IRISMustangMetrics (version 2.4.6)

STALTAMetric: 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)

Value

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

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)

Author

Jonathan Callahan

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().

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

  if (FALSE) {
# 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)
  }