Table of Content

30 September 2010, Volume 32 Issue 3

Previous Issue    Next Issue

Brief Report

ELECTRIC STRUCTURE OF THE CRUST BENEATH THE ORDOS FAULT BLOCK

ZHAO Guo-ze, ZHAN Yan, WANG Li-feng, WANG Ji-jun, TANG Ji, CHEN Xiao-bin, XIAO Qi-bin

2010, 32(3):  345-359.  DOI: 10.3969/j.issn.0253－4967.2010.03.001

Asbtract ( )   PDF (5423KB) ( )  

Related Articles | Metrics

The Ordos fault block is a stable block since the Cenozoic time.Whether low-resistivity layers exist in the middle and lower crust of this kind block is an open question.This work attempts to reveal the entire crustal structure of the Ordos fault block based on interpretation of magnetotelluric data collected along the profile across this region.The result shows that a layered structure characterizes the crust of the Ordos fault block,with a low-resistivity layer at depth of about 20km,presumably associated with fluids there.On contrast,in the areas of active tectonics in the east and west of the fault block,there is no such layered electric structure in crust,while the low-resistivity zones may be related with the detachments(or ductile-shear zones) in crust.The difference in electric structure of crust between the Ordos fault block and neighboring areas is of significance to the analysis of activity and deformation in varied blocks.

STUDY OF THE STRUCTURE OF SHENZHEN FAULT ZONE WITH MAGNETOTELLURIC METHOD

CHEN Pang-long, XIAO Qi-bin, ZHAO Guo-ze, MA Hao-ming

2010, 32(3):  360-371.  DOI: 10.3969/j.issn.0253－4967.2010.03.002

Asbtract ( )   PDF (6206KB) ( )  

Related Articles | Metrics

The magnetotelluric method was used to study the active fault in Shenzhen city.Four magnetotelluric profiles with densified sites were laid out across Shenzhen Fault zone.The remote reference technique was used in both data observing and processing to eliminate the electromagnetic noise near the survey sites,and rather smooth apparent resistivity curves were obtained finally.TM mode data and two-dimensional inversion method as NLCG were used to obtain the electrical structures underground.According to the surficial geology survey results on regional strata and distribution of magmatic bodies and faults,the electrical structures of the depth less than 2000m of each profile were interpreted firstly,two regional faults,namely,the Henggang-Luohu Fault and the Liantang Fault,and seven local faults consistent with the electrical boundaries were verified or found.The strata in the survey area were then related with the change of resistivity.The horizontal electrical slices of depths less than 5000m indicate the Henggang-Luohu Fault and the Liantang Fault bifurcate at the shallow part but tend to merge at depths.

EFFECT OF PROFILE LENGTH ON THE TWO-DIMENSIONAL MAGNETOTELLURIC INVERSION OF TM MODE

YANG Jing, CHEN Xiao-bin

2010, 32(3):  372-381.  DOI: 10.3969/j.issn.0253－4967.2010.03.003

Asbtract ( )   PDF (5035KB) ( )  

Related Articles | Metrics

Magnetotelluric sounding method(MT),the most important geophysical means of detecting the crust and upper mantle electrical structure,is more and more widely used.The study of the inversion depth of MT(the effective detection depth) is relatively rare,and the previous view believed that the depth of effective detection was only in association with frequency.With a large number of the inversion results of two-dimensional vertical fault models,we find that the length of the inversion profiles also has an important impact on the result.In this paper we designed a set of vertical fault models with different fault slips.Focusing on the TM polarization mode,we studied the relationship between the length of the inversion profile and the result in detail.The results show that,for a certain depth of the target area,when the bandwidth of frequency is wide enough and the length of the density of the site is appropriate,the length of the inversion profile directly influences the quality of inversion results.If the length of the MT inversion profile is short,the results cannot respond to target depth correctly,and if the length is appropriate,the results may be good.The study also found that,with the fault slip increasing,the length of the inversion profile also needs to increase,and there is a linear relationship between them.This conclusion has great significance both for the field observation and theoretical studies.

