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An earthquake is a mechanism of stress release along plate boundaries due to relative motion between the Earth's lithospheric blocks. The period in which stresses are accruing across the plate boundary is known as the interseismic portion of the earthquake cycle. This dissertation focuses on interseismic portion of the earthquake cycle to extract characteristics of fault, shear zone and rock properties. Global Positioning System (GPS) data are used to observe the pattern of deformation across two primarily strike-slip fault systems: the Carrizo Segment of the San Andreas Fault (SAF) and the Eastern California Shear Zone (ECSZ). Two sets of GPS data are processed, analyzed and applied to analytic and numerical models describing the interseismic behavior of the earthquake cycle. The Carrizo segment is mature (i.e., had many earthquakes) and has juxtaposed terrains with varying rock properties laterally across the fault system. Lateral variations in rock properties affect the pattern of deformation around strike-slip faults and affect how surrounding rock deforms and if not considered may bias the interpretation of the faulted system. The Carrizo segment separates Franciscan terrain northeast of the fault from Salinian block to the southwest. GPS data are well fit to a model with a 15-25 km weak zone northeast of the Carrizo segment. The long-term slip rate estimated on the SAF is 34-38 mm/yr, with 2-4 mm/yr accommodated on faults to the west. The viscosity for the combined lower crust/upper mantle is estimated at 2-5x10^19 Pa s. This model is consistent with the distribution of rock type and corresponding laboratory data on their material properties, paleoseismic, seismic and magnetotelluric data. The ECSZ is a young (<10 >Myr) system of strike-slip faults including the Owens Valley - Airport Lake, Panamint Valley - Ash Hill - Hunter Mountain and Death Valley - Furnace Creek fault systems. The ECSZ study concentrates on fault evolution by finding the current position of maximum shear across the shear zone and estimating fault rates. Geologic studies suggest that the Death Valley - Furnace Creek fault system on eastern end of the ECSZ was the primary accommodator of slip early in the ECSZ history. This study suggests that the current locus of shear has shifted westward, and resides in the center of the ECSZ under the Panamint Valley - Ash Hill -Hunter Mountain fault system. The model dependent estimated geodetic rate of the Ash Hill - Panamint Valley -Hunter Mountain fault system (4.91-6.11 mm/yr) is faster than geologic estimates (1.6 - 4 mm/yr). The result is interpreted as a simplification of the ECSZ with time, combined with progressive westward migration of deformation. The best estimate for a combined rate across the shear zone is 10 mm/yr (20% of total Pacific-North America motion). The summation of rates obtained by this study is 49 mm/yr, well within estimates obtained by previous studies using independent techniques.

The Little San Bernardino Mountains (LSBM) Fault Set are N-S dextral faults, east of the restraining bend of the San Andreas Fault (SAF) in southern California, that may form a tectonic linkage between the SAF and the Eastern California Shear Zone. The NW LSBM are a complexly deformed structural domain characterized by the young N-S dextral faults and older NW-oriented Dillon Shear Zone faults. Before the 1992 Joshua Tree (Mw 6.1) and Landers (Mw 7.3) earthquakes, the rugged NW LSBM was the subject of few geologic studies. This bedrock mapping study has further delineated the geometry, distribution, and relative chronology of brittle structures. A 2015 NCALM award of 51 km2 of lidar imagery on Eureka Peak Fault was used to correct fault locations. Bedrock mapping in the epicentral areas of the 1992 Joshua Tree earthquake on Eureka Peak Fault and Landers aftershocks (Mw 5.7, 5.8) focused on the brittle structures of the evolving fault systems and potential connections with historic seismicity. The N-S dextral fault offsets from west to east are; Long Canyon (470 m), Wide Canyon (~150- 340 m), Eureka Peak (~ 225 m), California Riding Trail (850-965 m) and Deerhorn (105 m) faults with a cumulative offset of approximately 2 km. Dolomitic marble, clinopyroxene-hornblende skarn, garnet-epidote skarn and gabbro-diorite intruded by monzogranite are key lithologies used in determining offsets. Joshua Tree Fault, defined by seismicity by Kaven and Pollard (2013) is supported by additional mapped fault data. A “new” fault (Black Rock Canyon) links Wide Canyon and northern Eureka Peak faults. The distribution of aftershock seismicity plotted by depth and latitude along the N-S faults, a prominent broad seismicity trend and bedrock mapping are all consistent with interpreting the N-S faults as an incipient set of faults developing upward from a deeper through-going crustal shear zone. The seismicity since the onset of the Joshua Tree- Landers earthquake sequence on April 23, 1992, forms two distinct trends. Temporally these two trends occurred in sequence; first a N-propagating trend April 23- mid-June along Joshua Tree Fault from the Joshua Tree earthquake epicenter to north of the Pinto Mountain Fault, and secondly a prominent SE trend of Landers aftershocks (including Mw 5.7, 5.8) June 28 onwards, from the Landers earthquake epicenter, along Eureka Peak Fault to the SAF. AFT and (U-Th)/He thermochronology indicate an abrupt boundary on Long Canyon Fault between rapid uplift within ~ 12 km of the SAF and slower uplift more than 12 km north. This boundary is projected along the Dillon Shear Zone structural grain to the 1992 Joshua Tree earthquake epicenter on southern Eureka Peak Fault, dividing the N-striking faults into northern and southern domains. The 14.7 km hypocentral depth of the Joshua Tree earthquake coincides roughly with the depth of the NE dipping SAF intersection with Eureka Peak Fault, forming a hypothesized flower structure which is consistent with rapid uplift of the LSBM escarpment near the SAF. The LSBM Fault Set may be initiated by the upward migration of a through-going mid-crustal break and eastern migration of the current SAF trace bypassing the Big Bend slip impediment. Eureka Peak Fault with a slip rate of 10-20 mm/yr, is the proposed structure tectonically linking the SAF and the Eastern California Shear Zone.

