• Volume 30,Issue 4,2008 Table of Contents
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    • Research on Crustal Density Structure in the Piedmont Fault Zone  of Taihang Mountain Area Using the Bouguer Gravity Data

      2008, 30(4):305-309.

      Abstract (740) HTML (0) PDF 427.96 K (1374) Comment (0) Favorites

      Abstract:Using the Bouguer gravity anomaly data with topographic correction, the investigation of deep structure in the piedmont fault zone of Taihang Mountain area is done. Based on the Geosoft software processing platform, we use the GM-SYS gravity inversion module for gravity inversion with the constraint of Deep Seismic Sounding (DSS ) profile results which completed in the last two decades. From the four lines of gravity measurement in Taihang Mountain region, the crustal densit) structure in the piedmont fault zone is gotten and the three-dimensional gravity profiles are drawn by interpolation method. The gravity inversion shows that the Conrad and Moho discontinuities increase northwestward gradually from 18 km and 34 km in the eastern coast plain to 28 km and 43 km in the northwest Taihang Mountain, respectively. Both discontinuities deepens abruptly when crossing NNE-trending Taihang zone, indicating that the piedmont thrust fault of Taihang Mountain could extend deep cutting through the Moho. The sediment thickness is generally less than 3 km in mountainous region, but is much thicker (3 - 10 km) over North China rift basins with variations on a series of second - order NNE depression and upheaval structures. The results are basically concordance with the previous studies in this area.

    • Monitoring Co-seismic Deformation Field of Bam Earthquake  in Iran Using D-InSAR Technique

      2008, 30(4):310-316.

      Abstract (1019) HTML (0) PDF 1021.91 K (1157) Comment (0) Favorites

      Abstract:The principle of differential interferometric (D-In) technique, the method for selecting proper D-In data pairs, and the flowchart of 3-pass D-In data processing are introduced firstly. Then using the differential interferometric on synthetic aperture radar(D-InSAR) technique and the ENVISAT ASAR data, the monitering to co-seismic deformation field in the Barn Mw6.5 earthquake in Iran, on December 26, 2003, is taken as application. As the result, the butterfly shap co-seismic deformation field of the Barn earthquake is gotten successfully, the isoline map of the defermation is generated, and the position, distribution and area of seriously destruction region are determined according to the coherence map. The test proves that D-InSAR technique is a powerful tool to measure surface deformation and to study earth- quake.

    • Damages on Brick-concrete Rural Buildings in Qingchuan County,  Sichuan Province, during the Great Wenchuan Earthquake

      2008, 30(4):317-325.

      Abstract (806) HTML (0) PDF 1.29 M (1175) Comment (0) Favorites

      Abstract:The Wenchuan M8. 0 Great Earthquake in 2008 had caused enormous damage to buildings. Of all the damages, rural buildings were the most vulnerable and suffered extensive damage. In this paper, based on investigation, the damage on the brick-concrete buildings in rural area are summarized from topography, foundation and construction, the causes of severe earthquake damages on this buildings are analyzed and problems for the building construction are singled out. In the end, some suggestions for improving seismic safety of rural buildings are proposed.

    • 3-D Seismic Response Analysis of Free-field Soft Soil in Shanghai

      2008, 30(4):326-331.

      Abstract (765) HTML (0) PDF 423.31 K (1114) Comment (0) Favorites

      Abstract:Three-dimensional calculation model of Shanghai soft soil is built, in which the Davidenkov model is proposed to describe non-linear dynamic characterisric of the soft soil based on the testing data. The rules of seismic response are studied. It is showed from calculation that: ( 1 ) the content of high frequcy in seismic wave is decreased and low frequcy part is increased from the bottom of the soft soil to its top ; (2) the seismic response is not always been enlarged, its influence lies on the characters of soft soil and seismic waves ; ( 3 ) it is feasible to simplify the seismic response analysis of free-field as plain strain problem; (4) the calculation curves and testing curves between dynamic shear modulus and dynamic shear strain are agree well with each other, which testified that it is ratonal to consider the non-linear characteristic of soft soil by the Davidenkov model. The study results can provide reference for engineering seismic design in soft soil area.

    • Forming Mechanism and Stability Analysis of Shixiakou Landslide  at Jiuzhou, Lanzhou

      2008, 30(4):332-336.

