• Volume 32,Issue 1,2010 Table of Contents
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    • Characteristics of Ground Motion during Strong Earthquakes in Some Regions of Gansu Province

      2010, 32(1):1-10.

      Abstract (804) HTML (0) PDF 577.22 K (1043) Comment (0) Favorites

      Abstract:Based on the strong motion recordings,especially the recordings of the great Wenchuan Earthquake in Gansu and Shaanxi,the characteristics of ground motion during strong earthquakes and the response features of different sites in Gansu province are studied.It is denoted that local earthquakes have special characteristics of ground motion which are identified from the interplate events,and they have big difference from events in western U.S.A..Also the characteristics of ground motion are closely depended on the site conditions and local topography,so the Gansu territory is able roughly departed into 4 areas with different site conditions,i.e.,Hexi Corridor,the loess regions in central part of Gansu,the mountain region in Southern Gansu and the plateau in Southern Gansu.Every area possesses special features of ground motion and its characteristics are depended upon the earthquake mechanism.The author proposes to study the recordings of the great Wenchuan Earthquake should be in details.

    • The Calculation Method of Apparent Emergence Angle of Seismic First-arrival Wave

      2010, 32(1):11-15.

      Abstract (1033) HTML (0) PDF 266.56 K (1409) Comment (0) Favorites

      Abstract:In time domain or frequency domain,using displacement,velocity or acceleration of seismic first-arrival wave,the apparent emergence angles are separately calculated.In theory it is proved that calculating apparent emergence angle is not limited by displacement records and time domain.Considering the difference between frequency ranges of interference signal and effective signal,respectively in time domain and frequency domain the apparent emergence angles are calculated,the result shows that the apparent emergence angle in frequency domain basically is equal to the theoretical value,has nothing to do with the azimuth,but the angle has big fluctuation with theoretical value in time domain.It indicates that the apparent emergence angle is less affected by interference signal in frequency domain.Appling the method and using real seismic wave records,the apparent emergence angles of seismic first-arrival wave in some stations are calculated,the results indicate that the apparent emergence angle is more stable and credible in frequency domain than in time domain.

    • Inverse Problem of The One-dimensional Continuous Conductivity Profile

      2010, 32(1):16-20.

      Abstract (800) HTML (0) PDF 254.26 K (1159) Comment (0) Favorites

      Abstract:Based on the Coen inverse algorithm,the inverse determination of one-dimensional continuous conductivity profile from the measurements of apparent resistivity with Schulunberger array is studied.The inversions of presise data and noise data in different conductivity profiles,such as constant function,linear function,power function,exponential function and piecewise function,are given.Using a real field example in which the conductivity profile is determined with layered model by Inman in 1975,we compare the results between our continuous conductivity profile and Inman's and it is found that the method is valid.

    • Study on the Definition of Basokur Apparent Resistivity Based on MT Method

      2010, 32(1):21-24.

      Abstract (761) HTML (0) PDF 197.05 K (1395) Comment (0) Favorites

      Abstract:Different definitions of apparent resistivity can educe dissimilar inversion results in electrical exploration.A finer definition can improve the inversion accuracy.The traditional Cagniar apparent resistivity which was defined by Cagniar in 1953 only make use of modulus values of wave impedance,but Basokur defined the apparent resistivity in 1994 including real part and imaginary parts of wave impedance.In this paper the forward and inversion based on the Basokur definition for four different models are done.The results show that new resistivity can imagine different models with thin layers,and also with common layers in model.

    • Extraction of Human Cardiac Electric Signal from the Earthquake Ruins

      2010, 32(1):25-29.

      Abstract (1014) HTML (0) PDF 288.14 K (1215) Comment (0) Favorites

      Abstract:The life detector based on the signal of cardiac electric field is now the most advanced life detector,but the difficulty is how to extract the weak signal of cardiac electric field effectively from earthquake ruins.In this paper the signal interference situation in earthquake disaster ruins that maybe affect human electric field is analyzed and the method of receiving weak ultra-low frequency electric filed signals in the ruins is put forward.According to the characteristics of human cardiac electric field,a special filters is designed for filtering off interference signals.Only the expansion 360° ultra-low-frequency non-uniform electric field which produced by beating human heart can be left.

