Basin Structure Revealed in Teleseismic Receiver Functions from a Dense Nodal Seismic Array in the Northern Los Angeles Basins

Ritu Ghose, Patricia Persaud, & Robert W. Clayton

Published August 15, 2020, SCEC Contribution #10769, 2020 SCEC Annual Meeting Poster #041

As part of the BASIN (Basin Amplification Seismic Investigation) project, we are mapping the structure of the San Gabriel (SG) and San Bernardino (SB) basins. We are analyzing results from 232 nodal seismic stations installed along 5 profiles in the two basins. Receiver functions at different frequencies were computed using recordings of three to four teleseismic earthquakes of magnitude >5.9 and distance 30º-90º for the N-S oriented SG3, SG4, SB2 and SB3 lines, and the E-W oriented SB6. SB2 is located in the eastern part of SB basin between the San Andreas and San Jacinto fault zones; SB3 is in the central part of the basin. SB6 is an E-W trending line in the eastern part of SB basin that crosses the middle of SB2. 2 Hz receiver functions reveal a sediment-basement interface at ~1 s in the northern and at ~1.5 s in the central to the southern parts of the SB2 line. The SB3 line has a sediment-basement interface at ~1 s and ~0.5 s near a projected fault. Previously published results for the SB4 line shows basement depth at ~0.7 s in the north to ~ 1.5 s in the central and ~ 1 s in the southern part. SB6 shows basement depths at ~1.5 s. The SG basin lines, SG3 and SG4 are located in the region where the SB basin and SG basin connect. SG3 has the sediment-basement interface at ~1 s in the north and ~1.2 s in the south. SG4 shows a shallow basement at ~0.5 s. The previously published SG1 line has the basement at ~1 s in the NW to ~1.5 s in the SE and the SG2 line showed ~0.5 s in the North to ~1 s in the south. A general southward deepening of the basin is observed and our results show variabilities in the details. The SB2 and SB3 lines both show higher frequency receiver functions to the north and lower frequency receiver functions to the south. Previously published results for SB4 showed a similar pattern in the receiver functions which may indicate different basement blocks. A previous study using gravity data shows Pelona Schist basement along SB2 and Peninsular Ranges rocks along SB3. However, our initial interpretation from the receiver functions suggests a potentially more heterogeneous basement beneath the SB basin. We will show the interpreted sediment-basement interface across the five profiles converted to depth.

Citation
Ghose, R., Persaud, P., & Clayton, R. W. (2020, 08). Basin Structure Revealed in Teleseismic Receiver Functions from a Dense Nodal Seismic Array in the Northern Los Angeles Basins. Poster Presentation at 2020 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology