Search:
wiki:evanstrig
Last modified 18 months ago Last modified on 03/25/12 13:32:22

# Earthworm Module: evanstrig

Contributed by:

## Function

Evanstrig monitors waveforms for long-period signals; evansassoc associates LP triggers into events.

## Details

The evanstrig program is an adaptation of lptrig. Evanstrig runs John Evans' long-period trigger algorithm on single-channel TYPE_TRACEBUF messages and produces single-channel triggers. These triggers can then be associated into "events" by the module evansassoc.

The evansassoc program associates long-period triggers from several scn's. The association rule is that triggers from a certain number of scn's must be received within a specified time interval. The association parameters are specified in evansassoc's parameter file .

NOTE: evanstrig will only work on 100 hz data!

The details of John Evans' long period trigger algorithm are discussed in the following two papers:

A Teleseism-Specific Detection Algorithm for Single Short-Period Traces, Bull. Seism. Soc. Am. 73, 1173-1186, Evans and S.S. Allen, 1983.

Reliable Automatic Detection of Long-Period Volcanic Earthquakes at Long Valley Caldera, California, Bull. Seism. Soc. Am. 85, 1518-1522, Evans and Pitt, 1995.

### Example Configuration File

    #
    #                  Evanstrig's Configuration File
    #
    MyModuleId    MOD_EVANSTRIG # module id for this program,
    InRing        WAVE_RING     # Transport ring to find waveform data on
    OutRing       PICK_RING     # Transport ring to write all output to
    LogFile       1

    HeartbeatInt  0     # Heartbeat interval (seconds)
                        # if 0, no heartbeats will be sent.

    Log_triggers 1      # If 1, log to screen only
                        # If 2, log to log file only
                        # If 3, log to screen and log file

    Debug_enabled  0    # If 1, print debug messages

    # List the message logos to grab from input transport ring
    #              Installation       Module       Message Type
    GetWavesFrom   INST_WILDCARD   MOD_WILDCARD   # TYPE_TRACEBUF msg

    # Define the maximum gap (in # of sample intervals) between
    # consecutive tracbuf messages to interpolate thru without a restart.
    # The number of samples that will be interpolated is MaxGap-1.
    MaxGap 3

    #  Magic numbers from John Evans for configuring the trigger:
    @evanstrig_params.d      # file with integer & floating-point parameters

    # Optional command for changing the maximum number of channels
    # which can be triggered on.  Default is 32.
    # MaxSCN 20

    # List the SCN's to trigger on:
    #           site  comp  net
    TriggerOn    MPR  VHZ  NC
    TriggerOn    MCM  VHZ  NC
    TriggerOn    MCV  VHZ  NC
    TriggerOn    MDC  VHZ  NC
    TriggerOn    MTU  VHZ  NC
    TriggerOn    SLK  VHZ  NN
    TriggerOn    MMP  VHZ  NC
    TriggerOn    MLM  VHZ  NC
    TriggerOn    MGP  VHZ  NC
    TriggerOn    MLK  VHZ  NC

## Helpful Hints

### Download in other formats:

- Plain Text