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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Geophysics and Geophysical Exploration
Journal Basic Information
Journal DOI :
Korean Society of Earth and Exploration Geophysicists
Editor in Chief :
Volume & Issues
Volume 11, Issue 4 - Nov 2008
Volume 11, Issue 3 - Aug 2008
Volume 11, Issue 2 - May 2008
Volume 11, Issue 1 - Feb 2008
Selecting the target year
Optimal Determination of Marine Seismic Data Processing Parameter for Domi-Sediment Basin
Cheong, Snons ; Kim, Won-Sik ; Koo, Nam-Hyung ; Yoo, Dong-Geun ; Lee, Ho-Young ; Shin, Won-Chul ; Park, Keun-Pil ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 279~285
Korea Institute of Geoscience & Mineral Resources (KIGAM) carried out 2 dimensional multi-channel seismic surveys for Domi-Basin of east-southern part of Jeju Island, South Sea, Korea in 2007. The purpose of this survey is to investigate the structure of acoustic basement and the potential of energy resources in the Korean shelf. It is essential to produce fine stack and migration section to understand the structure of basement. However a basement can not be clearly defined where multiples exist between sea surface and seafloor. This study aimed at designing the optimal data processing parameter, especially to eliminate the peg-leg multiples. Main data processing procedure is composed of minimum phase predictive deconvolution, velocity analysis and Radon filter. We tested the efficiency of processing parameter from stack sections of each step. Our results confirmed that processing parameters are suitable for the seismic data of Domi-Basin.
Correction of the Sea Effect in the Magnetotelluric (MT) Data Using an Iterative Tensor Stripping During Inversion
Yang, Jun-Mo ; Lee, Chun-Ki ; Yoo, Hai-Soo ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 286~301
When magnetotelluric (MT) data are obtained in vicinity of the coast, the sea can distort observed MT responses, especially those of deep part of subsurface. We introduce an iterative method to correct the sea effect, based on the previous topographic correction method which removes the distortions due to topographic changes in seafloor MT data. The method first corrects the sea effect in observed MT impedance, and then inverts corrected responses in a model space without the sea. Due to mutual coupling between sea and subsurface structure, the correction and inversion steps are iterated until changes in each result become negligible. The method is validated for 1-D and 2-D structure using synthetic MT data produced by 3-D forward modeling including surrounding seas. In all cases, the method closely recovers the given structure after a few iterations. To test the applicability of the proposed method to field data, we generate synthetic MT data for the Jeju Island whose 1-D conductivity structure is well known, using 3-D forward modeling. The distortions due to the surrounding sea start to appear below the frequency about 1 Hz, and are relatively severe in the electrical field perpendicular to the coastline because of the location of the observation sites. The proposed method successfully eliminates the sea effect after three iterations, and both 1-D and 2-D inversion of corrected responses closely recover the given subsurface structure of the Jeju Island model.
Imaging of Fractures and Tunnel by 3-D ERT
Yi, Myeong-Jong ; Kim, Jung-Ho ; Son, Jeong-Sul ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 302~309
ERT imaging, especially 3-D method, is a very powerful means to obtain a very high resolution image of the subsurface for geotechnical or hydrogeological problems. In this paper, we introduce two examples of successful case histories, where the imaging targets were three-dimensional. First example is the case of 3-D fracture imaging for hydrogeologic application. In this example, the borehole deviation was a critical problem in the ERT imaging and we could obtain real 3-D attitude of fracture system by including the borehole deviation in the inversion. In the second case, we did field experiment to image the empty tunnel with the size of
and the target was very clearly imaged in 3-D space. In these examples, we could show that 3-D ERT imaging is a very powerful tool for the 3-D subsurface imaging and the method can provide enhanced imaging capabilities especially for the 3-D targets such as fractures and cavities or tunnel.
The study of Reversed Two Station Method on Korea-Japan Seismic Data to Obtain Lg Attenuation of Korean Peninsula
Chung, Tae-Woong ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 310~317
Lg amplitude decrease
is very important because the Lg phase is the largest seismic phase in Korea if hazardous earthquakes occurred at neighbor nations such as Japan and China. Since reliable
from two station method can be obtained by long pair distance of stations or events, we used seismic stations both Korea and Japans recording Korean events. The obtained
values, however, were anomalously high; these misguided values, inconsistent with tectonic activity of Korean Peninsula, seems to be related with high
values of Japan region.
