Ground Motion Simulation
Transcript of Ground Motion Simulation
Ground Motion Simulation
Case Study: 1906 San Francisco Earthquake
Brad Aagaard
November 2, 2007
Project Personnel
Collaboration among scientists from USGS and 4 other institutions
USGS Menlo Park Brad Aagaard, John Boatwright, Thomas Brocher,Howard Bundock, Russell Graymer, Thomas Holzer, RobertJachens, Dave Keefer, Linda Seekins, Robert Simpson, CarlWentworth, Mary Lou Zoback
USGS Golden Stephen Harmsen, Stephen Hartzell
Stanford University Greg Beroza, Paul Segall, Seok Goo Song
Lawrence Livermore National Laboratory Shawn Larsen, KathleenMcCandless, Stefan Nilsson, Anders Petersson, Arthur Rodgers,Bjorn Sjogreen, Hrvoje Tkalcic
URS Pasadena Robert Graves
UC Berkeley David Dolenc, Doug Dreger1
Outline
• Overview of SF06 simulation project
• Validation with 1989 Loma Prieta earthquake
• Comparison of MMI: synthetics versus instrumental (ShakeMap)• Comparison of velocity waveforms: synthetics versus observed
• Simulations of the 1906 San Francisco earthquake
• Comparison of MMI: synthetics versus Boatwright’s ShakeMap• Ground motions from 1906 and scenario events• Response of 20-story SMRF buildings (brittle vs. ductile welds)
• Data availability
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The SF06 Simulation Project
Objectives:
• Estimate ground motions for the 1906 earthquake and similarhypothetical events on the San Andreas fault
• Examine the impact if they happened today
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Project Plan
Wald et al. (1991)
Beroza (1991)
Source Models
ground motionsRecorded
ShakeMap
Constraints
(validation)1989 M6.9 Loma Prieta
GeologicStructure
Ground MotionSimulations
Song et al.
Source Models
Boatwright et al.ShakeMap
Constraints
Earthquake EffectsModeling
1906 M7.9 San Francisco
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Jachens et al. 3-D Geologic Model
Unified representation of fault surfaces and lithologies
• Fault surfaces and lithologic boundaries
• Active and inactive faults• Depositional surfaces and unconformities• Topography & bathymetry
• Hierarchical structure (how to assemble blocks from surfaces)
• Easy to refine/update model• Easy to extract subsets of features
• Constructed in Earth Vision (Dynamic Graphics)
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Geologic Model: Geographic Coverage
Detailed model is surrounded by low-resolution, simple model
-126˚ -125˚ -124˚ -123˚ -122˚ -121˚ -120˚ -119˚35˚
36˚
37˚
38˚
39˚
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41˚
0 100 200km
Detailed Velocity Model
Regional Velocity Model
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Brocher et al. 3-D Seismic Velocity Model
Create seismic velocity model from geologic model
• Assign material properties to lithologies in geologic model
• Develop regressions based on variety of data• Check against tomographic models
• Given longitude/latitude/elevation return material properties
• Vp• Vs• Density• Qp• Qs• Lithology & depth from free surface
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Ground Motion Modeling Groups
Five groups using variety of domains with different features
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0 100 200km
Harmsen et al.
Aagaard
Larsen et al.G
raves
Petersson et al.
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Numerical Models
Same general features but minor implementation differences
• Similarities
• Solve dynamic elasticity equation for rupture on finite-fault• Include 3-D variations in physical properties
• Differences
• Simulation domains• Minimum period and minimum shear-wave speed• Spatial & temporal discretization schemes• Attenuation: values and implementation• Accommodating topography
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Reality Check: 1989 Loma Prieta Eq
Gauge level of accuracy of ground motion modeling
• Simulate earthquake with Wald and Beroza source models
• Compare wave propagation implementation across modelers
• Are source models closer than wave propagation implementations?• What wave propagation implementations match observations?
• Test geologic and seismic velocity models
• What areas seem to be well-characterized by models?• What areas seem to be poorly-characterized by models?
