200 The Philippine Journal of Science ms 



great fault in the earth's crust, which is marked by the Straits of 

 Messina. 



The work of the Italian Geologic Survey has demonstrated 

 that these disturbances are propagated along very definite lines. 

 So thoroughly did the Italian geologists do their work that by 

 superimposing upon a geologic and topographic map of the Prov- 

 ince of Calabria another map showing the location of cities and 

 all the works of man, with all historical data regarding earth- 

 quakes, one can see at once that: (1) Certain points are more 

 subject to earthquakes than others; (2) points removed from 

 these lines have suffered less or not at all; (3) at intersections 

 of these lines the greatest disasters occurred. These lines, which 

 follow more or less definite systems, proved to be the projections 

 of various earth lineaments such as fault lines, joint lines, forma- 

 tion contact lines, and axes of mountain ranges. 



The great California earthquake of April, 1906, is a striking 

 example of this. This earthquake was due to a dislocation along 

 the well-known San Andreas rift, and, although the waves from 

 this disturbance were propagated, to varying distances, on both 

 sides, the greatest disturbance occurred along the line of this 

 fault. 



When one can indicate a point on a map and say definitely 

 that here the crust of the earth is unstable, seismic geology is 

 shown to be of very great practical interest to humanity in gen- 

 eral and to engineers in particular, and especially is it pertinent 

 in geologically young parts of the world like the Philippine 

 Islands where mountain building is in progress and where the 

 evidences of recent vertical movement of various portions of 

 the island mass actually can be measured. 



Concrete examples of what these disturbances mean are to be 

 had in the earthquakes of Messina and of San Francisco and 

 in the eruption of Taal Volcano. 



The people of Messina had been warned repeatedly, but com- 

 mercial interests were so great that they took no heed of their 

 danger, and consequently millions of dollars worth of property 

 as well as thousands of lives were lost at the time of that disaster. 

 The same is true of San Francisco. The reported property loss 

 at the time of that catastrophe amounted to 490,000,000 dollars. 



The disturbances in the region of Taal were primarily due to 

 the volcano, but Taal Volcano is located along a line of crustal 

 weakness, and at that time a very appreciable displacement 

 occurred along one or more lines passing through Taal Volcano. 



