Strong Ground Motion Observation by the Committee of Earthquake Observation and Research in the Kansai Area (Ceorka)

Kagawa, Takao; Iemura, Hirokazu; Irikura, Kojiro; Toki, Kenzo

doi:10.5610/jaee.4.3_128

Cited by 12 publications

(4 citation statements)

References 1 publication

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“…2(a) shows the depth distribution of the bedrock of the Osaka basin velocity structure model by Iwata et al (2008) and the strong motion stations used in this study. The strong motion stations are maintained by the following networks and organizations: the Committee of Earthquake Observation and Research in the Kansai Area (CEORKA; Kagawa et al 2004b); K‐NET and KiK‐net by the National Research Institute for Earth Science and Disaster Prevention (NIED; Kinoshita 1998; Aoi et al 2001); the seismic intensity observation network of the Japan Meteorological Agency (JMA); the strong motion network project of 10 electric power companies (Denkyo‐net); the Osaka City Waterworks Bureau (OCWB) and Kansai International Airport Co., Ltd (KIAC). The K‐NET, KiK‐net and JMA networks have accelerographs, while the other networks have servo‐velocity type strong motion seismographs.…”

Section: Ground Motion Simulation Of a M65 Earthquakementioning

confidence: 99%

Simulation of long-period ground motion in the Osaka sedimentary basin: performance estimation and the basin structure effects

Iwaki

Iwata

2010

Geophysical Journal International

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S U M M A R YWe assessed the applicability of the 3-D subsurface velocity structure model of the Osaka sedimentary basin in western Japan for simulations of long-period ground motion (3-20 s) based on two types of long-period ground motion characteristics: (1) strong ground motion from a specific earthquake and (2) site-specific, event-independent horizontal-to-vertical spectral ratio (HV) characteristics obtained from earthquakes with various azimuths. For the first type, we compared the observed and synthetic ground motions in terms of velocity waveforms and pseudo-velocity response spectra; we then proposed an objective index to evaluate the goodness-of-fit from one site to the next. The simulation satisfactorily reproduced the observed ground motion at many stations; however, the model needs improvement for reproducing the ground motion at some stations. For the second type, we first demonstrated that site-specific HV characteristics can be obtained from the coda portion of strong motion observation records for earthquakes with various azimuths. We then demonstrated that the HVs obtained from 3-D ground motion simulations for earthquakes with various azimuths (3DHV) also have sitespecific stable values. The synthetic 3DHV was compared with the observed HV, and the 3-D basin velocity structure model was demonstrated as able to reproduce the HV peak periods within ±1 s at many stations. However, at some stations, the peak periods of the 3DHV were systematically longer than those of the observed HV by more than 1.5 s, which corresponded to the stations of poor goodness-of-fit scores in the ground motion simulation. 3DHV was also compared with the theoretical ellipticity of the fundamental Rayleigh wave (1DHV). The peak periods of 3DHV and 1DHV were inconsistent with each other at some sites, which implies that 3DHV is affected by the lateral heterogeneity of the structure around the site. We found the systematically biased characteristics of the discrepancy in 3DHV and 1DHV peaks in specific regions. The spatial extent of the area that affects 3DHV is related to the complexity in the bedrock structure and the dominant period of 3DHV.

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Section: Ground Motion Simulation Of a M65 Earthquakementioning

confidence: 99%

Simulation of long-period ground motion in the Osaka sedimentary basin: performance estimation and the basin structure effects

Iwaki

Iwata

2010

Geophysical Journal International

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“…We collected records of the observed ground motion in and around the Osaka sedimentary basin, in the form of acceleration time histories from the K-NET and KiK-net stations operated by NIED (Aoi et al 2011), the Seismic Intensity Observation Network Systems of the JMA, Osaka, Hyogo, Kyoto, Wakayama and Nara prefectures and the city of Kyoto (Nishimae 2004), the Building Research Institute (BRI; Kashima 2004), and Port and Airport Research Institute (PARI; Nozu 2004). The strong motion stations belonging to the Committee of Earthquake Observation and Research in the Kansai Area (CEORKA; Kagawa et al 2004a) and the Disaster Prevention Research Institute of Kyoto University (DPRI) provided strong motion data obtained by the three-component broadband velocity sensors at each station.…”

