214 



The Philippine Journal of Science 



1913 



Table I. — Number and intensity of shocks preceding the eruption of Camiguin. 



[Reported from Camiguin.] 



Date. 



Earthquakes. 



Remarks. 



Feb. 16 



Two slight earthquakes - .. 





17 



Frequent shocks during day and night 



do _ . _ 





18 



One of intensity VIII. 

 One of intensity VII. 



One of intensity IX. 

 One of intensity VIII. 



One of intensity VI. 



19 



do 



20 



do 



21 



do 



22 



do . 



23 to 28 



do 



Mar. 1 to 3 



do 



4 



do . 



5 to 7 





8 



do 





9 ■ 



do 



Do. 



10 ■—. — 



do 



11 to 13 



do 



14 to 17- 



Less frequent; 4 or 5 per day 



18 to 19 









ceding days. 





20 to 31 



Less frequent; not exceeding 6 per day 





Apr. 1 to 29 



Frequent during the entire month; number 







never less than 6 to 10 per day. 





30 



At 7 a. m., with a terrific detonation and 

 emitting a cloud of vapor, rocks, and 









ashes, a volcano burst on the north- 







northeastern end of the island, only a 







few meters from the shore. After this 







explosion, semifluid lava continued to 







rise quietly for about three years, build- 







ing up a cone approximately 400 meters 







high. The ashes of the first explosion 







were carried to distances of 200 kilo- 







meters. Within a radius of 2 to 3 kilo- 







meters from the new crater, the destruc- 







tion was complete. The earthquakes 







ceased almost completely a few days 







after the eruption. There was no loss of 







life as the people of Catarman, the town 







nearest to the volcano and the only one 







destroyed by it, had deserted their homes 







long before, some having left for other 







islands as early as the end of February. 





The tectonic type of earthquakes is caused by the sudden 

 relief of strains, due to contractions and foldings in the crust 

 of the earth; when these pass the limit of equilibrium and the 

 modulus of elasticity of the crust, they give rise to rents and 

 fractures and other sudden movements of more or less severity 

 depending on the degree of the accumulated strain. This type 



