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 KGS Seismic Hazard Mapping – Kentucky Plan 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

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

Seismic and Hurricane Hazards and Risk 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 Only Seismic Hazards Are Considered by KGS

Ground Motion Secondary: Amplification (NEHRP soil) Liquefaction Slope failure Primary: USGS maps Policy considerations: IBC, IRC, and etc.

USGS Memphis Project (Cramer and others, 2006) De-amplification 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 Ground Motion Attenuation Faults Occurrence frequency Maximum magnitude Ground Motion Attenuation Methodology PSHA DSHA

Earthquake Sources 1. Where? 2. How Big? 3. How Often? Thousands years Historical Event: White County EQ? (~M7.5?, Mueller et al., 2004) Paleo-liquefactions (Obermeier et al.) 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

Ground Motion Attenuation 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

Notes: 1) based on CA geology: bedrock Vs~2,500 ft/s (B/C boundary) Example 1 Example 2 Average Equation Vs=500 (ft/s) d=30 (ft) Vs=500 (ft/s) d=70 (ft) Vs=1000 (ft/s) d=40 (ft) Vs=1500 (ft/s) d=50 (ft) Vs=4000 (ft/s) (bedrock) Vs=4000 (ft/s) (bedrock) Vs=4000 (ft/s) (bedrock) 100/(70/500+30/4000)=678 (ft/s) => D (600 - 1200 ft/s) 100/(30/500+40/1000+30/1500)=833 (ft/s) => D (600 - 1200 ft/s) 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 (?)

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

Further analysis based on: SPT, CPT, Vs values and INPUT MOTION 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 Moderate Alluvial fan and Plain Lacustrine and playa Colluvium Talus Tuff Residual soils 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

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