A long-lasting question in earthquake physics is why slip on faults occurs as creep or dynamic rupture. We compute passive measurements of the seismic P wave velocity gradient across the San Andreas Fault near Parkfield, where this transition of slip mode occurs at a scale of a few kilometers. Unbiased measurements are obtained through the application of a new Bayesian local earthquake tomographic code that avoids the imposition of any user-defined, initial velocity-contrast across the fault, or any damping scheme that may cause biased amplitude in retrieved seismic velocities. We observe that across-fault velocity gradients correlate with the slip behavior of the fault. The P wave velocity contrast decays from 20% in the fault section that experience dynamic rupture to 4% in the creeping section, suggesting that rapid change of material properties and attitude to sustain supra-hydrostatic fluid pressure are conditions for development of dynamic rupture. Low Vp and high Vp/Vs suggest that fault rheology at shallow depth is conversely controlled by low frictional strength material.

Piana Agostinetti, N., Giacomuzzi, G., Chiarabba, C. (2020). Across-Fault Velocity Gradients and Slip Behavior of the San Andreas Fault Near Parkfield. GEOPHYSICAL RESEARCH LETTERS, 47(1) [10.1029/2019GL084480].

Across-Fault Velocity Gradients and Slip Behavior of the San Andreas Fault Near Parkfield

Piana Agostinetti, N
;
2020

Abstract

A long-lasting question in earthquake physics is why slip on faults occurs as creep or dynamic rupture. We compute passive measurements of the seismic P wave velocity gradient across the San Andreas Fault near Parkfield, where this transition of slip mode occurs at a scale of a few kilometers. Unbiased measurements are obtained through the application of a new Bayesian local earthquake tomographic code that avoids the imposition of any user-defined, initial velocity-contrast across the fault, or any damping scheme that may cause biased amplitude in retrieved seismic velocities. We observe that across-fault velocity gradients correlate with the slip behavior of the fault. The P wave velocity contrast decays from 20% in the fault section that experience dynamic rupture to 4% in the creeping section, suggesting that rapid change of material properties and attitude to sustain supra-hydrostatic fluid pressure are conditions for development of dynamic rupture. Low Vp and high Vp/Vs suggest that fault rheology at shallow depth is conversely controlled by low frictional strength material.
Articolo in rivista - Articolo scientifico
acrosso fault velocity gradients; Fault rheology and slip behavior; fully non-linear tomography;
English
20-dic-2019
2020
47
1
e2019GL084480
open
Piana Agostinetti, N., Giacomuzzi, G., Chiarabba, C. (2020). Across-Fault Velocity Gradients and Slip Behavior of the San Andreas Fault Near Parkfield. GEOPHYSICAL RESEARCH LETTERS, 47(1) [10.1029/2019GL084480].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/340529
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