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http://hdl.handle.net/2122/14419
Authors: | Piana Agostinetti, Nicola* Giacomuzzi, Genny* Chiarabba, Claudio* |
Title: | Across-Fault Velocity Gradients and Slip Behavior of the San Andreas Fault Near Parkfield | Journal: | Geophysical Research Letters | Series/Report no.: | 1 / 47 (2020) | Publisher: | Wiley Agu | Issue Date: | 16-Jan-2020 | DOI: | 10.1029/2019GL084480 | Keywords: | Fault rheology and slip behavior; acrosso fault velocity gradients; fully non‐linear tomography | 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. |
Appears in Collections: | Article published / in press |
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Agostinetti_et_al-2020-Geophysical_Research_Letters.pdf | 6.73 MB | Adobe PDF | View/Open |
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