228 T'/jp Philippine Journal of Science isis 



SEISMIC GEOLOGY 



The seismic disturbances in this island have been discussed 

 already." It seems reasonably certain that the majority of the 

 disturbances which have occurred there are local and are of the 

 rockfall type. I have seen some landslips which have resulted 

 from the slipping of the sediments, particularly the shales, over 

 one another along bedding planes. If these are large enough, 

 they can easily set up vibrations which would be recorded by 

 seismographs. 



Other disturbances have been of greater intensity and were 

 due to displacements along the line of contact between the 

 sediments on the western side of Guimaras Island and the ig- 

 neous formation on the east. 



It is possible, also, that other differential movements have 

 taken place between the valley alluvium and the mountain mass, 

 which would give rise to seismic disturbances. 



There is no evidence as far as I know of vulcanism on the 

 island since the Pleistocene, at least, to which we could attribute 

 any of these disturbances. Whatever their origin, they have 

 been of minor importance, and Panay is now one of the most 

 stable parts of the Archipelago. 



SUMMARY AND CONCLUSIONS 



The relation of geology to the topography and indirectly the 

 bearing it has upon the distribution and activities of the people 

 has been shovni. 



The vegetation of the country shows the devastating effects 

 of the caifigin system, and the effect of this upon the economic 

 welfare of the people has been indicated. 



The existence of a hitherto suspected but unverified new-old 

 formation, almost certainly Jurassic in age, has been proved. 



Attention has been called to new prospects in mining and the 

 favorable geologic features connected therewith. Deeper drill- 

 ing for oil in the vicinity of Janiuay is recommended. 



The ground-water resources of a portion of the island have 

 been touched upon, and the possibility of utilizing the water 

 contained in the ancient buried gravels of the Iloilo plain has 

 been pointed out. 



Attention has been called to the seismic geology. Panay is 

 one of the most stable parts of the Archipelago, and the majority 

 of the few earthquakes occurring on the island are due to 

 rockfall and hence are local. 



" Saderra Maso, Miguel, and Smith, W. D., This Journal, Sec. A (1913), 

 8, 199. 



