Thermodynamic state shift observed prior to the 2011 Mw 9 East Japan earthquake through data mining using cellular automaton

In this study, we employed our previously developed data mining method to show that a thermodynamic state shift occurred preceding the 2011 Mw 9 East Japan Earthquake (GEJE), coinciding with the onset of crustal stress manifestations. Our discussion starts with the insights obtained from our prior research, which revealed that small ground vibration fluctuations (GVF) detected near the epicenter of the GEJE are thermodynamically equivalent to a cellular automaton (CA). This equivalence allowed us to consider the “Process to GEJE,” defined as the transition from GVF to catastrophic rupture in the GEJE, as analogous to the nonequilibrium-to-equilibrium thermodynamic transition in the CA. Therefore, if we find a thermodynamic state shift in the CA, it is reasonable to assume that a similar thermodynamic state shift may exist in the “Process to GEJE.” We successfully derived a thermodynamic state function that exhibits a significant change before the nonequilibrium-to-equilibrium thermodynamic transition in the CA. By evaluating this thermodynamic state function using the GVF data of the “Process to GEJE,” we discovered its maximum value occurring on 2007-10-28 at 10:30:00 JST, 1231 days before the GEJE occurred on 2011-03-11 at 14:46 JST. This maximum value can be considered as an indication of a thermodynamic state shift prior to the GEJE. Furthermore, near the timing of the thermodynamic state shift, it has been observed that the GVF state approaches thermodynamic equilibrium and a sudden increase in crustal stress was first noted on 2007-11-22 at 18:02:44 JST.