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MMI: Synthetics (Beroza Source) versus Instrumental
Synthetics capture large length-scale variations in shaking
Graves (f < 1.0 Hz) ShakeMap
-123˚ -122˚ -121˚
37˚
38˚
0 50km
IIIIIIIVVVIVIIVIIIIXX
MMI
San Francisco
San Jose
Santa Cruz
Livermore
Concord
Monterey
Hollister
-123˚ -122˚ -121˚
37˚
38˚
0 50km
IIIIIIIVVVIVIIVIIIIXX
MMI
San Francisco
San Jose
Santa Cruz
Livermore
Concord
Monterey
Hollister
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MMI Residuals: Graves Synthetic-Observed
Long-period synthetics underpredict MMI due to limited bandwidth
-123˚ -122˚ -121˚
37˚
38˚
0 50km
-2
-1
0
1
2
MM
I(sy
n)-M
MI(
obs)
San Francisco
San Jose
Santa Cruz
Livermore
Concord
Monterey
Hollister
0
100
200
300
400
500
Cou
nt
-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0MMI(syn)-MMI(ref)
mean = -1.27std dev. = 0.66
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MMI Residuals: Graves Broadband Synthetic-Observed
Broadband synthetics give reasonable fit to MMI (PGV/PGA)
-123˚ -122˚ -121˚
37˚
38˚
0 50km
-2
-1
0
1
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MM
I(sy
n)-M
MI(
obs)
San Francisco
San Jose
Santa Cruz
Livermore
Concord
Monterey
Hollister
0
100
200
300
400
500
Cou
nt
-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0MMI(syn)-MMI(ref)
mean = -0.34std dev. = 0.56
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Waveforms at AGNW: Modelers vs. Observed
Reasonable match in amplitude & duration for both source models
Time (s)
Vel
ocity
(m
/s)
AGNW
East Component
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−0.2
0.0
0.2
Time (s)
North Component
5 10 15 20 25 30
−0.2
0.0
0.2
Time (s)
Up Component
5 10 15 20 25 30
−0.2
0.0
0.2
ObservedGraves [Beroza]Harmsen [Beroza]Dolenc [Beroza]Aagaard [Beroza]Graves [Wald]Harmsen [Wald]Dolenc [Wald]Aagaard [Wald]
0 20 40
km
AGNW
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Waveforms at WATS: Modelers vs. Observed
Beroza source fits amplitude & duration better but not polarity
Time (s)
Vel
ocity
(m
/s)
WATS
East Component
5 10 15 20 25 30
−0.2
0.0
0.2
Time (s)
North Component
5 10 15 20 25 30
−0.2
0.0
0.2
Time (s)
Up Component
5 10 15 20 25 30
−0.2
0.0
0.2
ObservedGraves [Beroza]Harmsen [Beroza]Dolenc [Beroza]Aagaard [Beroza]Graves [Wald]Harmsen [Wald]Dolenc [Wald]Aagaard [Wald]
0 20 40
km WATS
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Summary of Loma Prieta Modeling
3-D geologic model successfully captures important 3-D effects
• We reproduce the duration and amplitude of shaking within the SanFrancisco Bay area
• Good agreement among wave propagation implementations (modelers)
• Better agreement among modelers than among source models• Finite-element implementation does better for vertical component
• We can tell the difference b/t the Beroza and Wald source models
• Wald source model radiates energy primarily to the north• Beroza source model radiates energy bilaterally
• Identified locations where velocity model may need adjustment
• Vs in La Honda basin too slow• Vs in Great Valley sequence too slow
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1906 and Scenario Earthquakes
Simulations of the 1906 earthquake and hypothetical variations
• 1906 earthquake
• USGS 3-D geologic and seismic velocity models• Song et al. source model
• 1906-like scenarios
• Other hypocenters• Rockport: north to south rupture• Bodega Bay: bilateral rupture w/central hypocenter• San Juan Bautista: south to north rupture
• Random slip• Random realization with different distribution than 1906
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Song et al. 1906 Source Model
Construct updated source model of the 1906 earthquake
• Find unique source model that satisfies all datasets
• Geodetic (triangulation data)• Seismic (teleseismic waveforms)
• Constrain distribution of slip and rupture duration
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Song et al. Source Model: Inversion Results
Inversion constrains slip and rupture duration
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Source Implementation: Slip and Rupture Time
Roughen up slip distribution and rupture propagation
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Comparison of MMI with Boatwright & Bundock
Simulations and intensity map agree on major features
Aagaard (f < 0.5 Hz) Boatwright & Bundock
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IIIIIIIVVVIVIIVIIIIXX
MMI
1906San Francisco
San Jose
Santa Rosa
Sacramento
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37˚
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39˚
0 50 100km
IIIIIIIVVVIVIIVIIIIXX
MMI
1906San Francisco
San Jose
Santa Rosa
Sacramento
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Misfit in Boatwright & Bundock Intensities
Simulations have larger intensities near rupture
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3M
MI(
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-MM
I(re
f)
1906San Francisco
San Jose
Santa Rosa
Sacramento
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Shaking in San Jose
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Shaking in Santa Rosa
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Waveforms (T > 2 s) in San FranciscoV
eloc
ity (
m/s
) East Component1906
0 20 40 60 80 100
−0.3 0.0 0.3
North Component
0 20 40 60 80 100
Up Component
0 20 40 60 80 100
Larsen et al.Petersson et al.GravesAagaardHarmsen et al.
Vel
ocity
(m
/s) RandomHypo06
0 20 40 60 80 100
−0.3 0.0 0.3
0 20 40 60 80 100 0 20 40 60 80 100
Vel
ocity
(m
/s) 1906HypoC
20 40 60 80 100 120
−0.3 0.0 0.3
20 40 60 80 100 120 20 40 60 80 100 120
Time (s)
Vel
ocity
(m
/s) RandomHypoC
20 40 60 80 100 120
−0.3 0.0 0.3
Time (s)20 40 60 80 100 120
Time (s)20 40 60 80 100 120
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Waveforms (T > 2 s) in San JoseV
eloc
ity (
m/s
) East Component1906
20 40 60 80 100 120
−0.3 0.0 0.3
North Component
20 40 60 80 100 120
Up Component
20 40 60 80 100 120
Larsen et al.Petersson et al.GravesAagaardHarmsen et al.
