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General Issues > Trigger
Trigger Philosophy
In the RED System, two totally different trigger
mechanisms are employed:
- A set of different logging trigger algorithms
is available for determining whether or not a faint seismic signal meets
the criteria for being stored in the system´s memory (a smart media
card)—there will be no radio message at first. The choice includes a
simple peak acceleration threshold, different artefact-rejection filters,
and a standard STM / LTM algorithm. Parameters regarding time and amplitude
can be set within a wide range by using a software menu. The option
of choosing different periods for pre-event and post-event data storage
is also available. Another option is to activate a self-learning trigger
algorithm that adapts its threshold to obtain a specified number of
positive trigger events per week. Depending on the cultural noise at
the specific site, data logging will normally be initiated between 0.02
and 2% g.
- Another algorithm, the messaging trigger,
decides whether or not an instant alert message should be transmitted.
Several standard methods for the evaluation of potential damage to civil
structures will be applied in this procedure. Finally, a set of key
parameters characterizing the event will be included in the alert message.
PSV spectra, arias intensity, and other time-integrated figures will
be available. Again, the exact parameters can be set by using another
software menu. Instant alert messaging will normally be conducted whenever
substantial shaking in the order of 2 to 10% g is found.
RED Systems Initiative is seeking to collaborate
with a Californian institution of earthquake engineering in the development
of these trigger and evaluation algorithms.
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