Full moment tensor retrieval for two earthquake swarms at the Alps-Dinarides junction

Abstract

We present the results of the analysis for the seismic source tensor of all events with Md ≥ 3.0 belonging to the Moggio Udinese swarm (1988 February, eight events analysed), and of the three events of the swarm that occurred between 1993 July 22 and 26 in the Tricesimo area. The latter sequence is particularly relevant for the assessment of seismic risk of Friuli (northeast Italy), since it is close to the densely populated area of Udine. We use a waveform inversion algorithm which allows us to retrieve the moment tensor rate functions (MTRFs) that can be factored into a moment tensor and a source time function (STF). From the orientation of the P-axis and of the nodal planes we can hypothesize that the Moggio Udinese swarm (P-axis orientated globally between southeast-northwest and east-west) reflects the influence of both the southeastern Alpine and external Dinaric stress field, while in the Tricesimo swarm (in which the P-axis orientations varies between southeast-northwest and north-south) the southeastern Alpine stress field seems to act on faults oriented southeast-northwest, belonging to the external Dinaric system. © 2005 RAS.