LISEM: A SINGLE-EVENT PHYSICALLY BASED HYDROLOGICAL AND SOIL EROSION MODEL FOR DRAINAGE BASINS. I: THEORY,INPUT AND OUTPUT

A new physically based hydrological and soil erosion model has been developed, which can be used for planning and conservation purposes: the LImburg Soil Erosion Model (LISEM). The LISEM model is one of the first examples of a physically based model that is completely incorporated in a raster Geographical Information System. This incorporation facilitates easy application in larger catchments, improves the user friendliness by avoiding conversion routines and allows remotely sensed data to be used. Processes incorporated in the model are rainfall, interception, surface storage in micro-depressions, infiltration and vertical movement of water in the soil, overland flow, channel flow, detachment by rainfall and throughfall, detachment by overland flow and transport capacity of the flow. Special attention has been given to the influence of tractor wheelings, small roads and surface sealing. Vertical movement of water in the soil is simulated using the Richard's equation. Optionally, the user can choose the Holtan or the Green–Ampt infiltration model. For the distribution flow routing, a four-point finite-difference solution of the kinematic wave is used together with Manning's equation.     

CHRONOLOGY OF YICHANG GRAVEL LAYER BASED ON QUARTZ TI-LI CENTER ESR DATING AND ITS IMPLICATIONS FOR THE INCISION TIMING OF THE THREE GORGES VALLEY

Uplift of Tibet Plateau and formation of Asian Monsoon greatly affect East Asian geomorphological evolution, climate change and environment systems. Thus, those phenomena also control the origin, size and direction of river systems. The Yangtze River, as the most important linkage between Tibet Plateau and the East Asian marginal seas, delivers large volumes of water, sediment, and associated chemicals from its headwater regions and tributaries to the East China Sea, significantly influencing sedimentary system evolution in its drainage basin. Therefore, the formation of the modern Yangtze River and its geological-time evolution history have been paid more and more attention to since the beginning of the last century. After debated for more than a century, the First Bend in Shigu area and the Three Gorges have been known as the key capture point of the Yangtze River's evolution history. In particularly, the Three Gorges incision period remains greatly controversial, which mainly focuses on Cretaceous period-Neogene period, early Pleistocene period, and late Quaternary period. The Yichang Gravel, just located downstream and outlet of the Three Gorges with an inverted triangle shape, is mainly distributed in western Jianghan Basin with over 1 000km². Because of its wide distribution and key geographical location, many typical profiles of Yichang Gravel have been the critical materials for studies on stratigraphic division, geomorphic evolution, and paleoenvironment change in middle Yangtze River Basin, especially on the Three Gorges incision history. Based on the previous field investigation, the Yichang gravel unconformably overlies the Cretaceous bedrocks and underlies the mid-Pleistocene vermicular red earth. In addition, studies on heavy mineral assemblages, Pb isotopic compositions of detrital K-feldspar grains, magnetic characteristics as well as pollen assemblage characteristics have showed that sediments in Yichang Gravel are mainly derived from upper Yangtze River Basin, such as Jinshangjiang drainage, Minjiang drainage, Jialingjiang drainage and Wujiang drainage. Based on the above comprehensive analysis, researchers demonstrated that the depositing time of Yichang Gravel can best constrain the Three Gorges incising time. The absolute altitude of Yichang Gravel exceeds 110m, and many thick sand lens are developed from top to bottom of the profiles. In this study, we applied the quartz Ti-Li center ESR dating method in Yichang Gravel to determine its absolute formation age, and then to constrain the minimum cutting-through time of Three Gorges. Eight samples(SXY-1, SXY-2, YC-1-4, LJY-1, LJY-2)were collected from the sand lens at depths of 4m, 19m, 40m, 51m, 63m, 75m, 83m and 99m respectively from the top of the profile. At the same time, in order to evaluate the residual dose of Ti-Li center after sunlight bleaching, we also sampled four modern surface Yangtze River sediments near Yichang Gravel for ESR measurement. The result shows that the quartz Ti-Li center ESR signal intensity of the 4 modern fluvial sediments samples are zero, which implies that the Ti-Li center ESR signal intensity of quartz in Yichang Gravel sand lens could be bleached to zero before the last burial. Thus, the above results indicate that the ESR dating results of this paper are reliable. The ESR absolute age from top to bottom of the profile is 0.73Ma BP,0.87Ma BP,0.98Ma BP,1.04Ma BP,1.05Ma BP,1.10Ma BP, 1.11Ma BP, 1.12Ma BP, respectively. The ESR dating results show that the Yichang Gravel began to deposit at about 1. 12Ma BP until 0. 73Ma BP, and the Ti-Li center ESR age indicates that the Yangtze River cut through Three Gorges area no later than 1.12Ma BP.     

