Constraining Creep Rates Along the Central Creeping Section of the San Andreas Fault from Lidar Topographic Differencing Constraining Creep Rates Along the Central Creeping Section of the San Andreas Fault from Lidar Topographic Differencing The Central Creeping Section of the San Andreas Fault (CSAF) extends for 140 km from San Juan Baptista to Parkfield and is bounded by locked fault segments. There are several sources of seismic hazard along the CSAF that pose risk to the growing population centers in San Francisco and Los Angeles. Large earthquakes that initiate along the adjacent locked faults may propagate along the creeping fault in wall-to-wall ruptures. Earthquakes along the mostly creeping fault zone itself can cause damage in urban centers, for example, two ~M6 Bitterwater earthquakes in the 1880s produced moderate to severe shaking in San Francisco and heavy shaking in Santa Barbara. The risk to critical infrastructure from fault displacement hazard has gained attention in the scientific community and numerous industries and agencies. Urban infrastructure crossing the nearby Calaveras Fault (CF) in Hollister, CA is a prime example. Geodetic observations of fault creep from alignment arrays, GPS, and InSAR, etc., provide important constraints of fault creep rate, informing studies on fault mechanics and seismic hazard. However, these studies lack dense spatial resolution and/or sensitivity to the near-fault 3D deformation field, leaving a gap in the understanding of creep rate and the behavior of the shallow crust. We seek funding to resolve the 3D deformation field over >200 km of the CSAF and the CF by applying topographic differencing methods to the 2005 B4, 2007 EarthScope, and the 2018 FEMA airborne lidar datasets. We will calculate the 3D displacement field at the decameter-scale using a windowed implementation of the Iterative Closest Point (ICP) algorithm. We will measure creep rates every ~500 m that represent average rates during the 11-13 year dataset timespan. We will calculate the surface strain field, indicative of the localization of deformation along the fault zone. We will solve for the distributed fault creep using both topographic differencing and InSAR displacements. This proposed project represents an unusual case where the pre-event B4 and EarthScope lidar datasets were both acquired for topographic differencing (what we propose). We will develop differencing methods that reduce the uncertainty in creep rates in moderate-vegetation landscapes like central and southern California and the broader Southwestern US. We have strong expertise in topographic differencing, InSAR, and earthquake source inversions and are confident that we can successfully complete the proposed work. Our results will provide independent and spatially dense creep rate constraints along the CSAF and CF that will serve as input into future California Earthquake Rupture Forecasts. The fault and strain maps will be of great interest to fault displacement hazard activities. Our distributed fault creep model will support examining how creep rates change with depth, a critical input for understanding the mechanical behavior of the shallow crust and for calculating moment accumulation along the fault. The differencing methods that we develop will broaden the application of differencing techniques to ~M6 earthquakes and creeping faults that are increasingly likely to be covered by differential lidar data from a variety of programs including the UGGSs 3D Elevation Program (3DEP). We will make the new creep rates, fault map, slip inversion and developed methodology publicly available.
|Effective start/end date||3/1/21 → 2/28/22|
- DOI: US Geological Survey (USGS): $52,396.00
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