Temporal change in site response caused by earthquake strong motion as revealed from coda spectral ratio measurement

Sawazaki, Kaoru; Sato, Haruo; Nakahara, Hisashi; Nishimura, Takeshi

doi:10.1029/2006gl027938

Cited by 67 publications

(91 citation statements)

References 14 publications

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“…The sharp reductions of the peak frequency and peak spectral ratio followed by gradual recovery observed in this study (Fig. 3) are similar to the previous observations of nonlinear site response using spectral ratio approaches (e.g., Sawazaki et al, 2006;Wu et al, 2009a). Hence, we attribute the temporal changes of the spectral ratios to nonlinear site response during the main shock.…”

Section: Discussionsupporting

confidence: 79%

“…Previous studies have found clear evidences of soil nonlinearity after previous large earthquakes in Japan, including the 1995 M w 6.8 Kobe earthquake, 2000 M w 6.8 Western Tottori earthquake, 2003 M w 8.3 Tokachi-Oki earthquake, 2003 M w 7.0 Miyaki-Oki earthquake, and 2004 M w 6.6 Niigata earthquake (e.g., Pavlenko and Irikura 2002;Sawazaki et al, 2006;Rubinstein et al, 2007;Assimaki et al, 2008;Wu et al, 2009aWu et al, , 2010. The sharp reductions of the peak frequency and peak spectral ratio followed by gradual recovery observed in this study (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Previous measurements on nonlinear site response were mostly from PGAs in the range of a few tens of Gal to a few hundred Gal (e.g., Sawazaki et al, 2006;Wu et al, 2009a;Rubinstein, 2011). Their results are generally characterized by sharp reductions of the peak frequencies and peak spectral ratios during the large PGAs, followed by logarithmic recovery.…”

Section: Introductionmentioning

confidence: 99%

“…The analysis procedure generally follows those of Sawazaki et al (2006Sawazaki et al ( , 2009 and Wu et al (2009aWu et al ( , b, 2010, and is briefly described here. We use 6-s time windows that are moved forward by 2 s for all waveforms recorded by the surface and borehole stations.…”

Section: Analysis Proceduresmentioning

confidence: 99%

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Temporal changes of site response during the 2011 M w 9.0 off the Pacific coast of Tohoku Earthquake

Peng

2011

Earth Planet Sp

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The recent M w 9.0 off the Pacific coast of Tohoku Earthquake and its aftershocks generated widespread strong shakings as large as ∼3000 Gal along the east coast of Japan. Here we systematically analyze temporal changes of material properties and nonlinear site response in the shallow crust associated with the Tohoku main shock, using seismic data recorded by the Japanese Strong Motion Network KiK-Net. We compute the spectral ratios of windowed records from a pair of surface and borehole stations, and then use the sliding-window spectral ratios to track the temporal changes in the site response of various sites at different levels of peak ground acceleration (PGA). Our preliminary results show clear drop of resonant frequency of up to 70% during the Tohoku main shock at 6 sites with PGA from 600 to 1300 Gal. In the site MYGH04 where two distinct groups of strong ground motions were recorded, the resonant frequency briefly recovers in between, and then followed by an apparent logarithmic recovery. We investigate the percentage drop of peak frequency and peak spectral ratio during the Tohoku main shock at different PGA levels, and find that at most sites they are correlated.

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Analysis Proceduresmentioning

confidence: 99%

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Temporal changes of site response during the 2011 M w 9.0 off the Pacific coast of Tohoku Earthquake

Peng

2011

Earth Planet Sp

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“…Passive image interferometry (PII) uses this concept in detecting changes through the monitoring of auto-and/or cross-correlation of daily ambient noise (Sens-Schönfelder and Wegler, 2006;Wegler and Sens-Schönfelder, 2007), with successful applications to coseismic changes (Ohmi et al, 2008;Brenguier et al, 2008a;Wegler et al, 2009) and changes associated with volcanic eruptions (Brenguier et al, 2008b). There are two physical mechanisms that may explain postseismic changes in velocity; one is a relaxation of fault zone damage by healing (Vidale and Li, 2003); the other is a nonlinear change in very shallow subsurface regions caused by the incidence of strong motion (Sawazaki et al, 2006). For velocity changes associated with large earthquakes, it is quite difcult to distinguish which mechanism is responsible.…”

Section: Introductionmentioning

confidence: 99%

Seismic velocity decrease and recovery related to earthquake swarms in a geothermal area

2010

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We found a recurring seismic velocity decrease associated with small earthquake swarms experienced in 2007 in a geothermal area in Kyushu, southwestern Japan, by analyzing long-term changes in the autocorrelation function (ACF) of seismic noise. The seismic velocity decrease appeared just after two major periods of earthquake activity began in June and October of 2007. In both instances, conditions returned to normal within a characteristic time period of 4 months. The observed size of the velocity changes agrees well with the magnitudes of the swarms. The lag-time dependence of ACF changes can be systematically explained by seismic velocity changes induced by uid inclusion in a small, localized area deep within the hypocenter region.

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Seismic noise correlations to image structural and mechanical changes associated with the Mw 7.9 2008 Wenchuan earthquake

et al. 2014

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We locate temporal changes of seismic wave speed and scattering properties of the crust associated with the 2008 Mw7.9 Wenchuan earthquake. To that end, we analyze ambient seismic noise records from 2007 until the end of 2008 in the 1–3 s period band and in the 12–20 s period band measured in a region that covers the southern two thirds of the fault activated during the earthquake. To locate the changes, we use a refined imaging procedure based on the sensitivity of scattered waves to weak perturbations. This inverse method uses the radiative transfer approximation to describe the intensity of the noise correlation coda. Our results show that the largest structural changes are observed northeast of the Wenchuan epicenter, around the fault zone where aftershocks are distributed. The spatial and temporal characteristics of the behavior of the crust at depth around the Wenchuan earthquake suggest a postseismic and geology‐dependent signature of the middle crust. We also observe a clear seasonal signature within the Sichuan basin at depth that we relate to the heavy rainfalls during the monsoon season. This seasonality can also be observed at the surface in form of a waveform decoherence. Our study highlights that seismic velocity changes, and waveform decoherence are independent measurements that are sensitive to different parameters and can thus give complementary information. In our study we also point out the value of studying the evolution of the changes at different times in the coda.

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Temporal change in site response caused by earthquake strong motion as revealed from coda spectral ratio measurement

Cited by 67 publications

References 14 publications

Temporal changes of site response during the 2011 M w 9.0 off the Pacific coast of Tohoku Earthquake

Temporal changes of site response during the 2011 M w 9.0 off the Pacific coast of Tohoku Earthquake

Seismic velocity decrease and recovery related to earthquake swarms in a geothermal area

Seismic noise correlations to image structural and mechanical changes associated with the Mw 7.9 2008 Wenchuan earthquake

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