Group A, Poster #131, Fault and Rupture Mechanics (FARM)

What Controls the Shallow Fault Damage Zone and Fluid Flow? Insights from New High-Resolution Seismic Imaging

Travis V. Alongi, Emily E. Brodsky, Jared W. Kluesner, & Daniel S. Brothers
Poster Image: 

Poster Presentation

2023 SCEC Annual Meeting, Poster #131, SCEC Contribution #12904 VIEW PDF
The distribution and intensity of fault damage zones provide insight into the inelastic response of Earth to strain. Presently, measures of the in-situ distribution of fault damage remain limited and, in particular, connecting surficial features to damage at depth has been difficult. This study focuses on the fault damage zone on a 40 km segment of the Palos Verdes Fault, located offshore southern California, near metropolitan Los Angeles. To achieve this, we leverage newly collected high-resolution sparker multichannel seismic (MCS) lines and sub-bottom profiles (Chirp), employing specialized seismic processing workflows. Our emphasis lies in examining the previously inadequately resolved s...hallow fault zone (~400 m below the seafloor). Our approach involves a multi-trace similarity technique to identify discontinuities in the seismic data attributed to faults and fractures. The outcomes of this fault detection approach reveal notably diverse damage patterns in the vicinity of the fault on adjacent seismic profiles. However, a discernible average damage zone pattern emerges by stacking damage detection profiles along strike. The stacked damage zone results show that damage decays with distance and is concentrated around the active fault strand, confirmed in this study. Additionally, we observe that the width of the damage zone increases with displacement, while it does not narrow with depth in sedimentary rock overlying the basement (~ 2 km depth). Furthermore, our observations reveal a correlation between fault damage and seafloor seeps visible in the water column, suggesting that damage plays a role in controlling fluid flow around the fault.