2005, 27(2):97-100.
Abstract:Genetic Algorithm is improved in this paper,using production of initial population manually, introduction of immigration of population, searching in small population, adoption of adaptive probability of cross and mutation. In the example, the modified Genetic Algorithm has some improvement in preventing premature convergence and enhancing the searching efficiency. And finally, the stress field in Qinghai-Tibet Plateau is inversed with improved Genetic Algorithm, the result shows similar to geological one.
ZHANG Xue-min , DIAO Gui-ling , SHU Pei-yi , WANG Wei-min , ZHOU Cui-ying , ZHAO Ying-ping
2005, 27(2):101-108.
Abstract:Using pure S waveform fitting and T function method, the shear wave velocity structures in crust and upper mantle under seismic stations in Jiangsu and Shandong province are obtained. By employing T function method on long-period P wave records, S wave velocity struc tures about 800 km deep are also inversed under Lianyungang and Laiyang stations. The results show that : ( 1) the majority of stations in Jiangsu and Shandong province are located on where the shallow crust with high velocity, which is corresponding to the area with outcropping high-pressure and ultrahigh-pressure materials, and outcropping paleo-basement, respectively; ( 2) stations along Tancheng-Lujiang Fault present low velocity layers underneath, and the low velocity layer is deeper at south segment than that at north segment of the fault; (3) Great depth inversions under Lianyungang and Laiyang stations show that below the depth of 150 km both exhibits high velocity layer, which demonstrates that underthrust Yangtzi plate is under the depth of 100 km, with thickness of 100 kin, and delaminated slab can reach 300 km or deeper; (4) depth of earthquakes is closely related to the distribution of low velocity layers, along Tancheng-Lujiang and Yantai-wulian fault the locals are relatively deep, some even at the bottom of crust, which reflects that the cutting depth of two faults is larger and upper mantle there is active.
GAO Li-xin , ZHENG Si-hua , DING Feng-he
2005, 27(2):109-114.
Abstract:In this paper,the quality factor (Q) and the non-elasticity attenuation cofficient c(f) in Midwest area of Inner Mongolia are calculated using data of nine events recorded by 7 stations of hohhot digital seismic net based on genetic algorithm and Atkinson method. In the scope of studying frequency ,the correlation of the non-elastlcity cofficient c(f) and frequency f is not obvious,but the quality factor Q and frequency f have good linearity connection : Q( f)= 116. 8f^1.000 Meanwhile,the source parameters are inverted by using Moya toothed, and the relationships between the source parameters are discussed. The result shows that the correlation of the source parameters has good linerity connection . The site effects for seven stations are also obtained by GA and the Moya methods from nine earthquakes,the result shows there is the amplification at the rock sites in the whole frequency band. The principium and approach of the Atkinson and Moya methods are introduced in this paper.
YUAN Zhong-xia , WANG Lan-min , DENG Jin
2005, 27(2):115-121.
Abstract:SEM microstructure images of loess, used properly, can be important means for the explanation of soil mechanics properties of loess. In this paper, the proper selection to SEM microstructure images under different studing purpose is discussed. It is also believed that the fabric of loess has a "scale effect", which makes the fabrics revealed with different magnification times for image and so does their physical substantiality. The authors define the classification of loess fabric to avoid the uncertainty in description the nature of the fabrics at different scale due to the using of the generalized term "microstructure". For the convenience of soil mechanics study, the authors also propose a new classification of pores to reflect the reality of pores, to reflect nature of their formation mechanism and their relationship with the classification of grains. Finally, some general ideas on selection of SEM images in study are summarized.
2005, 27(2):122-127.
Abstract:Consideration is being given to the correlation between theoretical concepts of the probability of occurrence of resonance phenomena and experimental data by the example of stiffly frozen coarse ground layer lying on the half-space that is also composed of frozen rocky grounds. An assessment of resonance frequencies is made in reference to relative frequency characteristics of the layer obtained for longitudinal and transverse waves from 14 earthquakes recorded in three sites. The velocities of the longitudinal and transverse waves vary in the frozen coarse grounds of Pribaikalye and Trans-Baikal area with regard to humidity and temperature. The generalized values of these velocities in combination with an equality of relationships between the resonance frequencies and velocities of longitudinal and transverse waves are used in the assessment of the probability values of velocities of lingitudinal and transverse waves alone in the investigated layer. It shows a possibility to determine the probability values of velocities of the wave propagation in a loose ground layer from the earthquake records with the availability of generalized data on the values of velocities alone obtained on the laboratory scale and through full-scale measurements.
