We have conducted microtremor array measurements to estimate shallow S-wave velocity (⁠VS⁠) structures at two sites (the 921 Earthquake Museum of Taiwan and the Taiwan Provincial Consultative Council) located near surface ruptures of the Chelungpu Fault. Ten stations, consisting of three different-aperture triangles and a central station, are adopted for each array deployment. Using the array data, we calculate dispersion curves of Rayleigh waves using the frequency-wavenumber spectrum method and then estimate VS structures by the surface-wave inversion technique. The obtained 2D VS profiles could clearly show compressive and flexural deformation structures with the surface ruptures located at relatively weak (low VS⁠) zones. This indicates compressive buckling as the most likely mechanism for surface rupturing along these low VS zones. Importantly, this study successfully depicts strata disturbances in a fault fracture zone using microtremor array measurements and forward numerical modeling of trishear fault-propagation folds.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.