TWO－DIMENSIONAL MATHEMATICAL MODEL FOR STUDYING EROSION AND SEDIMENTATION OF A WANDERING STRETCH IN THE LOWER YELLOW RIVER

ＴＷＯ－ＤＩＭＥＮＳＩＯＮＡＬＭＡＴＨＥＭＡＴＩＣＡＬＭＯＤＥＬＦＯＲＳＴＵＤＹＩＮＧＥＲＯＳＩＯＮＡＮＤＳＥＤＩＭＥＮＴＡＴＩＯＮＯＦＡＷＡＮＤＥＲＩＮＧＳＴＲＥＴＣＨＩＮＴＨＥＬＯＷＥＲＹＥＬＬＯＷＲＩＶＥＲ￥ＺＨＡＮＧＳｈｉｑｉｒ（Ｓｅｎｉｏｒ...     

APPLICATION OF THE TRRL FLOOD ESTIMATION MODEL IN HYDROLOGICAL FORECASTING FOR CATCHMENTS WITH LIMITED DATA A CASE STUDY

１ＩＮＴＲＯＤＵＣＴＩＯＮＯｎｔｈｅｍｏｒｎｉｎｇｏｆ３０ｔｈＪａｎｕａｒｙ１９９２,ａＮａｉｒｏｂｉｂｏｕｎｄｐａｓｅｎｇｅｒｔｒａｉｎｆｒｏｍＭｏｍｂａｓａｏｎｔｈｅｍａｉｎｌｉｎｅｄｅｒａｉｌｅｄｉｎｔｏａｎｅｍｂａｎｋｍｅｎｔｔｈａｔｈａｄｂ...     

华北盆地强震的震源模型兼论强震和盆地的成因

华北盆地自第三纪以来产生不均匀沉降,形成众多凹陷和隆起.传统的热张裂模型或是拉一分模型均不适用于华北盆地.我们根据反射和折射地震探测以及地震体波层析成象的结果,说明震源区附近存在Moho界面断裂,而且有明显的迹象表明,上地幔高温物质（低速度）向地壳下部入侵.因此,作者提出华北盆地强震以及凹陷形成的新模型,即在水平板块构造应力场的背景中,上地幔热物质向地壳下部入侵,它所产生的扰动应力场不仅在横向是不均匀的,而且在垂向也是不均匀的.它能够在地壳上部产生足够大的伸张应力场,同时在地壳中部或下部产生水平切应力场.这个新模型也能解释华北盆地的地壳厚度没有减薄,而地面热流又较大的现象. 由于地壳中力学性质随深度而改变,所以强震可能是由中部地壳的塑性形变以及上部地壳的脆性断层所组成的,即所谓两层破裂的震源模型.     

华北盆地强震的震源模型兼论强震和盆地的成因

华北盆地自第三纪以来产生不均匀沉降,形成众多凹陷和隆起.传统的热张裂模型或是拉一分模型均不适用于华北盆地.我们根据反射和折射地震探测以及地震体波层析成象的结果,说明震源区附近存在Moho界面断裂,而且有明显的迹象表明,上地幔高温物质（低速度）向地壳下部入侵.因此,作者提出华北盆地强震以及凹陷形成的新模型,即在水平板块构造应力场的背景中,上地幔热物质向地壳下部入侵,它所产生的扰动应力场不仅在横向是不均匀的,而且在垂向也是不均匀的.它能够在地壳上部产生足够大的伸张应力场,同时在地壳中部或下部产生水平切应力场.这个新模型也能解释华北盆地的地壳厚度没有减薄,而地面热流又较大的现象. 由于地壳中力学性质随深度而改变,所以强震可能是由中部地壳的塑性形变以及上部地壳的脆性断层所组成的,即所谓两层破裂的震源模型.     

STUDY OF THE LAVA FLOW HAZARD ZONING BASED ON THE KINEMATIC THERMO-RHEOLOGICAL MODEL:EXAMPLE STUDY FOR THE ASHIKULE VOLCANO,XINJIANG

