TIMES AND PLACES OF EARTHQUAKES 537 



THE TIMES AND PLACES OF EAETHQUAKES 1 



By Professor H. H. TURNER, F.R.S., 



OXFORD UNIVERSITY 



npHE occurrence of several disastrous earthquakes and eruptions 

 ■*- during the last few months inevitably suggests the question 

 whether all these events may not have a common and determinable 

 origin. To avert any of these disasters, even to modify them in the 

 slightest degree, may be entirely hopeless; but the vaguest foreknowl- 

 edge of their probable occurrence might be of untold value in saving 

 life and property. Has modern research obtained any clues which 

 enable predictions to be made, or promise that prediction may be pos- 

 sible in the near future? It must be frankly admitted that as yet our 

 knowledge is so slight as to have no commercial value; but still, there 

 are one or two clues in the hands of those working at the subject which 

 may ultimately lead them to more directly useful knowledge. We have 

 learnt something of the regions where earthquakes occur, and something 

 of the times when we may specially expect them ; and, though the some- 

 thing is in each case a very little, the magnitude of the issues involved 

 lends it interest. 



Systematic observation of earthquakes is only about a quarter of a 

 century old, and for fairly complete records of all the shocks occurring 

 in different parts of the globe we can date only from 1892. Before 

 that date information could only be collected on the spot, and was thus 

 frequently lost; but it was realized about 1890 that a series of earth- 

 quake observatories, with delicate instruments, could obtain records of 

 shocks in any quarter of the globe, and identify the spot with certainty, 

 even if there were no witnesses of the actual occurrence. From the 

 records of these observatories it appears that there are every year some 

 30,000 minor shocks of earthquake in different localities, but of these 

 only 60 are ' world-shaking ' and observable from a great distance. 

 Such numbers indicate immediately that, from one point of view, the 

 San Francisco earthquake can not be regarded as exceptional; it was 

 only one event out of 60 per annum. What rendered it disastrous was 

 the existence of a great town in the shaken locality. But was the neigh- 

 borhood known to be a dangerous one ? Was it at any rate, suspected, 

 so that the building of a great city there was an error of judgment? 

 and is it advisable to rebuild the city in the same place? These are 



1 From the London Times. 



