Guralp Systems CMG-6TD - Manual (Page 90)

CMG-6TD Command-line interface
Z­secs, N­secs, and E­secs are the time periods over which to calculate
the average for the Z, N, and E 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 LTA will calculate long-term averages for 15 seconds
for the Z component, and for 20 seconds for each of the horizontal
components.
7.5.5 RATIOS
Syntax: Z­ratio Z­ratio Z­ratio RATIOS
Sets the ratio of STA to LTA above which a trigger will be declared in the
STA/LTA triggering algorithm.
Z­ratio, Z­ratio, and Z­ratio are the time period over which to calculate
the average for the Z, N, and E 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 RATIOS will cause the 6TD to trigger if the STA/LTA
ratio is above 4 for the Z component, or above 10 for the horizontal
components.
7.5.6 BANDPASS
Syntax: tap filter BANDPASS
The 6TD passes the stream(s) which generate STA/LTA triggers through a
band-pass filter before examining them. The corner frequency of the
band-pass filter can be changed with the BANDPASS command.
The parameter filter takes an integer argument which must be 1, 2 or 5,
where:
•
filter = 1 creates a filter with a corner at 10 % of the Nyquist
frequency for tap tap (i.e. 5 % of its sample rate)
•
filter = 2 creates a filter with a corner at 20 % of the Nyquist
frequency for tap tap (i.e. 15 % of its sample rate)
•
filter = 5 creates a filter with a corner at 50 % of the Nyquist
frequency for tap tap (i.e. 25 % of its sample rate)
7.5.7 PRE­TRIG
Syntax: time PRE­TRIG
Sets the pre-trigger recording time. time is the number of seconds of data to
output from before a trigger is declared.
MAN-T60-0002 90 Issue F - February 2014