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Simulating big earthquakes Accessing the inaccessible with models
Subduction zone earthquakes Two stories of deformation and stress
Pacific Ocean
Eurasia NorthAmerica
1: 1995 M8 Jalisco, Mexico quake 2: 2004 M9
Sumatra-Andaman quake
NorthAmerica
PacificOcean
North AmericanPlate
MexicoM
idd
leAm
erica
Trench
Pacific Ocean
Mid
dle
America
Trench
0 100 200
kilometers
N
4 cm
/yr
RiveraPlate
1. The M8 Jalisco Earthquake: A natural laboratory for stress-triggering
M8 Jalisco Quake
Subduction zone Converging tectonic plates
North AmericanPlate
MexicoM
idd
leAm
erica
Trench
Pacific Ocean
Mexico
4 cm
/yr
North AmericanPlate
Mid
dle
America
Trench
0 100 200
kilometers
N
Pacific Ocean
North AmericanPlate
Mexico
Mexico
RiveraPlate
Rivera Plate North American Plateoceanic crust continental crust
M8 Jalisco Quake
Earthquakes Release of built-up tectonic stress
Rivera Plate North American PlateRivera Plate North American Plate
cross-section
oceanic crust continental crust
M8 Jalisco Quake
Study site 1995 Jalisco earthquake
RiveraPlate
North AmericanPlate
MexicoM
idd
leAm
erica
TrenchPacific Ocean
Mid
dle
America
Trench
0 100 200
kilometers
N
1995 Feb, GPS sites installed
Oct 9, M=8
Dec 11, M=6
GPS site
0.5 m
4 cm
/yr
NorthAmerica
PacificOcean
M8 Jalisco Quake
Observations Earthquakes close together in both space & time
October 9, M=8
December 11, M=6
0 100 200
kilometers
63 d
ays
* earthquakes linked together
rupture plane
M8 Jalisco Quake
Storage and release of elastic energy • Tectonic stresses load fault • Rocks store elastic energy • Frictional resistance of fault is overcome
Stress-triggering 101: The interaction of earthquakes
M8 Jalisco Quake
Storage and release of elastic energy • Tectonic stresses load fault • Rocks store elastic energy • Frictional resistance of fault is overcome
Stress-triggering 101: The interaction of earthquakes
M8 Jalisco Quake
Storage and release of elastic energy • Tectonic stresses load fault • Rocks store elastic energy • Frictional resistance of fault is overcome
Stress-triggering 101: The interaction of earthquakes
M8 Jalisco Quake
tectonicstress
normalstress
friction
Storage and release of elastic energy • Tectonic stresses load fault • Rocks store elastic energy • Frictional resistance of fault is overcome
Stress-triggering 101: The interaction of earthquakes
M8 Jalisco Quake
tectonicstress
normalstress
friction
tectonicstress(winch)
normalstress
(gravity)
friction(sandpaper)
Storage and release of elastic energy • Tectonic stresses load fault • Rocks store elastic energy • Frictional resistance of fault is overcome
Stress-triggering 101: The interaction of earthquakes
M8 Jalisco Quake
Earthquake coupling • Stress release from loads other faults • Quake 1 may trigger Quake 2
fault 1quake 1
fault 2quake 2
Stress-triggering 101: The interaction of earthquakes
M8 Jalisco Quake
Earthquake coupling • Stress release from an earthquake loads other faults • Quake 1 may trigger Quake 2
1
stresstransfer
friction
normalstress
2
tectonicstress
normalstress
Stress-triggering 101: The interaction of earthquakes
M8 Jalisco Quake
1
stresstransfer
friction
normalstress
2
tectonicstress
normalstress
tectonicstress(winch)
normalstress
(gravity)
friction(sandpaper)
normalstress
(gravity)
stresstransfer
(elastic material)
2 2
1
Stress-triggering 101: The interaction of earthquakes
Earthquake coupling • Stress release from an earthquake loads other faults • Quake 1 may trigger Quake 2
M8 Jalisco Quake
What about the time lag? A good model must also account for the 63-day lag
October 9, M=8
December 11, M=6
0 100 200
kilometers
63 d
ays
* earthquakes linked together
rupture plane
lag
M8 Jalisco Quake
Hypothesis
October 9, M=8 0 100 200
kilometers
fault
stress
(from M=8 quake)
pore pressure along fault slowly increases after M=8 quake
pore pressure
(along fault of M=6 quake)
triggered M=6 quake
+
pore pressure: pressure of water in the pores of the rock.
definition
M8 Jalisco Quake
Poroelastic mechanics Physical interaction of rock and pore water
saturated
rockrock matrix
fluid-filledpore
0– +
pore pressure
tension
0– +
pore pressure
compression
M8 Jalisco Quake
Earthquake mechanics The meaning of and
pore pressure tension
0– +
pore pressure tension
0– +
compression
0– +
pore pressure
compression
0– +
pore pressure
fault
M8 Jalisco Quake
Rivera plate North American plate
M = 8( t = 0 )
M = 6( t = 63 days )
tension
tension
compression
compression
cross-section ofsubduction zone
pore pressure near M=6 fault0
– +
t = 63 days
fluid flow0– +
t = 0+
Conceptual model Earthquake released stress and pore pressure
M8 Jalisco Quake
* Coulomb stress along fault can change due to fluid flow changing pore pressure
Coulomb stress tendency for slip to occur along a fault
definition0
– +
shearstress
normalstress
pore pressure
faultpore pressure
shear stress
normal stress
friction
Fault stability: Coulomb stress Combination of stress, pore pressure, and friction
M8 Jalisco Quake
Fault Stability: Coulomb Stress Experiment apparatus
0– +
shearstress
normalstress
water pressure
fault
shearstress
normalstress
water pressure
fault
M8 Jalisco Quake
Fault Stability: Coulomb Stress Experiment apparatus
normalstress
fault
water pressure = 0
shear stress = 0
normal stress 0
initial conditions
M8 Jalisco Quake
Fault Stability: Experiment Earthquake changes Coulomb stress
earthquake
shear
stress
normal
stress
fault
M8 Jalisco Quake
Fault Stability: Experiment Pore pressure changes Coulomb stress changes
earthquake
shear
stress
normal
stress
fault
water pressureexcess water pressure induction device
M8 Jalisco Quake
Fault Stability: Experiment Pore pressure changes Coulomb stress changes
shear
stress
normal
stress
fault
water pressureexcess water pressure induction device
M8 Jalisco Quake
- GPS station
1800
km
1300 km
250
km
220 km
oceanic crustcontinental crust
mantle
FEM: numerical model; predicts deformation, stress, and pore pressure due to earthquakes.
