Poster #043, Seismology

Crustal Structure Along a Nodal Seismic Line in the San Bernardino Basin From Teleseismic Receiver Functions

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Poster Presentation

2020 SCEC Annual Meeting, Poster #043, SCEC Contribution #10559
The goal of the Basin Amplification Seismic Investigation (BASIN) project is to determine the structure, depths, and shape of San Bernardino and San Gabriel basins, which are expected to trap, channel, and amplify seismic waves, for the purpose of better predicting ground motions in the Los Angeles area. We use receiver functions computed from five teleseismic earthquakes recorded along one of the 10 BASIN profiles (the SB3 line) to map the crustal structure by identifying P-to-S conversions associated with the Moho discontinuity and an intracrustal interface. Here, we focus on a magnitude 6.3 teleseismic event that occurred in North Alaska. SB3 is a N-S line located in the middle part of th...e San Bernardino basin. The line is ~22 km long and has 87 nodal stations spaced about 250 m apart. Our results show a shallower Moho in the north at ~3 s that deepens to ~4.5 s in the south and shallows again to 4 s before the southern end of the line. We interpret an intracrustal interface close to the middle of the SB3 line at ~2 s that can be traced up to 5.25 km southward but does not appear to continue to the end of the line in the 1 Hz receiver functions. The change in depth of the Moho could possibly have resulted from regional compression. In comparison, the SB4 line located ~11.5 km to the west has a Moho that is mostly at 4 s and deepens to ~5 s just before Chino Hills, but shallows before the end of the line back to 4 s indicating an overall thicker crust along SB4 relative to SB3. An inflection in the Moho is observed along SB3 close to the surface trace of the Red Hill-Etiwanda fault that has also been interpreted to cross SB4. We will show our detailed structural interpretations along SB3 and discuss their relationship to previous work.