21.6 Detection program for continuous data, CONDET

The CONDET program is a detection program works on data that is organized in a SEISAN continuous database or a BUD or SeisComp archive. It performs a detection process similar to real-time processing systems, but of course the data is already there. The program works in two steps, first to run a detector on a single channel, and second to detect events that are on more than a minimum number of stations. Optionally, the detected events can be extracted, registered and copied into a data base. Possible applications are processing of data from a temporary deployment (e.g., aftershock monitoring, where continuous were recorded without event detection) and adjustment of detection parameters used in real-time monitoring.

The program has three built-in detection algorithms: 1) standard squared STA/LTA, 2) Carl Johnson's detector (that is for example used in the Earthworm processing system (http://folkworm.ceri.memphis.edu/ew-doc/) and 3) correlation with master event. The program writes out a list of detections (file condet.out, which gives station name, component code, trigger time and trigger duration), but also a batch file that can be used to extract the corresponding event data from the continuous data (file extract.batch). Note that wavetool by default takes data from all continuous databases listed in SEISAN.DEF.

Running step by step, first station detection, then event detection

When started without any command line options, the program works on all stations/databases given by the STATION parameter. The output file has detections from all stations, and the extract.batch file has extract commands for all detections. This is all required if only one station is available. For more than one station, it is possible to search for times at which more than a minimum number of stations have triggered. This is done by starting the program with the command line argument `-net'. In this mode, the output file condet.out from the first run is used and the file extract.batch is overwritten. The extract script can now be used to get data for the network detected events. The script can be sources in Unix, under windows run comman in script or rename script to extract.bat and then run it. Condet is intended to run without questions and the parameter file condet.par must be in working directory or DAT. An example of condet.par is in DAT.

Running the whole process from station detection, event detecion, wave extraction and event registration.

The parameters in condet.par can be set up to run all or part of the detection process. This means that it is possible to detect the events, make the s-files and copy the waveform files to WAV with one command. This is partly done by running AUTORG from CONDET. This option can e.g. be useful for a network running SeisComP to get all CONDET detections into a database for daily processing.

Below is an example:

~/WOR/condet
 Give operator
jh
  Start time (yyyymmdd...), at least yyyymmdd
20210318
  Stop time (yyyymmdd...), at least yyyymmdd, blank is end of day
2021031803

....
....
....


       5 events detected within   50.0s on   3+ stations

Number of detections on all stations   81

YEAR MODA HR MM SEC NDET
2021 0318 00:05  30   12
2021 0318 01:57  21    3
2021 0318 02:03  25    3
2021 0318 02:40   3    4
2021 0318 03:12  36   11

A lot of listing comes out while running like missing channels. At the end there is a summary of what has been detected. In this case there were 81 detection on all stations and 5 events with more then 3 detections in window.

The input parameters are given in condet.par:

STATION: give continuous database name, station and component code. If an archive, the data base name is not used.

STATION                               LICOC       LICO  HH Z 
STATION                               LIGLC       LIGL  HH Z

The BASE TYP is SEISAN (blank), Archive (arc)

BASE TYPE                             arc 
STATION                               LIGLC       LIGL  HH Z

START DATE and STOP DATE: give time interval, can be larger than data availability

START DATE          yyyymmddhhmmss        200802270000 
STOP DATE           yyyymmddhhmmss        200803122359

WAVEOUT: Set to 1. to write out waveform files with the original data and trigger channels.
EXTRACT DURATION: Length of extraction window in seconds, used in extract.batch
PRE EVENT TIME: Time to start extract before detection time in seconds, used in extract.batch
INTERVAL: Length of data segment read at a time. The default is 60 minutes.

DET ALGORITHM: choices for the detection algorithm are STA for squared STA/LTA, COR for correlation and CAR for Carl Johnson's detection algorithm

MIN TRIG DURATION: Minimum duration the trigger level needs to be exceeded for
MIN TRIG INTERVAL: Only allow for one detection within this time, given in seconds
FILTER LOW: Low cut for bandpass filter
FILTER HIGH: High cut for bandpass filter

If DET ALGORITHM is STA:

STA LENGTH: Short term duration in seconds
LTA LENGTH: Long term duration in seconds
TRIGGER RATIO: Ratio of STA/LTA required for trigger
DETRIGGER RATIO: Ratio to detrigger
FREEZE LTA: LTA can be frozen at time STA/LTA goes above TRIGGER RATIO, 1.=to freeze

If DET ALGORITHM is CAR, see Earthworm documentation for details:

CARL RATIO
CARL QUIET

If DET ALGORITHM is COR:

CORRELATION MIN: Minimum correlation between waveforms of master event and the data required for a trigger
MASTER WAVEFORM: Name of waveform file that is used as master event, the master event is cross-correlated against the continuous waveform data

Network detection parameters:

NET MIN DET: Minimum of detections required from different stations with time window given by
NET WINDOW SEC: Time window for network detection in seconds. NET MAX DELT SEC: Allows the user to specify the maximum time allowed between arrivals on two consecutive stations (in addition to the overall time window for all arrivals given in the preexisting NET WINDOW SEC NET MIN RATIO: Gives the minimum STA/LTA ratio to keep. This lets one use a low STA/LTA ratio in CONDET and then to explore which STA/LTA level to reject during the much faster "CONDET -NET" phase. EXTRACT DURATION: Duration(sec) of extract.

Extra parameters needed for automated operation

#
#  parameter needed if net detection
#  else not

NET DETECTION  0: no 1: yes             1.0
#
#  paramter needed if waw extraction,
#  else not
#
WAV EXTRACT 0: no extract, 1: extract   1.0
#
#  parameter need if s-files made after extraction
#  else not
#
MAKE SFILE 0: no, 1: yes                1.0
#
#   following 3 can be omited if all default
#
BASE SFILE, base for s-files, blank def            
COPY WAV, move(m),copy(c), not(' ')     c                         
WAV BASE, ' ' WAV, or 5 letter

NET DETECTION: If set to 1.0, net detection will be run after station detection and there is no need to run again with -net flag.

WAV EXTRACT: if 1.0, wavforms will be extracted to working directory, one each time an event is found and the batch file is not used.

MAKE SFILE: An s-file in the data base is made.

BASE SFILE: The data base for the s-files, if blank, the default data base is used. A local data base '„' can also be used.

COPY WAV: Optionally copy extracted waveform files to WAV. If blank, no copy, if m, file is moved and if c file is copied.

WAV BASE: If blank, copy to WAV, else to data base given. NOTE, the parameter COPY_WAV_DIR in SEISAN.DEF is not used, data base must be given here.