The brain activity and seismicity share a remarkable similarity.
The Gutenberg-Richter law describing a power-law relation
between the frequency of earthquake occurrence and released
energy has its counterpart in the brain activity of a patient with
epilepsy, where the distribution of fluctuations of the voltage
difference measured by electroencephalogram (EEG) also obeys
a Gutenberg-Richter-like power law. However, the similarity in
the distributions does not directly tell us if the processes
underlying
these intermittent phenomena are memoryless (i.e., Markovian)
or not. Here, a new simple method is presented for quantitatively
evaluating (non)Markovianity and applied to seismicity and
the fluctuations of the voltage difference in EEG data. It is shown
that the seismic process is memoryless, whereas the process of
EEG signals has long-term memory.