- © 2014 by the Seismological Society of America
Online Material: Earthquake catalogs; color figures from article.
Structural estimation of unconsolidated sediments and basins is of fundamental importance for resources exploration, geohazard assessments, and other geophysical aspects. The estimation contributes not only to the understanding of the tectonic settings, but also to the choice of parameters for possible further seismic processing, for example, predictive deconvolution, the result of which could be used for imaging the subsurface structures below the basin.
Within a number of conventional passive‐seismic methodologies, the Nakamura technique (Nakamura, 1989), initially proposed for the purpose of eliminating the effect of Rayleigh waves from noise records, is widely applied. This technique can be used to estimate the resonance frequencies of the subsurface of a region of interest by taking the amplitude spectral ratio between the horizontal and vertical components (H/V) of ambient‐noise records. In addition to the investigation of local site effects, if the velocity model is known, this resonance frequency can also be interpreted as the thickness of the geophysical and/or geologic layer, characterized by relatively high‐impedance contrasts on either side (Tsai, 1970). The top boundary of this layer is often the Earth’s surface, whereas the lower boundary could be the interface between basement and basin. The H/V spectral ratio has been applied to estimate the depth of sedimentary boundaries and basins (e.g., Delgado et al., 2002; De Luca et al., 2005; Lane et al., 2008; Bindi et al., 2009; Ruigrok, Campman, et al., 2012).
The H/V spectral ratio has been widely applied with ambient noise (e.g., Ohmachi et al., 1991; Field and Jacob, 1993; Lermo and Chavez Garcia, 1993), as well as with arrivals from earthquake records (e.g., Lermo and Chavez Garcia, 1993; Field and Jacob, 1995; Ferretti et al., 2007; Grecu et al., 2011; …