Fault plane solution for the earthquake of 25 November 1986 near Knin, Croatia

Abstract

By analyzing the P-wave first motion polarities we have obtained the fault plane solution for the Knin earthquake of 25 November 1986. The fault plane/auxiliary plane ambiguity was resolved by comparing the solutions to the known geological features of the area. We were able to obtain practically the same result by modeling the first 10 s of the P-wave as recorded on the broad-band instrument at GRF, thus confirming the relatively poorly constrained classical solution parameters. The earthquake has probably occurred on the northern section of the NW-SE striking right lateral reverse Knin fault. The pressure axis corresponding to the fault plane solution does not lie in the direction of the regional compressional stress filed as reported by others, thus indicating strong deformation of the local stresses that is probably the result of interaction of numerous block structures present in that area.