Abstract
Shallow S-wave velocity V S profiles were estimated for 26 temporary strong motion observation sites surrounding the epicenters of a sequence of the 2016 Kumamoto earthquake. The microtremor array method was used to gather the dispersion characteristics of Rayleigh waves. V S profiles were obtained by inverting the dispersion curves for each site and those of three permanent strong motion stations that recorded the sequence of seismic events. The shallow V S profiles near two of the permanent strong motion stations in the town of Mashiki were almost identical. However, the V S profiles at other stations varied. The V S profiles were found to have the common feature of the uppermost low-velocity layer being widely distributed from Mashiki to the village of Minami-Aso, and it was especially thick in the areas that suffered heavy damage. This low-velocity layer was a major contributor to the site amplification. The horizontal-to-vertical spectral ratios of the microtremors indicate that both the shallow soil and deep sedimentary layers may control the site response characteristics over a broad frequency range.
Highlights
This study focuses on the measurement of the S-wave velocity VS of near-surface materials at temporary strong motion stations of the 2016 Kumamoto earthquake by Yamanaka et al (2016)
In any type of geomorphology, the values of AVS30 evaluated from microtremors in the present study showed values similar to those obtained by Japan Seismic Hazard Information Station (J-SHIS) at most of the sites
This effect must be removed in future studies of the site effects if MK06 is used as a reference
Summary
This study focuses on the measurement of the S-wave velocity VS of near-surface materials at temporary strong motion stations of the 2016 Kumamoto earthquake by Yamanaka et al (2016). The dispersion curve at AS03 has one feature similar to those obtained at the sites experiencing heavy damage in Mashiki (Fig. 2b): It showed a constant velocity of 100 m/s at frequencies above 10 Hz and significant dispersion below 10 Hz. In the central part of Kumamoto, a non-dispersive trend was observed above 4 and 6 Hz at KC03 and KC04, respectively, with a velocity of approximately 150 m/s (Fig. 2e). In any type of geomorphology, the values of AVS30 evaluated from microtremors in the present study showed values similar to those obtained by J-SHIS at most of the sites
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