FEM USING ADAPTIVE TOPOGRAPHY IN 2D MT FORWARD MODELING

LIU Yun, WANG Xu-ben

2010, 32(3):  382-391.  DOI: 10.3969/j.issn.0253－4967.2010.03.004

Asbtract ( )   PDF (1882KB) ( )  

Related Articles | Metrics

Complex terrain causes great MT noise.This paper puts forward a modeling technique of FEM using adaptive topography and quadratic element based on studies of some scholars.This technique can model all kinds of complicated terrain and geoelectric bodies preferably.The numeric modeling,calculation of the auxiliary field and definition of resistivity are deduced by electromagnetic equations.Lastly,several examples show the method is rapid,effective and of high accuracy.

PARALLEL COMPUTATION OF 2-D MAGNETOTELLURIC FORWARD MODELING BASED ON MPI

LI Yan, HU Xiang-yun, WU Gui-ju, YE Yi-xin, LIAO Guo-zhong

2010, 32(3):  392-401.  DOI: 10.3969/j.issn.0253－4967.2010.03.005

Asbtract ( )   PDF (2703KB) ( )  

Related Articles | Metrics

Nowadays,the 2-D inversion of magnetotelluric data has been put into practice,however,the 3-D inversion is still in its infancy,not because of the backward inversion methods or theories from the real yield but the lag of the hardware development.It is the huge amount of time to calculate in 2-D and 3-D inversion processes that traditional single-computer calculation speed is unacceptable.The most time-consuming part of the inversion is forward calculation,so it is of great significance to take parallel processing technology to improve the efficiency of parallel calculation.The program for 2-D magnetotelluric forward problems presented in this paper is based on the classic finite element method put forward by Wannamaker.It combines FORTRAN and MPICH 2 on Linux system in compilation.The forward computing for two-dimensional magnetotellurics is done separately in each frequency,and the value of electromagnetic field in the corresponding frequency is independent,therefore it is fit for frequency-decomposing parallel computing.This paper presents the two-dimensional magnetotelluric forward parallel algorithm,based on the finite element.Using the development tools of Fortran and MPICH 2,we write a parallel program that combines the advantages of MPI,and adopt the master-slave parallel mode and the parallel program of frequency-decomposing parallel computing.In order to verify the program,we designed two models,and compared with the serial program to validate the feasibility and accuracy of this algorithm,the result provides a research base for the parallel computation for two-dimensional inversion and three-dimensional forward and inversion.

REGULARIZED SYNCHRONOUS JOINT INVERSION OF MT AND SEISMIC DATA

CHEN Xiao, YU Peng, ZHANG Luo-lei, LI Yang, WANG Jia-lin

2010, 32(3):  402-408.  DOI: 10.3969/j.issn.0253－4967.2010.03.006

Asbtract ( )   PDF (1077KB) ( )  

Related Articles | Metrics

All the geophysical inversion problems are ill-posed.The application of regularization theory and joint inversion provide us ideas to solve the ill-posed inverse geophysical problems.Regularization theory has been widely used in single geophysical inversion problem which has achieved certain effects;however,what geophysicists concerned in the previous studies on joint inversion just was data misfit with little consideration about regularization theory.In this paper,based on the joint inversion method with random resistivity and velocity distributions proposed by YU Peng,the conception of regularization is introduced into synchronous joint inversion of magnetotelluric(MT) and seismic data.We use priori information to improve the stability of solution,and set stabilizer as the smallest model.How to meet the best trade-off between data misfit and model constraint,and what's intellectual choice for the regularization factor have always been the hotspots in the geophysical inversion problem.We use L-curve method to determine the quasi-optimal value of the regularization parameter,and apply it into joint inversion.To avoid immerging in local minimum of linear inversion method,nonlinear simulated annealing method is used to realize joint inversion.The forward modeling of MT data is obtained by using finite element method and the seismic travel-time computing is obtained by using improved ray-tracing method.Testing the regularized and conventional synchronous joint inversion on synthetic data sets shows that regularized joint inversion with effective model constraint has powerful availability to improve stability of solution and efficiency of computation,and to help us to obtain a stable solution which is close to the fact.