      Abstract (767) HTML (0) PDF 481.04 K (1088) Comment (0) Favorites

      Abstract:Based on geological environment where landslide located, the characteristics and forming mechanism of the Shixiakou landside at Jiuzhou, Lanzhou, are researched systematically in terms of regional geological investigation, large scale topographical mapping, measurement of micro physiognomy and failure, geophysical survey, soil microtextures in the slipping zone analysis by Scanning Electron Microscope(SEM). The results show that this landslide has the characteristics of remarkable classification and partitioning, the key elements of inducing the landslide to be revivable are rainfall, unreasonable false virescence irrigation and the high and steep topography in the landslide region. The stability of state is evaluated by different limit equilibrium methods, combining geological environment, on effects of natural state, or rainfall, or earthquake, or rainfall and earthquake. The resuh can take a theoretic guide rule in treatment of the landslide.

    • Seismic Risk Estimates for the Maxianshan North-margin Fault

      2008, 30(4):337-343.

      Abstract (958) HTML (0) PDF 492.02 K (1113) Comment (0) Favorites

      Abstract:The Maxianshan north-margin fault is a left-lateral reverse strike-slip fault during late Pleistocene to Holocene periods, and it primarily controls seismieity of Lanzhou city. From west to east, it can be divided into 4 segments:Wusushan, Maxianshan, Qidaoliang and Neiguanying segment. Wusushan segment is the seismogenic structure of Lanzhou M7. 0 earthquake in 1125, and the average recurrence interval of its characteristic earthquakes is 2 250 - 3 590 a. Considering only 882 years have elapsed since 1125, probability of another strong event is low during future 200 years. Average recurrence interval on Maxianshan segment is about 3 120a, and there were several moderate destructive earthquakes occurred on it in history. So we should pay attention to the potential seismic risk on this segment. The paleo-earthquake recurrences interval on Qidaoliang segment and Neiguanying segment are not obtained yet, but moderate-strong earthquakes have occurred on them in history, and will occur in future. The recurrence of earthquakes on them can make reference to Maxianshan north margin-fault's approximately.

    • High-resolution Shallow Seismic Prospecting Techniques for  Active Fault Investigation in Lanzhou Basin

      2008, 30(4):344-353.

      Abstract (761) HTML (0) PDF 1.23 M (1144) Comment (0) Favorites

      Abstract:Focused on some technique problems in the shallow seismic prospecting for active faults in urban area, research work on the high-resolution shallow seismic prospecting technique is taken across the Jinchengguan fault and the Liujiapu fault in Lanzhou basin. Both P- and SH- wave CMP reflection methods are used to find out the characteristics of active fault in the very shallow strata( ≤50 m). Those seismic profiles of the target area reveal the characteristics of tectonic deformation evidently, especially the SH-reflection profiles. In the paper, the key technical points such as data acquisition, data processing and profile interpretation are summarized by using HYC and SFXX survey lines as the examples. The result will be beneficial to further geophysical investigation for active faults in Lanzhou and other area.

    • Application of Seismic Modeling in the Shallow Seismic Prospecting Methods  to Urban Active Fault Detection

      2008, 30(4):354-359.

      Abstract (1011) HTML (0) PDF 697.38 K (1023) Comment (0) Favorites

      Abstract:The wave equation finite-difference method is used to the synthetic seismic records in the seismic prospecting of shallow high resolution in urban active fault detection. For improving the resolution and prospecting efficiency of the seismic modeling, some suitable finite-difference method, source wavelet, boundery conditions and dispersion elimination method are adopted. The result shows that the seismic modeling can be used to analyse the influence of the stratigraphic thickness and the obliquity, depth and scale of fault on the seismic synthetic common-shot profiles. From comparision this common-shot profiles with the real experimental data, we can approximately determine the location, scale and depth of fault in field work. The method can improve the prospecting efficiency and resolution rate in the shallow seismic prospecting in urban active fault detection.

    • Possible Precursor Mechanisms and Characteristics of Natural  Geoelectrical Field before Earthquakes in Chinese Mainland

      2008, 30(4):360-365.

