Seismic Response of Soft Soil Deposit Using Simplified Models

Abstract

Near surface soils can greatly influence the amplitude, duration, and frequency content of ground motions. Surveys of the damage caused by earthquakes indicates that the lowest levels of damage occur in structures founded on rock or hard soil, while most of the damage occurs usually in structures founded in soft soil sites. With the aim to understand better the seismic response of soft soils deposits, not susceptible to liquefaction, this study made a comparison between the real seismic response registered in soft soil deposit in the 2011 Tohoku earthquake (Mw=9.1), with the response predicted by a propagation analysis with the equivalent linear method using the computer program SHAKE2000 [1]. An additional comparison is made applying the simplified method of Carlton (2014), developed specifically for soft soils. The site chosen for this analysis was a soft soil deposit, with NEHRP site classification type F, monitored by the seismic station TKCH07 of the KiK-net network located in Hokaiddo, Japan. The estimated response showed and acceptable approximation with the real response, although the response calculated with SHAKE2000 predicted high levels of amplification near the natural frequencies of the soft soil deposit.