STALTAMetric {IRISMustangMetrics}

Maximum STA/LTA of a signal

Description

The STALTAMetric() function calculates the maximum of STA/LTA over the incoming seismic signal.

Usage

STALTAMetric(st, staSecs, ltaSecs, increment, algorithm)

Arguments

st

a Stream object containing a seismic signal

staSecs

length of the short term averaging window in seconds (default=3)

ltaSecs

length of the long term averaging window in seconds (default=30)

algorithm

algorithm to be used (default="classic_LR")

increment

increment used when sliding the averaging windows to the next location (default=1)

Details

Currently supported algorithms include:

• "classic_RR"

• "classic_LR"

• "EarleAndShearer_envelope"

This metric applies the STALTA method of Trace objects to every Trace in st with the following parameter settings:

• demean=TRUE

• detrend=TRUE

• taper=0.0

The final metric value is the maximum STALTA value found in any Trace in this Stream.

Further details are given in the documentation for STALTA.Trace().

Value

A list with a single SingleValueMetric object is returned. The metric name is max_stalta.

Note

The STALTA method of Trace objects returns a numeric vector of STA/LTA values that has the same length as the signal data. This is a moderately time consuming operation. By comparison, finding the maximum value of this vector of STA/LTA values is very fast.

Author(s)

Jonathan Callahan [e-mail]

References

First break picking (Wikipedia)

Automatic time-picking of first arrivals on large seismic datasets (Wong 2014)

Automatic first-breaks picking: New strategies and algorithms (Sabbione and Velis 2010) )

Examples

  ## Not run: 
# Open a connection to IRIS DMC webservices
iris <- new("IrisClient")

# Get the waveform
starttime <- as.POSIXct("2012-02-12",tz="GMT")
endtime <- as.POSIXct("2012-02-13",tz="GMT")
st <- getDataselect(iris,"AK","GHO","","BHN",starttime,endtime)

# Calculate the STA/LTA metric and show the results
metricList <- STALTAMetric(st)
dummy <- lapply(metricList, show)
  
## End(Not run)