The lava flow hazard is an important and frequent disaster for residents in the volcanic area. In this paper, we focus on the lava flow inundation hazard zoning based on the example case of the Ashikule volcano in Xinjiang, China. Firstly, the parameters of magma such as density, viscosity and temperature are calculated by the empirical formula of magma utilizing results of previous field geological survey and petrology analysis. Then, using the kinematic thermo-rheological model, we simulated the inundation area of lava flow from Ashi volcano at the effusion rates of 200m³/s and 500m³/s. The simulation results of Ashi volcano well coincide to the geological map and verify that the method and parameters are valid. Then the applied simulations were carried out to calculate the lava flow inundation area in future eruption at Ashi, Wuluke and Daheishan crater with different effusion rates. At last, according to the analysis of the applied simulation results and drawing lessons from the foreign disaster zoning method, the four-level hazard zoning was built and set with different colors. The first level with red color is the extra-dangerous zone that is always inundated in any eruption but only distributes near the lava spillway of the crater. The second level with orange color is the dangerous zone that is inundated in the medium scale eruption. The third level with yellow color is the sub-dangerous zone that is corresponding to the large eruption. The fourth level with blue color is the potential dangerous zone that is only inundated in the extra-large eruption. In addition, we put forward the suggestion to respond to and avoid the disaster in future. Although China has not been affected by the lava flow for nearly three hundred years, the prospective study in this paper will lay the foundation for the study of related disasters, and provide the reference for the major construction projects in the volcanic area.     

亚暴膨胀相近磁尾位形不稳定性模型Ⅰ．近磁尾位形不稳定性

用单流体和双流体ＭＨＤ近似，研究了近磁尾位形不稳定性（ＮＥＴＣ）．分析表明，ＮＥＴＣ可能存在两种漂移不稳定情况Ｃ１和Ｃ２与卫星观测资料对比显示，Ｃ２较容易在亚暴膨胀相前夕出现，它可以解释亚暴膨胀相期间磁场和等离子体扰动的特征周期、尾向传播速度、磁场扰动和等离子体压强扰动之间的位相关系，场向电流的周期性结构，西向涌浪头部的电子沉降和极光隆起等观测特性和现象．薄电流片的极端情况（Ｒｃ≈ｒｉ）不在本文的讨论范围之内．     

亚暴膨胀相近磁尾位形不稳定性模型Ⅰ．近磁尾位形不稳定性

用单流体和双流体ＭＨＤ近似,研究了近磁尾位形不稳定性（ＮＥＴＣ）．分析表明,ＮＥＴＣ可能存在两种漂移不稳定情况Ｃ１和Ｃ２与卫星观测资料对比显示,Ｃ２较容易在亚暴膨胀相前夕出现,它可以解释亚暴膨胀相期间磁场和等离子体扰动的特征周期、尾向传播速度、磁场扰动和等离子体压强扰动之间的位相关系,场向电流的周期性结构,西向涌浪头部的电子沉降和极光隆起等观测特性和现象．薄电流片的极端情况（Ｒｃ≈ｒｉ）不在本文的讨论范围之内．     

亚暴膨胀相近磁尾位形不稳定性模型Ⅰ．近磁尾位形不稳定性

用单流体和双流体ＭＨＤ近似，研究了近磁尾位形不稳定性（ＮＥＴＣ）．分析表明，ＮＥＴＣ可能存在两种漂移不稳定情况Ｃ１和Ｃ２与卫星观测资料对比显示，Ｃ２较容易在亚暴膨胀相前夕出现，它可以解释亚暴膨胀相期间磁场和等离子体扰动的特征周期、尾向传播速度、磁场扰动和等离子体压强扰动之间的位相关系，场向电流的周期性结构，西向涌浪头部的电子沉降和极光隆起等观测特性和现象．薄电流片的极端情况（Ｒｃ≈ｒｉ）不在本文的讨论范围之内．     

龙陵-澜沧断裂带双震型强震活动破裂模型讨论

龙陵地震和澜沧－耿马地震是龙陵－澜沧断裂带上两次典型的双震型强震活动,但它们在地质构造背景、应力场分布、发震构造和烈度分布等方面却具有截然不同的特点。龙陵地震发生在主要由花岗岩构成的地块内,地质构造比较均一;地震处在ＮＮＷ向挤压的统一应力场中;两主震的发震构造走向和两个Ⅸ度区长轴近于直交。澜沧－耿马地震发生在一古板块边界附近,震区构造复杂,耿马７．２级地震和澜沧７．６级地震发生于不同的应力环境中,发震构造和极震区长轴近于平行,呈斜列状分布。通过对龙陵地震和澜沧－耿马地震的对比分析,提出了双震型强震活动的共轭型和牵动型两种破裂模型,并对各自的特点及形成条件进行了初步分析     

