# Apply McNamara PSD algorithm to a seismic signal The `psdList` function subsets a seismic `Stream` object into a series of shorter segments with 50% overlap and uses the `McNamaraPSD` method to return a smoothed (aka binned) Power Spectral Density (PSD) for each segment. ```r psdList(st) ``` ## Arguments - `st`: a `Stream` object ## Details A `Stream` will be subset into segments depending upon the channel identifier (@stats@channel) associated with this seismic data. The binning frequencies are also channel dependent as exemplified in this code extract where `Z` is the segment length in seconds: ``` alignFreq <- 0.1 if (stringr::str_detect(channel,"^L")) { Z <- 3 * 3600 loFreq <- 0.001 hiFreq <- 0.5 * tr_merged@stats@sampling_rate } else if (stringr::str_detect(channel,"^M")) { Z <- 2 * 3600 loFreq <- 0.0025 hiFreq <- 0.5 * tr_merged@stats@sampling_rate } else { Z <- 3600 loFreq <- 0.005 hiFreq <- 0.5 * tr_merged@stats@sampling_rate } ``` Each new segment starts half way through the previous segment. (50% overlap) ## Returns A list of `PSD` objects is returned. Each element of the list is an `list` object with the following elements: ``` freq, spec, snclq, starttime, endtime ``` Note: Individual PSDs have not had instrument correction applied. ## References [Seismic Noise Analysis System Using Power Spectral Density Probability Density Functions](https://pubs.usgs.gov/of/2005/1438/pdf/OFR-1438.pdf) (McNamara and Boaz 2005) ## Author(s) Jonathan Callahan jonathan@mazamascience.com ## See Also `McNamaraPSD`, `psdList2NoiseMatrix`, `psdPlot`, `psdStatistics`, ## Examples ```r ## Not run: # Create a new IrisClient iris <- new("IrisClient", debug=TRUE) # Get seismic data starttime <- as.POSIXct("2011-05-05", tz="GMT") # 2011.125 endtime <- starttime + 1*24*3600 st <- getDataselect(iris,"IU","GRFO","--","BHE",starttime,endtime) # Generate power spectral density for each hour long segment psdList <- psdList(st) # Plot uncorrected PSDs period <- 1/psdList[[1]]$freq plot(period, psdList[[1]]$spec, log='x', type='l', xlab="Period (Sec)", ylab="Power (dB)", main="Uncorrected PSDs") for (i in seq(2:length(psdList))) { points(period, psdList[[i]]$spec, type='l') } ## End(Not run) ```

psdList function