Intraplate Deformation and Seismicity: Implication for Seismic Hazard and Risk Estimates in the Central United States

Zhenming WangKentucky Geological Survey

University of KentuckyLexington, KY 40506

EarthScope Annual MeetingMonterey, CAMarch 27-29, 2007

Outline

• Introduction

• Seismicity in the central United States

• Deformation in the central United States

• Implication for seismic hazard and risk assessments

• Summary

Problems in Kentucky

1) Mr. David Mast (a staff member from KY congressman Ed Whitfield office): Why can I not build a regular two-story house in Paducah?

2) DOE will not get permit from Ky-EPA to build a landfill at PGDP for clean-up.3) Design ground motion for bridges will be much higher than those in CA 4) One of the main reasons that Kentucky lost the centrifuge facility ($2B) to Ohio.

San Francisco Paducah

Problems in Memphis

“$100M seismic retrofit of Memphis VA hospital, removing nine floors, bringing it to California standard. Whether this makes sense depends on perspective.” – Stein and Tomasello (1995)

Seismicity(Stein et al., 2003)

(Frankel et al., 1996)

For seismic hazard: M vs. MRI?

Deformation (Stephane et al., 2005)

(Calais et al., 2006)

(Newman et al., 1999)

For seismic hazard: M vs. MRI?

SFB: M7.8 or MMI VIII and greater vs. ~100 years MRICUS: M7.8 or MMI VIII and greater vs. 500~1,000 years MRIIf loss: $100B (same) (not easy to compare)

Seismic Hazard Comparisons: CUS vs. San Francisco Bay

SFB: 39% PE in 50 years of M7.8 or MMI VII and greater CUS: 5~10% PE in 50 years M7.8 or MMI VII and greater

39% Vs. 5~10% for $100B loss in 50 yearsSFB has much higher exposure (people and properties)

This is why most of resources goes to CA for EARTHQUAKES

Seismic Risk Comparisons: CUS vs. San Francisco Bay

(Poisson model)

Hazard and Risk Comparison in CUS: Earthquake, Flood, and Tornado

New Madrid earthquake

Miss. River Flood (1993)

Event 2005 Tornado

(Evansville)

~M7.7 ? Size F3

~500 ~100? τ (years) ~50?

~10% in 50 years/0.2% in 1 year

39%

in 50 years/1% in 1 year

Risk(probability)

~63% in 50 years/2% in 1

year

PGA/MMI/

PSA

Flood level Hazard at a specific

site

Wind speed

(200MPH)

$X $~15B Loss $~92M

x 50 Fatality 25

-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

(Schaefer, 2006)

Risk posed by several hazards to the dams along Ohio River

Summary• It does not make sense that Paducah and Memphis

have to design the same level of ground motion (or even higher) as San Francisco

• In the central US, large earthquakes are of safety concern. Characterizing these large earthquakes is very important for seismic hazard and risk assessment, as well as policy consideration.

• It is very important that scientists (seismologists,

geologists, etc) communicate their research in a clear and understandable way.

• “If an earthquake has a 1000-year recurrence interval, should a 1000-year return period be assigned the ground motion it generates at a site?”

– Return Period: “the mean time between occurrences of a certain ground motion at a site”