利用地面激光与地质雷达综合探测活断层浅层三维结构——以川西理塘毛垭坝盆地北缘正断层为例

快速获取活断层的高精度微地貌形态和对应的浅层三维结构是揭示活断层浅地表形迹与活动特征的关键。文中综合利用地面三维激光扫描仪和地质雷达技术,以川西理塘地区毛垭坝盆地北缘主边界断裂禾尼段的正断层崖为研究对象,获取了该处正断层错动2期最新地貌面的精确地表垂直位移量和浅层二维地质雷达图像,并初步建立了基于地面三维激光与地质雷达的活断层微地貌精细化三维测量方法,构建了断层崖微地貌的精细三维模型和浅表三维图像,揭示了正断层崖处发育的伸展地堑结构,同时初步实现了断层微地貌地表地下三维数据的一体化融合显示及相互解译。应用结果表明,该方法可以同时快速、高效、无损地获取大范围内的活断层微地貌及浅层结构的多层次、多视觉的空间数据,极大地提高了对活动断层微地貌形态与浅层结构进行快速调查与研究的精度和认识水平,也为更全面地认识和理解活断层的空间分布与变形特征、活动习性和多期古地震遗迹等提供重要的数据和方法支持。因此,对该方法的继续探索和完善,将显著提升和扩展其在活断层定量化和精细化研究中的实用性及应用前景。     

THE DELINEATION OF THREE-DIMENSIONAL SHALLOW GEOMETRY OF ACTIVE FAULT BASED ON TLS AND GPR: A CASE STUDY OF AN NORMAL FAULT ON THE NORTH MARGIN OF MAOYABA BASIN IN LITANG,WESTERN SICHUAN PROVINCE

It is crucial to reveal the surface traces and activity of active faults by obtaining high-precision microtopography and three-dimensional shallow geometry. However, limited by the traditional geological investigation methods in the field and geological condition factors, the measurement method on microtopography and shallow geometry of active fault is badly insufficient. In this study, the TLS and GPR are firstly used comprehensively to delineate the microtopography and shallow geometry of the normal fault scarp on the north margin of Maoyaba Basin in Litang. Firstly, the vertical displacements of two landforms produced by the latest two periods of normal faulting and the two-dimensional GPR profiles are obtained separately. Secondly, the three-dimensional measurement method of active fault based on TLS and GPR is preliminarily established. On this basis, three-dimensional model of fault scarp and three-dimensional images of subsurface geometry are also obtained. These data all reveal a graben structure at normal fault scarps. Thirdly, the fusion and interpretation of three-dimensional data from the surface and subsurface are realized. The study results show:1)the vertical displacements of the T₁ and T₂ terraces by the normal fault movement is 1.4m and 5.7m, the GPR profile shows a typical fault structure and indicates the existence of small graben structure with a maximum width of about 40m in the shallow layer, which further proves that it is a normal fault. 2)the shallow geometry of the normal fault scarp can be more graphically displayed by the three-dimensional radar images, and it also makes the geometry structure of the fault more comprehensive. The precise location and strike of faults F₁ and F₂ on the horizontal surface are also determined in the three-dimensional radar images, which further proves the existence of small graben structure, indicating the extensional deformation characteristics in the subsurface of the fault scarps. Furthermore, the distribution of small graben structure on the surface and subsurface is defined more precisely. 3)the integrated display of microgeomorphology and shallow geometry of normal fault scarp is realized based on the three-dimensional point cloud and GPR data. The fusion of the point cloud and GPR data has obvious advantages, for the spatial structure, morphological and spectral features from the point cloud can improve the recognition and interpretation accuracy of GPR images. The interpreted results of the GPR profiles could minimize the transformation of the surface topography by the external environment at the most extent, restore the original geomorphology, relocate the position and trend of faults on the surface and constrain the width of deformation zones under the surface, the geological structure, and the fault dislocation, etc. In a word, the TLS and GPR can quickly and efficiently provide the spatial data with multi-level and multi-visual for non-destructive inspection of the microgeomorphology and shallow structure for the active fault in a wide range, and for the detection of active fault in the complex geological environments, and it is helpful to improve the accuracy and understanding of the investigation and research on microtopography and shallow geometry of active faults. What's more, it also offers important data and method for more comprehensive identification and understanding of the distribution, deformation features, the behaviors of active faults and multi-period paleoseismicity. Therefore, to continuously explore and improve this method will significantly enhance and expand the practicability and application prospects of the method in the quantitative and elaborate studies of active faults.     

1998年海原4.7级地震前平凉地区的前兆异常及观测资料的映震能力检验

介绍了１９９８ 年７ 月２９ 日宁夏海原４ ．７ 级地震前,平凉地区几个观测台站的水氡、水位和地电阻率的异常反映,及对该次地震的预报情况．研究表明,平凉地区的几种观测手段对该地区及邻近的宁夏西海固地区５ 级左右地震和南北地震带北段６ 级以上地震有较好的映震能力．     

1998年海原4.7级地震前平凉地区的前兆异常及观测资料的映震能力检验

介绍了１９９８年７月２９日宁夏海原４．７级地震前,平凉地区几个观测台站的水氡、水位和地电阻率的异常反映,及对该次地震的预报情况。研究表明,平凉地区的几种观测手段对该地区及邻近的宁夏西海固地区５级左右地震和南北地震带北段６级以上地震有较好的映震能力。