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The 20 January 2007, Mw 4.48, Odaesan, Korea, earthquake
Namdae Jo,Chang-Eob Baag 한국지질과학협의회 2007 Geosciences Journal Vol.11 No.1
Jo, N.-D. and Baag, C.-E., 203, Estimation of spectrum decayparameter κ and stochastic prediction of strong ground motionsin southeastern Korea. Journal of the Earthquake EngineeringSociety of Korea, 7, 5970. (in Korean with English abstract)Junn, J.-G., Jo, N.-D. and Baag, C.-E., 2002, Stochastic prediction ofground motions in southern Korea. Geosciences Journal, 5, 1726.Kang, T.-S. and Baag, C.-E., 2004, The 29 May 2004, Mw=5.1, off-shore Uljin earthquake, Korea. Geosciences Journal, 8, 115123.KIGAM, 2007, http://quake.kigam.re.kr.Kim, W., Kim, S. K. and Baag, C.-E., 206, Optimum design foraccelerograph network and instrumental intensity in South Korea.Technical Report to Korea Meteorological Administration, Pre-pared by Earthquake Engineering Society of Korea, 107 p. (in Korean)Kim, W., 2007, Earthquakes in Stable Continental Region, 1-dayworkshop for seismic observation and analysis Earthquakes in
The 29 May 2004, Mw=5.1, offshore Uljin earthquake, Korea
강태섭,Chang-Eob Baag 한국지질과학협의회 2004 Geosciences Journal Vol.8 No.2
We present results of a preliminary analysis for sourceparameters of the 29 May 2004 offshore Uljin earthquake. Theanalysis is based on a set of broadband and short period velocityseismograms, and accelerograms recorded by seismic networks insouthern Korea. The estimated parameters of the mainshock are asfolows: origin time 19:14:25.82 in Korean local time (10:14:25.82UT), latitude 36.626N, longitude 130.054 E, depth 18 km, mag-nitude Mw 5.1, stress drop 28 bars, one focal plane 337 , 56 and78 , and the other plane 178 , 36 and 107 in strike, dip and rake,respectively. Three aftershocks of Mw 2.3, 2.0 and 2.4 occurredwithin source region of the mainshock, and two other events of Mw2.5 and 3.5 at epicenters beyond the rupture area are presumed tobe triggered dynamically by the 29 May 2004 earthquake. Thelargest ground acceleration, 2.62 %g, was instrumentally recordedat Pohang, 90.4 km south-west of the mainshock epicenter. Themaximum instrumental intensity is estimated as V and VI in Mod-ified Mercalli Intensity scale excluding and including local effects,respectively. There is a possibility that the mainshock-aftershocksequence and one of the dynamically triggered events are directlyrelated to the Ulleung Fault.
Generalized Frequency-wavenumber Migration Implemented by the Intrinsic Attenuation Effect
박창업,심재헌,Baag Chang-Eob,Shim Jae-Heon The Korean Society Of Petroleum Geology 1993 한국석유지질학회지 Vol.1 No.1
지진파의 전파속도와 감쇠정도가 불균질한 매질에서 2차원 지진파 단면자료에 대한 주파수-파수 영역에서의 구조보정 방법 및 그 결과를 제시한다. 파동전파의 감쇠효과를 포함시키기 위해 일반화된 주파수-파수 구조보정 방법을 개선하여 파동장의 상향 및 하향 외삽연산자에 복소수 전파속도를 사용한다. 이 복소수 전파속도의 허수 부분은 지진파 감쇠 척도인 Q 값을 포함하도록 한다. 불균질한 전파속도와 비탄성을 가진 매질 속에서의 전파방정식의 해를 얻기 위해, 불균질한 매질자체를 일정한 전파속도와 비탄성을 갖는 평균적 매질과 가상적 파동원의 불균질한 분포로 규합된 등가의 시스템으로 취급한다. 가상적 파동원은 전파속도와 매질비탄성의 불균질 정도에 따라 그 세기가 좌우된다. 이 방법에 의해 수 개의 구조 모델에 대해 수치적으로 계산된 결과는 기존의 일반화된 파수-주파수 구조 보정 방법에 의한 것보다 더욱 선명한 단면 영상을 보여주며 파의 비탄성에 의해 불명확하게된 영상신호가 복원된다. 이 방법은 석유나 천연가스가 부존된 구조 또는 파쇄대가 존재하는 지역에서 획득된 자료를 구조보정하는데 유용하게 쓰일 것이다. A method and results of computations are presented for the 2-D seismic migration process in the frequency-wavenumber domain for the laterally and vertically inhomogeneous medium. In order to take the intrinsic attenuation effect into account in the migration process the complex-valued wave velocity is used in the wavefield extrapolation operator, improving the generalized frequency-wavenumber migration technique. The imaginary part of the complex-valued wave velocity includes the seismic quality factor Q value. In derivation of the solution of the wave equation for the medium of inhomogeneous wave velocity and anelasticity, the inhomogeneous medium is mathematically converted to an equivalent system which consists of a homogeneous medium of averaged slowness and an inhomogeneous distribution of hypothetical wave source. The strength of the hypothetical wave source depends on the deviation of squared slowness from the averaged value of the medium. Results of numerical computation using the technique show more distinct geologic images than those using the convensional generalized frequency-wavenumber migration. Especially, the obscured images due to the wave attenuation by anelasticity are restored to show sharp boundaries of structures. The method will be useful in the imaging of the reflection data obtained in the regions of possible petroleum or natural gas reservoir and of fractured zone.