Earthquake Nucleation Size: Evidence of Loading Rate Dependence in Laboratory Faults

Autor: Giulio Di Toro, Stefano Giani, Stefan Nielsen, Simon Guerin‐Marthe, Robert E. Bird
Rok vydání: 2019
Předmět:
010504 meteorology & atmospheric sciences
Nucleation
Volcanology
Slip (materials science)
01 natural sciences
Structural Geology
nucleation length of earthquakes
laboratory fault
Earthquake Dynamics
Geochemistry and Petrology
Earth and Planetary Sciences (miscellaneous)
Shear stress
Rheology and Friction of Fault Zones
Fault mechanics
Geodesy and Gravity
seismicity patterns of subduction zones
Geophysics
Space and Planetary Science
Monitoring
Forecasting
Prediction
Seismology
Earthquake Interaction
Forecasting
and Prediction
Research Articles
Mineralogy and Petrology
0105 earth and related environmental sciences
Subduction Zone Processes
Fracture mechanics
Mechanics
Marine Geology and Geophysics
Seismic Cycle Related Deformations
Tectonics
Geochemistry
Tectonophysics
Shear (geology)
Time Variable Gravity
Direct shear test
Natural Hazards
Geology
Research Article
Zdroj: Journal of Geophysical Research. Solid Earth
ISSN: 2169-9356
2169-9313
1365-246x
DOI: 10.1029/2018jb016803
Popis: Recent Global Positioning System observations of major earthquakes such as the 2014 Chile megathrust show a slow preslip phase releasing a significant portion of the total moment (Ruiz et al., 2014, https://doi.org/10.1126/science.1256074). Despite advances from theoretical stability analysis (Rubin & Ampuero, 2005, https://doi.org/10.1029/2005JB003686; Ruina, 1983, https://doi.org/10.1029/jb088ib12p10359) and modeling (Kaneko et al., 2017, https://doi.org/10.1002/2016GL071569), it is not fully understood what controls the prevalence and the amount of slip in the nucleation process. Here we present laboratory observations of slow slip preceding dynamic rupture, where we observe a dependence of nucleation size and position on the loading rate (laboratory equivalent of tectonic loading rate). The setup is composed of two polycarbonate plates under direct shear with a 30‐cm long slip interface. The results of our laboratory experiments are in agreement with the preslip model outlined by Ellsworth and Beroza (1995, https://doi.org/10.1126/science.268.5212.851) and observed in laboratory experiments (Latour et al., 2013, https://doi.org/10.1002/grl.50974; Nielsen et al., 2010, https://doi.org/10.1111/j.1365-246x.2009.04444.x; Ohnaka & Kuwahara, 1990, https://doi.org/10.1016/0040-1951(90)90138-X), which show a slow slip followed by an acceleration up to dynamic rupture velocity. However, further complexity arises from the effect of (1) rate of shear loading and (2) inhomogeneities on the fault surface. In particular, we show that when the loading rate is increased from 10−2 to 6 MPa/s, the nucleation length can shrink by a factor of 3, and the rupture nucleates consistently on higher shear stress areas. The nucleation lengths measured fall within the range of the theoretical limits L b and L∞ derived by Rubin and Ampuero (2005, https://doi.org/10.1029/2005JB003686) for rate‐and‐state friction laws.
Key Points The nucleation length decreases with loading rate, implying that smaller‐size asperities clusters can be triggered by accelerated slipThe nucleation position localizes on high coulomb stress patches with small‐scale inhomogeneities at high loading ratesThe measured nucleation length of laboratory earthquakes falls into the range predicted by numerical and theoretical studies
Databáze: OpenAIRE
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