SEGJ Technical Conference

Beyond the SPAC Method - Exploiting the Wealth of Alternative Circular-Array Methods for Microtremor Exploration

Abstract We have developed, along the extension of the popularly used spatial autocorrelation method, a number of new, alternative methods of microtremor exploration, which enable one to infer phase velocities of Rayleigh waves on the basis of vertical-component seismograms from a circular array of sensors. We illustrate four such methods here, which we tentatively call the CCA, H0, H1 and V methods respectively. Implementation to field records shows that these different methods have considerably different wavelength ranges of good resolution. The CCA and V methods, among others, produce reasonable estimates of phase velocities over a remarkably broad range of wavelengths, the upper limit extending as far up as several ten times the seismic-array radius. The maximum resolvable wavelength of the CCA method can further be prolonged by the use of a noise-compensation technique.