Annual Meeting - SCEC.org

Meeting Program | MONDAY
simulations of ground motions have shown that, for sites located close to faults, the high frequency ground motion
scales only weakly with magnitude for magnitudes greater than 6.5. For probabilistic hazard, the decreased rate for
larger magnitudes required to balance the moment-rate on the fault leads to lower overall hazard (and risk of core
damage) if larger magnitudes are included in the source characterization. Unusually large high frequency ground
motions that would exceed the design basis of nuclear power plants are most likely to come from nearby M6.5-M7
earthquakes that are unusually energetic (ground motions more than 2 standard deviations above the median) rather
than from unusually large magnitudes. In contrast to ground motions, tsunami waves heights scale strongly with
earthquake magnitude or slide dimension. For tsunamis hazard, the possibility of larger magnitude events is a key
factor.
11:40 Group Discussion
12:00 Tsunami Interaction with Nearshore Infrastructure (P. Lynett, USC)
In this talk, the well-established approaches of coupling tsunami generation to seismic seafloor motion and the
following trans-oceanic wave propagation will be briefly introduced. The focus of the presentation will be on the
complex transformation of the tsunami as it approaches very shallow waters, as well as how these possibly large and
fast-moving water waves interact with coastal infrastructure. Two examples of coastal impact will be discussed. First, a
simulation of a tsunami flooding an urban coastal town will be shown, and we the creation and behavior of the many
turbulent wakes that form behind each structure will be discussed. A conclusion of this example is that it is possible to
achieve very high fluid forces away from the immediate shoreline; having a row of structures seaward of a given
location does not necessarily protect against the flow. The second example will look at tsunami-induced currents in
ports and harbors. Tsunamis, or "harbor waves" in Japanese, are so-named due to the common observation of enhanced
damage in harbors and ports. However, the dynamic currents induced by these waves, while regularly observed and
known to cause significant damage, are poorly understood. We will show that the strongest currents in a port are
governed by horizontally sheared and rotational shallow flow with imbedded turbulent coherent structures. Without
proper representation of the physics associated with these phenomena, predictive models may provide drag force
estimates that are an order of magnitude or more in error. Such an error can mean the difference between an unaffected
port and one in which vessels 300 meters in length drift and spin chaotically through billions of dollars of
infrastructure.
12:20 Seismic Risk Challenges at Nuclear Power Plants (G. Hardy, SGH)
Recent earthquakes in Japan have exceeded their seismic design basis. The 2007 Niigataken Chuetsu-Oki Earthquake
(NCO) earthquake affected the Kashiwazaki nuclear power plant with exceedances of more than a factor of two on the
design in-structure accelerations. The process that Japanese utility Tokyo Electric Power has undergone to establish the
seismic safety of the Kashiwazaki plants (largest nuclear plant in the world with 7 units) has ramifications for all
nuclear plants, including SONGS and Diablo Canyon in California. Likewise, the 2011 Tohoku earthquake resulted in
ground motions at several of the Japanese nuclear power plants that exceeded their new seismic design basis which had
been increased following the NCO earthquake. The Nuclear Regulatory Commission as well as the nuclear utility
industry are studying the results of the Tohoku earthquake and the resulting tsunami on the nuclear power industry.
Lessons learned will help reduce risks in the US in the future.
This presentation will focus on the lessons learned from these recent earthquakes affecting nuclear power plants in
Japan. The focus will be on characterizing the nature of the design basis exceedances, the seismic upgrades that were
required at these Japanese plants, and the expected ramifications for US nuclear power plants.
12:40 Group Discussion
13:00 – 14:30 Lunch (Poolside / Terrace)
13:00 – 14:30 “What’s Next?” Student Luncheon (Tapestry Room)
14:30 – 16:00 POSTER SESSION II: Group A (Plaza Ballroom)
16:00 – 18:00 PLENARY SESSION III: Are We Properly Characterizing Extreme/Rare Events?
Moderator: J. Hardebeck (USGS)
Location: Horizon Ballroom
16:00 22 February 2011 Christchurch Earthquake (B. Bradley, Cantebury)
An overview of the 22 February 2011 Christchurch earthquake is presented in the context of characterization of
extreme/rare events. Focus is given to the earthquake source, observed near-source strong ground motions, and effects
of site response, while structural response and consequences are mentioned for completeness. For each of the above
topics comparisons and discussions are made with predictive models for each of phenomena considered. In light of the
6 | Southern California Earthquake Center