EARTHQUAKES OF MAY 1960 IN CHILE — SAINT-AMAND 351 



and in the valley was compacted and settled, placing the land surface 

 lower than before. The earthquake shook water out of the ground, 

 and the normal discharge of the rivers was greatly augmented. All 

 these factors, coupled with the almost continuous rain, put a number 

 of rivers in full flood and added to the problems of the inhabitants 

 (pi. 7). 



Among the landslides produced, one was especially notable both 

 for its size and the amount of damage done. This slide took place 

 on the Rio San Pedro about 4 km. downstream from Lago Rinihue 

 (fig. 2 and pi. 9, fig. 1). The slide was some 3 km. in length and 

 consisted almost entirely of clay. An oversteepened bank on the 

 north side of the river slid over the old river channel along a bed 

 of water- saturated clay. 



Tlie slide dammed the river, and the level of Lago Rinihue rose 

 about 20 m. before the stream overflowed the natural dam (fig. 2). 

 Engineers of the National Power Co. worked feverishly to cut a 

 channel across and around the slide to prevent additional rising of 

 the lake. The drainage from several nearby lakes contributing to 

 Rinihue was shut off artificially in order to prevent excessive rise of 

 the water in Rinihue. The dam was opened in July and the lake 

 drained, causing a flood of the sort that occurs every few years during 

 seasons of heavy rain. 



LUMINOUS PHENOMENA 



Several people reported luminous phenomena associated with the 

 earthquakes. The most interesting reports come from the Arauco 

 Peninsula, w^here, it was reported, people in Canete (fig. 1) saw a 

 luminous glow in the air associated with these larger aftershocks. 

 The phenomenon was described by a pilot who, with three passengers, 

 was trying to sleep in his plane. The plane bounced around a great 

 deal during the night, sliding some 4 m. southward over the slippery 

 surface of the field. 



The light was described as coming from the air, beginning abruptly 

 with the sound from the aftershocks, and rising to a fairly constant 

 level in less than 1 second. It continued for perhaps 40 to 50 sec- 

 onds, dying out more slowly, wath a decay time of a few seconds. 

 It was seen only during the stronger aftershocks. The light was de- 

 scribed as a "fosforescencia del aire de un color azulverdoso." The 

 effect seemed brightest at the horizon to the south and east. The sky 

 was quite clear. There was no electric power available anywhere 

 on the peninsula, which could have caused the phenomenon, all the 

 power having been shut off because of the earthquakes. 



The pilot also reported changes in compass headings during this 

 time, but this might have been due to jostling of the aircraft or to 

 imagination. This account is reported here as being typical of in- 



