Annual Meeting - SCEC.org

Meeting Program | TUESDAY
15:30 – 17:00 PLENARY SESSION VIA: New Directions in Earthquake Forecasting
Moderator: I. Zaliapin (UNR)
Location: Horizon Ballroom
15:30 UCERF3 – Progress on an Operational Earthquake Forecast for California (E. Field, USGS)
The Working Group on California Earthquake Probabilities (WGCEP) is actively building the 3rd Uniform California
Earthquake Rupture Forecast (UCERF3). The main innovations for this model will be: 1) the relaxation of fault
segmentation assumptions and the inclusion of multi-fault ruptures; and 2) the addition of spatiotemporal clustering
(earthquake triggering and aftershocks), which will form the basis of an operational earthquake forecast. Our plan for
both these enhancements was bolstered tragically by the 2011 Tōhoku, Japan and Christchurch, New Zealand
earthquakes. In addition to giving an overview and progress report on the UCERF3 development, this talk will strive to
emphasize the following more general themes: a) building a useful, state-of-the-art, system-level model inevitably leads
to unearthing deep and interesting scientific questions; b) object-oriented design and programming, plus high
performance computing, are key to success; c) physics-based simulators are becoming more and more critical to the
forecasting enterprise; and d) none of this could happen without SCEC (including the intern program).
16:00 Group Discussion
16:15 The Future of Earthquake Forecasting: The Role of Earthquake Simulators (J. Dieterich, UCR)
Earthquake simulators provide a physics-based and self-consistent framework for generating region-specific models of
earthquake occurrence. Simulations typically consist of ≥100,000 events and span tens of thousands of years.
Earthquake simulation capabilities are rapidly evolving – current capabilities now include detailed portrayals of
geometrically complex fault systems at regional scales that incorporate physics-based representations of earthquake slip
(including space-time clustering effects) slow slip events, and continuous fault creep. Some areas where simulators
may make unique contributions to earthquake forecasting include 1) deterministic modeling of short-term clustering of
large events that is linked to material parameters and evolving stress conditions; 2) integration of the short-term
(minutes to years) predictability of earthquakes, and long-term processes (100-1000 years) that condition fault systems
to fail in great earthquakes; 3) characterization of possible location-specific interactions that control the statistics of
earthquake occurrence; 4) statistical characterizations of earthquake occurrence over time scales that greatly exceed our
observational record (which is short compared to the typical recurrence times for large and great earthquakes); 5)
possible precursory, or triggering, interactions between slow slip events and great earthquakes in subduction zones; 6)
generation of multiple synthetic catalogs to test proposed forecasting algorithms.
16:45 Group Discussion
17:00 – 18:30 PLENARY SESSION VIB: SDOT Interdisciplinary Group - What Is Needed To Make Progress On
Understanding Stress Transfer From Plate Motion To Crustal Faults?
Moderator: K. Johnson (Indiana)
Location: Horizon Ballroom
17:00 An Integrated View of the Mw 6 Earthquake Sequence at Parkfield (S. Barbot, Caltech)
Advances in geophysical monitoring now provide an extensive set of observations of all aspects of the earthquake cycle.
Yet, unifying physical models that connect these observations into a coherent picture are lacking. At the same time,
laboratory experiments and theoretical developments provide an increasingly detailed understanding of the fault
physics, offering the basis for an extrapolation to natural conditions.
In this study, we bridge the gap between observations and fault physics by developing the first model of the full
earthquake cycle that explains a number of interesting and robust observations of the crustal dynamics at Parkfield.
Despite the similarities between the repeating Mw 6 earthquakes and their short recurrence times (from 12 to 32 years
for 5 events until 1966), the latest rupture of 2004 defied the odds by taking place a decade later than anticipated and
initiating at the south end to propagate northward, contrarily to all previous events.
We build our model of fault friction using the spatial patterns of microseismicity, the time series of GPS displacements
in the 1999-2010 period, the InSAR data, and the GPS offsets of the 2004 earthquake. We also consider the slip
distribution of the 1966 event and the historical catalog of recurrence times and hypocenter locations. We show the
special role of microseismicity, which marks the transition between stable and unstable friction and circumscribes the
seismogenic zone. We use the program BICYLE (Boundary Integral Cycles of Earthquakes) of Lapusta & Liu (2009) to
solve the elasto-dynamic equations that govern the fault slip evolution. We obtain a sequence of Mw~6 earthquakes
that can explain the observed variability of hypocenters and reproduce the geodetic observations of surface deformation
in the co- and postseismic periods associated with the 2004 event. The change of hypocenter between 1966 and 2004
and the delay of the latest event is consistent with the occurrence of a swarm of smaller-magnitude earthquakes during
the 1992-1994 period and these two locations being close to the boundary of the seismogenic zone. Our study
introduces a methodology capable of integrating seismological and geodetic observations into a coherent physical model
of the earthquake cycle. Our approach can serve as an important tool to investigate the effect of other components of
earthquake physics and to help understand and mitigate seismic hazards around active faults.
10 | Southern California Earthquake Center