    • Study on the Influence of Water Content to Subsidence Characters of Loess

      2010, 32(1):30-35.

      Abstract (829) HTML (0) PDF 337.07 K (1098) Comment (0) Favorites

      Abstract:Water content of loess is a very important parameter for seismic subsidence.The subsidence characters of the typical Q3 loess,located on third terrace of Tao River are systemically investigated.The samples taken at depth of 4 m,8 m,12 m,16 m,20 m in a 20 m depth pit are researched in laboratory.The results show some primary achievements:(1) the seismic subsidence capacity of natural loess gradually weakens with depth increasing;(2) there is a obvious law that the seismic subsidence capacity of loess increases with the growth of water content in same depth from experimenting 4 samples with 5%,10%,15% and 20% water content,which were acquired by humidification and dehumidification of the samples;(3)Through analyzing the experiment data,the quantitative law of water content influence on the seismic subsidence capacity of loess is found,and based on the law,the critical water contents of loess seismic subsidence are given under different dynamic stress.

    • Study on Shear Stress Relaxation Properties of Malan Loess

      2010, 32(1):36-41.

      Abstract (1056) HTML (0) PDF 352.16 K (1055) Comment (0) Favorites

      Abstract:Applying the Riemann-Liouville derivative of factional order theory and the classical model theory,the fractional order of standard linear model for the analytical expression of the shear stress relaxation is given by replacing the traditional Newton dashpot with Abel dashpot.The characteristics of the shear stress relaxation curves of Malan loess are studied based on 9 groups of shear stress relaxation test with different moisture contents under different pressure.Due to the unsatisfied fitting result from using the least squares method for the parameters of fractional order of standard linear model,the Monte Carlo method is used to fit the results.The results show that the shear stress relaxation characteristics of Malan loess can be described by the fractional order of standard linear model efficiently.Based on the fitting results the effective relaxation time and viscosity modulus are determined,and the shear stress relaxation properties is analyzed.

    • Analysis on Microstructural Variety in Seismic Subsidence of Loess with Dynamic Stress

      2010, 32(1):42-46.

      Abstract (726) HTML (0) PDF 366.55 K (1057) Comment (0) Favorites

      Abstract:Loess's microstructural parameters could be obtained well by dealing with the microstructural image.Based on the seismic subsidence experiment of loess samples taken from the Tongwei old earthquake area,we count the microstructural parameters,research the orderliness of microstructural parameters variety corresponding to different sine wave dynamic stress values and find the relation between the microstructural parameters and the dynamic stress using the soil microstructual quantitative analysis system.It appears that seismic subsidence of loess depends on its microstructure and external stress state.All microstructural parameters hold different variety in the seismic subsidence process of loess.Among them the variety of effective diameter of trellis pores,pore diameter dimension,connectivity and granule beamed degree is in conformity with the variety of residual deformation of loess.

    • Disaster characteristics of Huihuipu earthquake in 1785 in Yumen,Gansu Province,and Discussion on Its Seismogenic Structure

      2010, 32(1):47-53.

      Abstract (816) HTML (0) PDF 524.22 K (1139) Comment (0) Favorites

      Abstract:According to the detail textual research of the historical earthquake record and field investigation on Huihuipu earthquake in 1785 in Yumen city,Gansu province.It is found that the serious disaster area situated in Huoshaogou,between Huihuipu and Chijinpu.The magnitude of this earthquake is M63/4,and its epicenter intensity is about IX.Tectonically,the area lies in Jiuxi baisin,which is in western segment of Hexi Corridor.There are several Holocene faults developed in this area,such as Xinminpu fault、Yinwashan fault and Yumen fault,and so on.Most of them are reverse faults.Among them,the position and strike of Xinminpu fault are most consistent with the orientation of isoseismal long-axis of Huiningpu earthquake.And parts of deformation vestiges are still protected up to present.As analysing above,we consider that Xinminpu fault and Yinwashan fault is the seismogenic structure of Huihuipu earthquake in 1785.

    • The changing Characteristics of Seismic Correlation Length before Wenchuan M8.0 Earthquake

      2010, 32(1):54-58.

