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Recent Earthquakes

Nature volume 143, page 715 (29 April 1939) | Download Citation



AN earthquake giving rise to large amplitudes on seismograms is reported by European observatories to have taken place on April 18, the initial waves being received about 6h. 36m. G.C.T. and the tremors lasting about three hours. The shock was well recorded at Stonyhurst, near Blackburn; at Kew, o where it was received at 36m. 22s.; at Uccle, where it was received at 36m. 31s.; and at Zurich, where it was received at 36m. 18s. A very prominent feature of the seismograms at the latter three observatories was the ScPcS or SKS wave, which is a pulse starting at the epicentre as a transverse wave, being transformed at the earth's core to a longitudinal wave, continuing thus to the other side of the core where it is again changed back to a transverse wave. It is received as a transverse wave at the observatory. The epicentral distance of the shock from Uccle is calculated from the arrival times of the various pulses to be approximately 105°, which is consonant with an epicentre in Chile, though the azimuth has been difficult to determine, and confirmation or otherwise is awaited from the American observatories.

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