R/aux_picknetwork.R
In coffeemuggler/eseis: Environmental Seismology Toolbox
Defines functions
aux_picknetwork
Documented in
aux_picknetwork
#' Pick seismic events with a sensor network approach
#'
#' The function allows detection of discrete seismic events using the STA-LTA
#' picker approach and including several stations of a seismic network. It
#' will pick events at all input stations and identify events picked by more
#' than a user defined minimum number of stations, within a given time window.
#' It further allows rejecting events that are too short or too long, or occur
#' to short after a previous event. The function can be used to process long
#' data archives organised in a consistent file structure.
#'
#' The data will be imported time slice by time slice. Optionally, a signal
#' deconvolution can be done. The data will be filtered to isolate the
#' frequency range of interest, and tapered to account for edge effects. The
#' taper size is automatically set be the two-sided buffer (see below).
#' Optionally, a signal envelope can be calculated as part of the preprocessing
#' work. For all successfully imported and preprocessed signal time snippets,
#' events will be detected by the STL-LTA approach. Events from all input
#' signals will be checked for a minium and maximum allowed event duration, set
#' as thresholds by the user. All remaining events are checked for the number
#' of stations of the network that did consistently detect an event. That means
#' an event must be found in each signal within a user defined time window, a
#' window that corresponds to the maximum travel time of a seismic signal
#' through the network. The minimum number of stations that detect the event
#' can be set by the user. In addition, events can be rejected if they occur
#' during a user defined ban time after the onset of a previous event, which
#' assumes that no subsequent events are allowed during the implementation of
#' long duration events happening.
#'
#' The time period to process is defined by \code{start}, \code{end} and the
#' length of time snippets \code{res} (s). In addition, a left sided and
#' right sided buffer can and should be added \code{buffer = c(60, 60)} (s),
#' to account for artefacts during signal preprocessing and events that
#' occur across the time snippets. The \code{start} and \code{end} time should
#' be provided in \code{POSIXct} format. If it is provided as text string, the
#' function will try to convert to POSIXct assuming the time zone is UTC.
#'
#' There must be at least two seismic stations. The seismic components
#' \code{component} must be a vector of the same length as \code{station} and
#' contain the corresponding information for each station.
#'
#' Deconvolution of the input signals can be done, although usually this is
#' not essential for just picking events if the filter frequencies are in the
#' flat response range of the sensors. If wanted, one needs to provide the
#' additional vectors (all of the same length as \code{station}) \code{sensor},
#' \code{logger} and optionally \code{gain} (otherwise assumed to be \code{1}).
#' See \code{signal_deconvolve()} for further information on the deconvolution
#' routine and the supported keywords for sensors and loggers.
#'
#' STA-LTA picking is usually done on signal envelopes \code{enevelope = TRUE}.
#' However, for array seismology or other specific cases it might be useful to
#' work with the waveforms directly, instead of with their envelopes.
#'
#' The STA-LTA routine requires information on the length of the STA window,
#' the LTA window, the on-threshold to define the start of an event, the
#' off-threshold to define the end of an event, and the option to freeze the
#' STA-LTA ratio at the onset of and event. See the documentation of the
#' function \code{pick_stalta()} for further information.
#'
#' Events that last shorter than \code{dur_min} or longer than \code{dur_max}
#' are rejected. This criterion is applied before the test of how many stations
#' have commonly detected an event. Hence, the minimum and maximum duration
#' criteria need to be fulfilled by an event for all seismic stations, or at
#' least as many as defined as minimum number of stations \code{n_common}.
#'
#' A valid event should be detected by more than one station. At least two
#' stations (\code{n_common = 2}) should detect it to confirm it is not just a
#' local effect like rain drop impacts or animal activity. At least three
#' stations (\code{n_common = 3}) are needed to locate an event. Detection at
#' more stations increases the validity of an event as proper signal. However,
#' the likelihood of stations not operating correctly or that some stations
#' may be too far to detect a smaller event limits the number of stations that
#' are be set as (\code{n_common}).
