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Envelope broadening of spherically outgoing waves in threedimensional random media having power law spectra
https://niedrepo.bosai.go.jp/records/4460
https://niedrepo.bosai.go.jp/records/446023a833b4696142dd93c42514469cbe74
Item type  researchmap(1)  

公開日  20230330  
タイトル  
言語  en  
タイトル  Envelope broadening of spherically outgoing waves in threedimensional random media having power law spectra  
言語  
言語  eng  
著者 
T Saito
× T Saito
× H Sato
× M Ohtake


抄録  
内容記述タイプ  Other  
内容記述  [1] Highfrequency S wave seismogram envelopes are broadened with increasing travel distance due to diffraction and scattering. The basic mechanism of the broadening has been studied on the basis of the scattering theory with the parabolic approximation for the scalar wave equation in random media. However, conventional models are not realistic enough since the plane wave modeling is too simple and the Gaussian autocorrelation function (ACF) is far from the reality to represent the inhomogeneity in the Earth. Focusing on the early part of envelopes, we formulated the envelope broadening of spherically outgoing scalar waves in threedimensional von Karmantype random media, of which the spectra decay according to a power law at large wave numbers. Random media are characterized by three parameters: RMS fractional velocity fluctuation epsilon, correlation distance a, and order kappa that controls the gradient of the power law spectra. This model predicts that the envelope duration increases with both travel distance and frequency when shortwavelength components are rich in random media, while the duration is independent of frequency when shortwavelength components are poor. Introducing phenomenological attenuation Q, we developed a method for estimating the parameters of inhomogeneity and attenuation from the envelope duration. Applying this method to S wave seismogram envelopes for the frequency range from 2 to 32 Hz in northeastern Honshu Japan, we estimated the random inhomogeneity parameters as kappa = 0.6, epsilon(2.2)a(1) approximate to 10(3.6) [km(1)] and f/Q = 0.0095 [s(1)], where f is frequency. The power law portion of the estimated power spectral density function is P( m) approximate to 0.01 m(4.2) [km(3)], where m is wave number.  
言語  en  
書誌情報 
en : JOURNAL OF GEOPHYSICAL RESEARCHSOLID EARTH 巻 107, 号 B5 

出版者  
言語  en  
出版者  AMER GEOPHYSICAL UNION  
ISSN  
収録物識別子タイプ  EISSN  
収録物識別子  21699356  
DOI  
関連識別子  10.1029/2001JB000264 