Static%20stress%20changes--Coulomb

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Static stress changes--Coulomb
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Coulomb theory
Hypothesis Faults interact by the transfer of
stress
SPRING
BRICK
WINCH
EARTHQUAKE! (only if stick-slip)
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 Steins Coulomb Training I
-Lisa Walsh
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Coulomb theory
Modeled after Ross Steins Coulomb Training I
Source fault
Receiver fault
SPRING
BRICK
WINCH
BRICK
SPRING
EARTHQUAKE!
EARTHQUAKE!

• Add another spring brick
• If you start cranking winch, PURPLE will move
  first.
• Then tension on spring will move GREEN.

?CFS closer to failure
- ?CFS 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 TotalSremoteSinduced
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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Southern California San Andreas
Stress Shadow
Landers M 7.3 (1st)
Big Bear M 6.5 (2nd - 3 hrs later)
Los Angeles
First 3 hr of Landers
aftershocks plotted
Stress trigger zone
from Stein (Nature, 2003)
1992 - Landers earthquake triggered Big Bear
earthquake 3 hrs later!
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Hector Mine
Los Angeles
First 7 yr of
aftershocks plotted
from Stein (Nature, 2003)
and promotes the M7.1 Hector Mine shock 7 years
later (1999).

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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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