#'
#' An event that happens just outside a seismic network will generate seismic
#' waves that travel through the network and will require a given time for
#' that. The time is set by the longest inter-station distance and the apparent
#' seismic wave velocity. For example, an event who's signal propagated with
#' 1000 m/s through a network with a maximum aperture of 1000 m will need up to
#' 1 s. Hence, the parameter \code{t_common} should be set to \code{1}, in
#' this case. This parameter is good to reject events that show a longer travel
#' time, e.g. because they are pressure waves that travel through the
#' atmosphere, like helicopter signals or lightning strikes.
#'
#' @param start \code{POSIXct} value, start time for event detection analysis.
#' If a character string (or vector) is provided, the function will try to
#' convert it to POSIXct.
#'
#' @param stop \code{POSIXct} value, start time for event detection analysis.
#' If a character string (or vector) is provided, the function will try to
#' convert it to POSIXct.
#'
#' @param res \code{Numeric} value, time resolution of the snippets used to
#' detect events, in seconds. A useful value would be one hour
#' (\code{res = 3600}).
#'
#' @param buffer \code{Numeric} vector, of length two. Size of the two-sided
#' buffer to account for signal pre-processing effects, in seconds. The first
#' value is used for the left side, the second for the right side. Events that
#' happen to be detected during the buffer time will be removed from the output
#' data set.
#'
#' @param station \code{Character} vector, seismic station IDs to be processed.
#'
#' @param component \code{Character} value or vector, seismic component to
#' be used. Information can be restricted to a single character, denoting the
#' last character of the station component code, i.e. \code{"Z"} would use the
#' first and last component of \code{c("BHZ", "HHE", "HHZ")}. If omitted,
#' the function will use \code{"BHZ"} by default.
#'
#' @param dir \code{Character} value, path to directory that contains the
#' seismic files. See \code{read_data} for details and constraints on the
#' data structure.
#'
#' @param f \code{Numeric} Numeric vector of length two, cutoff frequencies
#' (Hz) for the bandpass filter to be applied. If omitted, no filtering will
#' be performed.
#'
#' @param envelope \code{Logical} value, option to calculate signal envelopes
#' before detecting events. Default is \code{TRUE}.
#'
#' @param sta \code{Numeric} value, duration of short-term window. Attention,
#' this definition differs from the one in \code{pick_stalta}!
#'
#' @param lta \code{Numeric} value, duration of long-term window. Attention,
#' this definition differs from the one in \code{pick_stalta}!
#'
#' @param on \code{Numeric} value, threshold value for event onset.
#'
#' @param off \code{Numeric} value, threshold value for event end.
#'
#' @param freeze \code{Logical} value, option to freeze lta value at start of
#' an event. Useful to avoid self-adjustment of lta for long-duration events.
#'
#' @param dur_min \code{Numeric} value, minimum duration of an event (s). Picks
#' with a STA-LTA duration below this threshold will be discarded.
#'
#' @param dur_max \code{Numeric} value, maximum duration of an event (s). Picks
#' with a STA-LTA duration longer than this threshold will be discarded.
#'
#' @param n_common \code{Numeric} value, minimum number of stations at which
#' an event has to be registered.
#'
#' @param t_common \code{Numeric} value, time (s) within which the picks of an
#' event need to be registered by seismic stations.
#'
#' @param t_pause \code{Numeric} value, time period after the onset of an event
#' during which no other event is allowed to happen.
#'
#' @param verbose \code{Logical} value, option to allow detailed screen output
#' of information on the picking progress and results. Default is \code{FALSE}.
#'
#' @param \dots Further arguments passed to the function, i.e. keywords for
#' the signal deconvolution part. See details for further information.
#'
#' @return \code{data frame}, detected events (start time, duration in
#' seconds)
#'
#' @author Michael Dietze
#'
#' @keywords eseis
#'
#' @examples
#'
#'
#' picks <- aux_picknetwork(start = "2017-04-09 01:00:00 UTC",
#' stop = "2017-04-09 02:00:00 UTC",
#' res = 1800,
#' buffer = c(90, 90),
#' station = c("RUEG1","RUEG2"),
#' component = rep("BHZ", 2),
#' dir = paste0(path.package("eseis"), "/extdata/"),
#' f = c(0.1, 0.2),
#' envelope = TRUE,
#' sta = 0.5,
#' lta = 300,
#' on = 3,
#' off = 1,
#' freeze = TRUE,
#' dur_min = 2,
#' dur_max = 90,
#' n_common = 2,
#' t_common = 5,
#' t_pause = 30,
#' verbose = TRUE)
#'
#' print(picks)
#'
#' @export aux_picknetwork
aux_picknetwork <- function(
start,
stop,
res,
buffer,
station,
component,
dir,
f,
envelope = TRUE,
sta,
lta,
on,
off,
freeze,
dur_min,
dur_max,
n_common,
t_common,
t_pause,
verbose = FALSE,
...
