pick_kurtosis {eseis}

Kutosis based event picking

Description

The function picks (identifies) events from continuous data using the kurtosis of the signal, and when it reaches beyond a defined threshold value. The end of an event is determined by the signal-to-noise ratio (SNR)

Usage

pick_kurtosis(
  data,
  on,
  off = 1,
  dur_min = 0,
  dur_max,
  window_kurt,
  window_amp,
  time,
  dt
)

Arguments

data

eseis object, numeric vector or list of objects, data set to be processed.

on

Numeric value, kurtosis threshold that defines the onset of an event.

off

Numeric value, ratio of average post and pre event signal amplitude inside a running window. Default is 1.

dur_min

Numeric value, minimum duration of the event. This is required as the kurtosis routine tends to identify multipe picks in the beginning of an event.

dur_max

Numeric value, maximum duration of the event. This value can be omitted but would increase computational speed as it determines the length of samples to look for the amplitude ratio that signals the end of an event

window_kurt

Numeric value, size of the running window (in number of samples) in which the kurtosis is calculated.

window_amp

Numeric value, size of the running window (in number of samples) in which the running mean is calculated.

time

POSIXct vector, time vector of the signal(s). If not provided, a synthetic time vector will be created.

dt

Numeric value, sampling period. If omitted, either estimated from time or set to 0.01 s (i.e., f = 100 Hz).

Details

Further reading:

Baillard, C., Crawford, W.C., Ballu, V., Hibert, C., Mangeney, A., 2014. An automatic kurtosis-based p- and s-phase picker designed for local seismic networks. Bull. Seismol. Soc. Am. 104 (1), 394–409.

Hibert, C., Mangeney, A., Grandjean, G., Baillard, C., Rivet, D., Shapiro, N.M., Satriano, C., Maggi, A., Boissier, P., Ferrazzini, V., Crawford, W., 2014. Automated identification, location, and volume estimation of rockfalls at Piton de la Fournaise Volcano. J. Geophys. Res. Earth Surf. 119 (5), 1082–1105. http://dx.doi.org/10.1002/2013JF002970.

Value

data.frame, picked events.

Author(s)

Michael Dietze

Examples

## load example data set
data(rockfall)

## preprocess signal (aggregate to increase speed, filter, envelope)
s <- signal_aggregate(data = rockfall_eseis, n = 4)
s <- signal_filter(data = s, f = c(5, 20), lazy = TRUE)
e <- signal_envelope(data = s)

## pick events based on signal kurtosis
p <- eseis::pick_kurtosis(data = e, 
                          window_kurt = 200, 
                          on = 15, 
                          off = 5, 
                          dur_min = 10, 
                          dur_max = 90, 
                          window_amp = 300)

p$picks