Group B, Poster #086, Tectonic Geodesy

Estimating the surface creep rate of the central San Andreas fault from a 3D surface velocity field derived from UAVSAR and Sentinel-1 data

Li-Chieh Lin, & Gareth J. Funning
Poster Image: 

Poster Presentation

2024 SCEC Annual Meeting, Poster #086, SCEC Contribution #13658 VIEW PDF
Fault creep, as opposed to fault locking, refers to the stable movement across the fault interface without storing elastic strain energy. Fault patches which exhibit such creeping behaviors are considered to have lower seismic potential due to their reduced accumulation of elastic strain energy. Additionally, the material properties that result in such frictional stability are thought to be one of the key factors in inhibiting earthquake rupture propagation. Therefore, understanding the fault creep kinematics is essential to earthquake genesis and rupture propagation.
The central segment of the San Andreas fault (SAF) has long been recognized as a creeping fault whose creep depth ext...ends across the whole seismogenic layer of the crust, meaning the whole fault segment is exhibiting stable sliding. To better visualize and estimate the surface creep rates of the central SAF, we jointly used UAVSAR and Sentinel-1 SAR images to build the secular 3D surface velocity field. We then projected the East-West and North-South components into fault-parallel and fault-perpendicular directions and made 110 cross-fault profiles through the fault-parallel velocity field to estimate the distribution of surface creep rates along strike. The creep rates at the southern end (north of Parkfield and south of Bitterwater) exceeded 2 cm/yr with some parts reaching close to 3 cm/yr. At the northern end of the central SAF, creep appears to be partitioned between the SAF and the Calaveras fault and thus the SAF creep rates drop down to ~1cm/yr. These findings agree with previous investigations, and given the high spatial resolution that InSAR data offers, our results can be used as the starting step for identifying how creep varies temporally and/or spatially in order to understand its decadal kinematic evolution.
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Citation: Lin, L., & Funning, G. J. (2024, 09). Estimating the surface creep rate of the central San Andreas fault from a 3D surface velocity field derived from UAVSAR and Sentinel-1 data. Poster Presentation at 2024 SCEC Annual Meeting.
Keywords: InSAR, Creep rate, San Andreas fault, 3D surface velocity field
Relevant SCEC Themes:
Improving Observations and Closing Data Gaps