) {
## CONSISTENCY CHECKS -------------------------------------------------------
## extract ...-arguments
arg <- list(...)
## check/convert start time
if(inherits(start, "POSIXct") == FALSE) {
start <- try(as.POSIXct(start, tz = "UTC"))
if(inherits(start, "try-error") == TRUE) {
stop("Start date is not a POSIXct format!")
}
}
## check/convert stop time
if(inherits(stop, "POSIXct") == FALSE) {
stop <- try(as.POSIXct(stop, tz = "UTC"))
if(inherits(stop, "try-error") == TRUE) {
stop("Stop date is not a POSIXct format!")
}
}
## check if start time with time step is smaller than stop time
if(start + res >= stop) {
stop("Start time with time step is larger than stop time!")
}
## check or set component
if(missing(component) == TRUE) {
component <- rep("Z", length(station))
}
if(length(component) != length(station)) {
warning("n components does not match n stations, will be recycled!")
component <- rep(x = component, length.out = length(station))
}
## check or set filter frequencies
if(missing(f) == TRUE) {
f <- c(NA)
} else if(length(f) != 2) {
stop("f must contain two values!")
} else if(f[1] >= f[2]) {
stop("Filter frequencies flipped!")
}
## check if file pattern is provided
if("pattern" %in% names(arg) == FALSE) {
arg$pattern <- "eseis"
}
## check if interpolation option is provided
if("interpolate" %in% names(arg) == FALSE) {
arg$interpolate <- FALSE
}
## check if logger, sensor, gain information is present, set decon. flag
if("sensor" %in% names(arg) & "logger" %in% names(arg)) {
if("gain" %in% names(arg) == FALSE) {
arg$gain <- 1
}
deconvolve <- TRUE
} else {
deconvolve <- FALSE
}
## PREPARATION --------------------------------------------------------------
## define time steps
t <- seq(from = start, to = stop, by = res)
## compose parameter list
par <- list(res = res,
buffer = buffer,
station = station,
component = component,
dir = dir,
arg = arg,
deconvolve = deconvolve,
f = f,
envelope = envelope,
sta = sta,
lta = lta,
on = on,
off = off,
freeze = freeze,
dur_min = dur_min,
dur_max = dur_max,
n_common = n_common,
t_common = t_common,
t_pause = t_pause)
## PROCESS TIME STEPS -------------------------------------------------------
## create output data set
picks <- vector(mode = "list", length = length(t))
## set pick counter to zero
n_picks_count <- 0
## process all time steps
for(i in 1:length(t)) {
## read and preprocess station data
s <- lapply(X = 1:length(par$station), FUN = function(j, t_i, par) {
## read data
s <- try(eseis::read_data(start = t_i - par$buffer[1],
duration = par$res + par$buffer[1] +
par$buffer[2],
station = par$station[j],
component = par$component[j],
dir = par$dir,
pattern = par$arg$pattern,
interpolate = par$arg$interpolate),
silent = TRUE)
## optionally deconvolve
if(par$deconvolve == TRUE) {
if(inherits(s, "eseis")) {
s <- try(eseis::signal_deconvolve(data = s,
sensor = par$arg$sensor,
logger = par$arg$logger,
gain = par$arg$gain),
silent = TRUE)
}
}
## filter signal
if(inherits(s, "eseis") & !is.na(f[1])) {
s <- try(eseis::signal_filter(data = s,
f = par$f),
silent = TRUE)
}
## taper signal
if(inherits(s, "eseis")) {
s <- try(eseis::signal_taper(data = s,
n = floor(min(par$buffer) / s$meta$dt)))
}
## optionally calculate envelope
if(par$envelope == TRUE) {
if(inherits(s, "eseis")) {
s <- try(eseis::signal_envelope(data = s),
silent = TRUE)
}
}
## return successfully preprocessed data set
if(inherits(s, "eseis")) {
return(s)
}
}, t_i = t[i], par)
## remove erroneous data sets
i_ok <- sapply(X = s, FUN = function(s) {is.null(s) == FALSE})
s <- s[i_ok]
## generate verbose screen information
text_import <- paste0(length(s), " stations imported/preprocessed")
