engleski

In search of activated faults in the Petrinja (Croatia) earthquake sequence of 2020– 2021

Preliminary locations of over 12, 700 earthquakes in the Petrinja (Croatia) earthquake sequence (2020–2021) reveal that a number of smaller faults were activated in the first five months after the main strike-slip rupture along the Petrinja fault (mainshock Mw = 6.4). Unlike the nearly vertical Petrinja fault, most of the smaller faults dip to the NE, and can be related to reverse faulting mechanisms. The cross-sections through the epicentre clouds also point to a large area around the mainshock’s hypocentre where the density of aftershocks foci is rather low, thus indicating nearly complete stress release by the main event. Most of the aftershocks occurred in two well-defined clusters below this region, and to the SE of it. Focal mechanism solutions for 50 events from the sequence (2.6 ≤ Mw ≤ 6.4) show that the largest ones are characterized by strike-slip sources, but a considerable number of nearly pure dip-slip solutions were also found. The inferred orientations of the Paxes (SW–NE to SSW–NNE) are rather consistent, with only a few exceptions.

Aftershock locations, focal mechanisms, active faults

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