Tri-State Seismic Hazard Mapping-Kentucky Plan

Zhenming Wang

Kentucky Geological Survey

University of Kentucky

http://www.uky.edu/KGS/geologichazards/

February 23, 2006

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

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

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

Ground Motion

Primary: USGS maps

Secondary:Amplification (NEHRP soil)LiquefactionSlope failure

Policy considerations:IBC, IRC, and etc.

USGS Memphis Project(Cramer and others, 2006)

Amplification

De-amplification

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

Ground Motion Maps

• Earthquake Sources– Faults– Occurrence frequency – Maximum magnitude

• Ground Motion Attenuation• Methodology

– PSHA– DSHA

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?

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)

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?

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

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 (?)

(Street et al., 1997, Engineering Geology, 46:331-347)

C

D

C

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

Louisville Liquefaction Potential Map

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

Thank You