      Abstract (766) HTML (0) PDF 349.10 K (1368) Comment (0) Favorites

      Abstract:The time-space evolution of seismic correlation length before Wenchuan M8.0 earthquake is analyzed.We use ellipse which long axis is coincident with the strike of main fault belt in source area as the spatial window in analyzing on growing correlation length,and design the corresponding optimization procedure.The result shows that the growing correlation length before Wenchuan earthquake could be observed,and the significance of result is tested by the random synthetic seismic catalog.The result rejects the null hypothesis for the catalog and shows that the observed patterns are not a consequence of random fluctuations,with 93.9% confidence levels.

    • The Array Response Function of Lanzhou Seismic Array and Results of FK Analysis for Small Earthquakes in Different Azimuths

      2010, 32(1):59-64.

      Abstract (850) HTML (0) PDF 386.31 K (1418) Comment (0) Favorites

      Abstract:The array response function of Lanzhou seismic array is calculated in different frequencies.Four small earthquakes in different azimuths are analyzed with FK method.The results indicate that there is a main peak in the image of FK analysis in frequency smaller than 2 Hz,and many side slobes correspond with higher frequencies,which indicate that the array has good ability to resolve the signals with frequency less than 2 Hz.The results of FK method for 4 small earthquakes indicate that the azimuth and slowness estimated by FK analysis are mainly consistent with the results calculated by seismic catalog referring IASP91 velocity model,but there is difference between both results.The difference maybe caused by difference between the velocity structure beneath the array and the IASP91 model,as well as no application of array correction.

    • Engineering Geology and Seismology Conditions Evalution for Long-line Engineering Site——Taking the Yongdeng-Gulang Freeway as An Example

      2010, 32(1):65-71.

      Abstract (798) HTML (0) PDF 782.96 K (1060) Comment (0) Favorites

      Abstract:Taking the Yongdeng-Gulang Freeway as an example,through the field geology investigation,physical prospecting and borehole surveying,the detailed study and classification are implemented on topographical feature,hydrological geology conditions,lithologic characters of stratum,tectonic geology conditions and earthquake risk along the freeway.Based on above works,the engineering geology and engineering seismology conditions are evaluated on different segment of the freeway.The results show that in different segments of the freeway there are different geology problems and particular engineering earthquake conditions,so in design and construction it is necessary to take different corresponding measures for the problems and characteristics in each segment.This engineering project could be taken as an example for explicating the content and way of the work on engineering geology and seismology conditions evaluation in long-line engineering site.

    • Study on the Attenuation Relationship of Seismic Intensity in Gansu Province

      2010, 32(1):72-75.

      Abstract (759) HTML (0) PDF 242.26 K (1270) Comment (0) Favorites

      Abstract:For the purpose of acquiring the intensity attenuation relationship fitted the Gansu province,in this paper,20 earthquakes occurred from 1950-2004 in Gansu province are selected,the host shake's magnitude of which were all greater than or equal to 5.0 and the epicenter intensity were greater than or equal to V.On the basis of above materials,the attenuation relationship of this area was achieved and some analysis and comparison were made between the attenuation relationship of Gansu area and the existing results of western of China.

    • Study on Rapid evaluation Method of Earthquake Damage Based on Multi-Source Data

      2010, 32(1):76-81.

      Abstract (711) HTML (0) PDF 494.92 K (1037) Comment (0) Favorites

      Abstract:The recent rapid evaluation methods of earthquake damage based on GIS and remote sensing technologies are analyzed in detail and with the Wenchuan M8.0 earthquake case,the both achievements and problems in the methods are summarized.A new rapid evaluation method of earthquake damage which comprehensively using multi-source data,such as GIS,remote sensing and post-earthquake field investigation,is proposed in this paper,and its realization flow is given also.

    • Research on Low-frequency Wave of the Broadband Digital Data and the Information of Short-imminent Precursor before Strong Earthquakes

      2010, 32(1):82-87.

