654 CATALOGUE OF DESTRUCTIVE EARTHQUAKES 



some may fall, the ground may be badly cracked in places and 

 small landslips occur. 



III. Earthquake with this intensity are those which 

 destroyed towns and devastated districts. The ground has 

 been faulted and fissured whilst from these openings water, 

 mud, and sand may issue. In a hilly country landslips will be 

 common. The acceleration may exceed 8000mm. or 10ft. per 

 sec. per sec. Beyond the meisoseismic area up to a distance of 

 100 miles the effects produced may be similar to those of 

 Class I. 



The origin of all these earthquakes may generally be, 

 assumed to be along the line of fault or fracture in the earth's 

 crust. Motion sufficient to cause destruction may extend to the 

 right and left of such a line to distances of 100 miles. With 

 earthquakes of Class I this distance may not exceed 5 miles. 

 Should the fault or faults run parallel to a mountain range, 

 which is commonly the case, it is rarely that violent motion will 

 extend beyond such a barrier. Destruction frequently takes 

 place along the length of the valleys. In consequence of these 

 limitations and extensions, the area violently shaken is usually 

 eliptical in form, the major axis of an elipse corresponding to 

 the length of the fault or line from which the initial impulse or 

 impulses have originated. Tele- or eiyptoseismic motion 

 which cannot be felt, but which can, with proper instruments, 

 be recorded, does not appear to be limited by mountain barriers, 

 but extends farther in the direction of the primary impulses or 

 at right angles to fault lines than it does in the direction of 

 their length. For example, the movement which caused 

 destruction in Central California on April 18th, 1906, originated 

 along a line of faulting 400 or more miles in length. This ran 

 parallel to the coast of California. The most violent impulses 

 occurred near to the centre of this line but their destructive 

 effects were bounded on the East by the Sierras and other 

 ranges about 150 miles distant. Very marked teleseisms 

 however passed this barrier and extended in the direction of 

 the initial effort round the world. The corresponding tele- 

 seismic records obtained from South America were, however, 

 comparatively small. Notes on this subject will be found in 

 British Association Reports, 1908, p. 74, and in Nature. 



Principal Sources of Information. 



Mallet's Catalogues. — The Catalogues of Mr. Robert Mallet 

 are to be found in the British Association Reports for the years 

 1852-3-4. For each entry he gives one or more references to 

 the sources from which he obtained his information. His first 

 entry, 1606 B.C., which is given on the authority of Exodus, 

 XIX., 19, and his last, 1842 Dec. 4, for which seven references are 

 given from seven foreign publications. In the early part of his 

 work we find main' Biblical references which are intercalated 

 with or followed by the names of ancient writers, amongst 



