Behavior of Repeating Earthquake Sequences in Central California and the Implications for Subsurface Fault Creep
Behavior of Repeating Earthquake Sequences in Central California and the Implications for Subsurface Fault Creep

Author:

Publisher:

Published: 2007

Total Pages: 119

ISBN-13:

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Repeating earthquakes (REs) are sequences of events that have nearly identical waveforms and are interpreted to represent fault asperities driven to failure by loading from aseismic creep on the surrounding fault surface at depth. We investigate the occurrence of these REs along faults in central California to determine which faults exhibit creep and the spatio-temporal distribution of this creep. At the juncture of the San Andreas and southern Calaveras-Paicines faults, both faults as well as a smaller secondary fault, the Quien Sabe fault, are observed to produce REs over the observation period of March 1984-May 2005. REs in this area reflect a heterogeneous creep distribution along the fault plane with significant variations in time. Cumulative slip over the observation period at individual sequence locations is determined to range from 5.5-58.2 cm on the San Andreas fault, 4.8-14.1 cm on the southern Calaveras-Paicines fault, and 4.9-24.8 cm on the Quien Sabe fault. Creep at depth appears to mimic the behaviors seen of creep on the surface in that evidence of steady slip, triggered slip, and episodic slip phenomena are also observed in the RE sequences. For comparison, we investigate the occurrence of REs west of the San Andreas fault within the southern Coast Range. Events within these RE sequences only occurred minutes to weeks apart from each other and then did not repeat again over the observation period, suggesting that REs in this area are not produced by steady aseismic creep of the surrounding fault surface.

Observations and Modeling of Shallow Fault Creep Along the San Andreas Fault System
Observations and Modeling of Shallow Fault Creep Along the San Andreas Fault System

Author: Meng Wei

Publisher:

Published: 2011

Total Pages: 204

ISBN-13: 9781124449715

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This dissertation focuses on observations and modeling of fault creep in California aiming to understand the relationship between creep and earthquakes and assess the earthquake hazards in California. Chapter 1 gives an introduction of fault creep research in California, geodetic methods used to measure fault creep, and mechanism of fault creep. Chapter 2 documents an investigate on a creep event on the Supersitition Hills Fault in Southern California and the spatial and temporal variations in slip history between 1992 and 2008 using ERS, and Envisat Satellite data confirming that the fault creep is confined within the sediments layer and is probably due to the low normal stress in unconsolidated sediments. Chapter 3 presents a study on triggered slip on faults in the Salton Trough by the 2010 El Mayor-Cucapah Mw 7.2 earthquake. Chapter 4 compiles geodetic data and investigates the relationship between shallow stress accumulating rate and creep rate. Chapter 5 and 6 explores two technical projects related to fault creep observations in California. Chapter 5 analyzes decorrelation of L-band and C-band interferograms in California with implications for future fault creep study. Chapter 6 proposes an optimal way to combine GPS and InSAR to measure interseismic deformation, including fault creep. The proposed method is compared with other method and the improvements are observed. Chapter 7 presents the conclusions of the previous six chapters. Chapter 8 presents my work in the first two years in graduate school, which is not related to fault creep. We compute global maps of surface minus basal heat flow that show qualitative agreement with heat flow based on the inverse square root of age relation. In the beginning of each chapter, I provide you an earthquake safety tip. I borrowed them from an interesting website for your safety and interests. Hopefully it could be one more motivation to read through my thesis. I didn't bother to invent them, as Ralph Waldo Emerson noted "All my best thoughts were stolen by the ancients."