Fault-plane solution of the earthquake in Northern Italy, 6 May 1976, and implications for the tectonics of the Eastern Alps

Abstract

The fault-plane solution of the North Italian earthquake of May 6, 1976, has been constructed from long-period records of 37 stations (mainly WWNSS stations), assuming a focus in the crust. It is essentially a thrust type solution, the compressional axis having an azimuth of about 160°, perpendicular to the strike direction of the Eastern Alps. One nodal plane is very well defined from first P-wave motions: it is steeply dipping approximately SSE with a dip angle of 77°. The second nodal plane has been determined from S-wave polarisations at stations in the United States and Japan: it dips roughly NW with a dip angle of about 16°. The dip direction of this nodal plane is less well defined. From the two possible interpretations of the fault-plane solution, either a shallow thrust of Italy under the Alps or a steep thrust of the Alps under Italy, only the first one is geologically plausible. The slip direction of the underthrusting block (or plate?) has an azimuth of 348° and a dip angle of 13°.

           ARK: https://n2t.net/ark:/88439/y072059

Permalink: https://geophysicsjournal.com/article/280