ORCID Profile
0000-0002-9242-3996
Current Organisations
University of Potsdam
,
Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
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Publisher: Seismological Society of America (SSA)
Date: 22-12-2023
DOI: 10.1785/0120220155
Abstract: A key component in seismic hazard assessment is the determination of time histories for hard-rock site conditions, either as input motion for site response computations or for applications to installations built on this site type. The state of the practice is to apply physics-based corrections for removing site effects from surface recordings to obtain the underlying bedrock motion. Here, we propose and test the use of the generalized inversion technique (GIT) for deconvolving surface recordings to hard-rock time series at the lification-free seismic bedrock. As part of the proposed procedure, an event-specific phase scaling method is presented, which allows changes in signal duration to be considered. For validation purposes, we select a total of 90 Kiban–Kyoshin network (KiK-net) surface-downhole sites having no significant velocity contrasts below their downhole sensors and with the latter being located at sufficient depth so that they are not impaired significantly by downgoing waves. We evaluate the effectiveness of the empirical predictions by comparison with recorded time series at the downhole sensors. We find quite high correlations and small variations in both spectral shape and litude over the entire frequency range for the GIT deconvolution at the majority of the 90 KiK-net sites with all mean residuals less than 0.25 in contrast to empirical and 1D modeling approaches, which significantly overestimate the level of hard-rock ground motion for frequencies larger than a few Hertz.
Publisher: Seismological Society of America (SSA)
Date: 24-09-2019
DOI: 10.1785/0120190016
Abstract: In the Next Generation Attenuation West2 (NGA‐West2) project, a 3D subsurface structure model (Japan Seismic Hazard Information Station [J‐SHIS]) was queried to establish depths to 1.0 and 2.5 km/s velocity isosurfaces for sites without depth measurement in Japan. In this article, we evaluate the depth parameters in the J‐SHIS velocity model by comparing them with their corresponding site‐specific depth measurements derived from selected KiK‐net velocity profiles. The comparison indicates that the J‐SHIS model underestimates site depths at shallow sites and overestimates depths at deep sites. Similar issues were also identified in the southern California basin model. Our results also show that these underestimations and overestimations have a potentially significant impact on ground‐motion prediction using NGA‐West2 ground‐motion models (GMMs). Site resonant period may be considered as an alternative to depth parameter in the site term of a GMM.
Publisher: Seismological Society of America (SSA)
Date: 03-03-2020
DOI: 10.1785/0120190186
Abstract: In this investigation, we examine the uncertainties using the horizontal-to-vertical spectral ratio (HVSR) technique on earthquake recordings to detect site resonant frequencies at 207 KiK-net sites. Our results show that the scenario dependence of response (pseudospectral acceleration) spectral ratio could bias the estimates of resonant frequencies for sites having multiple significant peaks with comparable litudes. Thus, the Fourier litude spectrum (FAS) should be preferred in computing HVSR. For more than 80% of the investigated sites, the first peak (in the frequency domain) on the average HVSR curve over multiple sites coincides with the highest peak. However, for sites with multiple peaks, the highest peak frequency (fp) is less susceptible to the selection criteria of significant peaks and the extent of smoothing to spectrum than the first peak frequency (f0). Meanwhile, in comparison to the surface-to-borehole spectral ratio, f0 tends to underestimate the predominant frequency (at which the largest lification occurs) more than fp. In addition, in terms of characterizing linear site response, fp shows a better overall performance than f0. Based on these findings, we thus recommend that seismic network operators provide fp on the average HVSRFAS curve as a priority, ideally together with the average HVSRFAS curve in site characterization.
Publisher: Springer Science and Business Media LLC
Date: 14-07-2015
Publisher: Springer Science and Business Media LLC
Date: 17-10-2020
Location: Germany
No related grants have been discovered for Fabrice Cotton.