## check if minimum number of stations remains
if(length(s) >= par$n_common) {
## pick events at all stations
p <- lapply(X = s, FUN = function(s, par) {
p <- try(eseis::pick_stalta(data = s,
sta = round(par$sta / s$meta$dt),
lta = round(par$lta / s$meta$dt),
freeze = par$freeze,
on = par$on,
off = par$off))
if(inherits(p, "eseis")) {
return(p$picks[,c(2, 3, 5)])
}
}, par)
## remove too long and too short events
p <- lapply(X = p, FUN = function(p, par) {
p <- p[p$duration >= par$dur_min &
p$duration <= par$dur_max,]
return(p)
}, par)
## convert all pick start times to seconds
t_all <- try(as.numeric(do.call(c, lapply(p, function(p) {p$start}))))
## find mutually common events
p_ok <- lapply(X = p, FUN = function(p, par, t_all) {
if(length(p$start) > 0) {
## create output data set
p_ok_i <- rep(NA, length(p$start))
n_ok_i <- rep(NA, length(p$start))
## process all picks per station
for(i in 1:length(p$start)) {
## calculate time difference to all other picks
dt <- as.numeric(p$start[i]) - t_all
## count picks within common time window
n_ok <- sum(abs(dt) <= par$t_common)
## decide if pick is valid
n_ok_i[i] <- n_ok
p_ok_i[i] <- n_ok >= par$n_common
}
## convert list to data frame and append to initial picks
p_ok_i <- cbind(p, p_ok_i, n_ok_i)
p_ok_i <- p_ok_i[p_ok_i[,4] == TRUE,]
} else {
p_ok_i <- NULL
}
## return commonly identified picks
return(p_ok_i)
}, par, t_all)
## collect all remaining picks
p_ok <- do.call(rbind, p_ok)
if(inherits(x = p_ok, what = "data.frame")) {
## sort picks by time
p_ok <- p_ok[order(p_ok$start),]
## calculate time between events
p_ok_lag <- p_ok$start[-1] - p_ok$start[-length(p_ok$start)]
p_ok_lag <- c(max(par$t_common + 1, par$t_pause + 1), p_ok_lag)
## remove events within common time window size and pause range
p_ok <- p_ok[p_ok_lag >= par$t_common &
p_ok_lag >= par$t_pause,]
}
if(inherits(x = p_ok, what = "data.frame")) {
## remove events beyond buffer range
p_ok <- p_ok[p_ok$start >= t[i] & p_ok$start <= t[i] + par$res,]
}
} else {
## create empty output
p_ok <- data.frame(start = NULL, duration = NULL, max = NULL,
p_ok_i = NULL, n_ok_i = NULL)
}
## remove NA entries
p_ok <- p_ok[!is.na(p_ok$start),]
## get number of new picks
n_new <- ifelse(is.null(p_ok), 0, nrow(p_ok))
## optionally print progress
if(verbose == TRUE) {
print(paste0("Step ", i, " of ", length(t), " (",
text_import, ", ", n_new,
" picks added, n_final = ",
n_new + n_picks_count, ")"))
}
## assign output
picks[[i]] <- p_ok
## update pick counter
n_picks_count <- n_picks_count + n_new
}
## convert list to data frame
picks <- do.call(rbind, picks)
## account for empty object
if(is.null(picks)) {
## create empty data frame
picks <- data.frame(start = Sys.time(), duration = NA,
max = NA, stations = NA)
picks <- picks[-1,]
}
## prepare output
if(nrow(picks) == 0) {
## create empty data frame
picks <- data.frame(start = Sys.time(), duration = NA,
max = NA, stations = NA)
picks <- picks[-1,]
} else {
## remove temporary variables
picks <- picks[,c(1,2,3,5)]
## rename variable names
names(picks) <- c("start", "duration", "max", "stations")
## assign consistent row numbers
row.names(picks) <- seq(from = 1, to = nrow(picks))
}
## return output
return(picks)
}
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Defines functions aux_picknetwork
Documented in aux_picknetwork
#' Pick seismic events with a sensor network approach
#'
#' The function allows detection of discrete seismic events using the STA-LTA
#' picker approach and including several stations of a seismic network. It
#' will pick events at all input stations and identify events picked by more
#' than a user defined minimum number of stations, within a given time window.
