Fig. 8
From: Automated recognition of spikes in 1 Hz data recorded at the Easter Island magnetic observatory
Example of “false spike” seen on dF record (bottom) on the left. Spikes recognized by eye on initial records X, Y, Z and F are marked on the corresponding records with black. The “false spike” seen on dF record could be representative of low amplitude spikes on X, Y, Z and F records and therefore less visible in the background noise of the X, Y, Z and F recordings.