Analysis of fault-tip structures at seismogenic and creeping faults

Sofia Marino, Alba Rodriguez Padilla, & Michael E. Oskin

Published August 14, 2020, SCEC Contribution #10553, 2020 SCEC Annual Meeting Poster #135

Seismogenic faults grow coseismically through the propagation of earthquake slip to the surface, and are subject to episodic stress over the earthquake cycle. Conversely, faults creeping at steady rates experience a continuous delivery of stress to their tips. Despite these stark differences in stress state, creeping and seismogenic faults appear to be kinematically identical. Here, we examine varying slip gradients and fault tip process zones within normal faults at the Needles Fault District (Canyonlands National Park) and the Volcanic Tablelands (Bishop, CA). The Needles District fault array experiences steady-state aseismic slip at a constant rate of 2 mm/yr driven by gravitational collapse of a ~700m thick sandstone layer underlain by evaporites. Faults in the Volcanic Tablelands cut through a ~200m thick unit of the Bishop Tuff and slip when triggered by neighboring faults in the Eastern California Shear Zone, thus experiencing stick-slip behavior. Because faults grow by segment linkage of fractures at process zones tips, differences in the fracture density and orientation may be reflective of differences in stress state or propagation style for seismogenic and creeping faults. We map faults and fractures using high-resolution lidar data and aerial orthophotography from the Needles District and the Volcanic Tablelands, analyze fracture orientation and density, and discuss their implications for the kinematics of seismogenic and creeping faults.

Key Words
Fault creep, fault kinematics, fault zone evolution

Citation
Marino, S., Rodriguez Padilla, A., & Oskin, M. E. (2020, 08). Analysis of fault-tip structures at seismogenic and creeping faults. Poster Presentation at 2020 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)