Intraplate Deformation and Seismicity: Implication for Seismic Hazard and Risk Estimates in the Central United States Zhenming Wang Kentucky Geological Survey University of Kentucky Lexington, KY 40506 EarthScope Annual Meeting Monterey, CA March 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 San Francisco Paducah • Mr. David Mast (a staff member from KY congressman Ed Whitfield office): Why can I not build a regular two-story house in Paducah? • 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.
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?
Seismic Hazard Comparisons: CUS vs. San Francisco Bay SFB: M7.8 or MMI VIII and greater vs. ~100 years MRI CUS: M7.8 or MMI VIII and greater vs. 500~1,000 years MRI If loss: $100B (same) (not easy to compare)
Seismic Risk Comparisons: CUS vs. San Francisco Bay (Poisson model) 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 years SFB has much higher exposure (people and properties) This is why most of resources goes to CA for EARTHQUAKES
Risk posed by several hazards to the dams along Ohio River (Schaefer, 2006)
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”