The surface expression of upper crustal deformation varies widely based on geologic settings. Normal faults within an intra-arc basin, strike-slip faulting within a wide shear zone, and creeping fault behavior all manifest differently and require a variety of techniques for analysis. In this dissertation I studied three different actively deforming regions across a variety of geologic settings. First, I explored the drivers of extension within the La Pine graben in the Oregon Cascades. I mapped >20 new Quaternary faults and conducted paleoseismic trenching, where I found evidence for a mid-late Holocene earthquake on the Twin Lakes maar fault. I suggest that tectonics and not volcanism is responsible for the most recent deformation in the region based on fault geometries and earthquake timings, although more research is needed to tease out finer temporal and genetic relationships between tectonics and volcanism regionally. Second, I investigated the rupture pattern and earthquake history of the Calico fault system in the Eastern California Shear Zone. We mapped ~18 km of continuous rupture, with a mean offset of 2.3 m based on 39 field measurements. We also found evidence for two earthquakes, 0.5 - 1.7 ka and 5.5 - 6.6 ka through paleoseismic trenching. We develop a number of different multifault rupture scenarios using our rupture mapping and rupture scaling relationships to conduct Coulomb stress change modeling for the most recent earthquake on the Calico fault system. We find that the most recent event places regions adjacent to the fault in a stress shadow and may have both delayed the historic Landers and Hector Mine ruptures and prevented triggering of the Calico fault system during those events. Last, I studied the spatial distribution of the southern transition zone of the creeping section of the San Andreas fault at Parkfield, CA to determine if it shifted in response to the M6 2004 Parkfield earthquake. I used an Iterative Closest Point algorithm to find the displacement between two lidar datasets acquired 13 years apart. I compared creep rates measured before the 2004 earthquake to creep rates calculated from my lidar displacement results and found that there is not a discernible change in the overall pattern or distribution of creep as a response to the 2004 earthquake. Peaks within the lidar displacement results indicate complexity in the geometry of fault locking. / Doctor of Philosophy / Fault behavior varies widely across different regions, depending on the type of fault and local geology. In this dissertation I examine three regions with different mechanisms controlling deformation within them. First, I study the relationship between volcanic and tectonic induced faulting in the La Pine graben in the Oregon Cascades. While volcanoes and tectonics can both produce faults within a region, the surface expression of those faults changes depending on the underlying driver. I map > 20 new faults in the La Pine graben. I also conduct paleoseismic trenching on one of the newly identified faults, the Twin Lakes maar fault, and find that its most recent rupture occurred < 7.6 ka. I conclude that tectonism is the dominant driver of faulting within the La Pine graben based on the fault geometries and timing between identified regional earthquakes and volcanism. Second, I explore recent rupture on the Calico fault system in the Eastern California Shear Zone, which is a wide region across eastern California where deformation is distributed among many faults. Faulting in this region is complex, with some earthquakes occurring on multiple connected faults. I conducted a paleoseismic survey to determine the timing of the most recent earthquake(s) on the Calico fault system. This trenching effort found evidence for 1-2 earthquakes, the most recent occurring 0.5 – 1.7 ka. I use the rupture mapping and earthquake timing to develop a number of various rupture scenarios. I use these scenarios as inputs for computer modeling to explore the regional stress changes from these events and find that they reduce the overall stress in the area, elongating the amount of time between regional earthquakes. Last, I examine how creeping fault behavior on the San Andreas fault near Parkfield, CA changes as a response to an earthquake. Creeping behavior is where the two sides of a fault are continuously moving past one another. I examine the spatial distribution of where the San Andreas fault transitions from creeping to locked behavior by differencing two high-resolution lidar topographic datasets taken after the M6 2004 Parkfield earthquake. I compare my displacement results to pre-2004 datasets and conclude that the transition zone did not appreciably change as a result of the earthquake.

Understanding spatial and temporal variations in strain accumulation and release along plate boundaries is a fundamental problem in tectonics. Short-term and long-term slip rates are expected to be equal if the regional stress field remains unchanged over time, yet discrepancies between modern geodetic (decadal time scale) slip rates and long-term geologic (10^3 to 10^6 years) slip rates have been observed on parts of the Pacific-North American plate boundary system. Contemporary geodetic slip rates are observed to be ~2 times greater than late Pleistocene geologic slip rates across the southern Walker Lane. I use a combination of GPS geodesy, detailed field geologic mapping, high-resolution LiDAR geodetic imaging, and terrestrial cosmogenic nuclide geochronology to investigate the observed discrepancy between long- and short-term slip rates. I find that the present day slip rate derived from GPS geodesy across the Walker Lane at ~37.5°N is 10.6 ± 0.5 mm/yr. GPS data suggest that much of the observed discrepancy occurs west of the White Mountains fault zone. New dextral slip rates on the White Mountains fault zone of 1.1 ± 0.1 mm/yr since 755 ka, 1.9 +0.5/-0.4 mm/yr since 75-115 ka, 1.9 +0.5/-0.4 mm/yr since 38.4 ± 9.0 ka, and 1.8 +2.8/-0.7 mm/yr since 6.2 ± 3.8 ka are significantly faster than previous estimates and suggest that slip rates there have remained constant since the middle Pleistocene. On the Lone Mountain fault I calculate slip rates of 0.8 ± 0.1 mm/yr since 14.6 ± 1.0 ka and 0.7 ± 0.1 mm/yr since 8.0 ± 0.5 ka, which suggest that extension in the Silver Peak-Lone Mountain extensional complex has increased dramatically since the late Pleistocene.