#' It further allows rejecting events that are too short or too long, or occur
#' to short after a previous event. The function can be used to process long
#' data archives organised in a consistent file structure.
#'
#' The data will be imported time slice by time slice. Optionally, a signal
#' deconvolution can be done. The data will be filtered to isolate the
#' frequency range of interest, and tapered to account for edge effects. The
#' taper size is automatically set be the two-sided buffer (see below).
#' Optionally, a signal envelope can be calculated as part of the preprocessing
#' work. For all successfully imported and preprocessed signal time snippets,
#' events will be detected by the STL-LTA approach. Events from all input
#' signals will be checked for a minium and maximum allowed event duration, set
#' as thresholds by the user. All remaining events are checked for the number
#' of stations of the network that did consistently detect an event. That means
#' an event must be found in each signal within a user defined time window, a
#' window that corresponds to the maximum travel time of a seismic signal
#' through the network. The minimum number of stations that detect the event
#' can be set by the user. In addition, events can be rejected if they occur
#' during a user defined ban time after the onset of a previous event, which
#' assumes that no subsequent events are allowed during the implementation of
#' long duration events happening.
#'
#' The time period to process is defined by \code{start}, \code{end} and the
#' length of time snippets \code{res} (s). In addition, a left sided and
#' right sided buffer can and should be added \code{buffer = c(60, 60)} (s),
#' to account for artefacts during signal preprocessing and events that
#' occur across the time snippets. The \code{start} and \code{end} time should
#' be provided in \code{POSIXct} format. If it is provided as text string, the
#' function will try to convert to POSIXct assuming the time zone is UTC.
#'
#' There must be at least two seismic stations. The seismic components
#' \code{component} must be a vector of the same length as \code{station} and
#' contain the corresponding information for each station.
#'
#' Deconvolution of the input signals can be done, although usually this is
#' not essential for just picking events if the filter frequencies are in the
#' flat response range of the sensors. If wanted, one needs to provide the
#' additional vectors (all of the same length as \code{station}) \code{sensor},
#' \code{logger} and optionally \code{gain} (otherwise assumed to be \code{1}).
#' See \code{signal_deconvolve()} for further information on the deconvolution
#' routine and the supported keywords for sensors and loggers.
#'
#' STA-LTA picking is usually done on signal envelopes \code{enevelope = TRUE}.
#' However, for array seismology or other specific cases it might be useful to
#' work with the waveforms directly, instead of with their envelopes.
#'
#' The STA-LTA routine requires information on the length of the STA window,
#' the LTA window, the on-threshold to define the start of an event, the
#' off-threshold to define the end of an event, and the option to freeze the
#' STA-LTA ratio at the onset of and event. See the documentation of the
#' function \code{pick_stalta()} for further information.
#'
#' Events that last shorter than \code{dur_min} or longer than \code{dur_max}
#' are rejected. This criterion is applied before the test of how many stations
#' have commonly detected an event. Hence, the minimum and maximum duration
#' criteria need to be fulfilled by an event for all seismic stations, or at
#' least as many as defined as minimum number of stations \code{n_common}.
#'
#' A valid event should be detected by more than one station. At least two
#' stations (\code{n_common = 2}) should detect it to confirm it is not just a
#' local effect like rain drop impacts or animal activity. At least three
#' stations (\code{n_common = 3}) are needed to locate an event. Detection at
#' more stations increases the validity of an event as proper signal. However,
#' the likelihood of stations not operating correctly or that some stations
#' may be too far to detect a smaller event limits the number of stations that
#' are be set as (\code{n_common}).
#'
#' An event that happens just outside a seismic network will generate seismic
#' waves that travel through the network and will require a given time for
#' that. The time is set by the longest inter-station distance and the apparent
#' seismic wave velocity. For example, an event who's signal propagated with
#' 1000 m/s through a network with a maximum aperture of 1000 m will need up to
#' 1 s. Hence, the parameter \code{t_common} should be set to \code{1}, in
#' this case. This parameter is good to reject events that show a longer travel
#' time, e.g. because they are pressure waves that travel through the
#' atmosphere, like helicopter signals or lightning strikes.