      Abstract (749) HTML (0) PDF 421.37 K (1181) Comment (0) Favorites

      Abstract:Through the studing on the broadband digital seismic data from Gaotai,Lanzhou,Chengdu and Anxi seismic stations,the spectral variation of low-frequency wave before the west to Kunlun Mountain Pass earthquake with MS=8.1 in 2001,Wenchuan MS8.0 earthquake in 2008 and Minle-Shandan MS6.1 earthquake in 2003,is analyzed,and the characteristics of short-impending term precursory anomaly in the data is summarized in frequency domain.I t is found that the amplitude of frequency in 0.1~0.14 Hz increases gradually in a few days before strong earthquake.The mechanism of the anomaly is discussed also combined with tectonic features of the earthquake source area and the low-frequency wave is considered has relation with quiet-earthquake and slow-earthquake.

    • Study on Seismic Performance of Tall-pier and Long-span Continuous Rigid-framed Bridge

      2010, 32(1):88-91.

      Abstract (744) HTML (0) PDF 253.75 K (1239) Comment (0) Favorites

      Abstract:The seismic performance of tall-pier and long-span continuous rigid-framed bridge is studied by using the genreal analysis model with multi-plastic hinges,and compared with the similar continuous beam bridge.It is founded that the continuous rigid-framed bridge only suffers damage slightly in strong ground motions,and the earthquake resistant capability of this bridge is obviously more excellent than that of the continuous beam bridge.Compared with the elastic seismic response,seismic force at the base pier is significantly reduced when plastic hinges are formed in major pier.In addition,the seismic force is greatly reduced along with intensity of ground motion increasing,but increase of displacement at the pier top is not evident.

    • Analysis on Phase Characteristics of Mining-induced Earthquakes in Huating Mine Aera in Gansu Province

      2010, 32(1):92-94.

      Abstract (755) HTML (0) PDF 204.23 K (1317) Comment (0) Favorites

      Abstract:Based on the data of Lanzhou digital seismic broadband network,after getting rid of noise and wave filtering by using some data processing techniques,the typical record characteristics of mining-induced earthquakes in Huating mine area,eastern Gansu province,are analysed and interpreted.The result shows that in the records of mining-induced earthquakes,the large period surface wave from close stations is significant and the last time is longger.At Pingliang station,caused by site response amplifing the magnitudes are obviously bigger than other stations.

    • Characteristics of Secondary Typical Slope Disaster in Gansu Province Induced by the Wenchuan Earthquake

      2010, 32(1):95-98.

      Abstract (714) HTML (0) PDF 288.46 K (1247) Comment (0) Favorites

      Abstract:The great number of the slope disaster were caused by the Wenchuan earthquake in 2008 in the southern Gansu province.In this paper,the types,features and developing tendency of the secondary slope disaster in this region are studied.Meanwhile,the current status of a huge loess landslide is analyzed preminarily.Finally,several suggestions are proposed in accordance with the problems.

    • The Abnormal High Soil Temperature,Less Precipitation and Weakening of Stress Wave before Strong Earthquake

      2010, 32(1):99-104.

      Abstract (685) HTML (0) PDF 487.42 K (1338) Comment (0) Favorites

      Abstract:The relationship between the ground temperature field and the precipitation field within one year before the occurrence of strong earthquake(MS≧6.9,14 times in total) in western China over the past 30 years are analyzed.It is found that: ①A large area with abnormal high soil temperature at 3.2 m are identified one year before the occurrence of earthquake accompanied by less precipitation in this area.The abnormal mentioned could last for 2 to 6 months with a maximum dry area of 2-4×106 km2.② The fluctuation in both the soil temperature and precipitation fields with the wavelength less than 1 000 km are appeared 0.5-1 year before earthquake occurrence,namely,the so called "ultra low frequency stress wave".The wave is responsible for break of the curst.③ The stress wave weakens with a shorter wavelength and lower intensity,as well as a sharp turning of the propagation direction by nearly 90°.The above three stages could be called "the three stages for earthquake gestation".A hypothesis is proposed on the mechanism of strong earthquake based on the above mentioned facts as follows: There is a kind of unstable uplifting Benard convection in outer layer of the earth core with a horizontal scale of 106 km^2.The uplifting action push up the crust and the mantle.When arrives at the boundary layer between the earth core and the mantle.Following results are expected consecutively: The higher soil temperature field and the heat conductivity decreasing cause less rainfall.With the stress in the crust keeping increase a kind of unstable wave(strain wave) appears.The weakening of the stress wave happens right before the occurrence of the strong earthquake.

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