PRELIMINARY STUDY ON THE RELATIONSHIP BETWEEN THE M_S8.0 WENCHUAN EARTHQUAKE OF 2008 AND THE ANOMALIES OF EARTH RESISTIVITY OBSERVED AT QINGDAO SEISMIC STATION

ZHANG Ji-hong, ZHAO Guo-ze, WANG Jin-sheng, TANG Ting-mei, QI Li-jie

2010, 32(3):  409-416.  DOI: 10.3969/j.issn.0253－4967.2010.03.007

Asbtract ( )   PDF (1609KB) ( )  

Related Articles | Metrics

Near-surface earth resistivity and underground water level anomalies were recorded at Qingdao seismic observatory of Shandon Province before and after the M_S 8.0 Wenchuan Earthquake of May 12,2008.The observation data of the earth resistivity at the observatory revealed that the underground water level dropped and the resistivity increased.It is postulated that in the special tectonic setting as Qingdao observatory,the variation of stress and strain resulted in the change of water level beneath the station,leading to the variation of resistivity.The relationship between the variation of stress field and the change of earth resistivity before earthquake is analysed.

ANALYSIS TO THE ENERGETIC PARTICLES AROUND THE M8.8 CHILI EARTHQUAKE

HUANG Jian-ping, LIU Jing, OUYANG Xin-yan, LI Wen-jing

2010, 32(3):  417-423.  DOI: 10.3969/j.issn.0253－4967.2010.03.008

Asbtract ( )   PDF (4561KB) ( )  

Related Articles | Metrics

Based on the IDP data from French DEMETER satellite,the global distribution is shown,which corresponds to three precipitation zones:auroral precipitation zone,mid-high latitude precipitation zone and South Antarctic precipitation zone.Then the Chili earthquake with M8.8 on February 27,2010 is taken as an example.The IDP fluxes from repeated orbits are compared and the results show that there is a clear enhancement on February 26,just one day ahead of the Chili earthquake.In the south zone with L = 2.1 ～ 2.7,the flux on February 26 is higher than that on other days before.While in the north zone with L = 2.1 ～ 2.7,there is no clear change in the day time but a great enhancement during the night,which is close to the earthquake occurrence time.At the same time,the flux on February 26 over the epicenter is far lower than that on other days before during the day time while it reaches the peak at night.

IONOSPHERIC DISTURBANCES ASSOCIATED WITH STRONG EARTHQUAKES—RESULTS FROM LANGMUIR PROBE ONBOARD DEMETER SATELLITE

Ze-Ren-Zhi-Ma, ZHANG Xue-min, LIU Jing, OUYANG Xin-yan, XIONG Pan, SHEN Xu-hui

2010, 32(3):  424-433.  DOI: 10.3969/j.issn.0253－4967.2010.03.009

Asbtract ( )   PDF (5159KB) ( )  

Related Articles | Metrics

Using Ne(electron density) and Te(electron temperature) data of Langmuir Probe onboard DEMETER(Detection of Electro-magnetic Emissions Transmitted from Earthquake Regions) satellite,the paper studies the variations of electron density and electron temperature associated with strong earthquakes.The specific scientific objectives of Langmuir Probe are to map the bulk plasma parameters and to study their variations associated with seismic activity,volcanism and human activity and other sources of perturbations.Langmuir probe sweeps in voltage allow to obtain a current-voltage(Ⅰ-Ⅴ) characteristic every second.Bulk plasma parameters are obtained from the analysis of the Ⅰ-Ⅴ characteristics.The work principle,data format of Langmuir Probe onboard DEMETER is briefly introduced.We mainly studied the 2006 M_W 7.9 Tonga earthquake and the M_W 7.1 Taiwan earthquake in this paper.For each earthquake,we choose the orbits which passed over the area about 2000km around epicenter,including four months data before and two months data after the earthquakes.There are mainly three steps to reprocess the raw data,in order to avoid disturbances resulting from solar activities and geomagnetic activities.The result on the M_W 7.9 Tonga earthquake shows that at the equatorial region the electron density was relatively low before 28 April,while it began to increase from 28 April,and got the highest at 2 May one day before the earthquake.Until 4 May after the main shock,Ne began to decline.Based on comparison between revisited orbits,the orbit 097681(before shock) and 098721(after shock) observed certain disturbance.To further investigate the features of the preearthquake ionospheric anomalies,using 5 days as time window and 1 day as step size,we examined the temporal and spatial evolution of electron density within the area of 2000km around epicenter.Results show that the normal distribution of Ne kept at a relatively high level,except a relatively sharp reduction of Ne from 29 April to 2 May.The result on the M_W 7.1Taiwan earthquake shows that Ne changed randomly,while Te kept at a relatively high level,but dropped gradually before the quake.Currently we have no evidence to conclude that these changes are the results from the seismic activity,but based on data reprocessing,we can exclude the disturbances induced by solar activity and magnetic field at certain degree.If these changes of Ne/Te really resulted from earthquake,we may prudently conclude that ionospheric disturbance associated with seismic activity may possibly occur in a short time impending an earthquake with a short duration.

