static stress changes--coulomb
DESCRIPTION
Static stress changes--Coulomb. Coulomb theory. Hypothesis: Faults interact by the transfer of stress. WINCH. SPRING. BRICK. EARTHQUAKE! (only if stick-slip). Force Balance – Brick will not move until : Force on spring Force resisting motion - PowerPoint PPT PresentationTRANSCRIPT
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Static stress changes--Coulomb
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SPRING BRICKWINCH
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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SPRING BRICKWINCH
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! EARTHQUAKE!
Source fault Receiver fault
= shear stress change + (coefficient of friction x normal stress change)
ΔCFS = Δτs+μ' Δσn
Coulomb stress calculationCoulomb
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 spatiallyRemote: Sremote
Induced: Sinduced
Total:Sremote+Sinduced
Can change spatially
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From King et al (BSSA, 1994)
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From King et al (BSSA, 1994)
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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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from Todal et al (JGR, 2005)
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from Todal et al (JGR, 2005)
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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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LosAngelesLosAngeles
Big Bear M = 6.5 (2nd - 3 hrs later)
Big Bear M = 6.5 (2nd - 3 hrs later)
Landers M = 7.3Landers M = 7.3(1(1stst))
First 3 hr of Landers
aftershocks
plotted
First 3 hr of Landers
aftershocks
plottedfrom Stein (Nature, 2003)
1992 - Landers earthquake triggered Big Bear earthquake 3 hrs later!
Stress trigger zone
Stress Shado
w
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LosAngelesLosAngeles
Hector Mine Hector Mine
First 7 yr of
aftershocksplotted
First 7 yr of
aftershocksplotted
…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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from Lin & Stein (JGR, 2004)
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from Lin & Stein (JGR, 2004)
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from Lin & Stein (JGR, 2004)
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from Lin & Stein (JGR, 2004)
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from Lin & Stein (JGR,
2004)
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from Lin & Stein (JGR,
2004)
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from Lin & Stein (JGR,
2004)
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http://quake.usgs.gov/research/deformation/modeling/animations/index.html