Abstract:
We used the records of 82 near-field strong motion stations (KiK-net), which are within 200 km to the rupture fault of the Kumamoto
MW7.0 earthquake, as database to derive near-field horizontal peak ground acceleration PGA, peak ground velocity PGV and spectra acceleration (period
T=0.2, 1, 2, 3, 5, 10 s), after baseline correction we further compared them with the NGA-West2 ground motion model predictions. We investigated the attenuation and residuals distribution characteristics of these intensity measures (IMs), and shallow site-amplification effects by comparing surface and borehole ground motion records. The following conclusions can be drawn from our study: In the boreholes, NGA-West2 predictions are obviously greater than observations of PGA and
T=0.2 s spectra acceleration, but close to the measured value in long-period IMs (spectra acceleration with
T=1, 2, 3 s) and PGV. On surface, the residuals of observed PGV and
T=0.2–3 s spectra acceleration show linear decrease tendency with the increase of
vS30, but the site effects affect little on the long-period spectra acce-leration. Surface records are greater than borehole in PGA, PGV and
T=0.2, 1, 2 s spectra acceleration, and the amplification effects decrease with the increase of shallow site shear velocity; whereas the site amplification has little effects on the long-period spectra acceleration with
T=3, 5, 10 s.