Fault damage structure at depth extracted by FZTWs and receiver functions from teleseismograms possible monitor its variations during earthquake cycle

Yong-Gang Li

Submitted August 30, 2026, SCEC Contribution #15527, 2026 SCEC Annual Meeting Poster #187

We analyzed the teleseismograms recorded at a seismic nodal-array consisting of 100 stations deployed atop the Calico Fault (CF) in Mojave Desert, California, and identified the fault-zone trapped waves (FZTWs) characterized by large amplitudes at 0.5-2 Hz in ~3.5-4 s and ~6-8 s durations, respectively, following the transmitting P' wave and P-to-S converted S' wave from the Moho discontinuity at stations within the ~1-km-wide CF compliant zone. We interpret that these FZTWs are produced by constructive interference of reflective waves within the LVWG when the P' and S' waves enter the bottom of the low-velocity waveguide (LVWG) formed by the CF compliant zone at seismogentic depths. The receiver functions computed by deconvolution between the radial- and vertical-component teleseismograms confirm these newly identified FZTWs arising from the P' and S' waves. This new type of FZTWs appear to have great promise for diagnosing the depth extension of fault damage zone at seismogenic depths where the coverage of seismic waves from explosions and local earthquakes is poor. Our 3D finite-difference simulations of these FZTWs show that the CF compliant zone with the maximum ~40-50% velocity reduction in the fault core likely extends to seismogenic depth. Accurately extracting the fault damage zone structure by using the FZTWs identified in teleseismograms recorded at the dense array across the target active fault to monitor the spatiotemporal variations in its depth extension and velocity during the cycle of co-seismic damage and post-seismic healing may help evaluating earthquake generation and hazards.

Key Words
fault damage zone depth extension, low-velocity waveguide, teleseismogram, P-to-S converted wave at Moho, fault-zone trapped wave, receiver function

Citation
Li, Y. (2026, 08). Fault damage structure at depth extracted by FZTWs and receiver functions from teleseismograms possible monitor its variations during earthquake cycle. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology