Nonlinear site response evidence of K-NET and KiK-net records from the 2011 off the Pacific coast of Tohoku Earthquake
2011; Springer Nature; Volume: 63; Issue: 7 Linguagem: Inglês
10.5047/eps.2011.06.012
ISSN1880-5981
AutoresLuis Fabián Bonilla, Kenichi Tsuda, Nelson Pulido, Julie Régnier, Aurore Laurendeau,
Tópico(s)Seismology and Earthquake Studies
ResumoWe analyzed the acceleration time histories recorded by the K-NET and KiK-net stations of the Mw 9 Tohoku Earthquake in order to investigate site response issues related to near-source effects. Time-frequency analysis of K-NET stations in the Miyagi prefecture, closest to the rupture area, show that sites having a Vs30 < 400 m/s present a combination of deamplification at frequencies higher than 5 to 10 Hz and cyclic mobility (high acceleration peaks riding over a low frequency carrier). This suggests strong nonlinear site response at these stations. Furthermore, using KiK-net data we are able to compute borehole transfer functions from the mainshock and events having small PGA values from the local dataset. The ratio between weak-motion and strong-motion borehole transfer functions constitutes an indicator of nonlinear site response. This ratio reveals strong dependence on Vs30 and shows that widespread nonlinear behavior took place during this large earthquake.
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