• Journal of the Korean Geotechnical Society
• /
• v.28 no.5
• /
• pp.109-120
• /
• 2012

In marine site surveys, drilling boreholes are restrictively conducted, while geophysical surveys are used with ease. To overcome the limitations of marine site survey, various site survey data should be collected and analysed by adopting complementary pros and cons. In this study, the integration assessment was established to digitize 2D geo-layer based on the overlapping of a few borehole data to seismic refraction tomography and to determine 3D geo-information based on the kriging for the design of offshore-foundation. And the overlapping method was proposed considering spatial variability of the tomography and separation distance from borehole position to determine the 2D geo-layer. Finally, the integration assessment was applied to offshore wind-turbine site in Jeju-do, and its applicability was verified based on the cross-validation.

• Journal of the Korean earth science society
• /
• v.34 no.6
• /
• pp.588-601
• /
• 2013

In geophysics and geophysical exploration fields, we can use information about inclination and azimuth in various ways. These include borehole deviation logging for inversion process, real-time data acquisition system, geophysical monitoring system, and so on. This type of information is also necessarily used in the directional drilling of shale gas fields. We thus need to develop a subminiature, low-powered, multi-functional inclination and azimuth measurement system for geophysical exploration fields. In this paper, to develop real-time measurement system, we adopt the high performance low power Micro Control Unit (made with state-of-the-art Complementary Metal Oxide Semiconductor technology) and newly released Micro Electro Mechanical Systems Attitude Heading Reference System sensors. We present test results on the development of a multifunctional real-time inclination and azimuth measurement system. The developed system has an ultra-slim body so as to be installed in 42mm sonde. Also, this system allows us to acquire data in real-time and to easily expand its application by synchronizing with a depth encoder or Differential Global Positioning System.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.12a
• /
• pp.1-14
• /
• 2007

This paper briefly reviews the history of the Korean geophysics and analyze the current status of geophysical researches. And the future prospects of geophysics are discussed based on social demands for the science and technology in Korea. About thirty universities offer geophysics courses in their academic curricula. Although the number of Ph.D. graduates in geophysics had been small until the year of 1990, but is rapidly increasing. In recent years about $7{\sim}8$ Ph.D's are produced every year. The major geophysical methods used in Ph.D. theses are seismic, electrical and electromagnetic methods, and earthquake waves and research themes are computational geophysics, which involve data processing, modelling, inversion and tomography, geological structures, and paleomagnetic studies in the order of numbers. The Solid Earth Geophysics is generally distinguished in two categories such as "Global Geophysics" and "Exploration Geophysics". However, they are intimately connected, and overlap in many sectors, especially in large scale research projects. The global geophysics has a more academic and general scientific meaning, and several research groups in Korean universities are carrying out the earthquake seismology and paleomagnetic studies. On the other hand the exploration geophysics focuses on practical application of geophysical concepts, and the public research institutes conduct large projects for exploration of energy and mineral resources and to cope with environmental and natural disaster problems. The geophysical studies for local geology and regional crustal structure utilize various survey methods and usually cover both academic and exploration purposes. The computational geophysics constitutes the indispensable theoretical backgrounds for all geophysical sectors. Many young Korean geophysicists, who have strong background in mathematics and physics, devote to the computational geophysics and several groups have made the internationally highest level achievements. But, Korean geophysicists have to expand their research interests to include more global-scale, high-tech researches and collaborative works with various other science groups.

• The Journal of Engineering Research
• /
• v.2 no.1
• /
• pp.165-174
• /
• 1997

It is not possible to define the earth's interior because of it complicity. However, it can be interpreted directly and/ or indirectly. Geophysics is the subject of this study. To study the possibility of construction supervision by geophysical method, geophysical prospecting was performed and studied at the SamYang pumping well area in Cheju Island, where, although underground dam was constructed, the saline water invade the pumping well area. This study focuses on the construction supervision by electrical measurements. Two electric resistivity survey lines are installed in the pumping well site, and at each line electric survey was conducted at ebb and flow tides. To increase the data quality SP (self-potential) survey was also performed. As a result the geophysical exploration methods explained the defect of construction well, and It shows that geophysical probe can be a useful tool for the construction supervision.