Application of Two-Dimensional Boundary Condition to Three-Dimensional Magnetotelluric Modeling
Han, Nu-Ree ; Nam, Myung-Jin ; Kim, Hee-Joon ; Lee, Tae-Jong ; Song, Yoon-Ho ; Suh, Jung-Hee ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 318~325
Assigning an exact boundary condition is of great importance in three-dimensional (3D) magnetotelluric (MT) modeling, in which no source is considered in a computing domain. This paper presents a 3D MT modeling algorithm utilizing a Dirichlet condition for a 2D host. To compute boundary values for a model with a 2D host, we need to conduct additional 2D MT modeling. The 2D modeling consists of transverse magnetic and electric modes, which are determined from the relationship between the polarization of plane wave and the strike direction of the 2D structure. Since the 3D MT modeling algorithm solves Maxwell's equations for electric fields using the finite difference method with a staggered grid that defines electric fields along cell edges, electric fields are calculated at the same place in the 2D modeling. The algorithm developed in this study can produce reliable MT responses for a 3D model with a 2D host.
Time-lapse Inversion of 2D Resistivity Monitoring Data
Kim, Ki-Ju ; Cho, In-Ky ; Jeoung, Jae-Hyeung ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 326~334
The resistivity method has been used to image the electrical properties of the subsurface. Especially, this method has become suitable for monitoring since data could be rapidly and automatically acquired. In this study, we developed a time-lapse inversion algorithm for the interpretation of resistivity monitoring data. The developed inversion algorithm imposes a big penalty on the model parameter with small change, while a minimal penalty on the model parameter with large change compared to the reference model. Through the numerical experiments, we can ensure that the time-lapse inversion result shows more accurate and focused image where model parameters have changed. Also, applying the timelapse inversion method to the leakage detection of an embankment dam, we can confirm that there are three major leakage zones, but they have not changed over time.
Subsurface Investigation of Dokdo Island using Geophysical Methods
Kim, Chang-Ryol ; Park, Sam-Gyu ; Bang, Eun-Seok ; Kim, Bok-Chul ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 335~342
Electrical resistivity and seismic refraction surveys were conducted to investigate geologic structures and geotechnical characteristics of the subsurface, along with rock physical property measurements in Dokdo island. The survey results in Seodo island show that the fault adjacent to the fisherman's shelter is a normal fault and extended towards the NW direction, and that Bedded Lapilli Tuff in the downstream was more severely influenced by weathering and erosion than Trachy Andesite II in the upstream of the survey area. In Dongdo island, Trachy Andesite III and Scoria Bedded Lapilli Tuff were severely weathered and eroded, considered as weathered to soft rock formations, and their weathered zone becomes thicker towards the antiaircraft facility in the NE direction of the survey area. The study results also illustrate that Trachyte and Trachy Andesite are hardest, Massive Tuff Breccia is next, and Stratified Ash Tuff is the most soft rock in Dokdo island.
Inversion of the Magnetic Field Generated by a Car
Lim, Mu-Taek ; Park, Yeong-Sue ; Rim, Hyoung-Rae ; Koo, Sung-Bon ; Jung, Hyun-Key ; Kwak, Byoung-Wook ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 343~349
We have constructed a car-borne magnetic exploration system, in which a car drags a non-magnetic cart on which a magnetometer is installed. In the total magnetic field measured as a vectorial sum in this system, are included the magnetic field generated by the car itself. This magnetic field, doing the role of a magnetic noise, should be eliminated. For this purpose, we have set up a measurement condition to get the same effect as if we have put the car in one point and thereafter measured the magnetic field around it. In this case, if there is any magnetically anomalous body in the area, we can consider all the remaining magnetic field to have been generated by the car itself, once the geomagnetic field eliminated. We tried to invert the magnetic field considered to have been generated by the car and succeeded to derive the magnetic moment and the direction of the induced and remanent magnetic field of the car respectively. Once the magnetic moment and the direction of the induced and remanent magnetic field have been calculated, the magnetic field generated by them in specific points can be directly and analytically calculated. This result can be used in the future to eliminate the magnetic field generated by the car itself doing the role of a magnetic noise during the procedure of reduction of the measured magnetic exploration data by the car-borne magnetic exploration system.
