# envelope: Envelope of a seismic signal In IRISSeismic: Classes and Methods for Seismic Data Analysis

## Description

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

## Usage

 `1` ```envelope(x) ```

## Arguments

 `x` a `Trace` object

## 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) = √{T^2(t) + H^2(t)}

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

## Value

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

## Note

This algorithm is adapted from code in the seewave package.

## Author(s)

Jonathan Callahan jonathan@mazamascience.com

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22``` ```## 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') ## End(Not run) ```

IRISSeismic documentation built on Oct. 7, 2021, 9:10 a.m.