Guralp Systems CMG-3ESPCD - Manual (Page 66)

CMG-3ESPCD Digital Broadband Seismometer Command line interface
will calculate short-term averages for 1 second of the Z and N components,
and 2 seconds of the E and auxiliary components.
6.4.4 LTA
Syntax: Z­secs N­secs E­secs X­secs LTA
Sets the length of the “long-term” averaging period in the STA/LTA triggering
algorithm.
The arguments Z­secs, N­secs, E­secs and X­secs are the time period
over which to calculate the average for the Z, N, E, and auxiliary components
respectively. If a component is not considered by the triggering algorithm (see
TRIGGERS, above), the value you specify here will be ignored. For example,
15 20 20 20 STA
will calculate long-term averages for 15 seconds of the Z component and 20
seconds of the N, E and auxiliary components.
6.4.5 RATIOS
Syntax: Z­ratio N­ratio E­ratio X­ratio RATIOS
Sets the ratio of STA to LTA above which a trigger will be declared in the
STA/LTA triggering algorithm.
The arguments Z­ratio, N­ratio, E­ratio and X­ratio are the time
period over which to calculate the average for the Z, N, E, and auxiliary
components respectively. If a component is not considered by the triggering
algorithm (see TRIGGERS, above), the value you specify here will be ignored.
For example,
4 10 10 10 RATIOS
will cause the digitiser to trigger if the STA/LTA ratio is above 4 for the Z
component or above 10 for the remaining components.
6.4.6 PRE-TRIG
Syntax: time PRE­TRIG
Sets the pre-trigger recording time. The argument time is the number of
seconds of data to output from before a trigger is declared.
6.4.7 POST-TRIG
Syntax: time POST­TRIG
Sets the post-trigger recording time. The argument time is the number of
seconds of data to output after a trigger condition lapses. If an event persists
MAN-C3E-0002 66 Issue B - November 2013