Secondary Love Waves Observed by a Strong-Motion Array in the Tokyo Lowlands, Japan.

Kinoshita, Shūichi; Fujiwara, Hiroyuki; Mikoshiba, Tadashi; Hoshino, Tsutomu

doi:10.4294/jpe1952.40.99

Cited by 63 publications

(22 citation statements)

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“…However, the wave types and secondary source areas of these later arrivals could not be examined because no small aperture array observation was being made in the Mexico City valley at that time. Kinoshita et al (1992) detected Love waves with a period of 7s in the S later arrivals observed by a small aperture array in the Kanto basin located in central Honshu, Japan during shallow earthquakes. Phillips et al (1993) also detected Love waves with a period of 1 s in array data in the western Kanto basin during shallow earthquakes.…”

Section: Introductionmentioning

confidence: 89%

Basin-Induced Love Waves in the Eastern Part of the Osaka Basin.

et al. 1995

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Well-developed basin-induced waves with a predominant frequency of about 0.3 Hz were detected as later arrivals of a direct S-wave in seismograms observed in the Osaka basin located in western Honshu, Japan from three deep earthquakes occurring near Japan. The wave type and the secondary source area of the basin-induced waves were examined using a semblance technique and polarization analyses for small aperture array data in the center of the basin. The results well agree with the characteristics of the Love wave such as particle motion perpendicular to a propagation direction and dispersed apparent phase velocities. The arrival direction was evaluated to be almost due east. Seismograms from the east-west linear array crossing the basin show that the observed Love wave propagated from the east to the west after being excited at the eastern edge of the basin by incidence of the direct S-wave. Numerical simulations of two-dimensional SH problems were performed for the east-west cross section models of the Osaka basin subject to incidence of the direct S-wave. The synthetics agree well with the observed Love wave in a predominant frequency and a group velocity.

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Section: Introductionmentioning

confidence: 89%

Basin-Induced Love Waves in the Eastern Part of the Osaka Basin.

et al. 1995

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“…By using these separation methods of the wavefields, we can classify the surface waves secondarily excited in the basin. Therefore, the methods may be applicable to the interpretation of the secondarily excited surface waves reported by Kinoshita et al (1992).…”

Section: Discussionmentioning

confidence: 99%

“…It is well known that surface waves are excited in sedimentary basins from the analysis of earthquake records (Kinoshita et al, 1992) and numerical simulations (Bard and Bouchon, 1980 a, b). In order to estimate the surface waves, it is necessary to calculate wavefields in a two-or three-dimensional heterogeneous elastic medium.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Wavefield in a Two-Dimensional Basin Structure due to Point Source.

Fujiwara

1996

J,Phys,Earth

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Three-dimensional wavefield in a two-dimensional sedimentary basin is calculated by using the direct boundary element method and the characteristics of the wavefield are considered. The first derivatives with respect to the source coordinates of the Green's functions are calculated, which are basic functions to consider the wavefield excited from fault sources. Expressing the wavefield in the basin by the superposition of waves from the sources that are distributed on the basin-basement boundary and separating the Green's functions which express the contributions from distributed sources into the SH-wave part and the P-SV-wave part, we can separate the wavefield in the basin into the SH-wave part which consists of the SH-waves from the distributed sources on the boundary and the P-SV-wave part. In this separation, Love waves that are secondarily excited in the basin are included in the SH-wave part and Rayleigh waves excited in the basin are included in the P-SV-wave part. Furthermore, dividing the boundary into the positive part of the x-component from the observation point and the negative part, we can separate the wavefield into the part which consists of the waves whose x-component of the velocities have positive values and the part which consists of the waves whose x-component of the velocities have negative values.

