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TitleThe 2018 COSMOS blind trials - an assessment of Vs profiles obtained from phased microtremor observations
AuthorAsten, M W; Yong, A; Foti, S; Hayashi, K; Martin, A J; Stephenson, W J; Cassidy, J FORCID logo; Coleman, J; Nigbor, R; Castellaro, S; Chimoto, K; Cho, I; Cornou, C; Hayashida, T; Hobiger, M; Kuo, C -H; Macau, A; Mercerat, E D; Molnar, S; Pananont, P; Pilz, M; Poovarodom, N; Sáez, E; Wathelet, M; Yamanaka, H; Yokoi, T; Zhao, D
Source17WCEE: 17th World Conference on Earthquake Engineering, proceedings; 2021 p. 1
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20210216
PublisherInternational Association for Earthquake Engineering
Meeting17WCEE: 17th World Conference on Earthquake Engineering; Sendai; JP; September 27 - October 2, 2021
DocumentWeb site
Mediadigital; on-line
File formatpdf
Subjectsgeophysics; surficial geology/geomorphology; Science and Technology; Nature and Environment; Health and Safety; seismology; earthquake studies; earthquake mechanisms; earthquake risk; seismicity; seismic risk; seismic data; seismic waves; s waves; seismic methods; earthquake damage; array seismology; Consortium of Organizations for Strong Motion Observation Systems (COSMOS); Methodology; Data processing
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2021 12 01
AbstractSite response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site conditions of the local geology. Thus, a number of geophysical site characterization methods were developed to meet the demand for accurate and cost-effective results. As a consequence, a number of studies have been proposed over the past decade as blind trials to evaluate the state-of-practice on site characterization. We present results from the Consortium of Organizations for Strong Motion Observation Systems (COSMOS) blind trials, which used data recorded from surface-based microtremor array methods (MAM) at four sites where geomorphic conditions vary from deep alluvial valleys to an alpine valley.
Thirty-four invited analysts participated. Data were incrementally released to 17 available analysts who participated in all four phases: (1) two-station arrays; (2) sparse triangular arrays; (3) complex nested triangular or circular arrays; (4) all available geological control site information including drill-hole data. Another set of 17 analysts provided results from two sites and two phases only. Although data from one site consisted of recordings from three-component sensors, the other three sites consisted of data recorded only by vertical-component sensors. The sites cover a range of noise source distributions, ranging from one site with a highly directional microtremor wave field, to others with omni-directional (azimuthally-distributed) wave fields.
We review results from different processing techniques (e.g., beam-forming, spatial autocorrelation, cross-correlation, or seismic interferometry) applied by the analysts and compare the effectiveness between the differing wave-field distributions. We use a quality index based on estimates of the time-averaged shear-wave velocity of the upper 10 (Vs10), 30 (Vs30), 100 (Vs100), and 300 (Vs300) meters. Our findings are expected to aid in building an evidence-based consensus on preferred cost-effective arrays and processing methodology for future studies of seismic site effects.
Summary(Plain Language Summary, not published)
This invited contribution reviews the 'blind-test' results where many groups from around the world use common seismic datasets (for a wide variety of geological settings) and common processing techniques to determine the shear-wave velocity at the test sites. We then compare the results from different groups to see if the results are similar, or what is common (or different), in an effort to determine best data collection and processing practises for determining earthquake site response. The results of the study will aid in building an evidence-based consensus on preferred cost-effective arrays and processing methodology for future site-effect studies for direct application to earthquake hazard studies.

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