BUTSURI-TANSA(Geophysical Exploration)
Online ISSN : 1881-4824
Print ISSN : 0912-7984
ISSN-L : 0912-7984
Volume 60, Issue 4
Displaying 1-4 of 4 articles from this issue
Original Papers
  • —Complex Meyer Matching Pursuit—
    Hirotoshi Matsubayashi
    2007 Volume 60 Issue 4 Pages 283-295
    Published: 2007
    Released on J-STAGE: June 25, 2010
    JOURNAL FREE ACCESS
    Based on Fast Matching Pursuit (FMP), I have developed a new wavelet transform method “Complex Meyer Matching Pursuit (CMMP)” for overcoming the defects of current wavelet transform methods.
    Recently, wavelet transform method was popularly applied to analysis of various time series data. However, some wavelet transform methods could even result different interprets during the analysis data. As an example, single wave signal was multi-used by the continuous wavelet transform (CWT). Moreover, only because the different start point, the different transform results were gotten from the discrete wavelet transform (DWT).
    The Matching Pursuit (Mallat, 1993) and its extension FMP overcame the above mentioned defects. Their methods could get even results, respectively. However, the Matching Pursuit algorithms consumed computing loads, and caused biased estimation since it used the non-orthonormal wavelet function on the frequency domain. The wavelet function which was used in FMP was generally different shape to signal in time series. Therefore, single wave signal was transformed into many wavelets. Moreover there is some possibility that such signals are not transformed.
    I proposed a new definition of the complex Meyer wavelet with the phase component in the frequency domain. Further, I used the algorithm to develop the CMMP. The wavelet is orthonormal wavelet function. Therefore, it overcomes the problem of bias on the frequency domain. Moreover it can be similar to shape of original signals, because it has argument. Next, I designed a new algorithm of transform priority decision and a matching method for overcoming the other defects of the Matching Pursuit, FMP, CWT and DWT.
    The new method not only overcomes the defects but also expresses the signal shape as an argument of the complex Meyer wavelet. Therefore, the method can provide the new parameter “argument” of series data for interpretation in addition to the parameters of position on series data, frequency, and amplitude. I expect that the new parameter helps for interpretation of time series data.
    For the applications of this new wavelet transform, I analyzed the long-period tremor at Aso volcano that was recorded by the time series data of broadband seismograph network (F-net) of the National Research Institute for Earth science and Disaster prevention (NIED). I was able to extract the waveform features of tremor by using the CMMP. Finally, I found the differences between the data recorded terms in the waveform shape of tremor which indicated that the tremors source was changed in these terms.
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  • Masanori Saito
    2007 Volume 60 Issue 4 Pages 297-304
    Published: 2007
    Released on J-STAGE: June 25, 2010
    JOURNAL FREE ACCESS
    A new method is developed to estimate separately the longitudinal and transversal component frequency-wavenumber (f-k) power spectrum of microtremors by using a horizontal component seismic array. This method is a generalization of the conventional maximum-likelihood method (MLM) which applies only to single channel inputs. Validity of the new method is demonstrated by using synthetic microtremor records.
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  • Toshinao Yasui, Yoshinori Sanada, Hitoshi Mikada, Yuzuru Ashida, Toshi ...
    2007 Volume 60 Issue 4 Pages 305-313
    Published: 2007
    Released on J-STAGE: June 25, 2010
    JOURNAL FREE ACCESS
    A trench is sometimes used in order to cut down the ground vibrations caused by traffic, construction works, and factory machines. The shielding effect of vibrations by a trench has been often examined by laboratory experiments using ultrasonic waves and field experiments. Recent developments of personal computers enhance use of numerical analysis. In this study, DEM (discrete element method) is adopted for simulation tool. The reduction ratio of Rayleigh waves after passing through a narrow trench had been proposed by Yoshii (1971) and it is the function of the trench depth. Our simulation results can reproduce this behavior very well. In case of a wide trench, however, there is no empirical relationship describing the reduction behaviors. In this paper, we propose a new equation for Rayleigh wave reduction including the depth and width of a trench based on simulation studies.
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Technical Note
  • Keiichi Suzuki, Hiroto Nagamine, Kunio Toyota, Katsuyuki Harada
    2007 Volume 60 Issue 4 Pages 315-326
    Published: 2007
    Released on J-STAGE: June 25, 2010
    JOURNAL FREE ACCESS
    We have a problem that frost heaves by ice lenses sometimes damage buried constructions and pavements of road surface in the northern part of Japan in winter. Especially on the expressway, a bumpy road surface caused by frost heaves leads some serious traffic accidents.
    Generally, we estimate the frost heaves distribution by means of the roughness measurements at the road surface. But this method can not give us the frost penetration depth. If we estimate the frost heaves distribution with the frost penetration depth, we can plan the method to reduce the damage by the frost heaves, for example replacement method for non-heaving soil.
    We attempted a new nondestructive prospecting method for the frost penetration depth by the ground penetrating radar (GPR). One nanosecond monocycle pulse was used for transmitting waves of the GPR to obtain high resolution data.
    The time lapse measurements by the GPR were conducted in autumn before frost heave appearance (first stage) and in winter while frost heaves appearing (second stage) at Doutou expressway in Hokkaido prefecture. The obtained GPR profile in the first stage was different from the GPR profile in the second stage obviously.
    We conducted the common mid-point (CMP) gathers two times and confirmed the electromagnetic wave (EMW) became faster in the second stage than that in the first stage because of the frost soil.
    We carried out boring and excavation tests based on the GPR data and confirmed that the ice lenses existed where the GPR profiles and the EMW velocities between two stages were different. The frost penetration depth could be estimated from the differences of the two GPR profiles.
    The frost heaves can be easily produced in cutting sections due to much underground water, and hardly produced in banking sections due to lack of underground water. The estimated frost heaves areas from the GPR distributed in cutting sections showed consistent with mentioned above.
    The time lapse GPR, one of the nondestructive testing methods, shows the effectiveness for the estimation of the frost penetration depth.
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