definition
Method: Construct deformation models Finite Element Model (FEM)
M8 Jalisco Quake
M=6epicenter
(pore pressure initially drops after M8 quake)
1800
km
1300 km
oceanic crust
continental crust
10 5 0 -5 -10po
re p
ress
ure
(kP
a)
North
days after M=8 earthquake:
Predicted pore pressure Initial conditions following M8 earthquake
M8 Jalisco Quake
1800
km
1300 km
oceanic crust
continental crust
10 5 0 -5 -10po
re p
ress
ure
(kP
a)
North
days after M=8 earthquake:
Predicted pore pressure Gradual recovery to pre-earthquake equilibrium
M=6epicenter
(pore pressure slowly increases after M8 quake)
M8 Jalisco Quake
The M=8 earthquake triggered the M=6 earthquake, fluid flow accounts for the delay
the M=6 earthquake was a predictable event !
stress
(from M=8 quake)
pore pressure
(along fault of M=6 quake)
triggered M=6 quake
+
Conclusions Recall the hypothesis…
M8 Jalisco Quake
0.3
0.2
0.1
0.0
stress (MPa)
- GPS station
220 km
years after M=8 earthquake
The Project Continues Predicting deformation & stress evolution
brittle upper crust(stress accumulates)
ductile mantle(stresses relax)
M8 Jalisco Quake
Earthquake coupling • Stress release loads mantle• Flow relaxes stresses in mantle (silly putty) and transfers stress to fault 1
1
stresstransfer
friction
normalstress
2
tectonicstress
normalstress
Stress-triggering: Viscoelastic relaxation
viscous silly putty(slowly flows & relaxes stress)
M8 Jalisco Quake
M9 earthquake
tsunami
IndianOcean
Sumatra
India
Australia
2. Applying the lessons learned 2004 M9 Sumatra-Andaman earthquake & tsunami
M9 Sumatra-Andaman Quake
Indo-Australian Plate
Eurasian Plate
6 cm/yr
9.2
Rupture & deformation 2004 M9 Sumatra-Andaman earthquake & tsunami
Dec 262004
M9 Sumatra-Andaman Quake
Indo-Australian Plate
Eurasian Plate
6 cm/yr
9.2
Sumatra-Andaman FEM 1) Simulate poroelastic stress-triggering
6 cm/yr 8.7
9.2 Mar 282005
Dec 262004
M9 Sumatra-Andaman Quake
Are the aftershocks predictable in space and time?
not yet, but…we are working on it!
Coupling the 2004 & 2005 quakes What if models in place prior to these events?
M9 Sumatra-Andaman Quake
up
down
Indo-Australian Plate
Eurasian Plate
6 cm/yr
9.2
Dec 262004
Sumatra-Andaman FEM 2) Simulate seafloor deformation tsunamigenesis
M9 Sumatra-Andaman Quake
Predicting seafloor deformation Changes overlying water column
seafloor
ocean surface
cross-section
wat
er c
olu
mn
Indo-Aust Plate Eurasian Plate
fault
M9 Sumatra-Andaman Quake
Predicting seafloor deformation Changes overlying water column
seafloor
ocean surface
cross-section
wat
er c
olu
mn
Indo-Aust Plate Eurasian Plate
fault
M9 Sumatra-Andaman Quake
seafloor
cross-section
wave propagation
earthquakedeformation
India andSri Lanka
Sumatra &Thailand
Predicting seafloor deformation Drives tsunami propagation models
M9 Sumatra-Andaman Quake
seafloor
cross-section
wave propagation
Sumatra &Thailand
India andSri Lanka
M9 Sumatra-Andaman Quake
Predicting seafloor deformation Drives tsunami propagation models
seafloor
cross-section
earthquakedeformation
cross-section
ocean surface
wave propagation:velocity is a
function of depthslow fast fast slow
M9 Sumatra-Andaman Quake
Predicting seafloor deformation Drives tsunami propagation models run-up
seafloor
cross-section
earthquakedeformation
cross-section
wave propagation:velocity is a
function of depthslow fast fast slow
M9 Sumatra-Andaman Quake
Predicting seafloor deformation Drives tsunami propagation models run-up
In progress: Virtual Sumatra-Andaman subduction zone
M9 Sumatra-Andaman Quake
M9 Sumatra-Andaman Quake
In progress: Virtual Sumatra-Andaman subduction zone
M9 Sumatra-Andaman Quake
In progress: Virtual Sumatra-Andaman subduction zone
seafloordeformation
M9 Sumatra-Andaman Quake
In progress: Virtual Sumatra-Andaman subduction zone
seafloordeformation
Imagine the possibilities…
• deformation predictions (tsunami sources)
• stress evolution predictions ultimately, earthquake predictions
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