M. UENO , T. NISHIMURA , M. KATO , H. NAKAMURA , ZENG Si-wei
2005, 27(2):128-134.
Abstract:At Heifangtai terrace in China, farmland reclamation and settlement started in 1960's and irrigation farming began in 1968. Following to the irrigation, ground subsidence and landslides have occurred. The ground subsidence was due to collapse of loess soil caused by applying irrigation water. However, the effect of the collapse and the wetting on shear characteristics are still not clear. In order to investigate changes in the shear characteristics of loess soil when wetted, direct shear box test using the undisturbed and remolded samples of Malan loess soil was conducted. The results of the undisturbed soil showed decrease in both cohesion and internal friction angle occurred by wetting, while little change in the strength parameters was observed for the remolded soil. For the undisturbed soil, the cementating material is considered effective to the unsaturated cohesion, which disappears in the saturated state. The irrigated soil showed the different unsaturated strength parameters from the non-irrigated soil. Nevertheless, the may be strongly affected by the soil water content.
2005, 27(2):135-140.
Abstract:Based on consulting an ample historic data about Yinchuan-Pingluo M8 earthquake in1739 and combined with the former studies on some earthquakes in the Yinchuan Plain the distribution of the earthquake intensity and the characteristic of the earthquake disaster are researched. The result indicates that the earthquake was caused by the Helanshan fault in the the eastern piedmont of Helan Range, the most destroyed area lies its southeast area Yinchuan- Pingluo region, where is identical with the Quaternary sedimentation center of Yinchuan rift and affected mostly by the engineering geological conditions. The characteristic of this seismic disaster have important significance and active effects on the city layout and decreasing earthquake disaster in the future.
JIN Chun-hua , ZHANG Wen-xiao , REN Xue-mei , MA Wen-juan
2005, 27(2):141-145.
Abstract:Using the extreme value theory, b-value conforming to Gubmel distribution is caculated to replace normal b-value method,which needs higher quality data. According to the phenomenon that seismicity diverging Poisson distribution before moderate-strong earthquake, Pois- son distribution coincident degree Yn-value is given. The new parameters then are applied in Yinchuan-Hetao and Qilian Mt. -Liupan Mt. seismic belts for prediction test. The result shows that the b-value and Yn-value are correlated well with moderate-strong earthquakes.
WU Zi-quan , TAN Han-dong , WANG Cheng-hu
2005, 27(2):146-149.
Abstract:Facing the fact that strike slip fault is hard to detect, in the paper the physical characteristics of the fault are discussed, through the numerical simulation of actual model, the different variation characteristics of electrical resistivity for vertical and cross sections are discussed also. The result of numerical simulation demonstrats that the cross sections have more marked precedence compared with the vertical section, therefore, this method puts forward a new idea to detect the slip fault.
ZHANG Hui , ZHANG Xin-ji , SU He-jun , LIu Xu-zhou
2005, 27(2):150-153.
Abstract:The geochemical features of radon and mercury on Lanzhou Jinchengguan and the relation with fault position and occurrence are analyzed. The fault characters segments of Jinchengguan fault are also determined. Meanwhile, the main evidences of searching active fault by using fault gases are discussed.
WEN Ze-gang , Yang Ma-ling , YE Xue-wei , KANG Ying , Wang Zheng-shang
2005, 27(2):154-157.
Abstract:The shear-wave velocity structure in the east region of Guangdong prov. is studied by using the data of Guangdong Digital Seismic Network (GDDSN). The S waveforms of Solomon Islands Ms7.7 and Ms7.8 earthquakes on Nov. 16,2000, and New Ireland Ms 7.3 earthquake on Nov. 18,2000 were recorded by two stations of GDDSN, which are Shaoguan and Shantou station with distance of 347. 76 km between two stations. The data are used to determine the dispersion curve of phase velocity on the away between two station and invese the shear-wave velocity structure in crust of this region. The result shows that the crustal thickness in the region is about 30 km, the shear-wave velocity changes greatly in upper crust, but keep stable in lower crust, and there is no lower velocity layer in the crust.
2005, 27(2):158-162.
