2009, 31(1):1-7.
Abstract:Based on comprehensive analysis of seismic damage features of Wenchuan 8. 0 earthquake in 2008 in disaster area of Gansu province, the earthquake background is explained and the distribution of intensities of earthquake-stricken areas is given. The damage features in different intensity areas, and the stricken degrees of various structure types are presented. A series of countermeasure for reconstruction are offered from the general analysis of the damage features and the situation faced by Gansu disaster areas after the earthquake.
SUN?Rui , YUAN?Xiao-ming , LI?Yu-run , CAO?Zhen-zhong , CHEN?Long-wei
2009, 31(1):8-14.
Abstract:The effects of liquefaction on cyclic deformation of soil layers are investigated by shaking table tests. Taken the dry sand tests as a consult, the relations between the pore water pressure increasing and the accelerations and deformation of the soil layer are presented. The results show that the liquefaction greatly reduces the acceleration amplitude and inertia force of surface ground, meanwhile however, the cyclic deformations of the soil layer increase significantly. The cyclic shear strain in liquefied soil layers can reach 1 %-5% and the strain in the upper layer is less than that in the sub layer. The sensitive range for obvious change of the cyclic deformation appears when the water pressure ratio is about in 0.4-0.8 and reaches the maximum when is about 0.8 rather than 1.0. As a result, the liquefied soil layer reduces the vibration of the rigid superstructure, but the increasing cyclic deformation due to liquefaction can easily destroy the foundation and underground structures, especially for the part of the foundation and underground structures near the interface between the liquefied layer and non-liquefied soil layer.
2009, 31(1):15-20.
Abstract:As an important part of rock mass dynamics, the seismic dynamic failure of rock mass was short of study before. In this paper, the reason of this short is analyzed first. The seismic dynamic failure of rock mass is classified into 6 types of forms: landslide, rock avalanche, spalling, collapse, ground fissure and rock mass dynam-relaxation, among them the rock mass dy- nam-relaxation is an important factor for causing a lot of secondary geological hazards. According to the action manner of seismic dynamic loads, stress state and failure mechanism, the rock mass seismic dynamic failure is further divided, the earthquake landslide and non-earthquake landslide are differentiated. At last, the characteristics of the failure are discussed from its inhomogeneity, repeated failure, clustering, controlling by discontinuities, and universality.
REN?Zi-ming , Feng?Zhong-lin , Yin?Shi-lin
2009, 31(1):21-25.
Abstract:Using numerical analysis on the law of dynamic response of soil slope, it is found that there is a good corresponding relationship between the anomalous points of dynamic response and the location of potential sliding surface on soil-slope section. It shows that the dynamic property of soil where high shear strain has happened may have changed in the slope, and caused the dynamic transmission abnormal.
REN?Hui , SHANG?Shou-ping , LI?Gang
2009, 31(1):26-30.
Abstract:The mode-superposition method is applied to the analysis of seismic response of an inhomogeneous site which is excited by vertically propagating shear waves. The solutions for effective modal participation factor are presented for a single layer with a shear stiffness distribution exponentially increasing with depth. In an example the solutions are compared with those of a homogeneous site with an average shear wave velocity. The example also verifies that the natural frequency for the first mode can still be estimated from the formula in engineering and is an important parameter for estimating the high mode frequencies.
XU?Kai-jun , SHI?Shuang-hu , ZHOU?Jia-hui
2009, 31(1):31-34,85.
Abstract:In the forward simulation of 3D magnetotelluric using integral equation method, the Cole-Cole model is led into for studing characteristics of the induced polarization effect. For the first time the authors calculate the responses of 3D magnetotelluric in homogeneous half-space including a polarizable body, and summarize some response rules. The results show that the induced polarization effect makes the value of apparent resistivity decrease. The induced polarization effect of high-resistivity polarizable body is stronger then one of low-resistivity polarizable body,especially the body with high chargeability has great effection to the response, even cause false anomaly in apparent resistivity observation.
TANG?Qi-jun , HAN?Li-guo , WANG?En-li , LIU?Qian-kun
2009, 31(1):35-39.
Abstract:The random isotropic background of Von Kraman pattern is introduced into wave equations of viscoelastic monoclinic anisotropic media. The snap-shots and synthetic seismograms in this nonhomogeneous complex media are simulated by staggered grid finite difference. The result shows following chacacteristics: wave field in this complex media embodies the characteristics of both monoclinic media and random media; dilatational and shear quality factors attenuate the amplititude obviously. In detail, the scale length became smaller, the disturbance caused by random media became the stronger for the case of same variance. This work should be helpful to understand the basic characteristics of the fracture oil reservoirs.