STUDY ON THE IMPACT OF HVDC TO GEOELECTRIC FIELD OBSERVATION

FANG Wei, ZHANG Guo-qiang, SHAO Hui-cheng

2010, 32(3):  434-441.  DOI: 10.3969/j.issn.0253－4967.2010.03.010

Asbtract ( )   PDF (1157KB) ( )  

Related Articles | Metrics

HVDC is an important way to solve the electricity transmission over long distances.With the construction of the skeleton of HVDC network in recent years,a new interference anomaly in seismic geoelectric field observation is emerging in China.In this paper,we take Baoji,Qianling and Zhouzhi geoelctric field observations in Central Shaanxi as an example to analyze the changes in shape and characteristics of such anomalies interfered by the Baoji-Deyang ? 500kV DC transmission project,discuss their forming mechanism combined with the basic principles of HVDC,and calculate their possible effects to electric field observations with different distances,conductivities and current into the earth.The results show that,the theoretical and observed geoelectric field values match well when conductivity is 0.01.

APPLICATION OF CSAMT TO BURIED ACTIVE FAULTS INVESTIGATION

DONG Ze-yi, TANG Ji, ZHOU Zhi-ming

2010, 32(3):  442-452.  DOI: 10.3969/j.issn.0253－4967.2010.03.011

Asbtract ( )   PDF (4438KB) ( )  

Related Articles | Metrics

There are multiple Quaternary buried active faults in the eastern Beijing plain region based on the results obtained from geological and geophysical studies.In order to investigate the condition of bedrock surface undulation,geometry of the buried faults and the extension of fault planes in the eastern Beijing plain area,two CSAMT profiles were completed in Miaojuan,Shunyi district and Sunhe,Chaoyan district in early 2010.The paper presents the advantages of CSAMT in exploration of buried active faults,the data collection procedure and the methods used for data processing.Combining with regional geological data,we make integrate interpretation to the geological structures of the study region.The results show that the CSAMT method can be used effectively in the exploration of buried faults.It can reveal the location,dip,displacement,and size of faults in the survey area,which provide reliable and elemental information for geological analysis.This method has become an important geophysical tool in buried fault detection and plays an increasingly important role in exploration of active faults in urban areas.

1-D OPTIMIZATION INVERSION OF CSAMT DATA WITH INTERVENTION MECHANISM

ZHOU Jun-jie, QIANG Jian-ke, TANG Jing-tian, WANG Hai-qing

2010, 32(3):  453-464.  DOI: 10.3969/j.issn.0253－4967.2010.03.012

Asbtract ( )   PDF (2305KB) ( )  