Vel
ocity
(m
/s) RandomHypo06
20 40 60 80 100 120
−0.3 0.0 0.3
20 40 60 80 100 120 20 40 60 80 100 120
Vel
ocity
(m
/s) 1906HypoC
40 60 80 100 120 140
−0.3 0.0 0.3
40 60 80 100 120 140 40 60 80 100 120 140
Time (s)
Vel
ocity
(m
/s) RandomHypoC
40 60 80 100 120 140
−0.3 0.0 0.3
Time (s)40 60 80 100 120 140
Time (s)40 60 80 100 120 140
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Waveforms (T > 2 s) in LivermoreV
eloc
ity (
m/s
) East Component1906
20 40 60 80 100 120
−0.4 0.0 0.4
North Component
20 40 60 80 100 120
Up Component
20 40 60 80 100 120
Larsen et al.Petersson et al.GravesAagaardHarmsen et al.
Vel
ocity
(m
/s) RandomHypo06
20 40 60 80 100 120
−0.4 0.0 0.4
20 40 60 80 100 120 20 40 60 80 100 120
Vel
ocity
(m
/s) 1906HypoC
40 60 80 100 120 140
−0.4 0.0 0.4
40 60 80 100 120 140 40 60 80 100 120 140
Time (s)
Vel
ocity
(m
/s) RandomHypoC
40 60 80 100 120 140
−0.4 0.0 0.4
Time (s)40 60 80 100 120 140
Time (s)40 60 80 100 120 140
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Comparison with NGA Models, Soft Soil Sites
Super-shear rupture creates discrepancies at distances of 10–100 km
T = 3.0 s T = 5.0 s
0.01
0.1
1
Spe
ctra
l acc
eler
atio
n (g
)
1 10 100Distance to rupture (km)
SyntheticsCampbell and Bozorgnia (2007)Chiou and Youngs (2006)
0.01
0.1
1
Spe
ctra
l acc
eler
atio
n (g
)
1 10 100Distance to rupture (km)
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Comparison with NGA Models, Hard Rock Sites
Hard rock sites more sensitive to directivity and super-shear
T = 3.0 s T = 5.0 s
0.01
0.1
1
Spe
ctra
l acc
eler
atio
n (g
)
1 10 100Distance to rupture (km)
SyntheticsCampbell and Bozorgnia (2007)Chiou and Youngs (2006)
0.01
0.1
1
Spe
ctra
l acc
eler
atio
n (g
)
1 10 100Distance to rupture (km)
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Implications for Tall Buildings
Anna Olsen et al. study with 20-story SMRF buildings
• 20-story, steel, special moment-resisting frame buildings
• UBC 1994• JBC 1992 (satisfies 1997 UBC static lateral force requirements)• Brittle welds (distribution of yield strain for welds)• Ductile welds (welds do not fracture)
• Nonlinear, 2-D finite-element model
• Fiber elements use nonlinear, hysteretic, steel model• Panel zones use nonlinear, hysteretic, moment-shear strain model• Only deterioration mechanism is weld fracture
• Evaluate performance using peak inter-story drift ratio
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Peak Interstory Drift: 1906 Earthquake
Tall buildings with brittle welds in SF & SCV would be vulnerable
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Peak Interstory Drift: Bodega Bay epicenter
Even some tall buildings without brittle welds would be vulnerable
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Peak Interstory Drift: San Juan Bautista epicenter
Tall buildings with brittle welds in SF & SCV would be vulnerable
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Implications for Tall Buildings: Summary
Buildings with brittle welds could collapse in large SAF earthquakes
% Urban Area with Simulated CollapsesScenario JBC UBC
Brittle Ductile Brittle DuctileLoma Prieta 0 0 0 01906 0.31 0 0.83 0Bodega Bay 1.1 0.061 6.7 0.21San Juan Bautista 0.031 0 0.64 0
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Ground Motions: Data Availability
Data will be accessible so anyone can use it
• PGV/PGA: 1/60 degree uniform lat/lon grid
• Velocity waveforms (resolution varies with population density)
• Boatwright intensity sites• Census track centroids (minimum dist b/t points is 2 km)
• Will be distributed as USGS Data Series
• Data has been collected• Time/workload is limiting factor in publishing Data Series• Have capable computer scientist contractor, but no funding
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Future Work
Ground motions from scenario events involving Hayward fault
• Similar collaborative effort to 1989/1906 simulations
• Expect to produce around 30 scenarios
• 5 combinations of Rodgers Creek, Hayward, Calaveras• 1-3 hypocenters for each rupture length• 3 slip distributions for each hypocenter• Hayward: vary average rupture speed and rise time
• Use latest tools for generating kinematic rupture models
• Target completion date: June 2008
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