Revised Accelerated Moment Release Under Test: Fourteen Worldwide Real Case Studies in 2014-2018 and Simulations

Periods of accelerated seismicity have been observed during the preparation process of many large earthquakes. This accelerating seismicity can be detected by the Accelerated Moment Release (AMR) method and its recent Revised version (R-AMR) when the two techniques are applied to earthquake catalogues. The main aim of this study is to investigate the seismicity preceding large mainshocks and possibly increase our comprehension of the underlying physics. In particular, we applied both the AMR and R-AMR to the seismicity preceding 14 large worldwide shallow earthquakes, i.e. with focal depth less than 40 km, with magnitude M > 6 for Mediterranean area, and M >= 6.4 in the rest of the world, occurred from 2014 to 2018. Twelve case studies were analysed in the framework of SwArm For Earthquake study project funded by ESA, comprising the period 2014-2016; two additional cases were also considered to confirm the goodness of the methodology outside the period of the project catalogues. In total, R-AMR shows better performances than AMR, in 11 cases out of 14. In particular, in four out of 14 cases (i.e. 28.6%), the R-AMR method shows that acceleration exists due to an evident clustering in time-space on the faults, thus guiding the convergence of the fit; in seven cases (i.e. 50%) the R-AMR discloses acceleration, although no clustering around the fault is present; the remaining three cases (i.e. 21.4%) show no emerging acceleration from background. Finally, when R-AMR is compared with simulations, we verify that in most of the cases the acceleration is real and not casual.