Abstract
In recent years, the permanent seismic networks worldwide have largely increased, raising the amount of earthquake signals and the applications using seismic records. Although characterization of the soil properties at recording stations has a large impact on hazard estimates, it has not been implemented so far in a standardized way for reaching high-level metadata. To address this issue, we built an online questionnaire for the identification of the indicators useful for a reliable site characterization at a seismic station. We analysed the answers of a large number of experts in different fields, which allowed us to rank 24 different indicators and to identify the most relevant ones: fundamental frequency (f0), shear-wave velocity profile (VS), time-averaged Vs over 30 m (VS30), depth of seismological and engineering bedrock (Hseis_bed and Heng_bed), surface geology and soil class. Moreover, the questionnaire proposed two additional indices in terms of cost and difficulty to obtain a reliable value of each indicator, showing that the selection of the most relevant indicators results from a complex balance between physical relevancy, average cost and reliability. For each indicator we propose a summary report, provided as editable pdf, containing the background information of data acquisition and processing details, with the aim to homogenize site metadata information at European level and to define the quality of the site characterization (see companion paper Di Giulio et al. 2021). The selected indicators and the summary reports have been shared within European and worldwide scientific community and discussed in a dedicated international workshop. They represent a first attempt to reach a homogeneous set of high-level metadata for site characterization.
Highlights
Mechanical properties and morphological setting of the ground are a key element in modifying locally the seismic ground motion in terms of amplitude, duration and frequency content, commonly known as site effects
Recordings from seismic stations can be significantly affected by the variation of site conditions close and below the station, influencing the studies based on earthquake ground motions collected by regional or local seismological networks
Amongst the remaining 13%, the respondents suggested additional and more advanced indicators, such as the dependence of the site response to the earthquake location, the lateral variability of geological formations (2D-3D behavior), the soil-structure interaction, the duration lengthening and the geometrical parameter. These last two indicators were initially included in the Questionnaire but were not accounted for in the analysis described in this paper, because there were few answers available
Summary
Mechanical properties and morphological setting of the ground are a key element in modifying locally the seismic ground motion in terms of amplitude, duration and frequency content, commonly known as site effects. To facilitate practical engineering design, site conditions are often characterized by a small number of site attributes (or proxies) or their combinations, aimed at describing their effects on seismic ground motion (Trifunac 2016; Bergamo et al 2021). The number of stations of permanent and temporary seismic networks worldwide has largely increased (Margheriti et al 2011; Mazza et al 2012; Michelini et al 2016; Moretti et al 2016; Hetényi et al 2018; Cara et al 2019; Chen et al 2019), rising the amount of recorded data (McNamara and Buland 2004; Pintore et al 2012; Lanzano et al 2019), without paying much attention on site characterization information
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