ONE-DIMENSIONAL NONLINEAR SEISMIC RESPONSE ANALYSIS FOR SEABED SITE EFFECT ASSESSMENT IN THE QIONGZHOU STRAIT

Building a sea-crossing projects constructed on the deep soft marine deposits subjected to might strong earthquakes and ensuring its seismic safety is a major engineering challenge. The typical four borehole profiles along the subsea tunnel crossing under the Qiongzhou Strait were selected to analyze the one-dimensional nonlinear site response. In the site response analysis, regional seismicity and bedrock motion characteristics, the engineering geology characteristics, and the DCZ and MKZ constitutive models for characterizing nonlinear hysteretic behavior of soil are considered in detail. The results imply that the DCZ model provides better ability to propagate the propagation of some high frequencies and medium-long period components through seabed deposits than the MKZ model. The significant amplification of seismic wave components ranging 0.6 Hz~1.1 Hz within the soils of 35 m and 80 m~160 m below the seabed surface are observed. For bedrock motion levels of 0.2 g, the calculated peak ground acceleration at the seabed surface is 0.297 g, corresponding to seismic intensity Ⅷ level, which is consistent with historical maximum earthquake effect intensity. The cumulative absolute velocity (CAV) is a more suitable proxy to characterize ground motion intensity measure according to the calculated characteristics of seabed site effects. The spectral accelerations given in the "Seismic ground motion parameters zonation map of China" at the periods from 0.05 s~0.5 s exist adverse consequences for seismic design of sea-crossing projects.