172 



Dr. C. Davison — The Pendleton Earth-shahe. 



Pendleton, though here probably aided by mining operations. 

 Within the last seven years there have been local shakes on three 

 occasions, namely, February 27th, 1899, April 7th, 1900, and 

 November 2oth, 1905. The materials for the study of the first two 

 of these shakes are not quite sufficient to determine the boundaries 

 of their disturbed areas with accuracy. The areas appear, however, 

 to have been approximately circular in form and about four or five 

 miles in diameter. In both cases the intensity of the shock was 4, 

 or nearly 5. In 1899 the centre of the disturbed area was about 

 half a mile north of Pendleton and a short distance on the north-east 

 or downthrow side of the Pendleton fault ; in 1900 it lay a mile or 

 two farther to the south or south-south-east of the former centre.^ 



^■urxi 



He-TjUfood. 



Oldha-m. 



Stocliport 



Fig. 1. — Isoseismal lines of Pendleton Earth-shake, Nov. 25th, 1905. 



The earth-shake of November 2oth, 1905, was strong enough to 

 be noticed in many besides local newspapers, and was investigated 

 without delay. The materials for its study are therefore abundant, 

 the following account being based on 139 records from 45 places, 

 and on negative records from 4 places. 



1 Geol. Mag., Dec. IV, Vol. YII (1900), p. 175 ; Dec. IV, Vol. VIII (1901), 

 p. 361. 



