Frequency-dependent horizontal-to-vertical (H/V) spectral ratios (HVSR) can provide information on one or more site resonant frequencies and relative levels of amplification at those frequencies. Such information is useful for predicting site amplification but is not present in site databases that have been developed over the last 15–20 years for the Next- Generation Attenuation (NGA) projects, which instead use the time-averaged shear-wave velocity (VS) in the upper 30 m of the site (VS30) as the primary site parameter and are supplemented with basin depth terms where available. In order for H/V-based parameters to be used in future versions of site databases, a publicly accessible repository of this information is needed. We adapt a relational database developed to archive and disseminate VS data to also include H/V spectra. Our intent with the database is to provide relevant H/V data and supporting metadata, but not parameters derived from the data. We consider the relevant data to be the frequency-dependent HVSR, where the horizontal component is taken from the geometric mean of as-recorded azimuths. Relevant metadata includes site location information, details about the equipment used to make the measurements, and processing details related to windowing, anti-trigger routines, and filtering. We describe the database schema developed to organize and present this information. We also describe and illustrate routines that can be used to derive parameters from the data that are implemented in Python on a Jupyter Notebook enabled by DesignSafe-CI. These routines compute H/V spectral ratios based on the median horizontal component, and polar plots that present azimuthal dependence of spectra. For median-component spectra, additional routines fit pulse functions that provide frequency, amplitude, and pulse width parameters. These routines interact with the database via cloud computing, but are not directly part of the database.
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|Titolo:||Supplementing shear wave velocity profile database with microtremor-based H/V spectral ratios|
|Data di pubblicazione:||2020|
|Appare nelle tipologie:||4.1 Contributo in Atti di convegno|