Narrow Results

Regional seismic loss and engineering applications generally require the simulation of spatially distributed ground motions using multiple intensity measures (IMs), which can be described by spatial correlations. In this study, a geostatistical analysis is conducted to obtain spatial correlations for peak ground acceleration and spectral acceleration using more than 2000 measured recordings from eight earthquake events that occurred in California recently. In general, the spatial correlations of IMs are higher under uniform site conditions than in areas with varying site conditions. Considering the effects of site conditions on spatial correlations, we establish a predictive equation linking spatial correlation range and $V_{s}30$ values. This facilitates the estimation of spatial correlation under varying site conditions in regions with limited observational records. Subsequently, we directly obtain the spatial correlations based on geological information. In addition, considering the high similarity of IMs within a small scale of less than 1km, the spatial correlations are replaced by lagged coherence at a small separation distance instead of IMs to describe the variation in the Fourier phase. The spatial variation in any region can be described by combining coherence and spatial correlations.

Compared with the marine structures such as sea-crossing bridges and offshore wind turbines, the marine artificial islands are bottom sitting structures and particularly sensitive to site conditions. Therefore, the study focuses on determining the effect of seabed site conditions and construction methods on the seismic performance of marine artificial islands. A seismic wave analysis model of seabed-seawater layer–artificial island coupling is developed by combining the self-programmed fluctuation analysis program and the dynamic analysis software. Firstly, the seismic response of marine artificial islands with different site conditions are analyzed by inputting P and SV waves. On that basis, the effects of incidence angles on the seismic response are explored. Then the study further explores the effects of different backfill materials and protective structures on the seismic response of the artificial island. Numerical results show that the silty soft soil layer can amplify the seismic response of seabed sites, and this amplification effect increases with the increase of the depth of silty soft soil layers. Moreover, the coral sand as backfill material can reduce the seismic response of marine artificial islands. The seismic response of marine artificial islands can also be reduced in the model with a protection structure. These results will provide some theoretical references for the site selection and construction method of marine artificial islands.

In October 1995 an earthquake with a magnitude of 7 on the Richter scale occurred in Sumatra, 450 km from Singapore. Tremors were felt by occupants of several buildings in Singapore and were recorded as an RMS acceleration value by instruments installed in a high-rise condominium. Based on this value and considering instrumental effects, site conditions and building characteristics, this paper investigates the ground motion accelerations and the building response.