April 26, 1906] 



NA TURE 



609 



built upon a peninsula; and the effects of the two 

 shocks, as revealed by the distribution of the damage, 

 were very similar. Although the whole of both cities 

 suffered severely, the chief destruction was confined to 

 houses built on low-lying " made " land. In San 

 Francisco this land is occupied by business houses and 

 warehouses, and, in the southern part, by cheap 

 terrerheht's and poorly-built lodging-houses. At 5 

 a.m. most persons were in bed, and thus there was 

 little loss of life in the business district, and much 

 in that covered by the tenements. The better-class 

 residential district, situated on the hills, escaped with 

 comparative impunity, so far as the earthquakes were 

 concerned, though the fires afterwards spread to that 

 quarter. 



That San Francisco was situated within or close 

 to the epicentral area is shown by the continuous 

 after-shocks, and by the effects of the shock. 

 Observers in the open air state that the streets could 

 be seen to bulge and wave as if about to crack 

 open. Three miles of railway have sunk out of sight 

 between Suisan and Benetia ; several railway tracks 

 have been destroyed for scores of miles ; and on the 

 harbour-front the earth appears to have sunk from six 

 to eight inches. