viii, a, 4 Saderra Maso and Smith: Seismic Disturbances 225 



of tectonic origin, and might be explained as due to a displace- 

 ment along the line A — A. 



The great number of earthquakes which occurred in 1871 

 were of volcanic origin, having as their epicenter the Island of 

 Camiguin. The destructive area includes Camiguin, Bohol, and 

 that part of Mindanao known as Misamis; also, the southwest 

 corner of Leyte. 



Earthquakes of July 11 (3) and of November 5, 1871 (17), 

 are both clearly of tectonic origin. The destructive area in the 

 case of the first comprises the Central Cordillera of Luzon ; and 

 that of the second is located along line E — E or, perhaps, line 

 P—P. 



Earthquake of December 29, 1872 (7) . The destructive area 

 comprises roughly that portion of Luzon adjacent to line F — F, 

 but it is possible that these disturbances originated from the 

 Taal Volcano fracture. No eruption of Taal Volcano is recorded 

 for this year. 



Earthquakes of August 25 (22, 23) and October 16, 1874 

 (8, 9). In the former, the destructive area comprises the 

 Zamboanga Peninsula, and is clearly tectonic, probably due to 

 dislocations along the line / — /; in the latter, the destructive 

 area comprises the region east of Manila Bay, more or less 

 elongated north and south, and possibly has some connection with 

 the line D — D. Taal Volcano was probably not the cause of this 

 disturbance. 



Earthquakes of May 1 (7, 8) and of July 5, 1877 (10, 11). 

 The former was felt over most of southwestern Luzon, probably 

 emanated from Taal Volcano, and probably was due to move- 

 ments propagated along the line G — G which follows the western 

 limit of the central plain of Luzon. The latter may have been 

 of volcanic origin, as the whole southeastern volcanic region is 

 comprised in the destructive area, or it may have had its origin 

 in some movement along the line marking the Philippine "deep" 

 (X— X). 



Earthquakes of August 13, 1878 (7, 8), and of July 1, 1879 

 (17). The former seems to have had its epicentral area located 

 near Manila Bay, resulting from disturbances along the line 

 G — G mentioned in the last paragraph. The latter had its 

 destructive area in northeastern Mindanao and Surigao Penin- 

 sula, and was possibly due to the Agusan line, but more likely to 

 displacements along the line E — E. 



Earthquakes of July 14 and 25, 1880 (5, 6, 8, 9). The 

 destructive area shown on this chart indicates that the disturb- 

 ances originated somewhere in the Eastern Cordillera of Luzon. 



