Abstract
A survey of published scientific literature was undertaken to identify
and catalog observed earthquake precursors. The earthquake precursors
selected for analysis included electric and magnetic fields, gas
emissions, groundwater level changes, temperature changes, surface
deformations, and seismicity. For each of these precursors, the published
scientific literature was searched to document the statistics of
each reported earthquake precursor (spatial extent, time, duration,
amplitude, signal/noise ratio), to analyze dependence of the observable
for each precursor on earthquake magnitude, and to explore proposed
physical models to explain each earthquake precursor. Some general
characteristics were observed for these precursory phenomena. First,
the largest amplitude precursory anomalies tend to occur before the
largest magnitude earthquakes. Also, the number of precursory anomalies
tends to increase the closer in time to the occurrence of the earthquake.
Finally, the precursory anomalies tend to occur close to the eventual
epicenter of the earthquake. In general, the physical models indicate
that all of the precursory phenomena are related to deformation that
occurs near the fault prior to the main earthquake. While the models
provide plausible physical explanations for the precursors, there
are many free parameters in the models that are poorly resolved.
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