Session 1A Ground Motions and Intensity Measures

1
Session 1A Ground Motions and Intensity Measures

• Paul Somerville
• Andrew Whittaker
• Greg Deierlein

2
Spectral Values and beyond ..

• NGA effort (response spectral prediction)
• things beyond spectra ground motions
• next phase of PEER LL-NGA ?? (not yet fully
  scoped out)
• Scaling of Records (do we agree on the approaches
  being used)
• Procedures in building codes have little
  scientific basis
• Spectral matching (not appropriate for nonlinear
  evaluation?)
• DOE (deagg. to separate spectra)
• PEER spectral scaling at T1 (or average of
  several spectral values, or vector intensity
  measures, e.g., Cornell-Somerville project)

3
Record Scaling (cont.d)

• Dependency of structural characteristics
  (strength, period, ductility demand) on the
  scaling question
• Scaling violates the earthquake physics. How
  does the earth science physics (fault rupture, )
  dictate the frequency content/magnitude of
  records as reflected in hazard curve (and
  epsilons from the median). Bias induced by
  scaling to spectral values (resulting in
  overscaling? use of epsilon to condition
  scaling)
• Frequency scaling?
• A nice interactive problem!

4
Other topics

• Transferability west coast hazard thinking to
  eastern earthquakes (smaller events, less
  frequent large events, different source
  characteristics, site conditions, etc.)
  north-west (subduction zone) versus
  south-west hazard
• PEER NGA project may shed some light on site
  effects.
• Intensity Measures (ground motion and structure
  dependent)
• Basin and edge effects (extreme effects,
  reflected in attenuation models and hazard maps,
  interaction with SSI issues)
• Extrapolation of motions to large magnitude
  events (Are we doing this correctly? Too
  conservative? Can SCEC develop suites of ground
  motions for use in research and design practice?).

5
Synthetic Motions

• Does SCEC or PEER-LL(NGA) have plans to make the
  various synthetic ground motions available (1D,
  3D)? How might the SCEC ITR group contribute.
  How does this relate the PEER-LL/CDMG project on
  ground motion selection.
• Validation and verification on synthetic and
  hybrid records. How is this being covered in the
  PEER-LL and SCEC research. Upon what basis does
  one validate the methods/records? Focus of SCEC
  in next two years?

6
NEES, Verticals, Design Practice

• NEES Data repository issues (links between
  experimental databases and ground motion
  libraries). SCEC proposal to generate times
  histories for NEES research. Links with grand
  challenge proposals.
• Vertical components of ground motions can be very
  important for long-span bridges and NS components
  in buildings.
• Guidance for design communities on ground motion
  issues (scaling, basin, SSI, ). FEMA is
  receptive to partnering with SCEC and other
  organizations. See FEMA 349 (445) PBD action
  plan.

7
Geographically Dist. Systems

• Geographically distributed scenarios versus
  specific site scenarios (correlations of motions
  at different sites).
• Spatial variation of motions for long structures
  (SCEC is working on it, but is there active
  collaboration with engineers).

8
IT issues

• Storage of data from strong motion sites, motions
  and site/bore hole data (Geotechnical Virtual
  Data Center)
• SCEC simulation capabilities should be made more
  public (design community, emergency response, ).
• IT can simplify the IM question by allowing one
  to access structure-specific hazard models (e.g.,
  on-line nonlinear spectral values).