222 The Philippine Journal of Science 1913 



Panay, passing through the center of the Island of Guimaras. We have 

 drawn a line along these points for the reason that there is a contact on 

 the Island of Guimaras between recent sediments to the westward and 

 the igneous rocks found toward the east. It is our belief that the earth- 

 quakes which have been experienced on the eastern coast of the Island 

 of Panay are due to displacements along this contact. The continuation 

 of this line also might explain the trend of this coast of Panay. 



Line L — L passes through an epicenter at the southern point of the 

 Island of Samar and another near the end of the southeastern prong of 

 Leyte, through the Island of Camiguin on which is located a dormant 

 volcano, and then follows the trend of Misamis Bay, in Mindanao, and 

 finally passes close to an epicenter situated in the middle of the sea between 

 Cotabato and Zamboanga. Formations at the lower end of Samar and 

 Leyte are but little known, but there is the volcano on the Island of Cami- 

 guin mentioned above, and where the line crosses Mindanao there is more 

 or less basalt. Misamis Bay probably marks some sort of a rift in the 

 formations. 



Line M — M passes through many epicenters in the Island of Mindanao. 

 It intersects the L line at a point east of Dumanquilas Bay, passes through 

 an epicenter west of Pollok, then follows very closely the trend of the 

 Cotabato River to the point where the river turns northward, and thence 

 through an epicenter east of Mount Apo. From here it passes close to an 

 epicenter located in the sea east of the southeastern point of Mindanao. 

 Note the agreement between this line and the lower course of the Cotabato 

 River which is probably more than a coincidence. 



Line N — N connects important epicenters in Camarines, Nueva Vizcaya, 

 Samar, Leyte, and the northeast coast of Mindanao. It passes through 

 the narrow Strait of San Juanico, separating Samar from Leyte, and along 

 the Camarines Valley northwestward it strikes the eastern coast of Luzon, 

 south of Casiguran Bay. In the Albay Valley it follows the contact line 

 of the northern volcanic cluster along which the most violent earthquakes 

 of the Camarines seem to originate, probably due to differential move- 

 ments between the sedimentaries and the volcanic area, or possibly in the 

 sedimentaries alone. Farther in the interior of Luzon this line would pass 

 very close to the Nueva Vizcaya epicenter, but this epicenter is considered 

 as rockfall. 



Line N' — N' is a secondary one which would pass through the Sorsogon 

 and northern Samar epicenters. This line nearly coincides with the contact 

 between the sedimentaries and extrusives, west of Sorsogon; eastward it 

 follows the alluvial and littoral deposits of the lowland extending from 

 Sorsogon to Gubat. In San Bernardino Strait and in the northern part 

 of Samar it nearly conforms to an indentation of the "Philippine trough," 

 along which are located some epicenters affecting Catanduanes, Albay, and 

 northern Samar. 



Line — begins close to the epicenter at the southern point of Samar, 

 continues southward to the Island of Dinagat, through the epicenter at 

 the northern point of Surigao Peninsula, then approximately conforms to the 

 Matutan Range, through the epicenter near Mount Apo, and finally passes 

 through the Island of Sarangani. We do not know the composition of 

 the rocks of the central part of the Island of Dinagat, but on Surigao 

 Peninsula crystalline schists flanked by Tertiary and recent sediments have 



