WUS and CEUS Graizer’s Ground Motion Models and Anelastic Attenuation of Response Spectral Accelerations
Description:
Ground Motion Models (GMMs) are a centerpieces of seismic hazard assessment and ShakeMaps. In the two recent GMMs: G-16v2 for the stable continental regions (SCR) (Graizer, 2017) and GK17 for the active crustal regions (ACR) (Graizer, 2018) uniform approach was used to the functional forms of the models each composed of two predictive equations (Graizer and Kalkan, 2007, 2009). The first equation predicts PGA, and the second equation constructs the spectral shape. In both GMMs I am assuming bilinear attenuation slope reflecting geometric spreading of shear and surface waves: The average transition points between body-waves R-1 and surface waves R-0.5 geometric spreading were found to be 50 km for the ACR (Graizer, 2018) and 70 km for the SCR (Graizer, 2017). In contrast to seismological Q, I introduced apparent anelastic attenuation of spectral accelerations QSA. Multiple inversions performed to estimate QSA(f) demonstrated the best fit to be ~ QSAA(f) ≈ 120 f 0.96 for the ACR for frequencies between 0.1 and 100 Hz and the best fit to be ~ QSAS(f) ≈ 186 f 0.99 for the SCR for frequencies between 0.1 and 40 Hz. Apparent attenuation was found to be magnitude dependent with QSA factor increasing with magnitude. Resulting apparent attenuations of response spectral amplitudes at rupture distances of more than 50 km for the ACR and more than 70 km for the SCR are practically linearly dependent upon frequency demonstrating significantly different behavior compared to the “seismological” Q-factor. Considering that seismological quality factor Q is usually determined using S-, Lg- or coda-waves not necessarily responsible for the SA attenuation it may not be used in GMPEs. Assuming QSA(f) ≈ QSA0 f 1 apparent anelastic attenuation becomes practically frequency independent and only dependent upon fault distance and magnitude. Regional QSA(f) different from the average one used in an ergodic model can be used in creating a partially non-ergodic GMM better reflecting area attenuation (e.g., Southern and Northern California).
Session: Site-specific Modeling of Seismic Ground Response: Are We Quantitative Enough to Predict? [Poster]
Type: Poster
Date: 4/19/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Vladimir Graizer
Student Presenter: No
Invited Presentation:
Authors
Vladimir Graizer Presenting Author Corresponding Author vladimir.graizer@nrc.gov Nuclear Regulatory Commission |
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WUS and CEUS Graizer’s Ground Motion Models and Anelastic Attenuation of Response Spectral Accelerations
Category
ShakeMap-related Research, Development, Operations, Applications and Uses