HE?Wen-gui , YUAN?Dao-yang , GE?Wei-peng , LIU?Xing-wang , LIANG?Ming-jian , ZHENG?Wen-jun
2009, 31(1):40-45.
Abstract:Up to now, most of scholars work in geology and earthquake engineering considered that a very important Liujiapu fault (also named Kongjiaya fault) exists in Anning district of Lanzhou city, and maybe extends east to Sanyyuanxia across the main urban region of Lanzhou city. The fault was determined as a Holocene active fault, so it had seriously influence to the urban engineering and architectures. In recent study, through drilling at some sites along the fault lines in Anning district, especialy a large trenching study at Wenhua Jiayuan site in Anning district, we find that "Liujiapu fault" is just a interface between different terranes.
YAO?Kai , LU?Da-wei , Liu?Xu-zhou , Zhou?Min-dou , Min?Xiang-yi
2009, 31(1):46-50.
Abstract:After Ms8. 0 Wenchuan great earthquake in 2008, we immediately installed digital strong earthquake instruments with same type near Wenxian county town, Gansu province, at mountain top, mountainside and foot of mountain respectively, and acquired 12 strong aftershock records. By analysis it is shown that difference of geography has effect to the peak ground acceleration (PGA) of observition point. The PGA values at top of mountain is 1.5 times or so to the value at foot of mountain which in same geological condition. The advantage frequency at the top of mountain are lower than at the foot of mountain, especially for that with bigger recorded values. Under strong ground motion, the differences of PGA and advantage frequency in same place caused by geography condition are main factor for earthquake damage being more serious at top of mountains. The result hints that the earthquake resistant design for engineering and building on difference geographic condition should be different.
SU?Yun , YIN?Yan-yu , GAO?Li-long , NEVER?Maimaiti
2009, 31(1):51-56.
Abstract:Research on risk perception of earthquake and its influencing factors helps to reveal the potential risk factors from a public visual angle, and provids basis for decision-making to disaster risk reduction. In this paper Kashgar and Urumqi in Xinjiang are taken as examples and 267 people were investigated by questionnaire. Survey data is analyzed using hypothesis test and Pearson correlation analysis to find out the influencing factors on risk perception such as hazard psychoanalysis, earthquake risk estimation, knowledge level of earthquake and preparedness behaviors for reducing earthquake. The results show that influencing factors include sex, .educational level, income level, family member constitute, building conditions and seismic hazard of resident area. The influencing factors and the risk perception factors link positive or negative feedback chains. Income level as a core factor influences weather the risk perception can be changed to the practical actions of reducing earthquake disaster. Based on the risk analysis, several suggestions for risk reduction are given.
2009, 31(1):57-60,103,107.
Abstract:A method of constructing the dynamic temporal and spatial evolution image of deformation field by using records of multi permanent deformation stations is attempted. On the base of this method, water-tube tiltmeter records of 47 deformation stations in China are analyzed, and images of temporal and spatial evolution of ground tilt are constructed. As a example, the dynamic change of ground tilt before and after the Ms8. 1 earthquake west to the Kunlun Mountain pass is studied. The result shows that there are obvious changes in the day average value of water-tube tiltmeter in many stations before and after the event. The spatial distribution of EW average, NS average and NW M2 tidal factor also appear noticeable difference, but there is no noticeable change in EW M2 tidal factor. This method is expected to use in the work of earthquake prediction through constructing the temporal and spatial deformation image of every month or every week with accumulation of observition data.
FENG?Jian-gang , DAI?Wei , DONG?Zhi-ping , HU?Yong-jun
2009, 31(1):61-65,103.
Abstract:Based on the Lanzhou seismic network observational report, using the multi-station methods, the seismic velocity ratio (Vp/Vs) of the 2 953 earthquakes in Northeastern margin of Qinghai-Tibet block during Jan. 2001 to Jun. 2007 are calculated. The research region are divided into little areas by 1°× 1° and 0.2°×0.2°, and the average seismic velocity ratios for every little areas are given. Through analysising the average seismic velocity ratios, following conclusion are gottern: (1) The average ratios in different regions of the research block are different, among them, the ratio in Southeastern of Gansu province is the highest, in Qilian seismic belt and along West Qinling fault are higher also, in middle Gansu province is the lowest. (2)The mine earthquakes often occurred in the 1°× 1° little areas with lower ratios, so the ratio could be used to distinguish mine earthquake. (3) The ratio values increase along with the increase of magnitudes of earthquake. The average seismic velocity ratios for each area in Northeastern margin of Qinghai-Tibet block can be a reference to analyze the variation of the ratio before strong earthquakes.
CHEN?Yong-ming , YUAN?Dao-yang , HE?Wen-gui , DAI?Wei
2009, 31(1):66-70.
