The collection of seismological data in the WDC B for SEP should be separated on four groups according to the processing levels. Seismograms - the instrumental records of vibrations of the Earth, especially earthquakes.
Seismograms are the primary data in seismology.
The sum of arrival times for one station or net of stations for any time interval makes up the seismological bulletin. Chronological sequence of events with such parameters makes up the earthquake catalogue. Catalogue may be worldwide or regional according to envelop area.