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“…In the Kanto Basin, dispersing waves having a predominant period of 5 to 10 s with a large amplitude are observed clearly for shallow earthquakes occurring at the west or south-west of the basin. Kinoshita et al (1992) revealed that those waves were Love waves excited at the Hachioji tectonic line. In the Osaka Basin, a strong later phase having a predominant period of about 3 s with amplitude larger than S wave is seen in the later phases even for deep earthquakes (Hatayama et al, 1995).…”

Section: Introductionmentioning

confidence: 98%

“…The seismograms observed in a basin have been investigated to evaluate the site effects of the basin by many researchers (e.g., Tanaka et al, 1979;Minamishima et al, 1986;Frankel et al, 1991;Kinoshita et al, 1992;Yamanaka et al, 1992;Hatayama et al, 1995). These studies have revealed that secondarily generated surface waves originating from body waves or surface waves, which were propagated from epicenters have been observed in the various basins.…”

Section: Introductionmentioning

confidence: 99%

Secondarily Generated Surface Waves in the Tokachi Basin, Hokkaido, Japan.

Furumura

Sasatani

1996

J,Phys,Earth

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In order to investigate the site effects of the Tokachi Basin, we have carried out seismic observation at a rock and basin station pair. A comparison of the seismograms observed at the basin site with those at the rock site reveals that later phases having large amplitude and long duration are observed at the basin site even for deep earthquakes. The predominant period of the later phases is 2 to 5 s. We have also carried out the seismic array observations at the basin site, to investigate the propagation characteristics and wave types of these later phases. By application of the semblance and the polarization methods to the seismograms observed in the array, many Rayleigh waves having a phase velocity of about 1.3 km/s and a few pure Love waves of about 1 km/s are found in the later phases. The arrival directions of these surface waves change quickly with time and are quite different from the backazimuth to the epicenters. This suggests that the later phases observed in the basin site are mainly composed of the surface waves which are generated at the edge surrounding the Tokachi Basin. IntroductionThe seismograms observed in a basin have been investigated to evaluate the site effects of the basin by many researchers (e.g., Tanaka et al., 1979;Minamishima et al., 1986;Frankel et al., 1991;Kinoshita et al., 1992;Yamanaka et al., 1992;Hatayama et al., 1995). These studies have revealed that secondarily generated surface waves originating from body waves or surface waves, which were propagated from epicenters have been observed in the various basins. Zama's review paper (1993) shows that the secondarily generated surface waves have different characteristics in each basin. In the Kanto Basin, dispersing waves having a predominant period of 5 to 10 s with a large amplitude are observed clearly for shallow earthquakes occurring at the west or south-west of the basin. Kinoshita et al. (1992) revealed that those waves were Love waves excited at the Hachioji tectonic line. In the Osaka Basin, a strong later phase having a predominant period of about 3 s with amplitude larger than S wave is seen in the later phases even for deep earthquakes (Hatayama et al., 1995). This phase is interpreted as a Love wave generated at the eastern edge of the basin.In this study, we investigate the site effects of the Tokachi Basin, Hokkaido, Received June 2, 1995; Accepted December 28, 1995 * To whom correspondence should be addressed . Japan. The Tokachi Basin extends about 100 km in the north-south direction and about 50 km in the east-west direction, surrounded by the Hidaka Mountains, the Taisetsu Mountains and the Shiranuka Hills (Fig. 1). It is covered with terrace deposits of Pleistocene, and the maximum thickness of the sedimentary layers is about 3,000 m (Matsushima, 1990). We first compare the seismograms observed at a rock and basin station pair in and around the Tokachi Basin. We show strong excitation of later phases at the basin site for both deep and shallow events. Next, we examine the wave types and propagation characte...

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Secondary Love Waves Observed by a Strong-Motion Array in the Tokyo Lowlands, Japan.

Cited by 63 publications

References 10 publications

Basin-Induced Love Waves in the Eastern Part of the Osaka Basin.

Basin-Induced Love Waves in the Eastern Part of the Osaka Basin.

Three-Dimensional Wavefield in a Two-Dimensional Basin Structure due to Point Source.

Secondarily Generated Surface Waves in the Tokachi Basin, Hokkaido, Japan.

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