Testing Waveform Predictions of 3D Velocity Models against Two Recent Los Angeles Earthquakes

Lee, En‐Jui; Chen, Po; Jordan, Thomas H.

doi:10.1785/0220140093

Cited by 39 publications

(25 citation statements)

References 38 publications

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“…Roughly speaking, RWM < 1 indicates a good waveform fit, whereas RWM > 1 indicates a poor fit [Lee et al, 2014]. We computed the RWMs for 43,496 earthquake waveforms, 10,853 Rayleigh waves on ANGF-high ambient-noise correlagrams, and 12,581 Rayleigh waves on ANGF-low ambient-noise correlagrams.…”

Section: Model Assessmentmentioning

confidence: 99%

Full‐3‐D tomography for crustal structure in Southern California based on the scattering‐integral and the adjoint‐wavefield methods

et al. 2014

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We have successfully applied full-3-D tomography (F3DT) based on a combination of the scattering-integral method (SI-F3DT) and the adjoint-wavefield method (AW-F3DT) to iteratively improve a 3-D starting model, the Southern California Earthquake Center (SCEC) Community Velocity Model version 4.0 (CVM-S4). In F3DT, the sensitivity (Fréchet) kernels are computed using numerical solutions of the 3-D elastodynamic equation and the nonlinearity of the structural inversion problem is accounted for through an iterative tomographic navigation process. More than half-a-million misfit measurements made on about 38,000 earthquake seismograms and 12,000 ambient-noise correlagrams have been assimilated into our inversion. After 26 F3DT iterations, synthetic seismograms computed using our latest model, CVM-S4.26, show substantially better fit to observed seismograms at frequencies below 0.2 Hz than those computed using our 3-D starting model CVM-S4 and the other SCEC CVM, CVM-H11.9, which was improved through 16 iterations of AW-F3DT. CVM-S4.26 has revealed strong crustal heterogeneities throughout Southern California, some of which are completely missing in CVM-S4 and CVM-H11.9 but exist in models obtained from previous crustal-scale 2-D active-source refraction tomography models. At shallow depths, our model shows strong correlation with sedimentary basins and reveals velocity contrasts across major mapped strike-slip and dip-slip faults. At middle to lower crustal depths, structural features in our model may provide new insights into regional tectonics. When combined with physics-based seismic hazard analysis tools, we expect our model to provide more accurate estimates of seismic hazards in Southern California.

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Section: Model Assessmentmentioning

confidence: 99%

Full‐3‐D tomography for crustal structure in Southern California based on the scattering‐integral and the adjoint‐wavefield methods

et al. 2014

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“…We used the SCEC (Southern California Earthquake Center) community velocity model CVM-S (version 4.26) [Magistrale et al, 2000;Lee et al, 2014] and the UCVM framework (Unified Community Velocity Model) [Gill et al, 2013] to generate a structural model representative of the conditions within the Landers fault system. The structural model includes small-scale heterogeneities [e.g., Savran and Olsen, 2016] and a low-velocity zone (LVZ) around the fault ( Figure S2 in the supporting information).…”

Section: Generation Of Crustal Modelmentioning

confidence: 99%

Off‐fault deformations and shallow slip deficit from dynamic rupture simulations with fault zone plasticity

Roten

Olsen

Day

2017

Geophysical Research Letters

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Kinematic source inversions of major (M≥7) strike‐slip earthquakes show that the slip at depth exceeds surface displacements measured in the field, and it has been suggested that this shallow slip deficit (SSD) is caused by distributed plastic deformation near the surface. We perform dynamic rupture simulations of M 7.2–7.4 earthquakes in elastoplastic media and analyze the sensitivity of SSD and off‐fault deformation (OFD) to rock quality parameters. While linear simulations clearly underpredict observed SSD and OFDs, nonlinear simulations for a moderately fractured fault damage zone predict a SSD of 44–53% and OFDs of 39–48%, consistent with the 30–60% SSD and 46 ± 10% (1σ) OFD reported for the 1992 M 7.3 Landers earthquake. Both SSD and OFDs are sensitive to the quality of the fractured rock mass inside the fault damage zone, and surface rupture is almost entirely suppressed in poor quality material.

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“…The centroid‐moment tensors of all but two of the sources were refined by Lee, Chen, Jordan, Maechling, et al (, Figure 1) during the full 3‐D tomographic inversions to obtain model CVM‐S4.26. The centroid‐moment tensors of the two exceptions, the 2014 Encino ( M W 4.4) and La Habra ( M W 5.1) earthquakes, were later reinverted by Lee, Chen, and Jordan () using the finalized CVM‐S4.26 structure. We confined the raypaths to the crust by restricting the epicentral distances to less than 150 km for P waves and 144 km for S waves, which is shorter than the mantle refraction crossover distances in most parts of Southern California (Hadley & Kanamori, ).…”

Section: Data Analysis and Inversionmentioning

confidence: 99%

Frequency‐Dependent Attenuation ofPandSWaves in Southern California

Lin

Jordan

2018

JGR Solid Earth

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Accurate models of crustal attenuation structure are important for simulating seismic wavefields at high frequencies (f > 1 Hz). In this study, we collected P and S waveforms from 160 regional earthquakes (3.3 ≤ M ≤ 5.7) recorded at 218 broadband stations of Southern California Seismic Network and measured spectral amplitudes of P and S waves in the 1‐ to 10‐Hz band using integrals over wavelet transforms. We accounted for source structure and geometrical spreading by referencing the spectral amplitudes to values computed from 1‐D synthetic seismograms. We inverted the spectral amplitude ratios for a 1‐D, frequency‐dependent crustal attenuation model. When plotted against wavenumber, the depth averages of both QP and QS are described by the same function, Q(k) = (240 ± 20) k0.40 ± 0.05 (1 km−1 ≤ k ≤ 17 km−1). Our results are consistent with attenuation dominated by first‐order Born scattering from an isotropic, self‐affine distribution of elastic heterogeneities with an outer scale of ~10 km, a root‐mean‐square relative amplitude of ~8% and a fractal dimension of ~3.8. The inversions accounted for frequency‐dependent variations in the source spectra and site response. The source spectra roll off at an average rate of about 2 for both wave types. The station residuals, which reflect unresolved lateral structure, show stronger attenuation in the Los Angeles region and weaker attenuation in the batholithic terrains to the north and south, as well as in the Proterozoic terrains on the eastern side of the study region.

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Testing Waveform Predictions of 3D Velocity Models against Two Recent Los Angeles Earthquakes

Cited by 39 publications

References 38 publications

Full‐3‐D tomography for crustal structure in Southern California based on the scattering‐integral and the adjoint‐wavefield methods

Full‐3‐D tomography for crustal structure in Southern California based on the scattering‐integral and the adjoint‐wavefield methods

Off‐fault deformations and shallow slip deficit from dynamic rupture simulations with fault zone plasticity

Frequency‐Dependent Attenuation ofPandSWaves in Southern California

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