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.