Even before his arrival in Israel, Pekeris was involved in efforts to organize a Scientific Advisory Committee for the establishment of a seismological observatory in Palestine. Between 1951 and 1955 a major share of the activities of DAM were related to geophysical prospecting. The geological survey started in the summer of 1950, and on September 23, 1955, oil was found in the Heletz field. Pekeris’s collaboration with Zipora Alterman started around this time. They used WEIZAC to perform accurate calculations that afforded the first full proof of the existence of “free vibrations of the Earth.” The calculated magnitudes of these vibrations were identical to those predicted by the existing theory.