Guralp Systems CMG-DM24 - Manual (Page 63)

Operator’s Guide DM-24 Digitiser
Issue G January 2003 61
10. STA/LTA TRIGGER OPTIONS
In it’s standard configuration the digitiser outputs continuous data at a user-selectable
sample rate. An additional powerful feature of the digitiser is the ability to
simultaneously run a STA/LTA event triggering algorithm in parallel with the
continuous acquisition. This permits the system to record continuously at a relatively
low sample rate, and record at a much higher sample rate during short periods when
triggered. Parameters controlling the triggering algorithm, and controlling the data
output once the system is triggered, are all selectable by the user, permitting the
maximum flexibility of operation and the most efficient use of available storage space.
Shown below in the upper window, is an example of a data stream recording over a two
month period. Two seismic events are shown highlighted in the two lower windows
which, given suitable triggering parameters, can be recorded in greater detail at a higher
sampling rate of upto 200 samples per second.
Triggering of all three components from vertical channel 100Hz tap, filter from 5 to 45 Hz
Sta = 1, Lta = 50, Sta/Lta = 10, pre-trigger = 40, post-trigger = 70