FROM SLAB WINDOW TO THE MTJ CRUSTAL CONVEYOR: BUILDING ON BILL DICKINSON’S FOUNDATIONAL INSIGHT TO UNDERSTAND THE DEVELOPMENT OF THE SAN ANDREAS PLATE BOUNDARY

2016 ◽  
Author(s):  
Kevin P. Furlong ◽  
Keyword(s):  
Plate Boundary ◽  
San Andreas ◽  
Slab Window

scholarly journals New geodetic constraints on southern San Andreas fault-slip rates, San Gorgonio Pass, California

Geosphere ◽  
2020 ◽  
Author(s):  
Katherine A. Guns ◽  
Richard A Bennett ◽  
Joshua C. Spinler ◽  
Sally F. McGill
Keyword(s):  
Velocity Field ◽  
Southern California ◽  
San Andreas Fault ◽  
Plate Boundary ◽  
Slip Rate ◽  
Fault Slip ◽  
Slip Rates ◽  
San Andreas ◽  
Fault Slip Rates ◽  
Gps Velocity Field

Assessing fault-slip rates in diffuse plate boundary systems such as the San Andreas fault in southern California is critical both to characterize seis­mic hazards and to understand how different fault strands work together to accommodate plate boundary motion. In places such as San Gorgonio Pass, the geometric complexity of numerous fault strands interacting in a small area adds an extra obstacle to understanding the rupture potential and behavior of each individual fault. To better understand partitioning of fault-slip rates in this region, we build a new set of elastic fault-block models that test 16 different model fault geometries for the area. These models build on previ­ous studies by incorporating updated campaign GPS measurements from the San Bernardino Mountains and Eastern Transverse Ranges into a newly calculated GPS velocity field that has been removed of long- and short-term postseismic displacements from 12 past large-magnitude earthquakes to estimate model fault-slip rates. Using this postseismic-reduced GPS velocity field produces a best- fitting model geometry that resolves the long-standing geologic-geodetic slip-rate discrepancy in the Eastern California shear zone when off-fault deformation is taken into account, yielding a summed slip rate of 7.2 ± 2.8 mm/yr. Our models indicate that two active strands of the San Andreas system in San Gorgonio Pass are needed to produce sufficiently low geodetic dextral slip rates to match geologic observations. Lastly, results suggest that postseismic deformation may have more of a role to play in affecting the loading of faults in southern California than previously thought.

scholarly journals Constraints on North American-Pacific Plate Boundary Deformation in Central California from VLBI and Ground-Based Geodetic Data

1988 ◽  
Vol 129 ◽  
pp. 353-353
Author(s):  
Jeanne Sauber ◽  
Thomas H. Jordan ◽  
Gregory C. Beroza ◽  
Thomas A. Clark ◽  
Michael Lisowski
Keyword(s):  
North American ◽  
A Priori ◽  
Plate Boundary ◽  
Pacific Plate ◽  
Rate Of Change ◽  
Geodetic Data ◽  
Central California ◽  
The North ◽  
San Andreas ◽  
Plate Boundary Deformation

To accommodate the relative motion across the North American-Pacific plate boundary predicted by global plate solutions, significant deformation on faults other than the San Andreas is necessary. In central California, this deformation is thought to include distributed compression perpendicular to the San Andreas as well as right-lateral strike-slip motion parallel to the San Andreas on faults such as the San Gregorio/Hosgri system. A self-consistent set of VLBI observations from experiments beginning in October 1982 is used to determine the vector rate of change of station position at central California VLBI sites Ovro, Mojave, Vandenberg, Fort Ord, Presidio, and Point Reyes. To estimate VLBI station positions, a procedure is used that minimizes the uncertainties in defining a reference frame by including a priori geologic and geodetic information. The vector rate of change of station positions provides constraints on the integrated deformation rates between stations. Geologic and geophysical data suggest that the rate and mode of deformation varies on both local and regional scales. Thus, the VLBI derived results are interpreted in the context of an overall tectonic framework by examining geologic and ground-based geodetic data.

scholarly journals Constraints on rock uplift in the eastern Transverse Ranges and northern Peninsular Ranges and implications for kinematics of the San Andreas fault in the Coachella Valley, California, USA

Geosphere ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 723-750
Author(s):  
James A. Spotila ◽  
Cody C. Mason ◽  
Joshua D. Valentino ◽  
William J. Cochran
Keyword(s):  
San Andreas Fault ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Fault System ◽  
Published Data ◽  
Strain Partitioning ◽  
San Bernardino Mountains ◽  
Coachella Valley ◽  
San Andreas ◽  
Peninsular Ranges