      Abstract (779) HTML (0) PDF 450.03 K (1043) Comment (0) Favorites

      Abstract:The development caurse of research on the precursor characteristics of natureal geoelectric field before earthquakes in Chinese mainland is reviewed firstly. Then the range, figure and period of the field, as well as the statistical relationship with earthquake magnitudes are discussed. Some possible mechanisms of natural electric field before earthquake, such as infiltration electrical field, diffuse-adsorption potential, electro-chemical potential, electro-mechanical transformation effect and natural self-potential variety of loess under pressure, are pointed out. The natural electric field is a summating potential (SP) made of many signals, the trend background, seasonal variation, seismic signal and interference factors can all cause the change of rock resistivity, ionization and solubility of solution in soil, permeability condition of underground water, also the geoelectric field and natural electric field charge. The research on these mechanism of anomalies and characteristics of electromagnetic response will help us to understand the earthquake precursors.

    • Random Response for Energy Dissipation Structure  Based on the Pseudo Excitation Method

      2008, 30(4):366-368.

      Abstract (751) HTML (0) PDF 204.44 K (1208) Comment (0) Favorites

      Abstract:With the pseudo excitation method appling in non-proportional damped energy dissipation structure , the higher accuracy numerical algorithm for response power spectrum is developed. The algorithm avoid complex mode operation. Numerical example showes the algorithm accord with engineering.

    • Scattering of Plane P1 Waves by a Circular Cavity Buried in  Semi-infinite Space Saturated Media

      2008, 30(4):369-375.

      Abstract (739) HTML (0) PDF 372.23 K (1121) Comment (0) Favorites

      Abstract:Considering the compression of soil grain and pore fluid, and viscid coupling of pore fluid with soil skeleton, adopting the amended Biot model, the amplitudes of P1 wave, P2 wave and SV wave which are reflected from the planc PI wave are calculated when the semi-infinite space surface is impervious. The semi-infinite surface is taken as a large curved arc, the potential functions of incident waves, reflected waves from the semi-infinite surface, scattered waves from the circular cavity and the curved arc are all expanded to the infinite serials of Fourier-Bessel functions based on the expansion method of wave functions, and then the single scattering problem of a cavity in semi-infinite space is turned to a multiple scattering problem of cavity and curved arc based on the Graf's addition theorem. According to the boundary conditions that the semi-infinite space surface and cavity are all free, the theoretical solutions the complex coefficients of the potential functions are obtained. The influence of the normalized incident frequency and the cavity depth on the normalized horizontal, vertical displacements of the semi-infinite space surface and the dynamic stress concentration factor of the cavity are studied by theoretical simulation when the P1 waves are vertically incident.

    • Analysis on Seismic Performance of Thin-waist Section Tall Building

      2008, 30(4):376-379.

      Abstract (732) HTML (0) PDF 248.51 K (1093) Comment (0) Favorites

      Abstract:By using PMCAD and SATWE softwares from China Academy of Building Research, taking a model building as the example, the analysis of seismic performance including vibration characteristics and components internal force status for thin-waist plane tall building is maken with the retraction of section plane. The result shows that the thiner the waist is, the worse the seismic performance is. It is considered that the thin-waist plane should be treated as one of three or more of extra-limit determinings, but not as single one.

    • The Data Processing Software of Source Parameters for Middle or Small Earthquakes Based on MATLAB

      2008, 30(4):380-384.

      Abstract (972) HTML (0) PDF 420.26 K (1620) Comment (0) Favorites

      Abstract:A date processing window software of source parameters for small earthquakes that is developed based on the MATAB platform and the brune model is designed. Its design reason, data processing and the usage of function modules in the visual software are introduced. Also some effects, produced by wave inelastic and heterogeneous attenuation, geometrical spreading, instrument and site response in the data processing, are analyzed. For easy use, in the design of the program the defaults of control parameters is set reasonably but keep the input interface for important control parameters.

    • Quantitative Study on Seismicity Character of Small-medium Events before  Mederate-strong Earthquakes in Tianshan Mountain Region, Xinjiang

      2008, 30(4):385-391.

