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Poster Abstracts | Group 1 – ShakeOut
1-048
SOCIAL AND ECONOMIC LOSSES EXPECTED FROM A LARGE EARTHQUAKE ON
THE SOUTHERN SAN ANDREAS FAULT: A COMPARISON OF ESTIMATES BASED
ON DYNAMICALLY-DERIVED VERSUS KINEMATICALLY-DERIVED SHAKEOUT
SCENARIOS Mayhew JE, and Olsen KB
Olsen et al. (this volume) simulated ground motion in southern California from an ensemble of 7
spontaneous rupture models of large (Mw7.8) northwest-propagating earthquakes on the southern
San Andreas fault (ShakeOut-D). Due to the less coherent wavefield excited by the spontaneousrupture
sources, ShakeOut-D predictions of long-period spectral acceleration within the basins of
the greater Los Angeles area were lower by factors of 2-3 than the corresponding kinematic
predictions (ShakeOut-K). Here, we estimate the differences in social and economic losses for
ShakeOut-D and ShakeOut-K using HAZUS-MH. We generated the Shake maps required for
calculations in HAZUS-MH with the assumption that PGA and spectral acceleration values are
proportional to the PGV values calculated from ShakeOut-D and ShakeOut-K. This proportionality
was gained by ratios between attenuation relationships of PGVs versus PGAs and spectral
accelerations at the given distances from the fault and site specific Vs30 values (Boore and
Atkinson, 2008, based on three Vs30 values: 300, 760, and 1300 m/sec). Our results are strikingly
different for the ShakeOut-D and ShakeOut-K scenarios. For example, we find that the direct
economic loss predictions from building and lifeline damage for ShakeOut-K (~$132.4 billion) are
significantly higher than those predicted from ShakeOut-D (~$18.7 billion). Only 3,787 buildings
(~3% of total inventory) incur complete irreparable damage from ShakeOut-D as compared to
46,125 (~18%) from ShakeOut-K. ShakeOut-D predictions indicate that 32,913 homes will be
without electricity after 7 days and 838,876 homes without potable water, while the numbers for
ShakeOut-K are 650,655 and 4,529,232, respectively. ShakeOut-D predicts 34 - 131 fatalities
dependent on the time of day, as compared to 883 – 3,545 for ShakeOut-K. In summary, due to
differences in ground motion levels, the expected social and economic losses due to a Mw 7.8
northwest-propagating earthquake on the southern San Andreas fault for our dynamically-derived
sources (ShakeOut-D) are significantly smaller than those estimated for the kinematically-derived
source (ShakeOut-K). Thus, while the HAZUS estimates are associated with a large uncertainty, the
details of the source description appears to be a key ingredient to obtain the most reliable estimate
of the social and economic impact in southern California from the next large earthquake on the San
Andreas fault.
94 | Southern California Earthquake Center