A Study on the Correlation Between Electrical Resistivity and Rock Classification
Kwon, Hyoung-Seok ; Hwang, Se-Ho ; Baek, Hwan-Jo ; Kim, Ki-Seog ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 350~360
Electrical resistivity is one of physical property of the earth and measured by electrical resistivity survey, electrical resistivity logging and laboratory test. Recently, electrical resistivity is widely used in determination of rock quality in support pattern design of road and railway tunnel construction sites. To get more reliable rock quality data from electrical resistivity, it needs a lot of test and study on correlation of resistivity and rock quality. Firstly, we did rock property test in laboratory, such as P wave velocity, Young's modulus, uniaxial compressive strength (UCS) and electrical resistivity. We correlate each test results and we found out that electrical resistivity has highly related to P wave velocity, Young's modulus and UCS. Next, we accomplished electrical resistivity survey in field site and carried out electrical resistivity logging at in-situ area. We also performed rock classification, such as RQD, RMR and Q-system and we correlate electrical resistivity to RMR data. We found out that electrical resistivity logging data are highly correlate to RMR. Also we found out that electrical resistivity survey data are lower than electrical resistivity logging data when there are faults or fractures. And it cause electrical resistivity survey data to lowly correlate to RMR.
A study on Algorithm Automatically Generating Ray Codes for Ray-tracing
Lee, Hee-Il ; Cho, Chang-Soo ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 361~367
When constructing a synthetic seismogram in the earthquake study or in seismic data interpretation by using a ray-tracing technique, the most troublesome and error-prone task is to define a suite of ray codes for the corresponding rays to trace in advance. An infinite number of rays exist for any arbitrarily located source and receiver in a medium. Missing certain important rays or an inappropriate selection of ray codes in tracing rays may result in wrong interpretation of the earthquake record or seismogram. Automatic ray code generation could be able to eliminate those problems. In this study we have developed an efficient algorithm with which one can generate systematically all the ray codes for the source(s) and receiver(s) arbitrarily located in a model. The result of this work could be used not only in analysing multiples in seismic data processing and interpretation, but also in coda wave study, study on the amplification effects in a basin and phase identification of the waves multiply reflected/refracted in earthquake study.
Application of Resistivity Technique for Identifying Cavities Near Surface in Karst Area, Muan-gun, South of Korea
Farooq, Muhammad ; Park, Sam-Gyu ; Song, Young-Soo ; Kim, Jung-Ho ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 368~372
This study evaluates the usefulness and capability of surface electrical resistivity technique for identifying the weak zones or subsurface cavities in karst area with limestone formation. Weak zones or cavities near surface can be potentially dangerous and several problems are associated with collapse of roads or buildings accompanied by subsidence phenomena. In this paper, both two and three dimensional resistivity investigation were conducted to investigate subsidence along a road in Yongweol-ri, Muan-gun, South Korea. The results of the resistivity survey using dipole-dipole array provide a clear view of the weathered regolith, the distribution of weak zones or cavities and bedrock. Several low resistivity areas were identified and subsequent drilling led to the discovery of several weak zone or clay-filled underground cavities. The drilling results show excellent correlation with the resistivity images. It is illustrated, the ability of electrical technique to produce high resolution images of subsurface, which are useful for subsidence assessment. Also the results of this study have demonstrated that two and three dimensional electrical resistivity surveys are useful for delineating the subsidence area. Based on resistivity imaging, the map of hazardous zone has been developed.
Preparation of Tomographic Maps Based on the R Package
Chung, Tae-Woong ; Lees, Jonathan M. ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 373~378
Being widely used for preparation of geographic maps in the field of earth sciences, Generic Mapping Tools (GMT) is difficult to understand the contents for user, and not working well with Microsoft (MS) Window PC. By utilizing R package, 'GEOmap', we can do mapping work at MS window PC with commands easier than those of GMT. In addition, the R commands offer interactive help. Here we introduce brief feature of 'GEOmap', and illustrate the procedure for preparing tomographic maps with an example.
Seismic Data Analysis using the R
Chung, Tae-Woong ; Lees, Jonathan M. ; Yoon, Suk-Yung ;
Geophysics and Geophysical Exploration, volume 11, issue 4, 2008, Pages 379~384
R is a free software for statical computing and graphics. It compiles and runs not only on UNIX platforms but MS Windows. The R commands are easy and offer interactive help. R is used in extensive field by implementing packages. RSEIS, the package of R, enable us to do easy graphic process of seismic data. Here we illustrate an example of the seismic data process using RSEIS.