Fine-scale Southern California Moho structure uncovered with distributed acoustic sensing

Area of Science:

• Geophysics
• Seismology
• Tectonics

Background:

• Moho topography provides critical insights into lithospheric evolution and lower crustal strength.
• The Moho reflected seismic phase (PmP) is a key indicator of this boundary and aids in determining crustal thickness.
• Distributed acoustic sensing (DAS) arrays offer unprecedented fine-scale spatial sampling for seismic observations.

Purpose of the Study:

• To investigate Moho variability and crustal thickness in Southern California using PmP seismic data.
• To develop and validate a technique for identifying and picking P-PmP differential times from DAS recordings.
• To map short-wavelength crustal thickness variations and their relationship to major geological structures.

Main Methods:

• Utilizing PmP seismic phase data recorded by a 100-km-long fiber optic DAS array.
• Developing a robust method for precise identification and picking of P-PmP differential times.
• Analyzing hundreds of well-recorded seismic events to constrain Moho depth.

Main Results:

• Successfully observed and analyzed PmP phases with high confidence using DAS data.
• Constrained Moho depth across Southern California, revealing abundant short-wavelength crustal thickness variability.
• Identified sharp changes in crustal thickness associated with the Garlock Fault and the Coso Volcanic Field.

Conclusions:

• DAS arrays are effective tools for high-resolution seismic imaging of the Moho.
• Southern California's crust exhibits significant short-wavelength thickness variations, indicating complex tectonic processes.
• The Garlock Fault and Coso Volcanic Field represent zones of substantial crustal modification.