Ancora sui tempi di tragitto delle Pn provenienti dalla Sicilia Tabelle numeriche per varie profondità ipocentrali

Abstract

This paper follows the foregoing studies by the A.A. already carried out on the earthquakes occurred in Western Sicily. The hypocentral data investigation concerning a further large earthquake of the swarm, has confirmed an hypocentral depth close to the "Molio". Grouping conveniently the investigated earthquakes it was possible to calculate the longitudinal waves travel-times curves at the following depths: 30, 35, 40, 45, 50, 00 km (A < 20°). Some interesting results concerning the first impulses of P„ waves have been found (existence of two series of waves, P,n and IJ„2 having a slightly different velocity). Five curves for each examined h have been calculated; the P„ (the general) using all the onsets including the ones whose residuals resulted later to be about three seconds: the Pni and the P„2 representing a Pn subdivision obtained by reducing the residuals range: the P„ -^13° and the P„ (10°M 20°) for 2» < A < 13° and 10° < A < 20° respectively calculated. (The P„ 13° approaches to a straight line, in accordance with other estimations for curves investigated along shorter paths). The paper contains also all numerical tables related to 29 travel-times curves calculated every 20 km; as well as the curve corresponding to li = 17.5 km. The last curve has been obtained averaging the values of depth from 5 km to 30 km in order to fill the gap 0 i—i 30 km.