#'
#' @param start \code{POSIXct} value, start time for event detection analysis.
#' If a character string (or vector) is provided, the function will try to
#' convert it to POSIXct.
#'
#' @param stop \code{POSIXct} value, start time for event detection analysis.
#' If a character string (or vector) is provided, the function will try to
#' convert it to POSIXct.
#'
#' @param res \code{Numeric} value, time resolution of the snippets used to
#' detect events, in seconds. A useful value would be one hour
#' (\code{res = 3600}).
#'
#' @param buffer \code{Numeric} vector, of length two. Size of the two-sided
#' buffer to account for signal pre-processing effects, in seconds. The first
#' value is used for the left side, the second for the right side. Events that
#' happen to be detected during the buffer time will be removed from the output
#' data set.
#'
#' @param station \code{Character} vector, seismic station IDs to be processed.
#'
#' @param component \code{Character} value or vector, seismic component to
#' be used. Information can be restricted to a single character, denoting the
#' last character of the station component code, i.e. \code{"Z"} would use the
#' first and last component of \code{c("BHZ", "HHE", "HHZ")}. If omitted,
#' the function will use \code{"BHZ"} by default.
#'
#' @param dir \code{Character} value, path to directory that contains the
#' seismic files. See \code{read_data} for details and constraints on the
#' data structure.
#'
#' @param f \code{Numeric} Numeric vector of length two, cutoff frequencies
#' (Hz) for the bandpass filter to be applied. If omitted, no filtering will
#' be performed.
#'
#' @param envelope \code{Logical} value, option to calculate signal envelopes
#' before detecting events. Default is \code{TRUE}.
#'
#' @param sta \code{Numeric} value, duration of short-term window. Attention,
#' this definition differs from the one in \code{pick_stalta}!
#'
#' @param lta \code{Numeric} value, duration of long-term window. Attention,
#' this definition differs from the one in \code{pick_stalta}!
#'
#' @param on \code{Numeric} value, threshold value for event onset.
#'
#' @param off \code{Numeric} value, threshold value for event end.
#'
#' @param freeze \code{Logical} value, option to freeze lta value at start of
#' an event. Useful to avoid self-adjustment of lta for long-duration events.
#'
#' @param dur_min \code{Numeric} value, minimum duration of an event (s). Picks
#' with a STA-LTA duration below this threshold will be discarded.
#'
#' @param dur_max \code{Numeric} value, maximum duration of an event (s). Picks
#' with a STA-LTA duration longer than this threshold will be discarded.
#'
#' @param n_common \code{Numeric} value, minimum number of stations at which
#' an event has to be registered.
#'
#' @param t_common \code{Numeric} value, time (s) within which the picks of an
#' event need to be registered by seismic stations.
#'
#' @param t_pause \code{Numeric} value, time period after the onset of an event
#' during which no other event is allowed to happen.
#'
#' @param verbose \code{Logical} value, option to allow detailed screen output
#' of information on the picking progress and results. Default is \code{FALSE}.
#'
#' @param \dots Further arguments passed to the function, i.e. keywords for
#' the signal deconvolution part. See details for further information.
#'
#' @return \code{data frame}, detected events (start time, duration in
#' seconds)
#'
#' @author Michael Dietze
#'
#' @keywords eseis
#'
#' @examples
#'
#'
#' picks <- aux_picknetwork(start = "2017-04-09 01:00:00 UTC",
#' stop = "2017-04-09 02:00:00 UTC",
#' res = 1800,
#' buffer = c(90, 90),
#' station = c("RUEG1","RUEG2"),
#' component = rep("BHZ", 2),
#' dir = paste0(path.package("eseis"), "/extdata/"),
#' f = c(0.1, 0.2),
#' envelope = TRUE,
#' sta = 0.5,
#' lta = 300,
#' on = 3,
#' off = 1,
#' freeze = TRUE,
#' dur_min = 2,
#' dur_max = 90,
#' n_common = 2,
#' t_common = 5,
#' t_pause = 30,
#' verbose = TRUE)
#'
#' print(picks)
#'
#' @export aux_picknetwork
aux_picknetwork <- function(
start,
stop,
res,
buffer,
station,
component,
dir,
f,
envelope = TRUE,
sta,
lta,
on,
off,
freeze,
dur_min,
dur_max,
n_common,
t_common,
t_pause,
verbose = FALSE,
...
