Constraining the Frictional Strength and State of Stress Along Coseismic Fault Ruptures using 3D Geodetic Imaging Data

Chris Milliner, Saif Aati, & Jean-Philippe Avouac

Published September 11, 2022, SCEC Contribution #11951, 2022 SCEC Annual Meeting Poster #068

Constraining the variation of stress on faults is important for improving our understanding of fault friction and the dynamics of earthquake ruptures. However, we still have little observational constraints on their absolute magnitude, or their variations in space and in time over the seismic cycle. Here we measure the 3D surface deformation of large coseismic ruptures to constrain the stress state and frictional properties of the ruptured faults using pixel tracking of ALOS-2 radar data and a new optical pixel tracking technique that we have developed. From measurements of the 3D slip vector made every ~150 m along the 2016 Mw 7.0 Kumamoto, 2016 Mw 7.8 Kaikoura and 2019 Mw 7.1 Ridgecrest surface ruptures we invert them for the 3D stress tensor. For the 2019 Ridgecrest earthquake sequence we find by assuming Mohr-Coulomb failure that the absolute magnitudes of shear stresses range from 4-9 MPa along the rupture in the shallow crust (~1.3 km depth). In addition, we find that the relatively immature faults that ruptured have an intermediate-strong static strength (frictional coefficient of 0.59 ± 0.08) but requires dynamic weakening with a reduced frictional coefficient of 0.28 ± 0.04 to explain slip observed along sub-optimally orientated faults. We will also present results comparing the stress state and frictional properties of other recent surface rupturing events and discuss them in light of their fault maturity and tectonic setting.

Citation
Milliner, C., Aati, S., & Avouac, J. (2022, 09). Constraining the Frictional Strength and State of Stress Along Coseismic Fault Ruptures using 3D Geodetic Imaging Data. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy