Variation of human perceptiveness of earthquakes during seismic sequences

This paper describes the variation of the
human perception of earthquakes under the peculiar
condition of seismic sequence occurrence. To this aim,
we chose and have analyzed four seismic sequences that
reflect the most common models of seismicity occurrence
in the Italian territory. Our data always refer to the
epicentral area, so that the contribution of the epicentral
distance to the earthquake sensitiveness is considered
constant. To search for recurrent behavior of people in
the perception of earthquakes, we crossed seismological
data to sensitivity data coming from the archives of the
Italian Civil Protection. In each sequence, we individuate
a number of “indicators”, such as the rate between
felt and not-felt events and the minimum magnitude for
which 100% of the events are felt. Such indicators are
proportional to the energy released by the sequence and
can be particularly affected by the time protraction of
the sequence, and/or by the different familiarity with the
seismic phenomenon, and/or by the intensity of the
emotional impact of a seismic crisis. The observed
trends of sensitiveness show a significant variation of
the people perceptivity within the sequence development.
From the analysis of the dataset, one can
distinguish the variation of perceptivity due to emotional
factors from those due to physical factors. An
important observation, which is confirmed by a statistical
analysis, is that the source depth does not affect the
perceptiveness of earthquakes. Finally, we find important
differences between on-sequence and off-sequence
human perceptiveness that are connected with the
different levels of alert.

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