CENTENARY OF THE DISCOVERY OF THE MOHOROVIČIĆ DISCONTINUITY (THE BOUNDARY BETWEEN THE EARTH'S CRUST AND ITS MANTLE)
Abstract
Croatian seismologist Andrija Mohorovičić discovered an important velocity discontinuity between Earth's crust and mantle when he analyzed seismograms from an earthquake which occurred one hundred years ago (on 9 October 1909) in the Kolpa Valley. This boundary was later named the Mohorovičić discontinuity. He discovered two types of P and S waves arrivals at the epicentral distances between 300 and 720 km. First arrivals visible on seismograms are Pn and Sn phases, which correspond to longer, refracted, but faster paths through the upper part of the mantel. Later Pg and Sg phases correspond to direct waves propagating through the Earth's crust only; these are characterized by lower seismic velocities. More recent investigations have shown big differences in the depth of the Mohorovičić discontinuity below Slovenia with some surprising jumps in transition zones.
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