Abstract
The Pacific–North American plate boundary in California is composed of a 400-km-wide network of faults and zones of distributed deformation. Earthquakes, even large ones, can occur along individual or combinations of faults within the larger plate boundary system. While research often focuses on the primary and secondary faults, holistic study of the plate boundary is required to answer several fundamental questions. How do plate boundary motions partition across California faults? How do faults within the plate boundary interact during earthquakes? What fraction of strain accumulation is relieved aseismically and does this provide limits on fault rupture propagation? Geodetic imaging, broadly defined as measurement of crustal deformation and topography of the Earth’s surface, enables assessment of topographic characteristics and the spatio-temporal behavior of the Earth’s crust. We focus here on crustal deformation observed with continuous Global Positioning System (GPS) data and Interferometric Synthetic Aperture Radar (InSAR) from NASA’s airborne UAVSAR platform, and on high-resolution topography acquired from lidar and Structure from Motion (SfM) methods. Combined, these measurements are used to identify active structures, past ruptures, transient motions, and distribution of deformation. The observations inform estimates of the mechanical and geometric properties of faults. We discuss five areas in California as examples of different fault behavior, fault maturity and times within the earthquake cycle: the M6.0 2014 South Napa earthquake rupture, the San Jacinto fault, the creeping and locked Carrizo sections of the San Andreas fault, the Landers rupture in the Eastern California Shear Zone, and the convergence of the Eastern California Shear Zone and San Andreas fault in southern California. These examples indicate that distribution of crustal deformation can be measured using interferometric synthetic aperture radar (InSAR), Global Navigation Satellite System (GNSS), and high-resolution topography and can improve our understanding of tectonic deformation and rupture characteristics within the broad plate boundary zone.
Highlights
For effective seismic hazard assessment, it is necessary to understand how plate motions are partitioned across the plate boundary zone and to characterize potential earthquake rupture sources within it
We focus here on crustal deformation observed with continuous Global Positioning
San Andreas fault, the Landers rupture in the Eastern California Shear Zone, and the convergence of the Eastern California Shear Zone and San Andreas fault in southern California. These examples indicate that distribution of crustal deformation can be measured using interferometric synthetic aperture radar (InSAR), Global Navigation Satellite System (GNSS), and high-resolution topography and can improve our understanding of tectonic deformation and rupture characteristics within the broad plate boundary zone
Summary
For effective seismic hazard assessment, it is necessary to understand how plate motions are partitioned across the plate boundary zone and to characterize potential earthquake rupture sources within it. Plate tectonics drive the accumulation and release of strain either via earthquakes or via aseismic slip such as creep or anelastic bulk deformation, but how faults interact within the plate boundary can be complex. Earthquakes occur within systems of faults [1,2] driven by plate tectonic motions. We focus on the Pacific–North American plate boundary across. We discuss deformation associated with repeated earthquakes and aseismic. Geosciences 2017, 7, 15; doi:10.3390/geosciences7010015 www.mdpi.com/journal/geosciences slip, concentrating on timescales of days to millennia. Initial deformation occurs quickly during and immediately following can significantly significantlyreorganize reorganizethe thelandscape landscape immediately followingananearthquake
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