      Abstract (717) HTML (0) PDF 405.17 K (1020) Comment (0) Favorites

      Abstract:The abnormal characters of seismic active state and rate for small-medium earthquakes before mederate-strong earthquakes in different regions of Tianshan seismic belt, in Xinjiang region, with the seismicity statistical parameter valueβn are analyzed quantatively, and the middle-term prediction index ofβn values before mederate-strong earthquake are refined. The result shows that whenβn value is satis- fied with abnormal index in different region, there may occur Ms5 - 6 earthquake within about one year in the northern Tianshan mountain and the east part of southern Tianshan mountain ; Ms5. 5 - 7.0 earth- quake within about one year in the Bachu--Atushi region and Kashi--Wuqia region. In the aspect of earthquake occurring time, mederate-strong earthquakes in Urumqi, Wusu--Shihezi and KashimWuqia region occur nearly afterβn value anomaly ends ; some mederate-strong earthquakes in BaichenmKuche and Bachu-Atushi occur whenβn value is in the state of anomaly. Small-medium earthquakes in different regions about one year before mederate-strong earthquake have regional character: small-medium earthquake activity increases in Urumqi region; increases and quiescent in the Wusu--Shihezi and Kashi--Wuqia region;quiescent in the Bachu--Atushi region; but are not obvious in the east of southern Tianshan and Akesu--Bachu region.

    • Restudy of the Guyuan Earthquake Occurred in the 3rd Year of  Xing-ding of Jin Dynasty (1219 A. D. )

      2008, 30(4):392-395.

      Abstract (832) HTML (0) PDF 438.80 K (1193) Comment (0) Favorites

      Abstract:In the 3rd year of Xing-ding for Xuanzong emperor of Jin dynasty ( 1219 A. D. ) , a strong earthquake occurred at today's south part of Ningxia Hui Autonomous Region, China. The number of earthquakes, mainshock time, and the epicenter, which are provided by different documentary records, are very different. Based on the earthquake history data, combined with the inscriptions and the local records found recently in Guyuan county, this earthquake is restudied in this paper. By textual research, the earthquake occurred about 10 o'clock, Aug. 6 in 1219, the epicenter is on the south of Guyuan (35.6°N 106.2°E) , the magnitude is 6 1/2, and the epieentral intensity is from Ⅷ to Ⅸ.

    • The Technique Problems and Solve Project  in Digital Radon Measure Process

      2008, 30(4):396-399,404.

      Abstract (695) HTML (0) PDF 341.68 K (1030) Comment (0) Favorites

      Abstract:In experiment and work practice, some problems which are needed to be solved urgently in the digital radon measure process and instrument calibration are founded and analyzed. In this paper, the concrete solutions for these problems, such as gas separating from water, pipe blocking, gas rapid exchanging in scintillation chamber, instrument calibration and foundational condition choice, are put forward.

    • GIS-Based study on the Relationship between Earthquakes  and Active Faults in the Southern Yellow Sea

      2008, 30(4):400-404.

      Abstract (1139) HTML (0) PDF 320.28 K (1071) Comment (0) Favorites

      Abstract:Based earthquakes and on the buffer and active faults in the overlay methods of GIS spatial analysis, the relationship between Southern Yellow Sea is quantificationally studied. Statistics on the overlay analysis between earthquake epicenters and 10 kin, 20 km fault buffers gives the number of earthquakes for each buffer region, and shows that NW - NEE strike faults are the major earthquake-related active faults. Analysis on the overlay analysis between earthquake buffers and active faults gives the number of active faults that influences the occurrence of earthquake.

    • Discussion on the Relationship between Wenchuan Mw 8 Great Earthquake  and the Low Velocity and High Conductive Layer in Mid-crust

      2008, 30(4):405-412.

      Abstract (788) HTML (0) PDF 577.79 K (949) Comment (0) Favorites

      Abstract:Some puzzles come from Wenchuan great earthquake: how did Wenchuan great earthquake took place and how can great earthquake avoid? The deep crust structure of Songpan--Ganzi folded belt in Sichuan shows that the focus depth of Wenchuan great earthquake ( 2008 ) , Maoxian great earthquake ( 1933 ) , Songpan-Pingwu great earthquake( 1996) were same with the low velocity and high conductive layer of the mid-crust, and they might be related to this layer. Moreover, Yinchuan earthquake, Haiyuan earthquake, Weinan earthquake, Tangshan earthquake, Haicheng earthquake were also related to the low velocity and high conductive layer. All of these earthquakes might be caused by the earth outgassing. Based on the integrative survey on the earthquake, forest fire and petroleum resources, some seismogenic structure region can be explored, and through effluent of oils and gases, the possibility of the earthquake might be decreased.

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