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Ambient noise cross‐correlation observations of fundamental and higher‐mode Rayleigh wave propagation governed by basement resonance
Author(s) -
Savage Martha K.,
Lin FanChi,
Townend John
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50678
Subject(s) - rayleigh wave , geology , resonance (particle physics) , rayleigh scattering , seismic noise , seismology , amplitude , love wave , ambient noise level , basement , mode (computer interface) , cross correlation , physics , surface wave , wave propagation , longitudinal wave , optics , geomorphology , mechanical wave , atomic physics , sound (geography) , mathematical analysis , civil engineering , mathematics , engineering , computer science , operating system
Measurement of basement seismic resonance frequencies can elucidate shallow velocity structure, an important factor in earthquake hazard estimation. Ambient noise cross correlation, which is well‐suited to studying shallow earth structure, is commonly used to analyze fundamental‐mode Rayleigh waves and, increasingly, Love waves. Here we show via multicomponent ambient noise cross correlation that the basement resonance frequency in the Canterbury region of New Zealand can be straightforwardly determined based on the horizontal to vertical amplitude ratio (H/V ratio) of the first higher‐mode Rayleigh waves. At periods of 1–3 s, the first higher‐mode is evident on the radial‐radial cross‐correlation functions but almost absent in the vertical‐vertical cross‐correlation functions, implying longitudinal motion and a high H/V ratio. A one‐dimensional regional velocity model incorporating a ~ 1.5 km‐thick sedimentary layer fits both the observed H/V ratio and Rayleigh wave group velocity. Similar analysis may enable resonance characteristics of other sedimentary basins to be determined.