Tri-State Seismic Hazard Mapping -Kentucky Plan
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Transcript of Tri-State Seismic Hazard Mapping -Kentucky Plan
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Tri-State Seismic Hazard Mapping-Kentucky Plan
Zhenming Wang
Kentucky Geological Survey
University of Kentucky
http://www.uky.edu/KGS/geologichazards/
February 23, 2006
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Outline
• Seismic Hazards – Primary Hazard – Ground Motion (on bedrock)
• Scenario ground motion
• USGS Hazard Maps (PSHA)
– Secondary Hazard• Ground Motion Amplification (NEHRP Soil type)
• Liquefaction
• Induced slope instability
• KGS Seismic Hazard Mapping – Kentucky Plan– Primary Hazard
– Secondary Hazard
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Seismic Hazard and Risk
• Seismic hazard and risk are fundamentally different
• Seismic Hazard– Natural phenomena generated by the earthquake, such
as surface rupture, ground motion, ground-motion amplification, liquefaction, and induced-landslide that have potential to cause harm
– Measurement: level of hazard and its recurrence interval
• Seismic Risk (More Subjective)– likelihood (chance) of experiencing a level of seismic
hazard for a given time exposure
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New Madrid earthquake
Event Hurricane (Katrina)
~M7.7 Size Category V
~500 τ (years) ~100?
~10% in 50 years
Risk ~39% in 50 years
PGA/MMI/PSA Hazard at a specific site
Flood level/Wind
speed
$X Loss $Y
Log-normal Uncertainty of measurement
Normal/Log Pearson
-1000
-500
0
500
1000
Acc
el (c
m/s
/s)
Strike Parallel
-1000
-500
0
500
1000Strike Normal
-1000
-500
0
500
1000Vertical
-50
0
50
Vel
ocity
(cm
/s)
-50
0
50
-50
0
50
10 20 30 40 50-20
-10
0
10
20
Dis
pl (c
m)
10 20 30 40 50-20
-10
0
10
20
Time (sec)10 20 30 40 50
-20
-10
0
10
20
529 1213 624
12 38 12
1.1 13 0.7
Seismic and Hurricane Hazards and Risk
Only Seismic Hazards AreConsidered by KGS
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Ground Motion
Primary: USGS maps
Secondary:Amplification (NEHRP soil)LiquefactionSlope failure
Policy considerations:IBC, IRC, and etc.
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USGS Memphis Project(Cramer and others, 2006)
Amplification
De-amplification
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Seismic Hazard Maps – KY Plan
• Ground Motion Hazard Maps– Level of ground motion– How often it could occur– A set of scenario maps (ground motion vs.
recurrence time)
• Secondary Hazard Maps– Amplification map– Liquefaction potential map
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Ground Motion Maps
• Earthquake Sources– Faults– Occurrence frequency – Maximum magnitude
• Ground Motion Attenuation• Methodology
– PSHA– DSHA
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Earthquake Sources
Historical Event: White County EQ?(~M7.5?, Mueller et al., 2004)
1993/1996 2005
Waverly 6.8 6.2
Vallonia 6.9 6.3
Skelton 7.2 6.7
Vincennes 7.8 7.3/7.1
Paleo-liquefactions (Obermeier et al.)
3. How Often? Thousands years
1. Where?
2. How Big?
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Ground Motion Attenuation
101
102
103
10-3
10-2
10-1
100
Distance (km)
Pea
k G
rou
nd
Acc
eler
atio
n (
g)
FrankelToroAtkinsonCampbellSomervilleComposite Model
M8.0
Conservative predictions (USGS WP, 2005)New attenuations (USGS WP, 2006)
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Methodology
• PSHA vs. DSHA– Same thing under certain conditions
(Characteristic earthquake)– But different expressions
PGA maps with 5% PE in 50 years(Cramer et al., 2006)=
The maps may good for NMSZ (AASHTO,KGS, and others)But good for the Tri-State Area?
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Ground Motion Amplification
• Directly- Vertical Strong Motion Stations - H/V spectral ratios (e.g.
earthquakes and ambient noise)
• Theoretical Modeling- Response based on
amplification thru the Vs gradient of the soils/ sediments (e.g., SHAKE, etc.)
• Empirical- NEHRP Soil Classification
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i i
i
ii
S
v
d
d
v
Vs=500 (ft/s)d=30 (ft)
Vs=4000 (ft/s)(bedrock)
Vs=4000 (ft/s)(bedrock)
Vs=1000 (ft/s)d=40 (ft)
Vs=1500 (ft/s)d=50 (ft)
Vs=500 (ft/s)d=70 (ft)
Vs=4000 (ft/s)(bedrock)
Example 2Example 1
100/(30/500+40/1000+30/1500)=833 (ft/s)
=> D (600 - 1200 ft/s)
100/(70/500+30/4000)=678 (ft/s)
=> D (600 - 1200 ft/s)
Average Equation
Notes: 1) based on CA geology: bedrock Vs~2,500 ft/s (B/C boundary)2) in CUS, bedrock Vs >2,500 ft/s (A or B), applicable (?)
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(Street et al., 1997, Engineering Geology, 46:331-347)
C
D
C
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Table 3. Estimated Susceptibility of Continental Deposits to Liquefaction (modified from Youd and Perkins, 1978).
Type of deposit Likelihood that Cohesionless Sediments, When Saturated, Would Be Susceptible to Liquefaction (by Age of Deposit)
<500 yr Holocene Pleistocene Pre-Pleistocene
River channel Very high High Low Very low
Flood Plain High Moderate Low Very low
Alluvial fan and Plain Moderate Low Low Very low
Lacustrine and playa High Moderate Low Very low
Colluvium High Moderate Low Very low
Talus Low Low Very low Very low
Tuff Low Low Very low Very low
Residual soils Low Low Very low Very low
Step 1.
Step 2.
Further analysis based on: SPT, CPT, Vs values and INPUT MOTION
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Louisville Liquefaction Potential Map
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Summary
• KGS will produce following maps for KY– Ground Motion Hazard Maps
• A set of scenario maps (ground motion level vs. recurrence time)
– Secondary Hazard Maps• Amplification maps (associated with the scenario
maps)
• Liquefaction potential maps (associated with the scenario maps)
• All data will be available after completion of the maps
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Thank You