Annual Meeting - SCEC.org

Poster Abstracts | Group 1 – EFP
the CSEP Testing Center, the CISN EEW Testing Center has been able to implement several of the
testing concepts originally developed on CSEP. These concepts include the following: (a)
earthquake, or ground motion, forecasts are reported in standardized data formats, (b) commonlyagreed
upon performance evaluation reports are used for all algorithms, (c) observed data is
retrieved from “authorized” data sources and the same observed data is used to evaluate all
algorithms, (d) only forecasts and observed data for a specific testing region are considered, and (e)
the testing center saves information indicating how results were produced. In this poster, we
present an overview of the CISN EEW Testing Center including the scientific design goals for the
system, and a description of the system’s current capabilities. We describe the performance
summaries specified by the CISN EEW algorithm development group, and how the current CISN
EEW Testing Center produces those summaries using the automated testing capabilities from the
CSEP software framework.
1-096
STATIONARY STATISTICS AND ERGODICITY: IMPLICATIONS FOR
EARTHQUAKE FORECASTING Tiampo KF, Klein W, Li H, Mignan A, Toya Y, Rundle JB,
and Chen CC
In recent years, several different forecasting methods based upon the quantification of patterns in
seismicity data, but relying on different approaches, have been proposed with varying degrees of
success (Keilis-Borok, 1982; Bowman et al., 1998; Tiampo et al., 2002). However, the physical basis
of these methods is not always well understood. This lack of understanding presents a significant
barrier to the determination of the accuracy of these methods, the best route to improving their
forecasting capability, and the possible limits to their accuracy as imposed by the physics. Recently
the equilibrium property of ergodicity was identified in an earthquake fault system (Tiampo, et al.,
2007). Ergodicity in this context not only requires that the system is stationary for these networks at
the applicable spatial and temporal scales, but implies that they are in a state of metastable
equilibrium in which the ensemble averages can be substituted for temporal averages when
studying their behavior in space and time. Here we show that this property can be used to identify
those regions of parameter space which are stationary using a particular measure of ergodic
behavior, the TM metric (Thirumalai et al., 1989). We apply this measure to one particular
seismicity-based forecasting tool, the PI index (Tiampo et al., 2002), in order to test the hypothesis
that the identification of ergodic regions can be used to improve and optimize forecasts that rely on
historic seismicity catalogs and to synthetic catalogs in order to better understand the physical
process that affects this accuracy. We show that these ergodic regions, defined by magnitude and
time, provide more reliable forecasts of future events in both natural and synthetic catalogs.
Ergodicity can be used to identify those spatiotemporal regions for which the statistics of these
fault systems are stationary and suggests that earthquake forecasting methodologies based upon
the linearized analyses of seismic catalog data require that certain equilibrium properties, such as
stationarity, are necessary to produce accurate results.
1-100
USING SEISMICITY TO IDENTIFY CHANGES IN THE LOCAL STRESS FIELD DUE
TO THE LANDERS 1992 EARTHQUAKE Latimer CD, and Tiampo KF
It has long been recognized that large earthquakes affect and are affected by the stress in the crust
in the region which they occur. The regional stress orientation is measured and used with
earthquake modeling, particularly those involving stress changes (King et al., 1994). The change in
the local stress field due to an earthquake is not so easily determined, but carries the same
importance in understanding the mechanics of earthquakes. Work has started with the goal of
determining the local stress field around the Landers 1992 Californian earthquake. To create our
120 | Southern California Earthquake Center