Earthquake Hazards and

Earthquake Risks in the Central US

Phyllis J. Steckel, RG

Earthquake Insight LLC

Washington, Mo.

In cooperation with the US Geological Survey

The plan for today….

• ‘Earthquakes 101’

• Regional Earthquake

history

• Earthquakes & structures

• Putting it all together

• Questions & discussion

Earthquake Vocabulary

• Magnitude

• Intensity

• Depth

• Duration

• Aftershocks

• Faults (not ‘fault lines’)

• Location

• And more….

Earthquake Magnitude

• Amount of energy

released

• Only one magnitude

for any one

earthquake

Earthquake Magnitude

• Logarithmic scale

• M2.0 ~30 times more

energy released

than M1.0

• M3.0 ~1000 times

more energy

released than M1.0

Earthquake Intensity

• Measures energy

delivered to any one

site

• Depends on location

• Many intensities for

any one earthquake

Earthquake Intensity

• Subjective measurement

• Estimated from felt

reports

• Depends on population

distribution

• More is better

Earthquake Depth

• Range from shallow to

deep – surface to ~450

miles

• Shallow = more energy

and intensity at the

surface

• Deep = less energy and

intensity at the surface

Earth’s Crust

• Thinner than an

apple peel

• Floats on viscous

mantle

• Pieces ‘bump and

grind’ along edges =

plate tectonics

Faults (Fault lines)

• Normal

• Thrust

• Strike-slip

Normal Faults

Thrust Faults

Strike-slip Faults

Earthquake Duration

• Felt for a few seconds

– Small earthquake, near

epicenter

• Felt for several minutes

– Large earthquake, farther

from epicenter

• Extreme earthquakes

‘ring the earth’ for hours

Aftershocks

• Occur after most large

earthquakes

• Become smaller and

less frequent over time

• Can cause significant

damage – sometimes

more than the main

shock

Did You Feel It?

• April 18, 2008

• 4:36 am (CDT)

• M5.4

• Depth ~11 km

• Epicenter near Bellmont, Ill.

Earthquake Locations

• Need three

earthquake records

(seismograms)

• Measure distance

from each recorder

• Common point is

epicenter

Earthquake Locations

• Regional velocity of earthquake waves is known

• Distance from epicenter is estimated

• More records = more accuracy

Where do earthquakes occur?

• Plate boundaries

• Near volcanoes

• Mountain ranges

• Just about

everywhere else,

too!

Plate Boundary Earthquakes

Near volcanoes

• Aleutians & Alaska

• Montserrat &

Caribbean

• Iceland

• Mount St. Helens

Near Mountain Ranges

• Apennines

• Andes

• Sierra Nevada

• Wasatch Range

• Southern

Appalachians

• Ouachitas (Ark. &

Okla.)

• Ozarks

Geologic Structures

Regional Mega-Structures

• Illinois Basin

• Kankakee Arch

• Ouachita Fold Belt

• Arkoma Basin

• Mississippi Embayment

• And lots more!

Mississippi Embayment

• Very clear on maps!

• Bedrock trough

• Dips & widens to the

southwest

Mississippi Embayment

• New Madrid fault

zone

– ‘Bottom’ of trough

– North end of trough

• Filled with

sediments

• Mississippi River

follows ‘easiest’

route

New Madrid fault zone

• Southeast Missouri &

northeast Arkansas

• Old crustal weakness

• Active for hundreds

of millions of years

New Madrid fault zone

• Active historically

• Active now

• Not ‘dormant’

• Not ‘shut down’

Central US Earthquakes

• SE Missouri & NE

Arkansas

• Old crustal weakness

• Active for hundreds

of millions of years

New Madrid fault zone

• 2013 research: weak rocks extend deeper into crust

• Consistent with past & future active seismicity

Central US Earthquakes

• New Madrid fault

zone

• Wabash Valley FZ

• East Tennessee FZ

• Meers FZ, Nemaha

FZ, etc.

New Madrid in 1811-12

• Founded in 1789 on

high ground

• Swamps surrounded

by heavy forests

• Largest settlement

between St. Louis &

New Orleans

New Madrid in 1811-12

• River was the 1811

super-highway

• Part of Louisiana

Purchase (1803)

• Spanish, French, and

US heritage

New Madrid Earthquakes 1811-12

• December 16, 1811

– ~M7.5

• January 23, 1812

– ~M7.3

• February 7, 1812

– ~M7.6

New Madrid Earthquakes 1811-12

• Thousands of

aftershocks

• Wracked land,

choked river

• Most residents left

the area

Eliza Bryan

• Born Pennsylvania

1780

• Arrived New Madrid

1791

• Survived 1811-12

• Wrote letter 1816

• Died New Madrid 1866

New Madrid Earthquakes 1811-12

• Eliza Bryan account….

