Ambient Noise and Site Response: From Estimation of Site Effects to Determination of the Subsoil Structure

摘要

Damage distribution during large earthquakes is frequently conditionedby site effects. Site effect are best determined using earthquake data. However, thatdata is not always available and ambient noise measurements have been used asan inexpensive alternative. Microtremor measurements have been used along twopaths to study site effects: estimation of a local transfer function, and estimation ofthe subsoil structure (once this structure is known, it is possible to compute expectedground motion amplification). Currently, the estimation of a transfer function usesH/V spectral ratios almost exclusively. Estimation of the subsoil structure exploitsdata from array measurements of microtremors applying techniques such as SPAC,ReMi and time domain analysis of cross-correlation. This paper discusses those twopaths and shows the results that were obtained in two dissimilar examples: Parkwaybasin and Colima city. It is shown that results need to be validated; it is unsafe touse a single technique. In addition, it is clear that no single technique is adapted toall possible cases.