eseis (version 0.6.0)

spatial_migrate: Migrate signals of a seismic event through a grid of locations.

Description

The function performs signal migration in space in order to determine the location of a seismic signal.

Usage

spatial_migrate(
  data,
  d_stations,
  d_map,
  snr,
  v,
  dt,
  normalise = TRUE,
  silent = FALSE
)

Value

A SpatialGridDataFrame-object with Gaussian probability density function values for each grid cell.

Arguments

data

Numeric matrix or eseis object, seismic signals to cross-correlate.

d_stations

Numeric matrix, inter-station distances. Output of spatial_distance.

d_map

List object, distance maps for each station (i.e., SpatialGridDataFrame objects). Output of spatial_distance.

snr

Numeric vector, optional signal-to-noise-ratios for each signal trace, used for normalisation. If omitted it is calculated from input signals.

v

Numeric value, mean velocity of seismic waves (m/s).

dt

Numeric value, sampling period.

normalise

Logical value, option to normalise stations correlations by signal-to-noise-ratios.

silent

Logical value, option to suppress messages during function execution. Default is FALSE.

Author

Michael Dietze

Examples

if (FALSE) {

## create synthetic DEM
dem <- raster::raster(nrows = 20, ncols = 20, 
                      xmn = 0, xmx = 10000, 
                      ymn= 0, ymx = 10000, 
                      vals = rep(0, 400))

## define station coordinates
sta <- data.frame(x = c(1000, 9000, 5000),
                  y = c(1000, 1000, 9000),
                  ID = c("A", "B", "C"))

## create synthetic signal (source in the center of the DEM)
s <- rbind(dnorm(x = 1:1000, mean = 500, sd = 50),
           dnorm(x = 1:1000, mean = 500, sd = 50),
           dnorm(x = 1:1000, mean = 500, sd = 50))

## plot DEM and stations
raster::plot(dem)

text(x = sta$x, 
     y = sta$y, 
     labels = sta$ID)

## calculate spatial distance maps and inter-station distances
D <- eseis::spatial_distance(stations = sta[,1:2],
                             dem = dem)

## locate signal
e <- eseis::spatial_migrate(data = s, 
                            d_stations = D$stations, 
                            d_map = D$maps, 
                            v = 1000, 
                            dt = 1/100)

## get most likely location coordinates (example contains two equal points)
xy <- matrix(sp::coordinates(e)[raster::values(e) == max(raster::values(e))],
             ncol = 2)[1,]
             
## plot location estimate, most likely location estimate and stations
raster::plot(e)
points(xy[1], 
       xy[2],
       pch = 20)
points(sta[,1:2])

}