The fine structure of the dynamics of seismicity before earthquakes in the area of Reggio Emilia (Northern Italy)

We present the results of studies of seismicity in the Reggio Emilia area (Northern Italy). The Istituto Nazionale di Geofisica instrumental earthquake catalogue (1975-1996) reported about three moderate-size earthquakes with M ³ 4.5 that occurred in this area (November 1983, May 1987, October 1996). The RTL prognostic parameter proposed by Sobolev and Tyupkin (1996a) was used for analysis. This parameter is designed in such a way that a seismic quiescence produces negative anomaly of the RTL parameter in comparison to its perennial background level and an activation of seismicity initiates the growth of its value. The RTL prognostic parameter indicates that all three earthquakes are preceded by activation of the seismicity. The interval between the commencement of the activation identified by RTL parameter and the event itself was about one year for the 1987 and 1996 earthquakes, and about three months for the 1983 earthquake.