Preliminary results of the analysis of site response across the San Gabriel and San Bernardino Basins using ambient-noise spectral-ratio measurements
- Anisha Tyagi (California State Polytechnic University-Pomona) | Margaret Grenier (California State Polytechnic University-Pomona) | Rachel Kreuziger (California State Polytechnic University-Pomona) | Jacob Kays (California State Polytechnic University-Pomona) | Jascha Polet (California State Polytechnic University-Pomona)
- Document ID
- Society of Exploration Geophysicists
- 2018 SEG International Exposition and Annual Meeting, 14-19 October, Anaheim, California, USA
- Publication Date
- Document Type
- Conference Paper
- 2018. Society of Exploration Geophysicists
- Noise, Passive acquisition, Spectral analysis
- 0 in the last 30 days
- 9 since 2007
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The San Gabriel and San Bernardino Basins are sedimentary basins located in southern California that are surrounded by a network of faults and comprised of soft sediments. Sedimentary basins are known to amplify earthquake ground motions and increase their duration. The San Gabriel and San Bernardino Basins are densely populated areas; therefore, it is important to determine site characteristics for seismic hazard mitigation. Furthermore, if a major rupture were to occur on the Southern San Andreas Fault, the San Gabriel and San Bernardino Basins could potentially amplify the ground motion and funnel the energy from the rupture into the Los Angeles Basin (Denolle et al., 2014), acting as a waveguide. Therefore, it is important to better characterize these basins and to understand their resonance period, amplification and site response. Three seismic profiles, containing over 200 threecomponent nodes, were installed across the San Gabriel and San Bernardino Basins in the first quarter of 2017 and collected approximately one month of continuous waveform data. We apply the Horizontal-to-Vertical Spectral Ratio (HVSR) method to the ambient noise waveform data from this experiment. The resulting spectral ratio curves show clear long period peaks (between 2 and 5 seconds) that likely correspond to basin resonance and that indicate significant variation in amplification factors and resonance frequencies across both basins. Preliminary results show these long period peaks for nodes to the South of the Raymond Fault along a profile in the Western part of the San Gabriel Basin, as well as across the central part of this basin. The peak frequencies for the Western profile suggest that the basin is relatively deeper in this area. Nodes in the Southern half of the Chino Basin indicate values for peak frequencies between those measured for the San Gabriel Basin lines. Peak amplitudes vary between 2 and 4.5, which indicates potential for significant ground motion amplification.
Presentation Date: Wednesday, October 17, 2018
Start Time: 1:50:00 PM
Location: Poster Station 14
Presentation Type: Poster
|File Size||2 MB||Number of Pages||5|
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