In:
Earthquake Spectra, SAGE Publications, Vol. 34, No. 1 ( 2018-02), p. 327-347
Abstract:
The Carquinez Bridge geotechnical arrays are operated by the California Strong Motion Instrumentation Program (CSMIP) and recorded a peak ground acceleration (PGA) of approximately 1.0g at ground surface during the 2014 South Napa earthquake. The recorded PGA was significantly larger than those at the nearby surface sites. This study considers surface and downhole recordings from the additional 28 earthquakes recorded at the same arrays to understand the effects of wave propagation and site response at these arrays. Several site response analyses are performed to understand soil nonlinearity using the observed ground accelerations during the 2014 South Napa sequence. Apparent shear wave velocities are calculated from downhole records, which show clear reduction as ground motion intensity increases. Empirical transfer functions (EFTs) are also calculated in which the resonance frequencies became lower during strong shaking during the 2014 South Napa main shock. The in-situ critical damping ratio appears to be frequency dependent in the soft clay deposits. Lower damping at frequencies greater than about 5 Hz may have contributed to the observed PGA at Array #1 during the main shock.
Type of Medium:
Online Resource
ISSN:
8755-2930
,
1944-8201
DOI:
10.1193/042317EQS074M
Language:
English
Publisher:
SAGE Publications
Publication Date:
2018
detail.hit.zdb_id:
2183411-8
SSG:
16,13