R library for searching the ANSS ComCat comprehensive earthquake catalog.
searches Comcat for basic hypocentral data using the csv format ( see http://earthquake.usgs.gov/earthquakes/feed/v1.0/csv.php although that documentation is missing the type parameter at the end )
usage:
save this file in searchcomcat.R (the name does not actually matter)
these functions only use the basic level R installation and so no other packages need to be installed or loaded.
in your R script or session do the following:
source("searchcomcat.R") (use the full path name if it is in another directory)
comcatdata <- comcathypocsv() (this retrieves all earthquakes for the past 30 days into a data frame called comcatdata)
to apply different search criteria see the parameters listed in the function call below or at https://earthquake.usgs.gov/fdsnws/event/1/, e.g.:
comcatdata <- comcathypocsv(minmagnitude=5) (this will return only M>=5 earthquakes)
comcatdata <- comcathypocsv(alertlevel="red") (this will return only earthquakes with a PAGER level of red)
this function returns a dataframe (comcatdata in the above examples) that has columns which are from the ComCat csv format
and one additional column, named rtime, which is the time converted to a POSIXlt format which can be used for computations in R
to explore the output of the frame try commands such as:
colnames(comcatdata) (will return the names of the columns)
nrow(comcatdata) (will return the number of events found by the search)
this script lets you set many parameters but only uses the ones that are set to something other than NA
it has few defaults beyond the ones applied by Comcat and it does very little parameter checking
ordering is always done by ascending time to make it easier to deal with the need to search by multiple windows
start, end, and updatedafter times should be given as R internal POSIXlt classes so that the script can work with them. See the R function Sys.time in the base class
numeric parameters (e.g. minmagnitude) should be given as numbers
character string parameters (e.g. eventtype or alertlevel) should be given as strings
time is assumed to be in UTC
the defaults it has are:
1: endtime defaults to 1 day in the future from system time. This lets you search without worrying that time is passing as the program does things
2: starttime defaults to defaultduration days in the past from system time, set below
3: I put in the default eventtype=earthquake so that it does not return blasts unless you want them, set to NA if you don't want this applied
parameter checking is limited to:
if min or max radius is set in both km or degrees then the km version takes precedence
it makes sure that starttime is before endtime
if a parameter is not set in the call to the function then it is not used in the search and Comcat defaults are used
see https://earthquake.usgs.gov/fdsnws/event/1/ for more info on parameters and their defaults
see the function itself for the full list of parameters in the function call. Parameters are shown with their defaults and do not need to be given unless you want to change them.