Related Articles | Metrics

In the application of CSAMT,the sounding curve is often distorted with the impact of electric dipole source,which produces confusions in data inversion and interpretation.Based on the 1-D layered earth conventional least-square inversion for CSAMT data,this paper introduces an optimized technique to get better result by discussing the forward modeling calculation,mechanism of inversion,selection of initial model,and iteration model controlling.Formulas of electromagnetic field components,E_x and H_y,given as integrations which contain Bessel functions of first kind of order 0 and 1,can be obtained using numerical method.During the calculation,the kernel functions of integrations are changed respectively in order to get better convergence properties.Taking the short transmitter-receiver distance into account,the relatively long grounded linear wire source should be assumed as an accumulation of dipoles,thus the theoretical apparent resistivity can be calculated by the field responses of dipole series.The forward calculation of CSAMT needs configuration parameters such as source location,measuring point position,current amplitude and so on,which are different from MT modeling.A primary objective of inversion is to recover a geologically interpretable model that can reproduce the set of observations.Based on the least square inversion theory,the method iteratively updates the vector of model parameters to get the minimum of the vector of relative mean square errors,where the Jacobi matrix can be obtained by difference method.Singular value decomposition method is adopted in equations solving,and we replace small singular value with zero.To get rid of falling into local minimum point during the iteration,it is necessary to control the model parameter excess when the model becomes abnormal.Actually the action will destroy the convergence,but it also increases the chance to find out the global minimum point.Numerical experiments show that the inversion result is better than the conventional one.The selection of initial model has an impact on the inversion results.Based on the theoretical similarity of CSAMT far-field data and MT data,the semi-quantificational Bostick resistivity-depth curve can be used as the base of initial model.Then,by decreasing the layers number according to the resistivity trend with apparent depth,and abandoning the deformed thin layers produced in layer cutting if necessary,the appropriate initial model is created.Some synthetic studies and a case of field data are followed to validate the inversion mechanism,and their resultant response fits the observed data well with acceptable inversion precision and computing time.In conclusion,it is available to adopt semi-quantificational Bostick resistivity-depth curve as the base of initial model for the CSAMT 1-D inversion.The multiplicity of solutions can be suppressed by the number of inversion parameters cut down using the Bostick curve optimization techniques.Appropriate initial models and iteration controlling are introduced to help enhance the capability of algorithm to find the global minimum,which satisfies the geophysical exploration requirements.

A PRIMARY STUDY ON THE FREQUENCY DOMAIN SOUNDING METHOD IN NEAR FIELD WITH LONG GROUNDED WIRE

ZHOU Lei, YAN Liang-jun, HE Zhan-xiang, CHEN Xiao-bin

2010, 32(3):  465-472.  DOI: 10.3969/j.issn.0253－4967.2010.03.013

Asbtract ( )   PDF (1698KB) ( )  

Related Articles | Metrics

The preliminary research result of electromagnetic prospecting of the near field(transition region) of long grounded wire in frequency domain is presented in this paper.And the full-region apparent resistivity is defined and calculated from some modeling results including the response of half space and the response of stratified space.From the results,we get the conclusion that the full-region apparent resistivity in the above situation defined from horizontal electric field and vertical magnetic field can yield a good outcome of underground electric structure.The full-region apparent resistivity calculated by using dichotomy after joining horizontal magnetic field and horizontal electrical field together can also reflect the change of electric structure underground.The full-region apparent resistivity defined by using a single component in the near field matches well with the single dimensional MT curve,therefore,mature MT inversion technology can be used to do the inversion of the near field,thus transforming the function with source to non-source types.It is available to prospect in the near field(transition region) with long grounded wire,even there are still some pending problems.

THE SOLUTION FOR THE ALL-TIME APPARENT RESISTIVITY IN TIME DOMAIN WITH LONG GROUND WIRE

ZHAO Fu-yuan, YAN Liang-jun, HE Zhan-xiang, CHEN Xiao-bin

2010, 32(3):  473-481.  DOI: 10.3969/j.issn.0253－4967.2010.03.014

Asbtract ( )   PDF (1777KB) ( )  

Related Articles | Metrics

Because the study in line source 1-D forward is few until now,in this paper,all-time apparent resistivity is attained by horizontal component in electrical field.Theoretical calculations indicate that the horizontal electrical field component is one-to-one correspondence with resistivity,which made the definition of all-time apparent resistivity unique and reliable.The paper uses horizontal electrical field component to define the apparent resistivity and calculate with dichotomy.The calculation example shows that the apparent resistivity defined by this method can accurately reflect the information of the model.In the following research,for time domain with line source we found that at near area there are bad results from later period data.Because of the quick electromagnetic wave spread and decay,we have bad results from early stage data in far area also,and the detection depth increases with the transmitter-receiver distance.Finally,we obtain the relationship between maximum detection depth and transmitter-receiver distance by adding 5% random noise and comparing with the theoretical results.