Abstract:The testing on the physical mechanical properties and dynamic characteristics of wall materials for main types of the rural row-soil building in loess area of northwestern China is performed. The compressive strengths,rupture strengths, shear strengths, dynamic elastic modulus and damping ratios for the ramming soil wall and adobe wall,which made from loess and loessal lain,are obtained from the tests. The strengths and seismic resistance performance of different materials and different forming typies for row-soil wall are analyzed and comparied,too.
YANG Cong-jie , FENG Zhi-sheng , SONG De-wei , ZHANG Xiu-xia , MEI Wei-ping , ZHANG Xiao-yong
2005, 27(2):163-167.
Abstract:The wavelet analysis is used to study the change characters of solid tide in well water level before three mid-strong earthquakes, which are Changshu earthquake in 1990, Cangshan earthquake in 1995 and Huanghai earthquake in 1996. The results reveal that the M2 tidal factor in well water level appear the abnormal signals which have a bigger amplitude, half or one months period. It indicates the wavelet analysis method may be an effective method in processing and analyzing water level tidal data for analyzing the change characters of abnormal signals.
ZHANG Xin-ji , ZHANG Hui , ZHANG Yu , LI Xiao-feng
2005, 27(2):168-173.
Abstract:The temporal and spatial characteristics of the subsurface fluid anomalous field and its evolution before Minle-Shandan earthquake on Oct. 25, 2003,are presented. The causing of anomalous field of subsurface fluid is analyzed. The research results show that the characteristics of subsurface fluid precursory field before Minle-Shandan earthquake are long anomalous period, much anomalies and large anomalous area. The reason for these characteristics is the increasing of tectonic and seismic activities of the whole Qinghai-Tibet Plateau and the influencing of west to Kunlunshan pass Ms8.1 earthquake on November 14 of 2001.
LIU Hong-mei , ZHANG Zheng-zhong
2005, 27(2):174-177.
Abstract:Through quantitative pore processing based on the SEM image of soil samples secured from the site under the effect of Yongdeng MS. 8 earthquake in 1995, the seismic subsidence of loess is explained from the viewpoint of soil microstructure. And the effect of loess microstructure on the seismic subsidence of loess is discussed.
CAO Ling-ling , WANG Zong-li , ZHONG Xin
2005, 27(2):178-181.
Abstract:Through studying on characters of muliti-subject precursors before moderately strong earthquakes in Qilian area, Gansu province, since 1990, it is found that all kinds of precursors show harmonious character in temporal-spatial. The harmonious characters for Ms ≥ 6 earthquake are obviously different from that for M s5.0-5.9 events, althought there are similar characters in both.
2005, 27(2):182-185.
Abstract:Through the study on the characteristics of historical moderate-strong earthquakes and seismic activity anomalies from 1980's in southeat of Gansu province and its neighboring area, It is considered that earthquakes of Maqu Ms4.8(4 March, 2004), Lixian Ms4. 5 (26 August, 2004), Minxian Ms5.0(7 September,2004) and Minxian Ms5.2 (13 November,2003) are all the members of a new earthquake group. They may indicate that a Ms6.0 or even a larger earth- quake is going to conceived in southeast of Gansu province and its neighboring areas.
PEI Zong-chang , LIU Yao-xing , WANG Xiao-qing , LIU Peng
2005, 27(2):186-189.
Abstract:The earthquake damage prediction of pipeline has heavy proportion in the earthquake damage prediction of lifeline system, and the pipeline is the brittle unit of lifeline when earthquake occurs. The earthquake damage to water supply pipeline is affected by the seismic motion and the site liquefaction, material and diameter of the pipes etc. The methods of earthquake damage prediction of pipeline which based on experience statistics are more practicality. In this paper the methods which based on theories account and experience statistics are introduced and compared respectively, and a new prediction model for pipeline according to comprehensive probability is put forward finally.
LILT Xu , WANG Lan-min , YIN Zhi-wen
2005, 27(2):190-192.
Abstract:In this paper, some opinions in the mechanical model for saturated soils with isolated pores are discussed. Based on the Carroll's mechanical response theory of fluid-saturated porous materials, the stress-strain relations and bulk modulus for this kind of soils are derived again. As a result, for the bulk modulus of quasi-statistic wave, the condition of isolated pores on soils has same effect with no relative movement between solid and fluid, zero permeability or infinite fluid viscosity, and there is no difference whether the pore is isolated or not. The bulk modulus derived here is the same as that in Blot's theory.
Sopyright:China Earthquake Engineering Journal