– ‘Violent shocks…’

– ‘Continuous agitation…’

– ‘Sand…from fissures…’

– ‘Twenty-foot waves…’

• Field evidence still

visible today

New Madrid Earthquakes 1811-12

• River recedes from bank

• ‘Waters gathered like a mountain’

• Boats torn from moorings

• “Water took groves of cottonwood trees’

• Evidence still visible today

• ‘Retrograde current…’

– Fault uplifted downstream

land surface

– Natural dam

– Backflow made Reelfoot Lake

– Channel soon reclaimed

• Evidence still visible today

New Madrid Earthquakes 1811-12

• Probably hundreds died

• African and Native Americans not counted

• Insurance records show losses of lives and insured cargoes

New Madrid Earthquakes 1811-12

• Aftershocks for years

• 2000+ felt reports from Louisville

• Damage in Cincinnati, Georgia, Annapolis, and New York

New Madrid Earthquakes 1811-12

• Aftershocks for years

• 2000+ felt reports from Louisville

• Damage in Cincinnati, Georgia, Annapolis, and New York

New Madrid Earthquakes of 1811-12

• Felt area larger than same-size California earthquake – Rock is

different here!

• What is odd about this map?

Other Central US Earthquakes….

• 1843 – NE Arkansas, M6+

• 1895 – SE Missouri, M5.9

• 1917 – St. Louis area, M5.1

• 1968 – Mt Vernon, Ill., M5.2

• 2008 – Mt Carmel, Ill., M5.2

• Many M3 – M4 – Minimal & “lucky” damage

• ‘Wake-up calls’ mostly ignored

Switching gears ….

From

“Earthquakes”

To

“What Happens to Structures During

Earthquakes”

Types of Structures

• Buildings – Wood-frame

– URM

– Steel-frame

– Concrete-frame

– Tilt-up

• Bridges

• Pipelines

• Levees, dams, embankments

• Utility towers

Structures & Earthquakes

• Compact vs Sprawl?

• Age & maintenance?

• Engineering design?

• Seismic design?

Structures & Earthquakes

• Flexibility?

• Center of gravity?

• Footprint?

• Earthquake energy input – direction?

Wood frame

• Most newer residential

• Flexible

• Low center of gravity

• Chimneys problematic?

• Foundation & utility connections critical

• Damage may be high, but few lives lost

Unreinforced masonry -- URM

• Inflexible

• Less resistant to ground shaking

• Many older and historic buildings

• Structural load on walls

• Heavy and brittle

• Not the best in Earthquake Country

If walls could talk….?

Braced Steel Frame

• Cross-bracing

• Lightweight & flexible

• Most newer mid- and high-rises

• Usually performs well if design & construction detailing done well

Concrete frame

• Concrete columns, beams & girders

• Exterior cladding or glass

• Strength depends on – Steel reinforcement

– Design quality

– Construction quality

• Devil is in the details!

Concrete frame

• Seismic design

needed

• Rebar needed!

• Uncompromised

construction

Concrete frame with URM Infill

Concrete Tilt-Up

• Poured concrete walls, then ‘tilted up’

• Critical connections at corners, foundation & roofline

• Many big retail, factories, warehouses, etc.

• Devil is in the details!

2011 Christchurch, NZ

1994 Northridge, Calif.

2010 Chile

1992 Landers, Calif.

1971 San Fernando, Calif.

2011 Christchurch, NZ

2002 Alaska

Bringing it all together

• Geoscience

• Engineering

• Building stock

• Building codes & jurisdiction

–Seismic building code not adopted everywhere

Geoscience

• USGS research results

• Detailed hazard maps – St. Louis

– Memphis

– Evansville, Ind.

• Groundshaking & liquefactions

• Not site-specific!

Engineering

• Earthquake engineering is not ‘automatic’

• Jurisdiction may not have or enforce building codes

• Earthquake engineering may not be required

• Building codes = life safety only

Building Codes

• Never assume….

• Negotiated document

• No statewide code in Missouri

• Recent effort in Tennessee to dismantle building codes in some areas, including fire, wind, and ADA

Regional vulnerabilities

• Most domestic structural steel is made in NE Arkansas

• Critical transportation corridors – highway, rail, river – straddle the New Madrid seismic zone

• Central US pipelines move fuels to northeast US

Regional vulnerabilities

• Only US uranium reprocessing plant

• Much of the US domestic inventory (FedEx) – Surgical instruments to consumer

goods

• Critical commodity transport (coal, steel, cotton, grains, fuels, ores, etc.)

• Critical national security facilities

Words to Remember

• Significant earthquake hazards exist in central US

• Future earthquakes will occur here

• Significant earthquake risks exist here

Consider these Action Items?

• Educate your organization

• Evaluate your portfolio

• Advise your legislatures – Penny wise, pound

foolish

Any questions?

Phyllis Steckel, RG Earthquake Insight LLC

psteckel@charter.net