Magnitude determination on LOWNET

Routine processing of seismic signals observed on LOWNET involves making measuremen"ts of (1) time and (2) amplitude and period. The time measure~ents contribute to a determination of the source position and origin time while the amplitude/period measurements allow a determination of its magnitude. The determination of source position and origin time 15 relatively straightforward relying on accuracy of onset t1ming and phase identification and a clear statement of which earth model is used. The position with magnitudes had al~ays been rather more confused and there are a number of magnitude scales in general. usc. This" reportdescrib~ s the methods of magnitude determination used on LOWNET, compares LOInmT results with those from the world network, and finally makes some attempt to link some of the S~21f!S using data from LOWNET plus some neighbouring stations. The results should be relevant to other networks set up vithin Britain. Finally some "magnitude/charge si~e" plots for quarries and underwater explosions are shown and brieflY discussed.