Standard Event Lists cont.
- Example of Standard Event List SEL3.
Based on the events listed in SEL1, additional data from auxiliary seismic stations are requested to refine the location of events that have already been listed. Requests are formulated automatically and sent to selected auxiliary seismic stations. With this additional information and with incoming infrasound data the next, more comprehensive and higher quality list of events is created, Standard Event List 2 (SEL2).
- Events listed in the Reviewed Event Bulletin have been examined by analysts.
The last of these event lists is Standard Event List 3 (SEL3), which includes additional information resulting from data that arrive late and later recorded signals. SEL3 is the most refined automatic list of events issued by the IDC.
This process is entirely automatic, carried out by specially designed computer programs. No human intervention in the data processing has taken place until this point.
Interactive analysis and the Reviewed Event Bulletin
The automatic processes to compile the Standard Event Lists from the original waveform data are quite sophisticated. It is still necessary, though, for the results of automatic processing to be reviewed by an analyst to provide reliable and comprehensive information to Member States.
Sometimes signals are associated to the wrong event. Occasionally, events are listed which are not real, and sometimes events are missed. Analysts at the IDC therefore review every single event listed in SEL3. In 2007, there were an average of 126 events each day.
The analyst discards events which are not real, adds signals which have not been associated to an event, and corrects and improves the location estimates of those events which are real.