Abstract:The Northern marginal fault of Xinglong Mountain, which is also the southern margin of Lanzhou basin, is one of the most important active fault in Lanzhou area. The fault is about 54 km shows an arc shape with the eastern segment in NW direction and the western segment in EW direction. During the Caledonian and Yanshan Movements, the tectonic stress field in Lanzhou area were mainly a feature of compressive stress with principal direction of NE-SW. The fault keeps a thrust movement from SW to NE. In the Cenozoic era(Himalayan Movement), the principal stress changed into NNE-SSW, and the activity of fault also changed to the thrust with left-lateral slip on eastern segment and normal with left-lateral slip on the western segment. The latest stage of activities was probably in the Early to Middle Late Pleistocene epoch, corresponding to the formation of Ⅲ terrace of Huanghe river in Lanzhou basin.
ZHOU?Zhou-hong , HE?Shao-lin , CHEN?Wen-kai
2009, 31(1):71-74.
Abstract:Population data in stricken-region is a fundamental and significarit aspect in fast assessment of destructive earthquake. In this paper, a county level population growth model for Gansu province is set up by means of GM( 1,1), and dynamic computing is operated based on static population data to better fit the actual situation, in order to provide more accurate population foundation data to fast earthquake disaster assessment.
GAO?Da-feng , LIU?Bo-dong , ZHANG?Jig-juan
2009, 31(1):75-79.
Abstract:Using the Generic-software ANSYS, numerical simulation analyzing on the dynamics characteristic of a Half-through reinforced concrete arch bridge is done. Its self-vibration parameters such as self-vibration frequencies, modes and so on, are given, as well as its modes characteristics are summarized. Besides, influence of the main structure parameters to the self-vibration characteristic is analyzed by varying these parameters of the arch bridge. The results show that self-vibration frequencies increase with rise/span ratio decrease; transverse support will help to enhance the lateral rigidity, reduce its out arch-plane vibration, and improve the stability in wind; the frequency of each vibration mode is increased with a approximate linearity with improvement of arch stiffness. So we can change arch stiffness to adjust its vibration characteristics. The results can offer reference to the seismic design of the similar bridge .
WANG?Ai?guo , YANG?Xiao-peng , LI?Ming-yong , LIU?Yu , SHI?Hang , SHI?Ji-ping
2009, 31(1):80-85.
Abstract:Based on the detailed disaster investigation in eastern Gansu province after Wenchuan Ms8.0 earthquake, the earthquake damage in the area is classified and researched, the seismic damage intensities and destruction features for different kinds of building and engineering structure are presented. According to the unique geological conditions, the reasons for earthquake damage being more severe than expected in this area are analyzed. It is considered that the reasons for the relatively severe damage is not only relevant to the quality and structure of the building itself, but also to the long period effect caused by the teleseism, the geography influence and the long duration time of seismic wave.
WU?Zhi-jian , CHE?Ai-lan , WANG?Lan-min , CHEN?Long-zhu , XING?Ai-guo
2009, 31(1):86-90.
Abstract:In order to investigate the damage characteristics and mechanism of buildings and secondary disasters, which caused by the Wenehuan Ms8.0 great earthquake on May 12, 2008, the field investigation was carried on in the earthquake disaster area of Gansu province after the event. The micro tremor measurements were surveyed on some building structures. It is proved that the test results are well agree with the structural damages.
2009, 31(1):91-96.
Abstract:The time sequence curves and spatial isolines of mobile gravity observational values from the Wenba net in Hebei province are drawn, and the response of gravity observation to earthquakes in the net and its surrounding area is analyzed. The gravitational anomalies showed the following characteristics: the anomalies might last out about 2 years, and its magnitude can reach tens μg; most anomalies showed continually decreasing and turning before earthquake; some high value region appeared in the gravitational field of Wenba net before Xingtai M5.4 and Wen'an M 5.1 earthquakes; the epicenter of Wen'an earthquake located near the 0 isoline of high grads region.
WEI?Hong-mei , HE?Man-qiu , HUANG?Shi-yuan , WANG?Tong-jun
2009, 31(1):97-101.
Abstract:Based on the single scatter model (Sato), using 48 earthquake wave form data with ML≥2.0 from January in 2004 to September in 2007 recorded by the Chongqing earthquake net, the Qc values of coda in Rongchang region is calculated, and relationship between Qc value and frequency is polyfitted. The result indicates that this region is low Qc value but dependence on frequency strongly. In addition, studied on Qc value in three segments of time, the result display that coda wave Qc value are steady in each segment, and the configuration of medium underground is steady in the region and each segment of time too.
Sopyright:China Earthquake Engineering Journal