟合该序列,在获得的参数重新构造的频度－线性化时间坐标中,这一组地震显示出与海城前震序列随时间变化震级出现非线性增强的共同特征。采用表征物质加速应变而失稳城前震序列随     

辽宁北票—义县地区NW向断裂的活动性分析及NW向断裂与朝阳—北票断裂的关系

在大量第一手资料的基础上,本文对北票－义县地区分布的１４条ＮＷ向断裂的发育特征和活动性进行了研究,并讨论了这一系列ＮＷ向断裂与朝阳－北票断裂之间在空间分布和活动特征上的相关性。结果表明,该地区ＮＷ向断裂与朝阳－北票断裂分处于不同的新构造运动单元,两者在空间上没有交汇;ＮＷ向断裂在晚更新世以来没有活动。     

长江流域汛期降水集中程度和洪涝关系研究

用新定义的降水集中度和集中期分别讨论了我国长江流域不同地段汛期降水在时间和空间上的分布特征和变化规律. 结果表明在对长江流域旱涝灾害研究方面,降水集中度和集中期能够定量地表征降水量在时空场上的非均匀性,提取出最大降水重心对应的时段,因此可以比较理想地分析旱涝灾害发生的基本特征及其形成机制. 并且在长江中下游地区的降水集中度与东亚副热带季风之间存在着比较密切的联系.     

THE HOLOCENE ACTIVITY AND STRIKE-SLIP RATE OF THE SOUTHERN SEGMENT OF XIAOJIANG FAULT IN THE SOUTHEASTERN YUNNAN REGION,CHINA

The southern segment of the Xiaojiang Fault (SSXF) is located at the intersection of the Xianshuihe-Xiaojiang Fault and Red River-Ailao Shan fault systems in the southeast margin of the Tibetan plateau. Based on the interpretation of remote sensing image, the SSXF clearly shows the linear feature and continuous distribution as a single, penetrating fault. It has a total length of about 70km, trends generally about 20° to the northeast and protrudes slightly in the middle to the east. A typically geomorphologic phenomenon about the synchronous left-lateral dislocation of ridges and gullies can be found at Liangchahe, Longtan Village along the SSXF. The distribution of faults, the sedimentary features, attitude variance and the primary dating results of the offset strata in the trench section across fault sag ponds reveal three paleoseismic events rupturing obviously the surface, which demonstrates that the SSXF has the ability of recurrence of strong earthquakes. High-precision topographic map about two gullies and the platform between them with synchronous dislocation is acquired by using the Trimble 5800 GPS real-time difference measurement system. The dislocation is (18.3±0.5)m. As the top geomorphologic surface between the above two gullies and their adjacent area, the terrace surface T₂ stopped accepting deposits at ~2606a, based on the linear regression analysis of three dating data. According to the geological method, a sinistral strike-slip rate of (7.02±0.20)mm/a on the SSXF in the Holocene is obtained, which has a good consistency with the results provided by using GPS data. The preliminary results about the Holocene activity and slip rate of the SSXF demonstrate that the southward or south-southeast motion of the Sichuan-Yunnan block in the SE Yunnan region has not been absorbed by the possible shortening deformation and the sinistral strike-slip rate of the SSXF has not been drastically reduced. The SSXF is a Holocene fault with obvious activity. This preliminary understanding provides some basic geological data for the seismic risk evaluation of the SSXF in the future, and for the establishment and inspection of the seismotectonic model about the Sichuan-Yunnan block.     

MACROPORE FLOW AND MASS WASTING OF GULLIES IN THE LOESS PLATEAU, CHINA

Due to the extensive gullying from historically excessive erosion in the loess plateau of China, much of this region is being converted to native grass and shrub vegetation. Tunnel scour and mass wasting are important gully erosion processes resulting from preferential flow through macropores （ pores 〉 1 mm diameter）. The objective of this study is to assess the changes with time in macropore flow characteristics of soils on the Loess Plateau following conversion to grass vegetation and the associated degree of mass wasting of gully faces. Ridge areas that had been revegetated for 1 year, 6 years, and 〉 15 years following tilling, and for 6 years following contour-ditching and the adjacent gully faces were characterized for their macropore and soil matrix properties on a 50 cm by 50 cm area. The total number of macropores increased from 11.6/m^2 to 39.6/m2 from 1 to 6 years and to 51.6/m2 after 15 years of revegetation following tillage. The macroporosity increased from 0.0008 m^3/m^3 to 0.0018 m^3/m^3 from 1 to 6 years of revegetation following tillage but the lowest macroporosity （0.0005 m3/m3） was 6 years of revegetation following contour-ditching. The contourditched area had the lowest infiltration rate （95 m/d） through the soil matrix （areas without macropores） with the tilled areas having similar infiltration rates regardless of the number of years of revegetation （averaged 146 m/d）. Due to tunnel scour erosion of macropores during infiltration into the area revegetated for 1 year, pore diameters enlarged by more than 200% resulting in this condition having the highest individual macropore infiltration rates （7967 m/d）. Macropores in all other areas were stable with no tunnel scour erosion of macropores. The total capacity for infiltration through macropores increased significantly with time following revegetation. The number of macropores on the gully faces was triple （92.8/m2） and the macroporosity quadruple （0.004 m3/m3） that of the ridge surfaces. The upper gully faces exhibited 1.1 slumps m^-1 for a total soil loss of 48622 kg per ha.     

云南景洪和越南莱州7.0级地震的预报

本文提供了1982年12月、1983年5月在景洪东北先后发生的5.8、5.3、5.7级地震及1983年6月莱州7.0级地震的中期、短期、临震预报的实况和主要依据。中期预报是通过∑E(1/2)释放速率变化出现异常,确定本区处于释放加速段,用最优分割等周期分析法处理得该区活动段将延迟到1983年6月底。利用地震活动位置演变确定活动地点在景洪—江城以南地区。短期预报主要根据孕震过程中依次出现的三个北东向地震条带,b值从1.3下降到0.55,并参考了省内大范围Rn值突变异常,推算出未来主震将大于6.5级。按文献[1]广义调制模式思路,确定震源体处于受调状态,进而外推对莱州7.0级地震作出临震预报。     

云南地壳和上地幔的岩石学结构

通过对地表出露变质岩、深部地震测深资料和高温高压岩石波速测试资料的综合分析 ,研究了云南地壳和上地幔岩石组成。结果表明 ,云南上、中、下地壳分别由绿片岩相 (顶部为沉积层 )、角闪岩相和麻粒岩相变质岩组成或分别由与之相当的花岗岩类、闪长岩类、辉长岩类组成 ,部分地区地壳底部有镁铁质榴辉岩存在。上地幔由橄榄岩组成 ,部分地区 (兰坪思茅坳陷和滇中坳陷 )壳幔过渡带可能由镁铁质榴辉岩和橄榄岩组成