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Teleseismic P-to-Rayleigh conversions from near-surface geological structure along the Newport-Inglewood fault zone in Long Beach, California

Jia Zhang and Charles A. Langston
Teleseismic P-to-Rayleigh conversions from near-surface geological structure along the Newport-Inglewood fault zone in Long Beach, California
Bulletin of the Seismological Society of America (March 2022) 112 (3): 1356-1372

Abstract

We investigate near-surface 3D structure giving rise to P-to-Rayleigh wave conversions from teleseismic P waves recorded by the Long Beach array, southern California. Our previous study demonstrated that a local Rayleigh wave having circular wavefronts with phase velocities of approximately 1 km/s arise from Signal Hill in array P wave data from a large Fiji Islands earthquake. A group of high-spatial frequency, low velocity 0.7-0.9 km/s Rayleigh waves having linear wavefronts also propagate away from strands of the Newport-Inglewood fault zone (NIFZ), suggesting that P-to-Rayleigh wave conversions from fault damage zones can also be observed. We compute synthetic waveforms using 3D finite difference to show that topography of Signal Hill accounts for much of the circular P-to-Rayleigh wave conversions. The NIFZ is best modeled by low-velocity, vertical tabular features above a depth of 500 m, with a width of 100-120 m, and approximately 15% reduction in VP and VS compared with the background model. We observe that structure from the northwestern part of the inferred southwest boundary fault of the Signal Hill anticline dominates the scattering from fault damage zones. It is remarkable that the combination of low, near-surface velocity with relatively small-scale heterogeneity can significantly affect the signature of long horizontal wavelength teleseismic P waves, suggesting additional complexities in interpreting receiver functions for stations on deep sedimentary basins or in areas of significant topography.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 112
Serial Issue: 3
Title: Teleseismic P-to-Rayleigh conversions from near-surface geological structure along the Newport-Inglewood fault zone in Long Beach, California
Affiliation: University of Memphis, Center for Earthquake Research and Information, Memphis, TN, United States
Pages: 1356-1372
Published: 20220314
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 67
Accession Number: 2022-018432
Categories: SeismologyStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N33°36'00" - N34°12'00", W118°24'00" - W117°35'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202215
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