• Journal of the Korean Geophysical Society
• /
• v.5 no.1
• /
• pp.19-27
• /
• 2002

Geophysical surveys(self-potential, electromagnetic, electrical resistivity, and seismic refraction methods) were performed to delineate the flow channel of leachate from a AMD (acid mine drainage) by correlating the anomalies to geochemical characteristics at an abandoned mine (Jangpoong mine). The geophysical responses attempted to be correlated with water sample analysis data(pH, EC, heavy metals, ${SO_4}^{-2}$). Electrical dipole-dipole resistivity sections represent the low-resistivity zone trending northwest, which indicates the leachate flow by AMD along the contact of the mine waste rock dump and the bedrock. From the overall points of geophysical and geochemical anomalies, it is summarized that the flow channel of leachate by AMD can be successfully imaged with composite interpretations on the geophysical and geochemical studies.

• Journal of the Korean earth science society
• /
• v.23 no.1
• /
• pp.15-29
• /
• 2002

Bayesian inversion for gravity and resistivity data was performed to investigate the cavity structure appearing as a lava tunnel in Cheju Island, Korea. Dipole-dipole DC resistivity data were proposed for a prior information of gravity data and we applied the geostatistical techniques such as kriging and simulation algorithms to provide a prior model information and covariance matrix in data domain. The inverted resistivity section gave the indicator variogram modeling for each threshold and it provided spatial uncertainty to give a prior PDF by sequential indicator simulations. We also presented a more objective way to make data covariance matrix that reflects the state of the achieved field data by geostatistical technique, cross-validation. Then Gaussian approximation was adopted for the inference of characteristics of the marginal distributions of model parameters and Broyden update for simple calculation of sensitivity matrix and SVD was applied. Generally cavity investigation by geophysical exploration is difficult and success is hard to be achieved. However, this exotic multiple interpretations showed remarkable improvement and stability for interpretation when compared to data-fit alone results, and suggested the possibility of diverse application for Bayesian inversion in geophysical inverse problem.

• Tunnel and Underground Space
• /
• v.3 no.1
• /
• pp.50-53
• /
• 1993

Geotomography, which reconstructs underground structures, is very important task in recent geophysical data processing. In this study, the field data acquired by U.S.Army was used for tomographic inversion and the result was compared with the tomographic inversion and the result was compared with the tomogram from theoretical model data.

• Proceedings of the KSRS Conference
• /
• v.2
• /
• pp.710-712
• /
• 2006

The aim of this study was to analyze limestone deposits potential using an artificial neural network and a Geographic Information System (GIS) environment to identify areas that have not been subjected to the same degree of exploration. For this, a variety of spatial geological data were compiled, evaluated and integrated to produce a map of potential deposits in the Gangreung area, Korea. A spatial database considering deposit, topographic, geologic, geophysical and geochemical data was constructed for the study area using a GIS. The factors relating to 44 limestone deposits were the geological data, geochemical data and geophysical data. These factors were used with an artificial neural network to analyze mineral potential. Each factor’s weight was determined by the back-propagation training method. Training area was applied to analyze and verify the effect of training. Then the mineral deposit potential indices were calculated using the trained back-propagation weights, and potential map was constructed from GIS data. The mineral potential map was then verified by comparison with the known mineral deposit areas. The verification result gave accuracy of 87.31% for training area.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.5
• /
• pp.319-326
• /
• 2003

In site investigation for tunnel designs, nowadays, geophysical exploration such as seismic exploration and electric resistivity exploration as well as drilling logging is frequently carried out. A method which can systematically make the utmost use of all available data obtained from investigation, therefore, is strongly required for the optimal evaluation of ground conditions in terms of rock mass class, etc. Many researchers have proposed using qualitative data to cope with the lack of quantitative data. In this study, an evaluation technique of rock mass classes in undrilled region was proposed based upon multiple indicator kriging method which is a geostatistical technique. It was shown that two types of data with different degree of uncertainty, for example, drilling logging data and geophysical exploration data, could be simultaneously utilized in evaluating rock mass classes for a real tunnel design.

• Economic and Environmental Geology
• /
• v.12 no.1
• /
• pp.17-28
• /
• 1979

Geodetic and geophysical quantities related to gravity data are analyzed using three-dimensional sin x/x method for the southern part of the Korean peninsula and adjacent Japan Sea. The thickness of isostatic crust is found as 26 km. The average isostatic gravity anomaly in this area is appeared to be +24.8 mgal, of which result indicates that the surface features are under-compensation or the thickness of the crust is thinner than normal. It is noteworthy that the general trend of the deflections of the vertical in direction is nearly perpendicular to the geological structure having a direction of NNE-SSW in the southern part of Korea.