5.1.5 Catalog and database work

Once a large database has been created, several programs are used to manipulate and analyze the data. The catalog can be searched for a large number of parameters. Selection criteria are: Magnitude range, magnitude types, event types (e.g. local, distant, volcanic, explosion), latitude, longitude and depth range, RMS of travel time residuals, number of stations used in the location, felt events, number of polarities, presence of certain stations etc. Events can also be selected in an area with the program used for hypocentral plots. SE has an even more sufisticated search facility

A very useful source of data is the ISC. Data from ISC CD ROM's can be read and converted to SEISAN format (hypocenters and phase data) and put into a database. However CD's are little used now and a better way is to download the data in ISF format (soon ISF2 format) and convert to SEISAN with IMSNOR. The data can then be used for e.g. seismic hazard, fault plane solution or it can be relocated. A general task with catalogs is to homogenize magnitudes. Magnitude relations between e.g. Mb and Ms or Ms from one agency to Ms from another agency can be done with the program MAG. The program will also convert one magnitude to another once the linear regression has been determined. Hypocenters from different agencies can be compared with COMPARE_HYP. This program can also be used to compare hypocenters and magnitudes from two files containing the same events but eg located with different models. Event statistics can be made with STATIS and b-values calculated with BVALUEi (good functioon for that also in SE). The number of events as a function of time is plotted with CATSTAT.