Urban Nodal Array Maps Structure of the Northern Los Angeles Basins with Teleseismic Receiver Functions

Patricia Persaud, Guibao Liu, & Robert W. Clayton

Published August 10, 2018, SCEC Contribution #8374, 2018 SCEC Annual Meeting Poster #276

Earthquake ground motions in the greater Los Angeles area are known to be affected by basin amplification and the channeling and focusing of seismic energy as it passes through the San Gabriel and San Bernardino basins in the northern part of this region. Accurate representations of basin shape and depth are therefore key for providing realistic estimates of basin amplification. Various studies have provided improvements to the shape of the northern basins, e.g., using gravity modeling, through finite difference simulations of ground motion and with active source seismic profiles across the San Bernardino basin. However, the current Southern California Earthquake Center velocity model, CVM-S4.26, still lacks sufficient detail on the structure of these basins.
To help increase the accuracy of ground shaking models for the Los Angeles area, we use an urban array of 384 nodal geophones. Our data set is comprised of teleseismic events recorded along three transects in the greater Los Angeles area in 2017 and three additional transects collected in 2018. In each year, the instruments recorded for ~35 days. We have computed receiver functions along the three 2017 profiles to map the depth and shape of the sediment-basement interface and to identify possible deep fault offsets (Liu et al., 2018). The results show the Moho discontinuity, the bottom of the basement, and intermediary sedimentary layers. There are also indications of mid-crustal offsets along strike of the Red Hill and Raymond Faults. The results are compared to receiver functions from nearby permanent broadband stations and the 1993 LARSE experiment. The images show that dense deployments of node-type sensors can be used to investigate structure at the basin scale in a noisy urban environment, and therefore have potential value for seismic hazard studies.

Liu, G., P. Persaud and R. W. Clayton (2018), Structure of the Northern Los Angeles Basins Revealed in Teleseismic Receiver Functions from Short‐Term Nodal Seismic Arrays. Seismological Research Letters. http://dx.doi.org/10.1785/0220180071

Key Words
San Bernardino basin, basin amplification, ground shaking, Los Angeles seismic hazard

Citation
Persaud, P., Liu, G., & Clayton, R. W. (2018, 08). Urban Nodal Array Maps Structure of the Northern Los Angeles Basins with Teleseismic Receiver Functions. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
San Andreas Fault System (SAFS)