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Earthquake Impacts - THE Midwest Threat

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Earthquake Impacts - THE Midwest Threat. Gregory L. Hempen, PhD, PE, RG Geophysicist (retired, St. Louis District) URS Corporation, St. Louis Office SAME Regional Conference, 5 OCT 06. Natural Hazard Issues. natural hazards: eqks, ... our special Midwest problems

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slide1

Earthquake Impacts -THE Midwest Threat

Gregory L. Hempen, PhD, PE, RG

Geophysicist (retired, St. Louis District)

URS Corporation, St. Louis Office

SAME Regional Conference, 5 OCT 06

natural hazard issues
Natural Hazard Issues
  • natural hazards: eqks, ...
    • our special Midwest problems
  • sustained-design environment
  • risk acceptance
  • probabilities of extremes
earthquakes where when no advance warning
Earthquakes - Where? When? No Advance Warning!
  • Tornadoes are more common in the Midwest, but impact far less area.
  • Some equivalence with other rapidly developing hazards: high wind threats, seismic related hazards (liquefaction, lateral spreading, slope instability), terrorism, …
  • An all-hazards approach is best.
where epicenters sources
Where? Epicenters & Sources

EQE International Inc.

slide8
When?
  • Multiple timeframes & reference sets.
    • For a future earthquake:
      • When will the earthquake occur? What year?
      • How long will the earthquake last?
      • One big earthquake, right?
    • Emergency response, response, recovery:
      • When will emergency help arrive?
      • How long will response take?
      • How long will recovery take? To get back to “normal?”
new madrid seismic zone
New Madrid Seismic Zone
  • Commerce-Benton Hills
  • East Prairie Limb, NMSZ
    • M: a 8.1, b 8.1, c 7.2
  • Reel-foot Thrust Limb, NMSZ
    • M: a 8.0, b 8.0, c 8.0
  • Blytheville Arch Limb, NMSZ
    • M: a 7.8, b 7.0, c 7.8

Tuttle, et al, 2002

    • a 1811 – 1812 AD
    • b 1450 AD
    • c 900 AD
when relative to the hazard
When relative to the hazard?
  • When will the earthquake occur?
    • Large events recur about every 550 years (Cramer, 2006).
    • Intraplate strains and energy release by the magnitude scale suggests a M6 event perhaps every 50 years.
    • M6, 70 - 90 yr; M7, 250 - 500 yr; M8, 550 – 1,200 yr (Rogers, 2005). Overdue for M6; M7 possible.
  • How long will the earthquake shaking last?
    • 60 sec, M8; 30 sec, M7; 18 sec, M6 (Krinitzsky & Chang, 1977).
  • One big earthquake, right?
    • No, likely a foreshock with one or more main events within days to months (several references).
when for response issues
When for response issues?
  • When will emergency help arrive for the public?
    • Hours to days later, depending upon event size, location within the damaged area, and government preparation. [Supplies for 7 days.]
  • How long will response take?
    • Weeks to months, depending upon extent of the event’s damage and government preparation.
  • How long will recovery take to get back to “normal?”
    • M6 recovery will take months to get back to some normalcy. M7 and larger will have long-term effects and may never return to present economic conditions.
no advance warning
No Advance Warning!
  • Even a M6.5 to 7.0 in the Midwest will be a devastating and society-changing event. There may be no warning at all.
  • Even the 1993 Mississippi flooding is a poor model for earthquake damage.
  • Hurricane Katrina is a more similar analogy in the wide spread damage to structures and lifelines (dominantly levee, electrical transmission, and telephone systems).
  • 1900 Galveston Hurricane, 1954 Hurricane Hazel & 1966 Hurricane Inez, having practically no warning but wide spread devastation, compare better to a large earthquake in the Eastern US.
special central us concerns
Special Central US Concerns
  • Complacency
    • Preparedness
    • Similarities to Katrina Disaster
    • Use of Eqk Codes
  • Low attenuation
    • Great area of significant ground shaking
    • Dispersion – long/tall structure impacts
  • Liquefaction / Lateral Spreading and Foundation impacts
structures risks
Structures & Risks
  • Significant ground motion at greater distance.
  • Due to dispersion of the waves, distant structures may be placed into resonance.
    • Long or tall structures are particularly susceptible to resonance effects.
    • More distant towns: tall buildings in Chicago; bridges across major rivers; dams; pipelines.
  • Evaluation of geotechnical issues: activation of slides, liquefaction/lateral spreading, bearing capacity, differential settlement.
new madrid seismic zone16
New Madrid Seismic Zone
  • Commerce-Benton Hills
  • East Prairie Limb, NMSZ
    • M: a 8.1, b 8.1, c 7.2
  • Reel-foot Thrust Limb, NMSZ
    • M: a 8.0, b 8.0, c 8.0
  • Blytheville Arch Limb, NMSZ
    • M: a 7.8, b 7.0, c 7.8

