Quick Report on the ML = 3.3 on 1 January 2023 Guidonia (Rome, Italy) Earthquake: Evidence of a Seismic Acceleration

Abstract

This paper investigates possible anomalies on the occasion of the ML = 3.3 earthquake, which occurred on 1st January 2023 close to Guidonia Montecelio (Rome, Italy). This earthquake followed another very close event recorded on 23 December 2022 with a magnitude ML = 3.1 (epicentral distance of less than 1 km). Seismological investigations clearly show an acceleration of seismicity in the preceding six months in a circular area of about a 60 km radius. Two conclusions coming from the time-to-failure power law fitting to the cumulative Benioff strain curve are the most probable: the ML3.3 of 1 January 2023 is the mainshock of the seismic sequence, or an incoming earthquake of a magnitude of about 4.1 provides a slightly better fit (higher determination coefficient) of the seismic data. Further investigations are necessary to assess whether the accumulated stress has been totally released. No atmospheric anomalies related to this seismic activity have been identified, even if some SO2 emissions seem to be induced by the tectonic and volcanic sources in the south Tyrrhenian Sea. Swarm satellite magnetic data show about 20 anomalous tracks six months before the Guidonia earthquake. In particular, on 16 December 2022, anomalous oscillations of the east component of the geomagnetic field are temporally compatible with the seismic acceleration, but other sources are also possible. Other anomalous magnetic signals are more likely to be associated with the ongoing seismic activity offshore of the Marche region in Italy (the strongest event up to now is Mw = 5.5 on 9 November 2022 close to Pesaro Urbino).