338 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 62 



was restored within 2 weeks by the Herculean efforts of the Chileans 

 and the relief expeditions of their North and South American 

 neighbors. 



THE FIRST PHASE 



The first large shock of this series of earthquakes occurred at about 

 6 a.m., local time, on the morning of Saturday, May 21, 1960, the 

 anniversary of the famous battle of Iquique. This shock, magnitude 

 7I/2 (on the Kichter scale), had its epicenter in the peninsula of 

 Arauco (fig. 1), a projection of the Chilean coast lying to the south 

 of Concepcion. This earthquake left, a zone of intensity of about 

 VIII on the Modified Mercalli (MJVI) scale, having a length of 

 some 100 km. and a width of about 40 km. Nowhere was there a 

 clear-cut zone of extremely high intensity. From tliis it was possible 

 to conclude that the focus of the earthquake had a depth of 50 km. 

 or more beneath the surface of the earth. The damage from this 

 earthquake was largely confined to the city of Concepcion (pi. 1, 

 figs. 1 and 2) and to the chain of coal-mining towns situated along 

 the Arauco Peninsula. There was some damage to towns in the 

 central valley and to roads and railroads. 



All day Saturday aftershocks were felt in the epicentral area, and 

 the activity continued through Sunday. At about 2 :45 p.m. on Sun- 

 day a strong but not seriously destructive shock was felt. Over all 

 of southern Chile people became alarmed and left their homes to 

 go into the streets. They were still standing in the streets when at 

 about 3 :15 p.m. the remezon struck. This fortunate circumstance 

 saved the lives of many thousands of people, who, had they remained 

 indoors, would surely have been killed by the fall of houses and of 

 architectural gingerbread as they fled to the streets. 



The motion of the ground during the remezon was as if one were 

 at sea in a small boat in a heavy swell. The ground rose and fell 

 slowly with a smooth, rolling motion, smaller oscillations being 

 superimposed on larger ones. In Concepcion cars and trucks parked 

 by the side of the road rolled to and fro over a distance of I/2 ^i. while 

 they bobbed up and down in response to the movement of the ground. 

 The tops of the trees waved and tossed as in a tempest. Some already 

 damaged buildings fell. The earthquake itself was silent; not a 

 sound came from the earth. The period of vibration was of the 

 order of 10 to 20 seconds or more. The shaking lasted fully 3i/^ 

 minutes and was followed for the next hour by other shocks, all 

 having a slow, rolling motion. It was learned later that in all parts 

 of the affected zone the movement was similar. Nowhere did anyone 

 report the short, brusque movement typical of a locality near an 

 epicenter. In the Eegion of the Lakes, for example at Llifen, the 

 movement began smoothly and continued for some 2 minutes, just 

 as in other localities, when, suddenly, a loud subterranean noise was 



