JaLCDOI 10.18926/ESR/61959
タイトル(別表記) Estimation of displacement waveforms by baseline correction of near-fault acceleration records of the 2016 Kumamoto earthquake with median filter
フルテキストURL esr_027_039_050.pdf
著者 渡邉 禎貢| 小松 正直| 竹中 博士|
抄録 The 2016 Kumamoto earthquake sequence occurred on April 14 (MJMA 6.5) and April 16 (MJMA 7.3). Seismic intensity of 7 on the Japan Meteorological Agency (JMA) scale was observed in Mashiki Town, Kumamoto Prefecture for the both events and in Nishihara Village, Kumamoto Prefecture for the April-16 event. We estimate the displacement waveforms from these acceleration records. Since the acceleration seismograms include the long-period noise due to tilting of the ground and instrumental effects, the baseline corrections are required to derive the accurate velocity and displacement waveforms. We apply a median filter to the velocity waveforms to identify the linear trends on them due to the steplike noise on the acceleration records, and determine the time at which baseline shifts take place and the step value of each shift for the baseline correction through trial and error. Our baseline correction can successfully reconstruct the velocity and displacement waveforms from the acceleration records. The displacement waveforms show the static components consistent with the geodetic data.
キーワード 2016 Kumamoto earthquake baseline correction median filter displacement
出版物タイトル Okayama University Earth Science Report
発行日 2021-03-31
27巻
1号
開始ページ 39
終了ページ 50
ISSN 1340-7414
言語 Japanese
著作権者 © 2021 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved
論文のバージョン publisher
NAID 120007037380
JaLCDOI 10.18926/ESR/61956
タイトル(別表記) Synthetic nearfield seismograms at a subsurface position in a horizontally layered half-space
フルテキストURL esr_027_029_038.pdf
著者 竹中 博士| 渡邉 禎貢|
抄録 We extend the computational code of Takenaka and Sasatani (2000) for synthetic nearfield seismograms for horizontally layered elastic media, based on the reflection/transmission matrices and the discrete wavenumber summation method, to calculate seismic motion and its spatial derivatives at a subsurface position in the attenuative media. In this paper we describe the theory of this extension and show some numerical examples to verify the extended code.
キーワード synthetic seismogram reflectivity method layered half-space
出版物タイトル Okayama University Earth Science Report
発行日 2021-03-31
27巻
1号
開始ページ 29
終了ページ 38
ISSN 1340-7414
言語 Japanese
著作権者 © 2021 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved
論文のバージョン publisher
NAID 120007037377
JaLCDOI 10.18926/ESR/58574
タイトル(別表記) Computation of non-linear site response by the time-domain finite-difference method
フルテキストURL esr_026_001_017.pdf
著者 鳥越 友輔| 小松 正直| 竹中 博士|
抄録 We have developed a time-domain staggered-grid finite-difference code for modeling non-linear response of a one-dimensionally inhomogeneous subsurface structure to a SH plane-wave incidence. It employs the velocity-stress formulation of elastodynamic equation for the linear part, and adopts a elastoplastic rheology model for the non-linear relation between the stress and strain. In this paper, we apply this code to four constitutive models from linear-elastic to nonlinear: (1) linear elastic model, (2) linear viscoelastic model, (3) elastoplastic model, and (4) viscoelastoplastic model, which simulate shallow sand and clay structures and are vibrated by a vertically incident SH plane-wave of Ricker wavelet, to compare the linear and the non-linear soil behaviors including low strains damping (viscoelastic effect) and/or hysteretic attenuation (non-linear effect). We also apply it to a local strong-motion record of the 2000 Western-Tottori earthquake (MW6.8). We then simulate characteristics of non-linear site response such as reduction of the spectral amplitude in the high frequency band and shift of the peak frequencies to lower frequencies.
キーワード finite-difference method non-linear site response strong motion
出版物タイトル Okayama University Earth Science Report
発行日 2019-12-27
26巻
1号
開始ページ 1
終了ページ 17
ISSN 1340-7414
言語 Japanese
著作権者 © 2019 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved
論文のバージョン publisher
JaLCDOI 10.18926/ESR/54116
タイトル(別表記) Application of simulated annealing to focal mechanism determination
フルテキストURL esr_022_1_009_023.pdf
著者 小松 正直| 竹中 博士|
抄録 Simulated annealing (SA) is known as one of the efficient methods for global optimization. It allows for getting an optimal solution by jumping out of local minimum. In this paper, we apply the simulated annealing to determination of focal mechanism solution. To investigate the feasibility of the application, we determine focal mechanism solution of the 14 March 2014 Iyo-Nada intermediatedepth earthquake. The computation of SA method is then 1278 times faster than that of the grid search method.
キーワード focal mechanism solution
出版物タイトル Okayama University Earth Science Report
発行日 2015-12-27
22巻
1号
開始ページ 9
終了ページ 23
ISSN 1340-7414
言語 Japanese
著作権者 © 2015 by Okayama University Earth Science Reports Editorial Committee All Rights Reserved
論文のバージョン publisher
NAID 120005728632