Annual Meeting - SCEC.org

Meeting Program | TUESDAY
Tuesday, September 13th
07:00 – 08:00 Breakfast
08:00 – 09:00 PLENARY SESSION IVA: Operational Earthquake Forecasting - State of Knowledge and Issues for
Implementation
Moderator: A. Michael (USGS)
Location: Horizon Ballroom
08:00 Operational Earthquake Forecasting and Decision-Making in a Low-Probability Environment: Lessons
from L’Aquila and Application in California (T. Jordan, SCEC/USC)
Operational earthquake forecasting (OEF) is the dissemination of authoritative information about the time dependence
of seismic hazards to help communities prepare for potentially destructive earthquakes. Most previous work on the
public utility of OEF has anticipated that forecasts would deliver high probabilities of large earthquakes; i.e.,
deterministic predictions with low error rates (false alarms and failures-to-predict) would be possible. This expectation
has not been realized; the seismic cycle is very unsteady, and the search for diagnostic precursors has not yet produced
successful short-term prediction schemes. An alternative to deterministic prediction is probabilistic forecasting based
on empirical statistical models of aftershock triggering and seismic clustering. During periods of high seismic activity,
short-term earthquake forecasts can attain prospective probability gains in excess of 100 relative to long-term forecasts.
The utility of such information is by no means clear, however, because even with hundredfold increases, the
probabilities of large earthquakes typically remain small, rarely exceeding a few percent over forecasting intervals of
days or weeks. Civil protection agencies have been understandably cautious in implementing OEF in this sort of “lowprobability
environment.”
The need to move more quickly has been underscored by recent seismic crises, such as the 2009 L’Aquila earthquake
sequence, in which an anxious public was confused by informal and inaccurate earthquake predictions. After the
L’Aquila disaster, the Italian Department of Civil Protection appointed an International Commission on Earthquake
Forecasting (ICEF), which I chaired, to review the state of knowledge and recommend guidelines for OEF utilization.
Our report has just been published (Ann. Geophys., 54, 4, 2011; doi: 10.4401/ag-5350;
http://www.annalsofgeophysics.eu/index.php/annals/article/view/5350). This presentation will review the ICEF
guidelines and comment on their application in California. I will emphasize how authoritative statements of increased
hazard, even when the absolute probability is low, can provide a psychological benefit to the public by filling
information vacuums that lead to informal predictions and misinformation. Formal OEF procedures based on
probabilistic forecasting appropriately separate hazard estimation by scientists from the decision-making role of civil
protection authorities. The prosecution of seven Italian scientists on manslaughter charges stemming from their actions
before the L’Aquila earthquake makes clear why this separation should be explicit in defining OEF protocols.
08:30 Group Discussion
09:00 – 10:00 PLENARY SESSION IVB: Ground Motion Simulation Validation
Moderators: N. Luco (USGS) and K. Olsen (SDSU)
Location: Horizon Ballroom
SCEC has established a Technical Activity Group (TAG) focused on Ground Motion Simulation Validation (GMSV)
in order to develop and implement testing/rating methodologies via collaboration between ground motion modelers and
engineering users. A SCEC workshop was held in January 2011 to kick off the GMSV TAG. During this workshop, the
discussion included selection of ground motion simulation scenarios, simulation models, goodness-of-fit methodologies
and metrics, engineering application targets, archival and distribution of the simulations/validations, appropriate
platform(s) for the validations, and operational issues (including funding issues and possible coordination with
OpenSees and NGA-E). During this plenary session the recommendations from the workshop will be reviewed and
opened up for additional input from interested SCEC participants.
10:00 – 10:30 Break
10:30 – 12:30 PLENARY SESSION V: How Do We Develop the Community Stress Model?
Moderator: T. Becker (USC)
Location: Horizon Ballroom
10:30 Fault Stress Heterogeneity and Implications for Rupture Dynamics (J.-P. Ampuero, Caltech)
I will present and discuss theoretical constraints and observational evidence on the spatial distribution of stress in
active fault zones, with emphasis on the statistical description of stress heterogeneities over a broad range of length
scales. I will illustrate through dynamic rupture simulations the possible implications of such heterogeneities on the
8 | Southern California Earthquake Center