Section: O B S E Rv E D G Ro U N D M O T I O N S D U R I N G T H E 0 mentioning

confidence: 99%

Modelling of wave propagation and attenuation in the Osaka sedimentary basin, western Japan, during the 2013 Awaji Island earthquake

et al. 2016

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an inland earthquake of M w 5.8 occurred in Awaji Island, which forms the western boundary of the Osaka sedimentary basin in western Japan. The strong ground motion data were collected from more than 100 stations within the basin and it was found that in the Osaka Plain, the pseudo velocity response spectra at a period of around 6.5 s were significantly larger than at other stations of similar epicentral distance outside the basin. The ground motion lasted longer than 3 min in the Osaka Plain where its bedrock depth spatially varies from approximately 1 to 2 km. We modelled long-period (higher than 2 s) ground motions excited by this earthquake, using the finite difference method assuming a point source, to validate the present velocity structure model and to obtain better constraint of the attenuation factor of the sedimentary part of the basin. The effect of attenuation in the simulation was included in the form of Q(f) = Q 0 (f/f 0 ), where Q 0 at a reference frequency f 0 was given by a function of the S-wave velocity, Q 0 = αV S . We searched for appropriate Q 0 values by changing α for a fixed value of f 0 = 0.2 Hz. It was found that values of α from 0.2 to 0.5 fitted the observations reasonably well, but that the value of α = 0.3 performed best. Good agreement between the observed and simulated velocity waveforms was obtained for most stations within the Osaka Basin in terms of both amplitude and ground motion duration. However, underestimation of the pseudo velocity response spectra in the period range of 5-7 s was recognized in the central part of the Osaka Plain, which was caused by the inadequate modelling of later phases or wave packets in this period range observed approximately 2 min after the direct S-wave arrival. We analysed this observed later phase and concluded that it was a Love wave originating from the direction of the east coast of Awaji Island.

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“…2, we show the basin stations used in the inversion scheme for each earthquake. The strong motion stations are maintained by the following networks and organizations: the Committee of Earthquake Observation and Research in the Kansai Area (CEORKA; Kagawa et al 2004b), municipalities of Osaka prefecture, K-NET and KiK-net by the National Research Institute for Earth Science and Disaster Prevention (NIED; Okada et al 2004), Japan Meteorological Agency (JMA), the strong motion network project of 10 electric power companies (Denkyo-net), Kansai Electric Power Co., Inc. (KEPCO) and Kansai International Airport Co., Ltd. (KIAC). The CEORKA, KEPCO and Denkyo-net networks have servo velocity-type seismographs, whereas the other networks have accelerographs.…”

Section: G Ro U N D M O T I O N M O D E L L I N G O F T H E Ta Rg E Tmentioning

confidence: 99%

Estimation of three-dimensional boundary shape of the Osaka sedimentary basin by waveform inversion

Iwaki

Iwata

2011

Geophysical Journal International

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S U M M A R YWe present a method for estimating the boundary shape of a 3-D basin velocity structure by waveform inversion, and we apply the method to real seismic data observed in the Osaka sedimentary basin in Japan. The initial model is the 3-D Osaka basin velocity structure model developed by Iwata et al. (2008. Basin and crustal velocity structure models for the simulation of strong ground motions in the Kinki area, Japan. J. Seism., 2, 223-234) based on bedrock depth information obtained from various geophysical exploration surveys. We adopt representation of the boundary shape of the seismic bedrock using a 2-D cubic B-spline function. The spline coefficients are estimated by minimizing the L2-norm of the difference between the observed and synthetic waveforms. The target of the inversion is the set of velocity waveforms in the period range of 3-10 s of the real seismic data observed in the Osaka basin during two regional M W 5.0 earthquakes that occurred 60-90 km to the east and southeast of the Osaka basin; they contain later phases with large amplitudes and long durations. We first perform a series of synthetic tests to validate the method and examine the effect of the choice of time window in the waveform inversion. We show that the later phases of the ground motion have a larger influence on the inversion and are affected by the structure of a wider area relative to the body-wave portion. We then apply the method to the real data in two successive steps:Step-1 involves the body-wave portion only and Step-2 involves the body-wave and later phases. We propose a multi-event inversion method in which ground motion data from two earthquakes with different azimuths are solved simultaneously. The updated basin velocity structure model obtained in our inversion analysis reproduces the ground motion better than the initial model at most of the stations. The bedrock depth of the updated model is smaller than that of the initial model in the central part of the basin, which is consistent with the bedrock depth information inferred from deep borehole data.

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Strong Ground Motion Observation by the Committee of Earthquake Observation and Research in the Kansai Area (Ceorka)

Cited by 12 publications

References 1 publication

Simulation of long-period ground motion in the Osaka sedimentary basin: performance estimation and the basin structure effects

Simulation of long-period ground motion in the Osaka sedimentary basin: performance estimation and the basin structure effects

Modelling of wave propagation and attenuation in the Osaka sedimentary basin, western Japan, during the 2013 Awaji Island earthquake

Estimation of three-dimensional boundary shape of the Osaka sedimentary basin by waveform inversion

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