Abstract The nexus of plate-boundary deformation at the northern end of the Coachella Valley in southern California (USA) is complex on multiple levels, including rupture dynamics, slip transfer, and three-dimensional strain partitioning on nonvertical faults (including the San Andreas fault). We quantify uplift of mountain blocks in this region using geomorphology and low-temperature thermochronometry to constrain the role of long-term vertical deformation in this tectonic system. New apatite (U-Th)/He (AHe) ages confirm that the rugged San Jacinto Mountains (SJM) do not exhibit a record of rapid Neogene exhumation. In contrast, in the Little San Bernardino Mountains (LSBM), rapid exhumation over the past 5 m.y. is apparent beneath a tilted AHe partial retention zone, based on new and previously published data. Both ranges tilt away from the Coachella Valley and have experienced minimal denudation from their upper surface, based on preservation of weathered granitic erosion surfaces. We interpret rapid exhumation at 5 Ma and the gentle tilt of the erosion surface and AHe isochrons in the LSBM to have resulted from rift shoulder uplift associated with extension prior to onset of transpression in the Coachella Valley. We hypothesize that the SJM have experienced similar rift shoulder uplift, but an additional mechanism must be called upon to explain the pinnacle-like form, rugged escarpment, and topographic disequilibrium of the northernmost SJM massif. We propose that this form stems from erosional resistance of the Peninsular Ranges batholith relative to more-erodible foliated metamorphic rocks that wrap around it. Our interpretations suggest that neither the LSBM nor SJM have been significantly uplifted under the present transpressive configuration of the San Andreas fault system, but instead represent relict highs due to previous tectonic and erosional forcing.

The San Andreas Fault Zone Drilling Project: Scientific Objectives and Technological Challenges

1995 ◽  
Vol 117 (4) ◽  
pp. 263-270 ◽  
Author(s):  
S. H. Hickman ◽  
L. W. Younker ◽  
M. D. Zoback ◽  
G. A. Cooper
Keyword(s):  
Fault Zone ◽  
San Andreas Fault ◽  
Fractured Rock ◽  
Fluid Pressure ◽  
Plate Boundary ◽  
Fault System ◽  
Earthquake Activity ◽  
Scientific Drilling ◽  
San Andreas ◽  
San Andreas Fault System

We are leading a new international initiative to conduct scientific drilling within the San Andreas fault zone at depths of up to 10 km. This project is motivated by the need to understand the physical and chemical processes operating within the fault zone and to answer fundamental questions about earthquake generation along major plate-boundary faults. Through a comprehensive program of coring, fluid sampling, downhole measurements, laboratory experimentation, and long-term monitoring, we hope to obtain critical information on the structure, composition, mechanical behavior and physical state of the San Andreas fault system at depths comparable to the nucleation zones of great earthquakes. The drilling, sampling and observational requirements needed to ensure the success of this project are stringent. These include: 1) drilling stable vertical holes to depths of about 9 km in fractured rock at temperatures of up to 300°C; 2) continuous coring and completion of inclined holes branched off these vertical boreholes to intersect the fault at depths of 3, 6, and 9 km; 3) conducting sophisticated borehole geophysical measurements and fluid/rock sampling at high temperatures and pressures; and 4) instrumenting some or all of these inclined core holes for continuous monitoring of earthquake activity, fluid pressure, deformation and other parameters for periods of up to several decades. For all of these tasks, because of the overpressured clay-rich formations anticipated within the fault zone at depth, we expect to encounter difficult drilling, coring and hole-completion conditions in the region of greatest scientific interest.

Viscoelastic relaxation of cyclic displacements on the San Andreas Fault

1979 ◽  
Vol 365 (1720) ◽  
pp. 121-144 ◽  
Keyword(s):  
Time Dependence ◽  
San Andreas Fault ◽  
Finite Thickness ◽  
Plate Boundary ◽  
Geological Time ◽  
Short Term ◽  
Newtonian Viscosity ◽  
Common Boundary ◽  
San Andreas ◽  
Plane Displacement

It is recognized that displacements on major plate margin faults such as the San Andreas Fault in California occur episodically. In this paper we construct a mathematical model of the fault as the boundary between two semi-infinite lithosphere plates of finite thickness, moving in opposite directions parallel to their common boundary with constant velocities at infinity but locked together on the boundary except during great earthquakes. The surface plates behave elastically but the underlying asthenosphere, although elastic in the short term, behaves as a viscous fluid on geological time scales and is treated as a viscoelastic half space linked to the lithosphere by continuity of stress and displacement. An analytic solution is obtained for the anti-plane displacement and shear stress on the surface in terms of the displacement on the fault. We apply the solution to compute the response to an infinite sequence of stepwise offsets on the fault, and to periodic displacements. The interaction of the plates with the asthenosphere damps out the time-dependence at large distances from the plate boundary, the relaxation process being characterized by a time scale T = η/G ( η = Newtonian viscosity, G = shear modulus). The results should be applicable to understanding the time dependence of the strain as a function of distance from the San Andreas Fault.

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