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

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G. Muller


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°.

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Muller, G. (1976). Fault-plane solution of the earthquake in Northern Italy, 6 May 1976, and implications for the tectonics of the Eastern Alps. Journal of Geophysics, 42(1), 343-349. Retrieved from https://journal.geophysicsjournal.com/JofG/article/view/280
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