Tuttle, et al, 2002

    • a 1811 – 1812 AD
    • b 1450 AD
    • c 900 AD
infrastructure dams levees wappapello s 2002 high water event
Infrastructure - Dams & LeveesWappapello’s 2002 High-Water Event

Emergency Overflow Spillway

Outlet Works & Tunnel

Embankment Dam with flat slopes & crest road

Designed in the 1930’s & completed in 1941, its defensive measures are the dam’s stiff, gravelly clay, wide embankment base, & high freeboard.

sustained design integration of the hazard
SUSTAINED DESIGN – Integration of the Hazard
  • Hazard assessment
  • Acceptance of risk OR mitigation of risk OR lessening of project requirements
  • Risk to be mitigated
  • Design to be resolved
hazard versus risk
HAZARD versus RISK
  • Hazard - an occurrence that imperils life or property [assessed by science].
  • Risk - quantification of a known hazard to an inventory (of life or property) that is vulnerable [mitigated by engineering]; the risk may be apportioned between acceptance of or mitigation of the hazard [distributed by the owner’s policy].
site hazard assessment
SITE & HAZARD ASSESSMENT
  • Earthquake sources and seismicity
  • Travel path parameters
  • Static & dynamic parameters of earth systems (naturally placed, not designed)
  • Site response analysis
  • Other hazard impacts
  • Engineering designs to abate the hazards’ risk and meet the projects’ requirements
seismic damage types
SEISMIC DAMAGE TYPES
  • Fault displacement (rupture)
  • Ground motion (induced inertia)
  • Indirect Physical Impacts
    • Tectonic Changes (seiches / tsunamis)
    • Liquefaction
    • Triggering Landslides
    • Foundation Failures (Diffrt’l Settlement)
    • Tertiary Lifeline Impacts
codes seismic provisions of the 2003 ibc
CODES - Seismic Provisions of the 2003 IBC
  • Sections 1613 through 1616 of the 2003
  • IBC pertain to Earthquake Loads on structures with rules for exceptions, existing structure additions, occupancy, alterations, QA, & wind.
  • Design spectral response acceleration, SA, is specified from
    • Mapped bedrock acc [Eqk Source Region]: SS & S1,
    • Site Class Determination [Site Assessment] – T 1615.1.1,
    • Site Class Coefficients - T 1615.1.2(1&2), &
    • The structure’s fundamental period, T, in s.
other seismic hazards not only the ground motion value
OTHER SEISMIC HAZARDS(not only the ground motion value)
  • Fault displacement
  • Tectonic Changes [seiches (waves) / tsunamis]
  • Foundation Impacts
    • Dynamic Bearing Capacity
    • Differential Settlement
    • Liquefaction (Flow Liq, Cyc Mobility, Cyc Liq)
  • Triggering Landslides
  • Tertiary Lifeline or Project Subsystem Impacts
probabilities of extremes
Probabilities of Extremes
  • Standard statistical assessments have been used. Earthquakes are not independent events.
  • Stresses within the plate increase in time so the risk increases with time.
  • Statistics of once or more occurrences.
  • 2% exceedance in 50 years

(x>1 in 2,450-year period).

statistics for the uncommon
Statistics for the Uncommon
  • Earthquake swarms: several events in one area
  • Foreshocks & Aftershocks use little of the main event’s energy
  • New Madrid Series, 1811-12, within 8 months:
    • 3 or 4 Great (?) Earthquakes
    • 10 – 15 Large Earthquakes
    • Scores of Major Earthquakes
actions for earthquakes
Actions for Earthquakes
  • For your awareness, you can improve your survivability and your resources’ sustainability.
    • Earthquake Preparation
    • During an Earthquake
    • Earthquake Recovery
earthquake preparation
Earthquake Preparation
  • Learn first aid,
  • have water, food and supplies for three days,
  • prepare the structure/community for eqk,
  • know what to do when we feel an eqk,
  • have a plan to meet at a specific place after an earthquake occurs, and
  • have an earthquake drill.
during an earthquake
During an Earthquake
  • When inside, stay inside at a protective location: door way, corner or beneath a sturdy table. Drop, cover, and hold. Try to be away from windows.
  • When outside, stay outside. Try to get away from tall buildings and overhead utilities.
  • In a car when an eqk is recognized, slow and pull off at a safe location.
earthquake recovery
Earthquake Recovery
  • Aid those nearby,
  • stay at a secure place until it is okay to go home,
  • go to your meeting place,
  • do not go sight-seeing, and
  • expect other earthquakes, called aftershocks.
summary
SUMMARY
  • Earthquakes should be regarded as a significant and special hazards, particularly near the New Madrid Seismic Zone.
  • Designs for many structures need to consider the acceptable earthquake risk.
  • Seismic Ground Motion appraisal may be developed from accepted code procedures.
  • Other seismic foundation impacts for the site should be considered.
  • Be aware of individual actions before, during and after earthquakes.
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