AN INTRODUCTION TO THE DEVELOPMENT OF SLF/ELF ELECTROMAGNETIC RECEIVER AND ITS EXPERIMENTAL OBSERVATION

WANG Lan-wei, ZHAO Jia-liu, ZHANG Shi-zhong

2010, 32(3):  482-491.  DOI: 10.3969/j.issn.0253－4967.2010.03.015

Asbtract ( )   PDF (1313KB) ( )  

Related Articles | Metrics

The electromagnetic method plays an important role in seismic activity monitoring and earthquake prediction and has become one of the important ways for earthquake prediction.During the past decades,many electromagnetic anomalous phenomena at available frequency bands(ELF,VLF,ULF,LF,FM etc.),especially at SLF and ELF bands were observed by scientists before earthquakes,which show that the electromagnetic effects do exist before shocks.Major earthquake may be predicted accurately if the corresponding relation between these electromagnetic anomalies and the physical process in the crust can be proved.In these studies,the objective is the natural electromagnetic field.Because its signal is characterized by instability,low precision and prone to influence of disturbance,especially at the sites with strong noise,the observational data often have low signal-tonoise ratio(SNR).Therefore,its applications are greatly limited.In order to improve the capability of identifying earthquake electromagnetic precursors,researchers must find a new source whose signal has higher stability and precision and wider coverage.In recent years,great progress has been made in the study.Russian scientists firstly applied the artificial SLF/ELF signal to probing the electrical structure of the crust in 1990s,since then,this technique has attracted much attention of geophysicists.Because the artificial SLF/ELF signal can be transmitted high precisely at each frequency under control and has the advantages of strong power,less influence of ionosphere,vast coverage,stable transmission and continuous observation,and the observed data can be analyzed by the correlation analysis technique,the SNR and precision of observed data,even in areas of strong noise,can be greatly enhanced.Measurement results show that in the same setting,the observed signal from SLF/ELF transmitter facility is much stronger than that from natural one,and the apparent resistivity obtained by the former has much higher precision than that by the latter.Therefore,this technique is very suitable for those studies requiring high-precision observational data,especially for earthquake monitoring and prediction.In our country,the study of the SLF/ELF technique started since late 1990s.In this paper,a newly developed SLF/ELF receiver's hardware system scheme,principle,main technical specifications and key technology are introduced in details.Results from a series of tests in lab and in field have shown that the SLF/ELF receiver can be used for observing the artificial SLF/ELF signal with frequency range from 0.1 to 300Hz.

A TRIAL STUDY OF MAGNETIC INDUCED POLARIZATION

LI Jian-hua, LIN Pin-rong, GUO Peng

2010, 32(3):  492-499.  DOI: 10.3969/j.issn.0253－4967.2010.03.016

Asbtract ( )   PDF (1248KB) ( )  

Related Articles | Metrics

Magnetic Induced Polarization(MIP) is one kind of electrical conductivity methods,which measures magnetic field point by point rather than measuring the electric field difference between two electrodes in Electric Induced Polarization(EIP).Compared to EIP,MIP surveys have certain merits,such as:bigger detection depth,higher resolution,capable to provide useful information through highly conductive overburden and high-resistance or low-resistance cover,no need for grounding,and etc.It will be a deep exploration technology and applied to areas such as low-resistance overburden,Gobi desert,bedrocks which have been a major impediment to EIP surveys.In order to test the ability of obtaining IP anomaly in MIP surveys,we carried out a trial comparative study between MIP and EIP(Time-domain IP method and multi-frequency phase IP method included) in a mining area in China.Test results show that there is a good consistency in the IP anomaly about the two detection methods measured in the same survey lines and it will provide a basis for the further studies of MIP.In the paper the basic principles,techniques,and data processing of this method(MIP) are discussed,and the results between Magnetic Induced Polarization and Electric Induced Polarization are analyzed.

