vhi, a, 4 Saderra Mas6 and Smith: Seismic Disturbances 227 



is suggestive of some prominent earth lineament. On Sep- 

 tember 6, 1862, October 9, 1901, and May 25, 1907, very similar 

 earthquakes occurred in the same region, having their main line 

 of propagation in nearly the same direction. 



On October 10, 1882, there was an earthquake, the destructive 

 area of which centers about San Miguel Bay in southeastern 

 Luzon (10). Very little is known about the formation on the 

 Caramuan Peninsula, so that we are unable to give any theory 

 for the disturbances here. 



Two earthquakes of February 10 (3, 4) and of July 14, 1883 

 (10) . The former originated in the Province of Nueva Vizcaya, 

 and probably was due to causes already mentioned. In the 

 latter, the earthquake clearly originated from volcanic disturb- 

 ances, as the destructive area comprises the southeastern 

 volcanic region of Luzon. 



Earthquake of July 27, 1883 (7, 8), is clearly volcanic, or 

 at least related to the fracture passing through Taal which is 

 included in the destructive area. 



Earthquakes of January 10 (10) and March 22, 1884 (5). 

 Both of these were very likely of tectonic origin ; one had its 

 epicenter in the northwestern portion of Pangasinan Province 

 where there is no sign of recent vulcanism. This probably is 

 due to displacements along line G — G. The second one had its 

 epicenter near the southeastern volcanic region, but on the west 

 side of the peninsula, where there is a slight uplift of Tertiary 

 sediments, which may indicate this to be due to tectonic causes. 

 Lately, in 1907, there occurred two destructive earthquakes in 

 the same region, probably due to the same causes. 



Earthquake of April 20, 1884 (7). This was not destructive, 

 but, according to the distribution of the effects of the earthquake, 

 it probably was of tectonic origin and can be attributed to 

 displacements along line G — G. 



Earthquake of October 29, 1884, had two destructive areas 

 (6, 8, 9) more or less separated, the epicenter of one being just 

 north of Laguna de Bay and the other just north of the south- 

 eastern volcanic cluster (10). As there is no sign of a volcano 

 at present north of Laguna de Bay, it is probable that the line 

 H — H runs through this region. 



Earthquakes of December 17 and 24, 1884 (5, 13) , are clearly 

 of tectonic origin. In the former, the displacement undoubtedly 

 took place along the line C — C; and that of the latter was 

 probably due to movement along the line which runs northwest 

 and southeast, through the straits between Leyte and Samar, 

 which is indicated by the line N — N. 



