Annual Meeting - SCEC.org

Poster Abstracts | Group 1 – CSEP
1-080
EARTHQUAKE PREDICTABILITY TEST OF THE LOAD/UNLOAD RESPONSE
RATIO METHOD Zeng Y, and Shen Z
In this paper, we extend our test of the Composite Load/Unload Response Ratio (CLURR) method
for intermediate-term earthquake forecast to large historical events in China. Our previous test in
the western US has found significant precursor anomalies for almost all of the M>6 earthquakes in
California since 1979. The method is modified from the Load/Unload Response Ratio (LURR)
method proposed by Yin and others (1995) for long and intermediate term earthquake forecasts.
The basic assumption and algorithm of LURR are that large earthquakes occur in response to
critical loading stress surrounding the seismogenic fault, whose state of criticality could be detected
through anomalous response monitoring of regional seismicity to the Coulomb stress changes on
faults induced by earth tides. We have developed an open source code for the LURR evaluation
using Agnew’s (1996) method to compute tidal induced Coulomb stresses on the fault and applied
both the stress “state” and “rate” as criteria for differentiating the loading and unloading events
based on those Coulomb stress changes. A range of frictional coefficients is used to calculate the
Coulomb stress change and the averages based on the root mean squares of those LURR functions
are then used to form the composite LURR function. We test against large Chinese earthquakes that
have occurred in the last 30 years, including the M7.3 Haicheng earthquake in 1975 and M7.6
Tangshan earthquake in 1976. We have found good success for most events except the most recent
M7.9 Sichuan earthquake on May 12, 2008.
112 | Southern California Earthquake Center