Annual Meeting - SCEC.org

Poster Abstracts
VISUALIZING COMPARATIVE HAZARD VULNERABILITY THROUGH GIS/SHAKEMAP INTEGRATION
(A-157)
S.C. Boss, F. Gutierrez, K.Y. Lin, T. Papikyan, and C.M. Valen
The 2011 SCEC Undergraduate Studies in Earthquake Information Technology (USEIT) internship program challenged the
Data Team to research information on specific earthquake sequences using global earthquake catalogs and incorporate the
data into Geographic Information Systems (GIS). The internship focused on being able to integrate GIS into SCEC-Virtual
Display of Objects (SCEC-VDO) software. The Data Team compiled information about six global earthquake sequences: the
2010 Maule sequence in Chile, the 2010 Port-au-Prince sequence in Haiti, the 2011 Tohoku sequence in Japan, the 2010 El
Mayor-Cucapah sequence in Mexico, the 2010 Canterbury sequence in New Zealand, and the 2004 Indonesian trench sequence
in Sumatra. Information on population density, transportation routes, and infrastructure was located for each of the six
countries and California. Data on hospitals, major airports, major roads, railways, and nuclear power plants was displayed
onto maps in GIS. This information can be used to assess the hazards and the impact an earthquake could have on society. In
addition, California data included locations of schools, fire stations, and police stations.
The Data team also incorporated earthquake catalogs that were used to gather information on each sequence as well as focal
mechanisms. Each earthquake sequence included the mainshock, aftershocks, and foreshocks. The global earthquake catalogs
that were used included the National Earthquake Information Center Preliminary Determination of Epicenters (NEIC PDE)
and the Global CMT (Global Centroid Moment Tensor). The Institute of Geologic and Nuclear Science (GNS) catalog was used
to gather earthquake information in New Zealand. Research was also conducted on the ShakeMaps that SCEC created. All of
the resulting information was then posted on the data team’s own website, which is organized by corresponding countries.
DO SMALL SURFACE STRAINS IN THE NEW MADRID SEISMIC ZONE REFLECT A PHYSICAL PROCESS?
(B-152)
O.S. Boyd, Y. Zeng, L. Ramirez-Guzman, and R. Smalley
We reevaluate GPS data over the decade from 2000–2010 and model the resulting observations with local deformation
mechanisms: viscoelastic relaxation subsequent to the 1811–1812 New Madrid, MO, earthquakes and slip across deeply buried
finite dislocations to represent interseismic strain accumulation. The reevaluation of the GPS data accounts for outliers, offsets
in the position time-series, and annual and bi-annual seasonal variations. Site velocities are found from the slope of the
position time-series and are relative to a reference, which is the stack of all position time-series for a given component. We find
that relative site velocities have a standard deviation of about 0.2 mm/yr with uncertainties on the order of 0.1 to 0.2 mm/yr
or more. Uncertainty is difficult to estimate directly because the random walk component of noise, which contributes most to
uncertainty in long geodetic time series, cannot be distinguished from the flicker and white noise components.
Multiple models can account for some of the variance in the GPS data. A viscoelastic response of the crust from the 7 February
1812 earthquake on the Reelfoot fault can account for 41% of the variance in the data. We perform an F-test and find that such
a model has a 99% chance of being better able to match the data than does a null hypothesis. In this model, viscosity and slip
are directly correlated such that increasing the viscosity by an order of magnitude requires an increase in slip by an order of
magnitude to generate the same surface deformation. A viscoelastic response due to an earthquake on the Cottonwood Grove
fault does not significantly improve our ability to model the data, but the lack of significance may be partly due to data
limitations. Alternatively, a lower crustal right-lateral dislocation along the Cottonwood Grove fault slipping between 2 and 3
mm/yr from 20 to 40 km depth can account for 25% of the variance and has a 70% chance of being better able to match the
data than does a null hypothesis, while slip on a down-dip extension of the Reelfoot fault cannot significantly reduce the
variance of the GPS data. These results suggest that having a good estimate of the subsurface rheology might allow for
estimation of mean slip and magnitude of the 1811–1812 earthquakes as well as ongoing loading of the seismic zone.
OPEN-SOURCE GROUND MOTION SELECTION USING THE GENERALIZED CONDITIONAL INTENSITY
MEASURE (GCIM) APPROACH (B-013)
B.A. Bradley
The increasing use of time domain analysis is seismic assessment has resulted in a frequent requirement for site-specific
ground motions. Many heuristic ground motion selection approaches have been proposed, and the use of a range of such
methods has been shown to result a in large range of seismic performance statistics. A theoretically-founded ground motion
selection methodology, based on the generalized conditional intensity measure (GCIM) approach, is presented. Both asrecorded
and simulated ground motions can be selected using a semi-automated algorithm that requires only the specification
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