Fine-scale Southern California Moho structure uncovered with distributed acoustic sensing
Abstract
Moho topography yields insights into the evolution of the lithosphere and the strength of the lower crust. The Moho reflected phase (PmP) samples this key boundary and may be used in concert with the first arriving P phase to infer crustal thickness. The densely sampled station coverage of distributed acoustic sensing arrays allows for the observation of PmP at fine-scale intervals over many kilometers with individual events. We use PmP recorded by a 100-km-long fiber that traverses a path between Ridgecrest, CA and Barstow, CA to explore Moho variability in Southern California. With hundreds of well-recorded events, we verify that PmP is observable and develop a technique to identify and pick P-PmP differential times with high confidence. We use these observations to constrain Moho depth throughout Southern California, and we find that short-wavelength variability in crustal thickness is abundant, with sharp changes across the Garlock Fault and Coso Volcanic Field.
Copyright and License
© 2024 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).
Acknowledgement
We would like to thank R. Clayton for providing his perspective on the implications of these crustal thickness variability measurements. We would also like to thank M. Gurnis for his discussions on the rheological implications of a mantle-penetrating fault. We would additionally like to thank the California Broadband Cooperative for providing access to the fiber used in this experiment.
Funding
This work was supported by the National Science Foundation GRFP grant 1745301 (J.A.), the National Science Foundation CAREER grant 1848166 (Z.Z.), and the Gordon Moore Foundation (Z.Z.).
Contributions
Conceptualization: J.A. and Z.Z. Methodology: J.A. and Z.Z. Investigation: J.A. and Z.Z. Visualization: J.A. Supervision: Z.Z. Writing—original draft: J.A. Writing—review and editing: J.A. and Z.Z.
Data Availability
All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. The earthquake data used to make the PmP relative arrival time measurements shown in this study are available at https://doi.org/10.22002/hhg7x-hgm42. Ray paths and expected differential times were computed using TauP67 functionality in Obspy (https://docs.obspy.org/). Synthetic tests were performed using the spectral element code Salvus (https://mondaic.com/) (69).
Supplemental Material
Figs. S1 to S11 (PDF).
Movie S1 (ZIP).
Files
Additional details
- National Science Foundation
- DGE-1745301
- National Science Foundation
- EAR-1848166
- Gordon and Betty Moore Foundation
- Accepted
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2024-10-24Accepted
- Available
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2024-11-27Published
- Caltech groups
- Division of Geological and Planetary Sciences, Seismological Laboratory
- Publication Status
- Published