Creeping Through a Stepover: Top-down View From Geomorphology, Seismology, and Geodesy
Description:
The geomorphic record preserves various stages of fault development, typically thought to evolve toward simpler geometries with slip accrual, though the relationship between past and presently active surface faulting with slip at depth is not always clear. This has implications for isolating which mapped structures are most relevant to current slip displacement hazard potential. The central San Andreas fault, extending ~150 km north of Parkfield, is a prime example of a mature fault, with large net right-lateral slip (~600 km). Today, the fault creeps with surface rates approaching 3 cm/yr. The aseismic behavior is attributed to frictionally weak, velocity-strengthening fault-gouge minerals and an overall well-developed, straight fault geometry. The fault, however, takes an uncharacteristic 1 km right step through a network of geomorphically well-preserved, subsidiary en echelon normal faults over a distance of several kms on top of Mustang Ridge. Similar complexity is reflected in historical deep seismicity, highlighting bends in the fault geometry from ~5-10 km depth. The absence of seismicity in the upper ~ 5 km when compared to the south along-strike, as well as the ambiguity of current activity from the geomorphic expression of surface faulting, leave open questions regarding the distribution of active shallow subsurface slip and surface creep. With three-dimensional displacements from improved, higher spatial resolution (0.5 m) lidar differencing (2007 to 2018) complemented by UAVSAR measurements (2009 to 2022), we aim to connect the surficial geologic, deep seismologic, and historic geodetic records to present day deformation. Results both connect present day cumulative slip signature from the surface to seismogenic depths, and illuminate the structural evolution of the stepover through geologic timescales.
Session: Exploring the Complexity of Fault Discontinuities - I
Type: Oral
Date: 4/17/2025
Presentation Time: 02:15 PM (local time)
Presenting Author: Catherine
Student Presenter: No
Invited Presentation:
Poster Number: 80
Authors
Catherine Hanagan Presenting Author Corresponding Author chanagan@usgs.gov U.S. Geological Survey |
Stephen DeLong sdelong@usgs.gov U.S. Geological Survey |
Nadine Reitman nreitman@usgs.gov U.S. Geological Survey |
Zhen Liu zhen.liu@jpl.nasa.gov NASA, Jet Propulsion Laboratory |
Travis Alongi talongi@usgs.gov U.S. Geological Survey |
Chelsea Scott cpscott1@asu.edu Arizona State University |
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Creeping Through a Stepover: Top-down View From Geomorphology, Seismology, and Geodesy
Session
Exploring the Complexity of Fault Discontinuities