Estimation Of Rayleigh Wave Dispersion Curves And Evaluating Array Configuration By F-K Spectrum

Local site condition, especially soil condition of the site, has a great effect on strong ground motion and the earthquake damage. Each soil dynamics parameters can be expressed by wave velocity, density, and ratio of damping. Generally,soil density and ratio of damping vary very little,then wave velocity,especaily shear-wave velocity is the principal parameter of soil. In order to get site shear-wave velocity structure, we can configurate some microtremors observation arrays on the site we need to study and analyse the observation records in order to get Rayleigh wave dispersive curve, then inverse the site shear-wave velocity structure.In this paper, two key problems of getting Rayleigh wave dispersive curve based on microtremors array records are investigated.First, method to analyse observation records of microtremors arrays. When array configuration shapes are different, methods to analyse their observation records are different too, spatial auto-correlation method and frequency- wavenumber method are popular analysis methods now in the whole world. In this paper, the principle of frequency-wavenumber method was generalized in detail, comparison between spatial auto-correlation method and frequency-wavenumber method were made, the program to calculate frequency-wavenumber spectrum was established. During the scheme of"Microtremors observation analysis on engineering site condition", supervisor of this paper's author cooperated with Professor Seo who comed from Tokyo Industry University in Japan, and got observation records in high quality in Hai jing yuan and Gold town arrays of XiMen city. Doctor Yamanaka analysed those records by frequency-wavenumber method, and got Rayleigh wave dispersive curves. Rayleigh wave dispersive curves of the two sites in XiMen city were estimated in this paper, and the result were compared with Doctor Yamanaka. Result proved that the program is reliable, and the reasons why those curves were difference were analysed.Second, array configuration. According to the real fact, what kind of array shape to configurate is reasonable? How many survey points should be configurated at least for the array? In this paper, maximum likelihood method was used to study arrays with different shape and survey points in simulating sinusoidal wave field, which including circle array with a fixed radius, array on circles, array on a cross, hybrid array, array on rhombuses and so on. By judging whether the wavenumber vector correspond with the frequency-wave power spectrum's extremum is stabilization or not, it can be known that the array configuration is reasonable or not and supply rules for reasonable array configuration scheme. At the same time, simulation wave field from seven directions demonstrated that the rectangle array with six survey points which configurated along Huilongguan to Heying station of Beijing's 13th sub-railway has enough observation ability.