vni. a, 4 Saderra Masd and Smith: Seismic Disturbances 203 



formulate rules which would be more practical than the ones 

 previously drawn up for the rebuilding and repairing of the city. 

 This second commission, therefore, was not directly concerned 

 with the study of the causes of the earthquakes of 1880, nor 

 with the determining the extent and probable epicenter of the 

 same. Jose Centeno, engineer of mines, was entrusted with this 

 task. His memoir 4 is one of the best that has been published 

 from a descriptive point of view. He personally covered the 

 whole territory in which these earthquakes had been most 

 violent, and hence was able to determine, with the precision 

 possible in such cases, the meizoseismic areas of the three de- 

 structive earthquakes that took place from July 14 to 21, 1880. 



It is to be regretted that in this investigation, which reflects 

 much credit upon him, he did not direct his observations to the 

 discovery of rifts and faults which would have indicated the 

 nature of the dislocation, which took place in the Eastern Cordi- 

 llera, and which were the causes of these earthquakes. He could 

 not prescind from the ideas then prevalent of the relation of 

 earthquakes to volcanoes, and, if he does not actually attribute 

 the July earthquakes to the influence of Taal Volcano, at least he 

 makes mention of several small eruptions which were supposed 

 to have occurred in the same year, as though he wished to in- 

 dicate in what direction investigations were to' be made if there 

 should be an inquiry as to the origin of those earthquakes. 



A short time before this, Centeno had been sent on a commis- 

 sion to the Peninsula of Surigao where several very severe earth- 

 quakes had taken place in 1879 and which had left indelible 

 impressions of their violence in the shape of numerous fissures 

 and subsidences. In his report, he assigns Mainit Lake as the 

 epicenter of the earthquakes. Like many other writers he sup- 

 posed this lake to be an extinct volcano. He could easily have 

 assigned another origin, because the great number of fissures 

 and subsidences along the ridge of mountains and especially in 

 Point Bilat — which is its extreme northwest extension — made it 

 rather clear that their character was tectonic. It may be that 

 some spasmodic movement had occurred which had closer relation 

 to the slower geologic movements in this part of the island, 

 and it was these the author took cognizance of, since he quotes 

 as proof that the depth of the port of Surigao had changed during 

 the earthquakes of 1879. 



* Temblores de tierra ocurridos en Julio de 1880 en la Isla de Luzon. 

 Madrid (1885). 