THE TECHNOLOGICAL MODEL FOR GEOPHYSICAL PROSPECTING IN POOR QUALITY GROUNDWATER REGIONS

WU Yi, ZHU Qing-jun, LI Feng-zhe, LI Guo-zhan

2010, 32(3):  500-507.  DOI: 10.3969/j.issn.0253－4967.2010.03.017

Asbtract ( )   PDF (1647KB) ( )  

Related Articles | Metrics

In nature,poor quality groundwater of high fluorine,high arsenic,and high salinity(referred to as the"three highs water"),is always associated with each other,and exists in fine-grained sedimentary formations such as clay,loam and etc.The fine grained soil and high salinity groundwater are featured with low resistivity.So,by delineation of low resistivity areas,the distribution of fine-grained rock formations and high salinity groundwater can be mapped,thus to achieve the goal of mapping potable water in large particle stratum in poor quality groundwater region.In this paper,through the research of the mathematical relationship of the stratum resistivity,groundwater resistivity and groundwater porosity,and groundwater salinity,the geophysical prospecting model of potable groundwater in poor quality groundwater region based on high resolution resistivity method was established.We applied this model to several areas in Xinjiang Uygur Autonomous Region and achieved approving effects.The geophysical model offers a new technological concept for poor quality groundwater prospecting.

SLIP RATES AT DEPTH ALONG THE BURIED FAULTS IN BEIJING PLAIN AREA ETSTIMATED FROM REPEATING MICROEARTHQUAKES

LI Le, CHEN Qi-fu

2010, 32(3):  508-519.  DOI: 10.3969/j.issn.0253－4967.2010.03.018

Asbtract ( )   PDF (4308KB) ( )  

Related Articles | Metrics

Slip rates along the buried faults in Beijing plain area were investigated with the seismic waveform data between 2001 and 2006 recorded by the Beijing Digital Seismic Network.Using cross-correlation analysis of available waveforms,we identified a total of 35 doublets and 20 multiplets that show high waveform similarity.Most of these sequences are aperiodic with recurrence intervals varying from a few minutes to hundreds of days.Given the limited quantity and quality of seismic data in the study area,we have chosen a more robust approach to constrain repeated event locations.The approach incorporates both seismogram similarity by requiring cross correlation threshold and location similarity by requiring differential S-P(dSmP) time between events pairs to be small and minor internal inconsistence in travel time picking at sub-sample precision.The composite selection approach improves the identification of repeating earthquake based on similarity in waveforms.Based on four repeating sequences,we obtained the slip rate about 1.0 ～ 1.2mm/a at seismogenic depths of Hangzhuang-Gaoliying Fault and Nankou-Sunhe Fault,and the slip rate of 1.5mm/a at 9.4km of the south boundary fault of Huai' an Basin,which is consistent with geological and geodetic measurements.

APPLICATION OF 2D SEISMIC METHOD IN REGIONAL GEOLOGICAL SURVEY IN NANTONG,JIANGSU PROVINCE

MIAO Wei-dong, ZHOU Guo-xing, FENG Jin-shun, GAO Li, E Jian

2010, 32(3):  520-531.  DOI: 10.3969/j.issn.0253－4967.2010.03.019

Asbtract ( )   PDF (7017KB) ( )  

Related Articles | Metrics

The 2D seismic method was applied in 2008 for geological survey on loose sediments in Nantong,Jiangsu Province,China with the seismic survey line about 20km long.The application indicates that the 2D seismic method can reflect intuitively the distribution characteristic of sediments stratum.5 layers are revealed and can be contrasted clearly with wave groups.By analysing the continiuty of waves,the speculated Yangtze River fault(F1) is validated,and other 5 faults and 1ancient river valley are displayed also.In the mean time,the 2D seismic method has very good effect on displaying the rock base of this area and some hidden hills in Xiaohai town.The results indicate that the 2D seismic method can be taken in some regional geological survey in the deep sediments covered area.