The Chilian Earthquake.

Samoanische Zeitung, Volume 22, Issue 46, 17 November 1922, Page 9

The Chilian Earthquake.

NOTES FROM APIA OBSERVATORY.. The Samoa Times in indebted to Mr. C. J. Westland, Director oi the Apia Observatory, ior the following notes ot great interest : An earthquake occurred oil the coast ot Chili, about 6,400 miles irom Apia, on Friday after* noon, November 10th, at 5.16 p.m. (local time Western Samoa). The first earthquake tremors passing through the earth reached Apia minutes later where tbey

produced an oscilatiou of the ground of about one fiftieth inch ainptitude. As the earthquakes involved considerable movement of the sea bottom a seismic sea wave was produced, which, spreading eastward, reached Apia at 7 12 am. Saturday. This was about two hours after low water. The extent of rise and fall of the water in the harbour caused by the seismic sea wave was a little over 20 inches. We see, therefore, that the wave must have travelled 6,400 miles in 13 hours 56 minutes; i.e., an average speed of practically 460 miles per hour. This speed agrees with previous results for the Pacific Ocean. In a shallow sea the speed would be somewhat smaller. With regard to the origin seismic sea-waves, any sudden disturbance of the ocean bed, either by crnstal movement or by submarine landslips must give rise to sea-waves of more or less magnitude. In a great earthquake, both causes may be in action. As a rule, however, it is probable that the abrupt formation of a submarine fault scarp is the more irtquent cause of seismic sea-waves of great magnitude, as for instance in the case of the Wellington earthquake of 1855.