Spatial variation and stochastic modelling of seismic differential ground movement

Abstract

SUMMARYSpecially designed arrays of strong motion seismographs located near earthquake sources are required for engineering studies of near-source earthquake properties as well as spatial variation of seismic waves. The SMART-I array in Taiwan provides good records for this type of study. Based on the SMART-1 array data, the analysis of the principal direction of wave propagation and the space-time correlation of some events recorded by SMART-I have been studied. A stochastic model for predicting the differential ground movement was also developed. This stochastic model includes the effect of source characteristics, attenuation of wave passage and spatial correlation characteristics. The performance of this model is discussed and compared with the ground movement recorded by the SMART-1 array. From the present study, it is found that spatial correlations d o exist as seismic waves propagate across the array site. Generally, the loss of coherence in the direction ofpropagation can be explained by energy at the same frequency exhibiting a slightly different velocity within the measurement intervals. It is also concluded that the phase velocity of seismic waves and the corner frequency of the ground displacement spectrum are controlling factors in the prediction of the root mean square of differential ground displacement.

Simulation of Ground Motion Using the Stochastic Method

“…It can be determined from ground deformation or from seismic waves. Table 1 Some references on methodology ATKINSON (1997, 1998a), BOORE (1983BOORE ( , 1984BOORE ( , 1989bBOORE ( , 1996BOORE ( , 2000, BOORE and JOYNER (1984), CAMPBELL (1999), CARTWRIGHT andLONGUET-HIGGINS (1956), CORREIG (1996), ERDIK and DURUKAL (2001), GHOSH (1992), HANKS and MCGUIRE (1981), HERRMANN (1985), JOYNER (1984JOYNER ( , 1995, JOYNER and BOORE (1988), KAMAE and IRIKURA (1992), KAMAE et al (1998), KOYAMA (1997), LAM et al (2000), LIAO and JIN (1995), PEZESHK (1998, 1999), LOH and YEH (1988), MILES and HO (1999), Ó LAFSSON and SIGBJO¨RNSSON (1999), HERRMANN (1990a, 1990b), PAPAGEORGIOU and AKI (1983a), PEZESHK et al (2001), RATHJE et al (1998), SABETTA andIt can be estimated from paleoseismological studies. It can be related to slip rates on faults.…”

“…are not captured by the simulated motions. It should be possible to include some of these effects in the method, and I am aware of some efforts along these lines (e.g., LOH, 1985;LOH and YEH, 1988;TAMURA et al, 1991;TAMURA and AIZAWA, 1992).…”

Inelastic dynamic analysis of RC bridges accounting for spatial variability of ground motion, site effects and soil–structure interaction phenomena. Part 1: Methodology and analytical tools

“…For the case of two points at a separation distance equal to 70 m and a uniform soil proÿle, the target frequency content of the Kalamata, Greece, 1986 earthquake and the Loh and Yeh [24] coherency model, a very good agreement is achieved in terms of the target response spectra. Figure 3 illustrates that even for the ÿrst cycle of analysis the matching is acceptable, while it can be further improved by the iterative optimization procedure described previously.…”

“…the smoothed cross-spectrum of motions between two points normalized to the corresponding power spectra, should then be selected among the coherency loss models available in the literature (i.e. References [22][23][24]). …”

Simplified method for simulation of ergodic spatially correlated seismic ground motion

“…Several models for the incoherency coefficient function have been proposed based on the analysis of the strong motion date from the strong motion array, such as the Loh and Lin model [34] , the Harichandran and Vanmarcke model [35] , the Feng and Hu model [36] , the Loh and Yeh model [37] , and the Hao model [2] . Many of the above proposed models are the exponential function of distance.…”