Slumping and shallow faulting related to the presence of salt on the Continental Slope and Rise off North Carolina

Seismic reflection profiles and long- and medium-range sidescan sonar were used to investigate a salt diapir complex and area of slope instability near the base of the Continental Slope off North Carolina. Within the area of investigation three diapirs are bounded on their upslope side by a scarp 60 m high and 50 km long. The slope above the scarp is characterized by a series of shallow rotational normal faults. The bottom below the scarp is furrowed by slide tracks, which were probably carved by large blocks that broke off the scarp face and slid downslope leaving rubble and scree lobes.Extensive slumping in this area appears to be a result of uplift and faulting associated with salt intrusion, which has fractured and oversteepened the slope leading to instability and failure. Sharply defined slide tracks suggest that slope failure above the breached diapir complex is a continuing process, in contrast to much of the surrounding slope area where few instability features were observed.     

Modeling of rainfall-triggered shallow landslide

By integrating hydrological modeling with the infinite slope stability analysis, a rainfall-triggered shallow landslide model was developed by Iverson (Water Resour Res 36:1897-1910, 2000). In Iverson’s model, the infiltration capacity is assumed to be equivalent to the saturated hydraulic conductivity for finding pressure heads analytically. However, for general infiltration process, the infiltration capacity should vary with time during the period of rain, and the infiltration rate is significantly related to the variable infiltration capacity. To avoid the unrealistically high pressure heads, Iverson employed the beta-line correction by specifying that the simulated pressure heads cannot exceed those given by the beta line. In this study, the suitability of constant infiltration capacity together with the beta-line correction for hydrological modeling and landslide modeling of hillslope subjected to a rainfall is examined. By amending the boundary condition at ground surface of hillslope in Iverson’s model, the modified Iverson’s model with considering general infiltration process is developed to conduct this examination. The results show that the unrealistically high pressure heads from Iverson’s model occur due to the overestimation of infiltration rate induced from the assumption that the infiltration capacity is identical to the saturated hydraulic conductivity. Considering with the general infiltration process, the modified Iverson’s model gives acceptable results. In addition, even though the beta-line correction is applied, the Iverson’s model still produces greater simulated pressure heads and overestimates soil failure potential as compared with the modified Iverson’s model. Therefore, for assessing rainfall-triggered shallow landslide, the use of constant infiltration capacity together with the beta-line correction needs to be replaced by the consideration of general infiltration process.     

Distribution of vertical crustal movement rates in the Tohoku district, Japan, predicted by least-squares collocation

Least-squares prediction using an empirically deduced local covariance function was performed to investigate the temporal change in the rates of vertical crustal movements in the Tohoku district, Japan. Levelling data covering an area of approximately 450 × 275 km² observed between 1966 and 1995 were used and the results shown in the form of contour maps. Firstly we derived a covariance function of the rates of vertical crustal movement with a Gaussian form function. We used this function to estimate the spatial distribution of the rates of vertical crustal movements. By the present method, a steady tilt of the Tohoku district to the east, toward the Japan Trench and an areal uplift in the southwestern part were well reproduced. Moreover, a significant temporal change in vertical movement rates is clearly seen. Received: 15 July 1996      

Slab behaviour and its surface expression: new insights from gravity modelling in the SE-Carpathians

We use lithosphere-scale gravity models to calculate gravity anomalies resulting from oceanic subduction, continental collision, slab steepening, delamination, and break-off. Local isostasy was assumed for determining vertical movements caused by mass changes related to these tectonic processes. Our results show that subduction is accompanied by basin subsidence on the upper plate caused by the heavy lithospheric root of the subducting slab. The basin evolution goes parallel with the slab evolution and shows considerable modifications when the processes at depth change (slab steepening, delamination, break-off). Characteristic gravity anomaly curves were acquired for the different tectonic scenarios. These curves together with other data (e.g. basin evolution on the upper and the lower plate) were used for the reconstruction of the tectonic evolution of the SE-Carpathians which includes Tertiary subduction and collision followed by slab steepening and delamination.     

Left upstream slope design for the Çatalan Dam, Adana, Turkey and its behaviour under actual earthquake loading

An investigation and remediation of instability along upstream cut slopes for an earthfill dam in differentially weathered rock in southern Turkey is described. The major instability problem was a 45-m high and 200-m long previously cut slope next to the main axis of the dam, above the diversion tunnels and water outlet structures. The slope was first designed and excavated in 1986 based on the temporary berm approach. Rising water level in the reservoir would change the shear strength parameters and the pore-water pressure in the slope; thus, probable deep failure would damage the entrance of the diversion tunnels and water outlet structures, as well as the earthfill embankment of the dam. In June 1996, the slope face was re-excavated and protected against wave erosion by placement of a layer of rock riprap over a layer of bedding and a filter material. A strong earthquake (M_S = 6.2) occurred during a period of rapid drawdown in 27 June 1998. The slope remained stable, although numerous tension cracks developed in Quaternary terrace deposits near the reservoir area.     

岩质高边坡稳定性支持向量机预测方法研究

提出一种基于支持向量机的岩质边坡稳定性预测方法。该方法地很好的表达了岩质边坡稳定性与其影响因素之间的非线性映射关系,并应用该方法建立了相应的模型。预测结果表明,利用该方法进行岩质边坡稳定性预测是可行的、有效的。     

坡面溅蚀发生过程及其与坡度关系的模拟研究

通过人工模拟降雨试验,分别观测降雨过程中不同方向上溅蚀强度的变化,根据各影响因子间相互消长及相互制约的关系特点,分析了雨滴溅蚀发生的过程特征及其变化原因,从溅蚀过程的变化特点及溅蚀强度的变化规律比较,定量地探讨了坡度对雨滴击溅侵蚀的影响作用,得出了溅蚀强度与坡度因子之间的关系方程。     

四川泸定磨西台地第四纪冰水台地边坡地质灾害易发性研究

河流冲刷对第四纪软弱地层岸坡的地质灾害起到控制性作用。本文以磨西台地冰水堆积物岸坡为例,充分考虑河流与岸坡地质灾害之间的内在联系,基于对实测地质灾害的分析结果,采用Logistic监督分类方法,评价各环境因子（尤其是河流冲蚀特性因子）在河流岸坡稳定性评价中的作用,进而采用高相关的环境因子进行地质灾害易发性预测。研究表明,河流弯曲度、河流流量、岸坡坡度、河床宽度、岸坡宽度与地质灾害的发育相关性强,采用这些参数和Logistic模型预测的地质灾害易发性能很好的反映现状和未来地质灾害的发育特点,进而提出了磨西台地岸坡地质灾害防治的初步建议。     

Seismically induced slope instabilities and the corresponding treatments: the case of a road in the Wenchuan earthquake hit region

On May 12, 2008, a magnitude 8.0 earthquake hit Wenchuan County, Sichuan Province resulted in great loss of life and properties. Besides, abundant landslides and slope failures were triggered in the most seriously hit areas and caused disastrous damages to infrastructures and public facilities. Moreover, abundant unstable slopes caused by the quake have the potential to cause damages for a considerable long period of time. The variety of these slopes and the corresponding treatments are connected with the topographical and geological conditions of the sites. It is decided to document and identify some of these major slope instabilities caused by the earthquake and their treatments. The paper shows the condition of a road in Dujiangyan through in situ explorations. The case history showed significant implications to the reconstruction of the quake-hit regions and future disaster prevention and management works.