Multichannel Interferometric Analysis of Surface Waves (IMASW) and Refraction Microtremors for the Calculation of Vs30 in Maracay, Venezuela

Abstract

Passive source seismic methods based on line arrays are common for shear wave velocity estimation of the shallow subsurface, especially in urban environments. The present work is focused on comparing two of these methods: interferometric multichannel analysis of surface waves (IMASW) and microtremor refraction (ReMi). Both methods were applied to a seismic dataset with ambient noise sources from Maracay. Seismic interferometry was used to generate virtual source records from ambient noise measurements. A multichannel surface wave analysis was applied to these records to construct a shear wave velocity map up to 30 m depth. The results include two-dimensional profiles highlighting the velocity distribution in the first 30m depth. These results show that both methods have limitations in retrieving information at low frequencies. The IMASW method offers a viable and less ambiguous (in terms of interpretation) alternative to the ReMi method. As an alternative, this methodology has the potential to be explored in the acquisition context (different arrays, acquisition times) and also in processing. This work intends to contribute to favor of this methodology for seismic microzonation.