Energy approach for earthquake induced slope failure evaluation

Earthquake-induced slope stability is evaluated by the force-equilibrium method in engineering practice. This method provides a safety factor against initiating failure or displacement according to the Newmark model along a fixed slip surface but it cannot evaluate failure deformations after failure occurs. An energy approach is proposed as an alternative means for evaluating slope failures and subsequent flow deformations. The driving energy for slope displacement is considered to be the earthquake energy and the gravitational potential energy. As a first step in the research, an energy balance is formulated for the model of a rigid block resting on an inclined plane. Then, an innovative model test is developed, in which the energy balance in a sliding slope is measured on a shake table. The earthquake energy used for the slope failure can be successfully quantified in the test and its contribution to displacement is discussed in the light of the energy balance established for the block model.     

基于岩石变形声发射实验结果讨论岩石失稳的可预测性

根据室内岩石变形声发射实验结果,计算了声发射序列的地震非均匀度GL值,并以此探讨了岩石破裂失稳的可预测性。在双轴压缩、等速率加载条件下,含障碍体断层、挤压雁列断层和Ⅲ型剪切断层等非连续岩石标本在临近滑动失稳前,声发射活动均出现了显著的均匀—非均匀的状态变化,表现为GL值出现持续大于1的异常变化,GL值异常的位置与破裂成核部位相重合,并与断层走向一致;改变统计窗长、窗内分割数及能级统计下限计算声发射序列的GL值,结果表明,GL值计算结果具有一定的稳定性。综合分析认为,地震非均匀度(GL值)可以较好地刻画岩石失稳前夕因破裂成核导致的声发射活动在时间分布上的状态变化,GL值持续异常是岩石失稳的显著性标志,对预测岩石失稳具有较好的指示意义。     

云南4个地震序列Q_c~(-1)值变化特征对比研究

对云南地区4个地震序列,分别为2000年姚安6.5级地震、2001年施甸5级震群、2001年永胜6.0级地震和2003年大姚6.2、6.1级震群,利用垂直向数字地震尾波分别计算地震序列周边台站3个频率段的Qc-1值,分析对比其时间演化趋势。发现对于主-余震型序列,主震后Qc-1值整体上变化幅度不大,趋于稳定。而对于震群(或双震)型序列,在第一个主震后,Qc-1值表现出上升-下降趋势,持续一段时间后强震发生。这些变化在序列周围的台站和三个频率段的变化整体趋势是一致的,但变化幅度不一致,可能与孕震区的位置和孕震应力的演变过程有关。上述研究为强余震的预报提供一个新的方法。     

Accurate Location of the Yao＇an Earthquake Sequence and the Yongsheng Earthquake Sequence

The Yao＇an Ms6.5 earthquake occurred on Jan. 15, 2000 and the Yongsheng Ms6.0 earthquake occurred on Oct. 27, 2001 in Yunnan Province, China. They are both located in the middle of the Dian block. Their epicenters are close to each other, the tectonic and strain characters of the earthquakes were similar, and there were many aftershocks after the two main shocks. In order to further study the spatial-temporal distributions and fault rupture characters of the main shocks and aftershocks, the latter are located using the Geiger earthquake location algorithm （Geiger） and the double difference earthquake location algorithm （DD） based on the seismic phase data of the two earthquake sequences. They were recorded by two Near Source Digital Seismic Networks （YNSSN and YSNSSN） deployed by the Yunnan Seismological Bureau （YNSB）. Then, two main shock parameters were relocated using DD based on the data of larger magnitude aftershocks and the two main shocks that were recorded by the Kunming Regional Digital Seismic Network （KMSN）. Combining the spatial- temporal distributions of the two earthquake sequences, the tectonic and strain characters of earthquakes, the rupture processes of the two aftershock sequences along faults are analyzed and discussed contrastively.     

Investigation on the Site of the 2003 South Bomi （Tibet） MsS. 7 Earthquake

An earthquake with magnitude of 5.7 took place on Aug. 18, 2003 in the Nyingchi Region, Tibet. The macroseismic epicenter was located in the unpopniated high mountain area, 13 km south of Zhamo town, Bond County. The seismic intensity in the meizoseismal region was Ⅶ degree. The Ⅶ and Ⅵ areas were 2000 km^2 and 11000 km^2 , respectively. This seismic event is related to the movements of the Lhari fault trending in the NW direction and the ZhamoManiweng fault trending in the NE direction. As a result of this earthquakes, the buildings in the areas were badly damaged.     

Site Response and Earthquake Design Spectra for Central Khartoum, Sudan

Khartoum, the capital of Sudan, is located at the confluence of White and Blue Niles. The city is heavily populated. Central Khartoum with its high-rise buildings is the center of governmental and business activities and is located on a strip adjacent to the Blue Nile. Geological and geotechnical data indicate that the subsoil conditions at Central Khartoum are characterized by alluvial deposits underlain by Nubian Sandstone at a depth of 25 m. The alluvial deposits, locally known as Gezira formations, consist of clays grading into silt and sand with depth. Macro seismic zonation of Sudan and its vicinities, developed by the authors, gave the ground acceleration at the bedrock surface. The effect of alluvial deposits in Central Khartoum on propagation of seismic motion parameters to the ground surface is investigated in this study. Correlations are proposed for pertinent cyclic soil properties such as shear modulus, damping, and shear wave velocity. The Equivalent-Linear Earthquake Response Analyses (EERA) Model was used to study the effect of local soil conditions on ground-motion parameters. In the absence of strong-motion records in Khartoum, available worldwide strong-motion records are used. Plots showing the time histories of ground motion parameters at the ground surface are obtained. The results indicate amplification of ground motion of up to 4.93. The predicted fundamental period of soils is about 0.5 s which is typical for these types of soils. The maximum spectral acceleration varied from 0.76 to 0.95 g. For design purposes, a response spectrum curve is proposed.     

Rescue Operations and Demolition Works: Automating the Pneumatic Removal of Small Pieces of Rubble and Combination of Suction Plants with Demolition Machines

The main problem in the rescue of people buried alive in damaged buildings are pieces of rubble with a diameter less than 150 mm. Since they cover the whole site, it is neither possible to scrutinize the structure of the rubble nor to estimate the dimensions of beams, columns, and parts of ceilings. The central idea of a project at the University of Karlsruhe, Institute for Technology and Management in Construction, is the automatic removal of small pieces of rubble by a suction unit. The computer-controlled pipe which is fastened to the boom of an excavator automatically follows the structure of the heap of rubble. Therefore, it can also work in areas which are out of the driver’s visible range. The suction plant replaces the dangerous manual removal which is current standard. Furthermore, a pneumatic extraction system has been designed and constructed in combination with demolition machinery, e.g. crushers and dry wire-saw technologies, to immediately suck off the crushed material (reinforced concrete, masonry).     

InSAR相位分解及其在生成DEM和研究地震形变场中的应用

InSAR是极具发展潜力的微波遥感新技术,可应用于数字高程模型的产生、制图和大范围微小地表形变的测量。考虑参考面、地形和地表形变等因素,本文从几何角度分析和讨论了In-SAR的相位分解,并给出了各相位分量的函数表达式,阐述了地表高程和形变信息提取的基本原理。最后以JERS和ENVISAT卫星数据为例,展示了合成孔径雷达干涉测量在生成数字高程模型和提取地震形变场中的应用及其数据处理过程。     

断裂带中的流体活动及其作用

大量证据表明活动断裂带中存在大量流体,不仅可以造成断裂带强度的变化,而且可以导致有效正应力减小,进而诱发地震。在野外观察与模拟的基础上,许多模式被用来解释这一现象。本文简要介绍了有关断裂带特征和分类、流体的来源和运动,以及流体对断裂带的影响和对地震的触发作用等方面的研究进展。     

云南地区地震视应变时空演变与强震发震地区的对应关系

在前人研究的基础上，利用云南及周边地区的地震资料，研究了1970年以来云南地区地震视应变场的分布和时空演化特征。结果表明，云南地区地震视应变的时空演变与强震具有较好的对应关系。在所研究的9个强震中，8个震前出现地震视应变异常区，5个发生在异常区内，3个发生在异常区附近。最后，对研究结果进行了初步论证。