  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, that is, the distribution of fluctuations
of the voltage difference measured by electroencephalogram (EEG) also obeys a
Gutenberg-Richter-like power law. The similarity in the distributions, however,
does not directly tell if the processes underlying these intermittent phenomena
are also similar to each other. Here, a new simple method is presented for
quantitative evaluation of (non-)Markovianity and is applied to the processes
of released energy in seismicity and fluctuation of the voltage difference in
EEG data. It is shown that the process in seismicity is almost memoryless,
whereas that in EEG has long-term memory.
