eventWindow: Return a portion of a trace surrounding an event.

Description

The eventWindow method of Trace uses the picker returned by the STALTA() method to center a window around the the event detected by the picker.

Usage

eventWindow(x, picker, threshold, windowSecs)

Arguments

a Trace object

picker

a picker as returned by the STALTA() method applied to this Trace

threshold

the threshold at which the picker is 'triggered'

windowSecs

the size of the window in secs

Value

A new Trace object is returned.

Details

This utility function uses the trace method triggerOnset() to determine p-wave onset followed by the slice() method to return a new Trace object of the desired size centered near the event onset.

When no threshold value is supplied, the default value is calculated as:

threshold=quantile(picker,0.999,na.rm=TRUE)

Examples

Run this code

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

starttime <- as.POSIXct("2002-04-20", tz="GMT")
endtime <- as.POSIXct("2002-04-21", tz="GMT")

# Get the waveform
st <- getDataselect(iris,"US","OXF","","BHZ",starttime,endtime)

# Seismic signal in third trace
tr <- st@traces[[3]]

# Create a picker
picker <- STALTA(tr,3,30)
threshold <- quantile(picker,0.99999,na.rm=TRUE)

# 3 rows
layout(matrix(seq(3)))

# Plot trace and p-wave closeups
closeup1 <- eventWindow(tr,picker,threshold,3600)
closeup2 <- eventWindow(tr,picker,threshold,600)
plot(tr)
plot(closeup1,subsampling=1)
abline(v=length(closeup1)/2, col='red')
plot(closeup2,subsampling=1)
abline(v=length(closeup2)/2, col='red')

# Restore default layout
layout(1)
# }