vni, a, 4 Saderra Mas6 and Smith: Seismic Disturbances 229 



also do not know enough about the geology of that portion to 

 say with any certainty that there is a tectonic line running 

 at an angle to the main Agusan line. The reader is referred 

 to an article by Saderra Maso 31 on this subject. On Plate VIII 

 of that paper the author has indicated the several epicentric 

 areas near the "Philippine deep." Most of these areas are 

 elliptical, with their long axes extending north and south or 

 northwest and southeast, but one of these has its long axis 

 extending slightly north of east and south of west. The second 

 seems to have had its center in the Cordillera of northern Luzon. 

 The third is a clear case of movement along line D — D, or the 

 Cagayan line. 



Earthquakes of January 1 (17), February 5 (22, 23, 25), May 

 26 (7, 8), and of October 6, 1889 (17, 20, 21). The first is 

 clearly due to movements along line E — E; and the second, to 

 movements along line M — M. The third without question is due 

 to the lines or fractures H — H and F — F. The fourth affected 

 the whole Agusan Valley region, and the eastern coast can be 

 attributed to the "Agusan line," or rather to the Pacific 

 structural "deep." 



In addition to the above list of earthquakes in the article 

 La Seismologia en Filipinas, we desire to add the following 

 important earthquakes. 



Earthquake of 1892, Pangasinan, Benguet, and La Union 

 Provinces (5). The nature of this earthquake seems to be 

 tectonic beyond doubt, since it occurred in a region where no 

 recent volcanic formations are to be found. The northern part 

 of its epicentral area comprises the uplands of Baguio, where 

 the tremendous upheavals which occurred in recent geologic 

 periods are clearly evident. Almost in the center of the epi- 

 central area rises Santo Tomas, an andesitic block mountain 

 due in part to faulting, while in the southern part lies the 

 alluvium of the Pangasinan plains. It seems highly probable 

 that the cause of this earthquake can be found in some important 

 dislocation which occurred near the Santo Tomas mountain 

 mass. This epicenter belongs to line C — C. 



Earthquake of 1893, Agusan Valley, Mindanao (20), is un- 

 questionably the greatest which has occurred in this region 

 during the last three centuries. The permanent sinking of part 

 of the floor of the valley and the faulting on the divide between 

 the headwaters of the Agusan Valley and the Gulf of Davao 

 suggest a folding movement of the Eastern Cordillera as a 



31 Bull. P. I. Weather Bur. (1910), 279. 



