Three‐dimensional V_S profiling using microtremors in Kushiro, Japan

Abstract

SUMMARYA practical method is presented for determining three-dimensional S-wave velocity (V S ) profile from microtremor measurements. Frequency-wave number ( f -k) spectral analyses of microtremor array records are combined, for this purpose, with microtremor horizontal-to-vertical (H/V ) spectral ratio techniques. To demonstrate the effectiveness of the proposed method, microtremor measurements using arrays of sensors were conducted at six sites in the city of Kushiro, Japan. The spectral analyses of the array records yield dispersion characteristics of Rayleigh waves and H/V spectra of surface waves, and joint inversion of these data results in V S profiles down to bedrock at the sites. Conventional microtremor measurements were performed at 230 stations within Kushiro city, resulting in the H/V spectra within the city. Three-dimensional V S structure is then estimated from inversion of the H/V spectra with the V S values determined from the microtremor array data. This reveals three-dimensional V S profile of Kushiro city, together with an unknown hidden valley that crosses the central part of the city. The estimated V S profile is consistent with available velocity logs and results of subsequent borings, indicating the effectiveness of the proposed method.

Planned Products of the Mars Structure Service for the InSight Mission to Mars

“…Accordingly, borehole information (e.g. Arai and Tokimatsu 2008) or surface wave dispersion (e.g. Dal Moro 2015) are often used as additional constraints.…”

Love wave contribution to the ambient vibration H/V amplitude peak observed with array measurements

“…This is even the case for studies where array data were actually available (e.g. Satoh et al, 2001;Arai and Tokimatsu, 2008) and not only single station H/V measurements.…”

“…Several studies have since applied this kind of joint inversion (e.g. Arai and Tokimatsu, 2005;Nagashima and Maeda, 2005;Parolai et al, 2005;Garcia-Jerez et al, 2007;Picozzi and Albarello, 2007;Arai and Tokimatsu, 2008;D'Amico et al, 2008). Others use additional data, for example from borehole or array measurements, to fix either the sediment thickness (e.g.…”

“…or the velocities of the sediment layers (e.g. Yamanaka et al, 1994;Satoh et al, 2001;Arai and Tokimatsu, 2008) and only invert for the respective complementary parameters. Arai and Tokimatsu (2004) conclude, after testing both of these options, that they lead to similar results.…”

Rayleigh Wave Ellipticity Modeling and Inversion for Shallow Structure at the Proposed InSight Landing Site in Elysium Planitia, Mars

“…Better results have been obtained when combining ellipticity curves with other information, e.g. stratigraphic layering (Mundepi et al 2015) or sediment velocities (Yamanaka et al 1994;Satoh et al 2001;Arai and Tokimatsu 2008) from borehole logging, or surface wave dispersion measured actively or passively with surface arrays Tokimatsu 2005, 2008;García-Jerez et al 2007;Picozzi and Albarello 2007;Hobiger et al 2013;Dal Moro 2015). In the later case, the inclusion of ellipticity information can significantly improve estimates of bedrock depth (Garofalo et al 2016;Gouveia et al 2016) and velocity .…”