Elastic scattering dominates high-frequency seismic attenuation in Southern California

Lin, Yu‐Pin; Jordan, Thomas H.

doi:10.1016/j.epsl.2023.118227

Cited by 4 publications

(2 citation statements)

References 43 publications

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“…Model #7 includes a more accurate subsurface fault geometry (also see Text S1) derived from the Salton Seismic Imaging Project (Fuis et al, 2017). Finally, in Model #8, we superimposed a statistical distribution of velocity and density heterogeneities (SSHs) by Lin and Jordan (2023) to include the effects of unresolved velocity structure at shorter wavelengths (Text S4 provides additional details).…”

Section: Numerical Methods and Velocity Modelsmentioning

confidence: 99%

Waveguide or not? Revised ground motion simulations for greater Los Angeles from the M7.8 ShakeOut earthquake scenario

Yeh,

Olsen

2024

Preprint

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The ShakeOut scenario of a M7.8 northwestward rupture on the southern San Andreas fault (SSAF) (Jones et al., 2008) predicted significant long-period ground motion amplification in the greater Los Angeles, CA, area, caused by a waveguide from interconnected sedimentary basins. However, the early ShakeOut ground motion simulations omitted important model features with immature versions of the velocity structure and fault geometry. Here, we present 0-1 Hz 3D numerical wave propagation simulations for the ShakeOut scenario including surface topography, as well as updated high-resolution velocity structure and SSAF fault geometry. Spectral Accelerations at 3s are increased by the local high-resolution basin models (25-45%) but decreased from complexity in velocity and density updates outside the basins (65-100%) and inclusion of surface topography (~30%). The updated model reduces peak ground velocities in the waveguide from ~250 cm/s to ~100 cm/s, significantly closer to the values predicted by a leading NGA-West2 ground motion model.

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Section: Numerical Methods and Velocity Modelsmentioning

confidence: 99%

Waveguide or not? Revised ground motion simulations for greater Los Angeles from the M7.8 ShakeOut earthquake scenario

Yeh,

Olsen

2024

Preprint

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“…Additionally, the limitations of the spectra fitting approaches in accurately capturing frequency-dependent patterns of seismic attenuation stem from the simple seismic response function 20 used to describe the shape of the spectra. Recently, alternative methods have been developed to overcome the limitations and accurately estimate the frequency-dependent attenuation structures in Southern California 21,22 .Commencing in 2017, the deployment of the Formosa Array (FMarray) in northern Taiwan sought to better understand the geometry of the magma chamber beneath the Tatun volcanic region.…”

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confidence: 99%

Unveiling attenuation structures in the northern Taiwan volcanic zone

Lin,

Ko,

Huang

et al. 2024

Sci Rep

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This cutting-edge study delves into regional magmatism in northern Taiwan through advanced 3-D P- and S-wave frequency-dependent attenuation tomography. Positioned at the dynamic convergence boundary between the Philippine Sea Plate and the Eurasian Plate, Taiwan experiences moderate earthquakes and intriguing volcanic activity, with a focus on the Tatun volcano group. Employing the Formosa seismic array for high-resolution results, our research identifies high-attenuation anomalies (low Q) beneath the northern Taiwan volcanic zone (NTVZ) and offshore submarine volcanoes, indicative of potential hydrothermal activities and magma reservoirs at varying depths. Additionally, we explore low-attenuation anomalies (high Q) in the forearc region of the Ryukyu subduction zone, suggestive of partial saturation linked to serpentinization processes resulting from seawater infiltration or forearc mantle hydration. These findings shed light on the complex geological features and provide essential insights into the crustal properties of northern Taiwan, contributing to a deeper understanding of its magmatic evolution and tectonic processes.

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Evidence for faulting and fluid-driven earthquake processes from seismic attenuation variations beneath metropolitan Los Angeles

Nardoni,

Persaud

2024

Sci Rep

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Seismicity in the Los Angeles metropolitan area has been primarily attributed to the regional stress loading. Below the urban areas, earthquake sequences have occurred over time showing migration off the faults and providing evidence that secondary processes may be involved in their evolution. Combining high-frequency seismic attenuation with other geophysical observations is a powerful tool for understanding which Earth properties distinguish regions with ongoing seismicity. We develop the first high-resolution 3D seismic attenuation models across the region east of downtown Los Angeles using 5,600 three-component seismograms from local earthquakes recorded by a dense seismic array. We present frequency-dependent peak delay and coda-attenuation tomography as proxies for seismic scattering and absorption, respectively. The scattering models show high sensitivity to the seismicity along some of the major faults, such as the Cucamonga fault and the San Jacinto fault zone, while a channel of low scattering in the basement extends from near the San Andreas fault westward. In the vicinity of the Fontana seismic sequence, high absorption, low scattering, and seismicity migration across a fault network suggest fluid-driven processes. Our attenuation and fault network imaging characterize near-fault zones and rock-fluid properties beneath the study area for future improvements in seismic hazard evaluation.

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Elastic scattering dominates high-frequency seismic attenuation in Southern California

Cited by 4 publications

References 43 publications

Waveguide or not? Revised ground motion simulations for greater Los Angeles from the M7.8 ShakeOut earthquake scenario

Waveguide or not? Revised ground motion simulations for greater Los Angeles from the M7.8 ShakeOut earthquake scenario

Unveiling attenuation structures in the northern Taiwan volcanic zone

Evidence for faulting and fluid-driven earthquake processes from seismic attenuation variations beneath metropolitan Los Angeles

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