ABSTRACTWe 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.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology