IRISSeismic (version 1.5.1)

envelope: Envelope of a seismic signal

Description

The envelope method of Trace objects returns a Trace whose data have been replaced with the envelope of the seismic signal.

Usage

envelope(x)

Arguments

x

a Trace object

Value

A Trace whose data have been replaced with the envelope of the seismic signal.

Details

Before calculating the envelope, the seismic trace is 'cleaned up' by removing the mean, the trend and by applying a cosine taper. See DDT for more details.

The seismic envelope is defined as:

$$ E(t) = \sqrt{T^2(t) + H^2(t)} $$

where \(T(t)\) is the seismic trace and \(H(t)\) is the Hilbert transform of \(T(t)\).

Examples

# NOT RUN {
# Open a connection to IRIS DMC webservices
iris <- new("IrisClient")

starttime <- as.POSIXct("2010-02-27 06:00:00", tz="GMT")
endtime <- as.POSIXct("2010-02-27 09:00:00", tz="GMT")

# Get the waveform
st <- getDataselect(iris,"IU","ANMO","00","BHZ",starttime,endtime)
tr <- st@traces[[1]]

# Demean, detrend, cosine taper
tr <- DDT(tr)

# Create envelope version of the trace
trenv <- envelope(tr)

# Plot signal data and envelope data
plot(tr@data, type='l', col='gray80')
points(trenv@data, type='l', col='blue')
# }