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Published byKatarina Bermingham Modified about 1 year ago

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Static stress changes-- Coulomb

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SPRINGBRICKWINCH Force Balance – Brick will not move until: Force on spring Force resisting motion (its length change x its stiffness) (the weight of the brick x friction on surface) Modeled after Ross Stein’s Coulomb Training I Hypothesis: Faults interact by the transfer of stress EARTHQUAKE! (only if stick-slip) -Lisa Walsh

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SPRINGBRICKWINCH Modeled after Ross Stein’s Coulomb Training I BRICKSPRING Add another spring & brick If you start cranking winch, PURPLE will move first. Then tension on spring will move GREEN. EARTHQUAKE! Source fault Receiver fault = shear stress change + (coefficient of friction x normal stress change) ΔCFS = Δτ s +μ' Δσ n Coulomb stress calculation Coulomb stress change + ΔCFS = closer to failure - ΔCFS = farther from failure -Lisa Walsh

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Key concepts: Source faults Receiver faults Optimally oriented faults Assume receiver faults are close to failure Triggering lag time is a problem

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Change of coulomb stress on faults of specified orientation Can change spatially Remote: Sremote Induced: Sinduced Total:Sremote+Sinduced Can change spatially

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From King et al (BSSA, 1994)

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Change of coulomb stress on faults of optimal orientation

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from Todal et al (JGR, 2005)

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Stress changes are permanent but seismicity is not from Todal et al (JGR, 2005)

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Los Angeles Los Angeles Big Bear M = 6.5 (2 nd - 3 hrs later) Landers M = 7.3 Landers M = 7.3 (1 st ) First 3 hr of Landers aftershocks plotted First 3 hr of Landers aftershocks plotted from Stein (Nature, 2003) Landers earthquake triggered Big Bear earthquake 3 hrs later! Stress trigger zone Stress Shadow

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Los Angeles Los Angeles Hector Mine First 7 yr of aftershocks plotted First 7 yr of aftershocks plotted …and promotes the M=7.1 Hector Mine shock 7 years later (1999). from Stein (Nature, 2003)

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from Lin & Stein (JGR, 2004)

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