TITLE:
Seismic Sequence Structure and Earthquakes Triggering Patterns
AUTHORS:
Giulio Riga, Paolo Balocchi
KEYWORDS:
Foreshock, Classification, Sequence, Cycle, Pattern, Trigger, Earthquake
JOURNAL NAME:
Open Journal of Earthquake Research,
Vol.5 No.1,
February
18,
2016
ABSTRACT: Within a time distribution of magnitude values, before any mainshock some earthquake triggering
patterns with several features develop, under tectonic processes’ influence, through which it is
possible to early identify the preparation phase of big earthquakes. The purpose of this article was
to identify and classify the warning patterns that develop before a big earthquake by considering
space-time seismicity variations. The methodological approach adopted was of graphical type,
based on procedures of technical analysis currently used to estimate the financial markets. In the
initial phase of the study we have analyzed the seismic sequences types described in the bibliography
(type 1: foreshocks-mainshock-aftershocks, type 2: mainshock-aftershock; type 3: swarm)
and the main structure of the seismic cycle, within which maximum and minimum magnitude values
characterize the pattern that it develops until the main event changes. Then, we assessed the
position of foreshocks, mainshock and aftershocks within the seismic cycle in order to identify the
warning pattern that characterized the exact time when the energy emission occurs. As to the
evolution normally shown over time, we have grouped the warning patterns in 2 categories: 1)
progressive earthquake pattern; 2) flash earthquake pattern. Finally, we have made a classification
of the warning pattern related to the fluctuations of maximum and minimum magnitude values,
compared its form with the mainshock’s focal mechanism and suggested some graphic procedures
in order to estimate the mainshock magnitude value associated with each warning pattern.
The results we obtained unquestionably allow a better comprehension of preparation
process of a large earthquake, improving the earthquakes forecasting probability in the next future.