) {
## CONSISTENCY CHECKS -------------------------------------------------------
## extract ...-arguments
arg <- list(...)
## check/convert start time
if(inherits(start, "POSIXct") == FALSE) {
start <- try(as.POSIXct(start, tz = "UTC"))
if(inherits(start, "try-error") == TRUE) {
stop("Start date is not a POSIXct format!")
}
}
## check/convert stop time
if(inherits(stop, "POSIXct") == FALSE) {
stop <- try(as.POSIXct(stop, tz = "UTC"))
if(inherits(stop, "try-error") == TRUE) {
stop("Stop date is not a POSIXct format!")
}
}
## check if start time with time step is smaller than stop time
if(start + res >= stop) {
stop("Start time with time step is larger than stop time!")
}
## check or set component
if(missing(component) == TRUE) {
component <- rep("Z", length(station))
}
if(length(component) != length(station)) {
warning("n components does not match n stations, will be recycled!")
component <- rep(x = component, length.out = length(station))
}
## check or set filter frequencies
if(missing(f) == TRUE) {
f <- c(NA)
} else if(length(f) != 2) {
stop("f must contain two values!")
} else if(f[1] >= f[2]) {
stop("Filter frequencies flipped!")
}
## check if file pattern is provided
if("pattern" %in% names(arg) == FALSE) {
arg$pattern <- "eseis"
}
## check if interpolation option is provided
if("interpolate" %in% names(arg) == FALSE) {
arg$interpolate <- FALSE
}
## check if logger, sensor, gain information is present, set decon. flag
if("sensor" %in% names(arg) & "logger" %in% names(arg)) {
if("gain" %in% names(arg) == FALSE) {
arg$gain <- 1
}
deconvolve <- TRUE
} else {
deconvolve <- FALSE
}
## PREPARATION --------------------------------------------------------------
## define time steps
t <- seq(from = start, to = stop, by = res)
## compose parameter list
par <- list(res = res,
buffer = buffer,
station = station,
component = component,
dir = dir,
arg = arg,
deconvolve = deconvolve,
f = f,
envelope = envelope,
sta = sta,
lta = lta,
on = on,
off = off,
freeze = freeze,
dur_min = dur_min,
dur_max = dur_max,
n_common = n_common,
t_common = t_common,
t_pause = t_pause)
## PROCESS TIME STEPS -------------------------------------------------------
## create output data set
picks <- vector(mode = "list", length = length(t))
## set pick counter to zero
n_picks_count <- 0
## process all time steps
for(i in 1:length(t)) {
## read and preprocess station data
s <- lapply(X = 1:length(par$station), FUN = function(j, t_i, par) {
## read data
s <- try(eseis::read_data(start = t_i - par$buffer[1],
duration = par$res + par$buffer[1] +
par$buffer[2],
station = par$station[j],
component = par$component[j],
dir = par$dir,
pattern = par$arg$pattern,
interpolate = par$arg$interpolate),
silent = TRUE)
## optionally deconvolve
if(par$deconvolve == TRUE) {
if(inherits(s, "eseis")) {
s <- try(eseis::signal_deconvolve(data = s,
sensor = par$arg$sensor,
logger = par$arg$logger,
gain = par$arg$gain),
silent = TRUE)
}
}
## filter signal
if(inherits(s, "eseis") & !is.na(f[1])) {
s <- try(eseis::signal_filter(data = s,
f = par$f),
silent = TRUE)
}
## taper signal
if(inherits(s, "eseis")) {
s <- try(eseis::signal_taper(data = s,
n = floor(min(par$buffer) / s$meta$dt)))
}
## optionally calculate envelope
if(par$envelope == TRUE) {
if(inherits(s, "eseis")) {
s <- try(eseis::signal_envelope(data = s),
silent = TRUE)
}
}
## return successfully preprocessed data set
if(inherits(s, "eseis")) {
return(s)
}
}, t_i = t[i], par)
