232 The Philippine Journal of Science ms 



5. Types of structures best suited to Philippine conditions : 



o. Bamboo houses. All the parts of a bamboo house are tied together 

 with rattan. These houses are strong, elastic, and light, and 

 behave like immense baskets. 



6. "Strong material," locally used to distinguished wooden, well-nailed 

 houses from bamboo structures. Floor joists well anchored. 



c. Sand-lime brick tied to steel frame should be cheaper than concrete, 



and in case of warping walls can be removed easily and new 

 steel put in. 



d. Reenforced concrete, perfectly safe if properly made, but expensive 



and apt to receive permanent warping and Assuring M from the 

 twisting motion of some earthquakes. 



Ordinary brick walls with roof of unanchored tiles make one 

 of the worst possible types of construction as demonstrated at 

 Messina. 



6. The necessity of geological examinations of all dam, pipe line, 

 and bridge sites should be emphasized. Tremendous damage 

 was done to these kinds of engineering structures in the San 

 Francisco earthquake. It is well known that the breaking of 

 the water mains by the earthquakes left the city at the mercy 

 of the fires which shortly broke out. 



7. The Harbors of Cebu, Iloilo, and Zamboanga, owing to 

 their approximating the shape of a funnel or double funnel, are 

 more or less in danger from tidal waves. 



8. Manila Harbor, owing to the comparatively small entrance 

 and rapidly widening basin, should be entirely safe in this 

 respect. 



SUMMARY AND CONCLUSIONS 



There is a close relationship between seismic disturbances and 

 geologic structure. 



The majority of earthquakes are of tectonic origin, in the 

 Philippines, at least. 



Volcanoes are secondary phenomena. 



The area of greatest seismicity in the Archipelago is in the 

 Agusan Valley, Mindanao. 



There is a close relationship between the orographic and other 

 geomorphic lines and the lines connecting the principal epicenters 

 in the Archipelago. 



Seismic disturbances can be studied and disasters can, to a 

 large extent, be avoided. 



"In the severe Sorsogon earthquake, November, 1912, a new school- 

 house of reenforced concrete and concrete blocks was considerably damaged 

 in both portions; the reinforced concrete portico sustained more or less 

 Assuring. 



