5.6 Working with catalogs

It is often convenient to have multiple solutions of hypocenters in the database S-files or the CAT-files. Typically data has been entered from different sources and merged to form a single catalog. The first hypocenter line in the file is then considered the prime hypocenter estimate and this is the one used by e.g. EPIMAP to plot the hypocenters. The order of the hypocenters can be rearranged by CAT_AGA. Several programs use all the hypocenter lines. The magnitude correlation program will search any hypocenter line and the database selection program SELECT will optionally also use all the hypocenter lines. When the data base is updated with a new location and magnitude (UPDATE, section 14), it is only the first hypocenter line which is overwritten. If there is a magnitude in the 3 position, it is left unchanged unless it has the same agency as used for updating. This is useful in normal observatory practice, where it is common to put in some external agency magnitude which then must be left unchanged. If more magnitudes than 3 are calculated, they will be placed on a subsequent hypocenter line identified by having the same year, month, day and hypocenter agency as given on the first line. In order to merge different catalogs, it might be an advantage to put all the data into a complete database where each event is one file, even when only hypocenters are available. This is done by first splitting up the catalogs with SPLIT and then using EEV to merge the events. Since there is no requirement for monthly directories to have data, this methodology can also work for historical catalogs. The data can then subsequently be put into the CAT database without relocation using the UPD command.