Lateral Variations Across the Southern San Andreas Fault Zone Revealed From Analysis of Traffic Signals at a Dense Seismic Array

Zhang, Hao; Meng, Haoran; Ben‐Zion, Yehuda

doi:10.1029/2023gl103759

Cited by 3 publications

(2 citation statements)

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“…The first uses ballistic waves generated by seismic sources such as earthquakes, explosions, and traffic events. These ballistic waves provide key data including arrival times, dispersion properties, and amplitude decay as a function of space and time for both body and surface waves (e.g., Dziewonski & Anderson, 1981; Nolet, 1977; Taner et al., 1979; Zhang et al., 2023). Modeling these measurements provides important insights into properties of the Earth interior, including velocity and attenuation structures.…”

Section: Introductionmentioning

confidence: 99%

“…This implies that a fully diffuse wavefield is stationary and lacks correlations across different frequencies. Such requirements are difficult to satisfy in natural environments with non‐random distribution of sources that typically include tectonic, environmental, and anthropogenic sources that are concentrated at specific locations (e.g., Díaz et al., 2017, 2023; Fan et al., 2019; Inbal et al., 2018; Johnson et al., 2020; Meng & Ben‐Zion, 2018; Zhang et al., 2023).…”

Section: Introductionmentioning

confidence: 99%

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A Frequency Domain Methodology for Quantitative Evaluation of Diffuse Wavefield With Applications to Seismic Imaging

Yang,

Meng,

et al. 2024

JGR Solid Earth

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Ambient Noise Imaging (ANI) of subsurface structures relies on seismic interferometry of diffuse seismic wavefields. However, the lack of effective methods to quantify and identify highly diffuse waves hampers applications of ANI, particularly in evaluating seismic attenuation and monitoring structural changes with high temporal resolution. Conventional ANI approaches require data normalization, which effectively suppresses the non‐diffuse component with large amplitude but also results in significant loss of amplitude and phase information in the continuous seismic records. In this study, we propose a frequency domain method to quantitatively evaluate the degree of diffuseness of seismic wavefields by analyzing their statistical characteristics of modal amplitudes for stationarity and randomness. Tests on synthetic waveform and field nodal records show that the proposed method can effectively distinguish between diffuse and non‐diffuse waveforms for either single‐ or three‐component data. As an application, we identify a 60‐s‐long diffuse coda of a local M 2.2 earthquake recorded by a dense nodal array on the San Jacinto Fault Zone, and successfully extract high‐quality dispersion curve and Q‐value without performing data normalization. These results are consistent with those obtained by conventional methods that assess the correlation between coherency and the Green's function, and by modeling ballistic waves generated by road traffic. Our proposed method can advance the imaging of subsurface velocity and attenuation structures as well as monitoring temporal changes for scientific studies and engineering applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Frequency Domain Methodology for Quantitative Evaluation of Diffuse Wavefield With Applications to Seismic Imaging

Yang,

Meng,

et al. 2024

JGR Solid Earth

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Advances in seismological methods for characterizing fault zone structure

Cai,

Wu,

Liu

et al. 2024

Earthquake Science

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Directional amplification across the San Jacinto fault zone, CA

Pischiutta,

Baker,

Fletcher

et al. 2024

Geophysical Journal International

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SUMMARY The amplitude, frequency and polarization of ground motion at the surface can be affected by the local geology. While low-velocity sediments and fill can amplify ground motions in certain frequency ranges, the low velocities found in fault zones can also produce prominent wavelets. In this paper, we provide further evidence that polarization of ground motion can be affected by the geological fabric in fault zones that have sustained significant brittle deformation. Aside from the well-known effect of fault-trapped waves in the low-velocity zone with polarization azimuths parallel to the fault strike, the effect of stiffness anisotropy was recently recognized with polarization azimuths at high-angle to the fault strike and orthogonal to the locally predominant fracture field in the fault damage zone. To clarify further such features, we investigate directional amplification effects across the San Jacinto fault zone in Southern California using seismic data recorded by permanent seismic stations and dense across-fault arrays. We observe three main polarization trends. The first trend parallel to the fault strike is ascribed to fault-trapped waves along the low-velocity zone, in agreement with several studies in the last decade in the same region. The second and third trends are orthogonal to the orientation of R and T Riedel planes, respectively. They are related to the stiffness anisotropy in densely fractured rocks in the damage zone, which are more compliant orthogonal to their fractures. At some locations the two effects are superimposed, occurring in different and distinct frequency ranges. Directional amplification at rock sites can be important for expected ground motion and seismic hazard. However, in seismic engineering the current prescriptions of seismic codes do not account for amplification effects at rock sites at frequencies of engineering interest.

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Lateral Variations Across the Southern San Andreas Fault Zone Revealed From Analysis of Traffic Signals at a Dense Seismic Array

Cited by 3 publications

References 41 publications

A Frequency Domain Methodology for Quantitative Evaluation of Diffuse Wavefield With Applications to Seismic Imaging

A Frequency Domain Methodology for Quantitative Evaluation of Diffuse Wavefield With Applications to Seismic Imaging

Advances in seismological methods for characterizing fault zone structure

Directional amplification across the San Jacinto fault zone, CA

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