## remove erroneous data sets
i_ok <- sapply(X = s, FUN = function(s) {is.null(s) == FALSE})
s <- s[i_ok]
## generate verbose screen information
text_import <- paste0(length(s), " stations imported/preprocessed")
## check if minimum number of stations remains
if(length(s) >= par$n_common) {
## pick events at all stations
p <- lapply(X = s, FUN = function(s, par) {
p <- try(eseis::pick_stalta(data = s,
sta = round(par$sta / s$meta$dt),
lta = round(par$lta / s$meta$dt),
freeze = par$freeze,
on = par$on,
off = par$off))
if(inherits(p, "eseis")) {
return(p$picks[,c(2, 3, 5)])
}
}, par)
## remove too long and too short events
p <- lapply(X = p, FUN = function(p, par) {
p <- p[p$duration >= par$dur_min &
p$duration <= par$dur_max,]
return(p)
}, par)
## convert all pick start times to seconds
t_all <- try(as.numeric(do.call(c, lapply(p, function(p) {p$start}))))
## find mutually common events
p_ok <- lapply(X = p, FUN = function(p, par, t_all) {
if(length(p$start) > 0) {
## create output data set
p_ok_i <- rep(NA, length(p$start))
n_ok_i <- rep(NA, length(p$start))
## process all picks per station
for(i in 1:length(p$start)) {
## calculate time difference to all other picks
dt <- as.numeric(p$start[i]) - t_all
## count picks within common time window
n_ok <- sum(abs(dt) <= par$t_common)
## decide if pick is valid
n_ok_i[i] <- n_ok
p_ok_i[i] <- n_ok >= par$n_common
}
## convert list to data frame and append to initial picks
p_ok_i <- cbind(p, p_ok_i, n_ok_i)
p_ok_i <- p_ok_i[p_ok_i[,4] == TRUE,]
} else {
p_ok_i <- NULL
}
## return commonly identified picks
return(p_ok_i)
}, par, t_all)
## collect all remaining picks
p_ok <- do.call(rbind, p_ok)
if(inherits(x = p_ok, what = "data.frame")) {
## sort picks by time
p_ok <- p_ok[order(p_ok$start),]
## calculate time between events
p_ok_lag <- p_ok$start[-1] - p_ok$start[-length(p_ok$start)]
p_ok_lag <- c(max(par$t_common + 1, par$t_pause + 1), p_ok_lag)
## remove events within common time window size and pause range
p_ok <- p_ok[p_ok_lag >= par$t_common &
p_ok_lag >= par$t_pause,]
}
if(inherits(x = p_ok, what = "data.frame")) {
## remove events beyond buffer range
p_ok <- p_ok[p_ok$start >= t[i] & p_ok$start <= t[i] + par$res,]
}
} else {
## create empty output
p_ok <- data.frame(start = NULL, duration = NULL, max = NULL,
p_ok_i = NULL, n_ok_i = NULL)
}
## remove NA entries
p_ok <- p_ok[!is.na(p_ok$start),]
## get number of new picks
n_new <- ifelse(is.null(p_ok), 0, nrow(p_ok))
## optionally print progress
if(verbose == TRUE) {
print(paste0("Step ", i, " of ", length(t), " (",
text_import, ", ", n_new,
" picks added, n_final = ",
n_new + n_picks_count, ")"))
}
## assign output
picks[[i]] <- p_ok
## update pick counter
n_picks_count <- n_picks_count + n_new
}
## convert list to data frame
picks <- do.call(rbind, picks)
## account for empty object
if(is.null(picks)) {
## create empty data frame
picks <- data.frame(start = Sys.time(), duration = NA,
max = NA, stations = NA)
picks <- picks[-1,]
}
## prepare output
if(nrow(picks) == 0) {
## create empty data frame
picks <- data.frame(start = Sys.time(), duration = NA,
max = NA, stations = NA)
picks <- picks[-1,]
} else {
## remove temporary variables
picks <- picks[,c(1,2,3,5)]
## rename variable names
names(picks) <- c("start", "duration", "max", "stations")
## assign consistent row numbers
row.names(picks) <- seq(from = 1, to = nrow(picks))
}
## return output
return(picks)
}
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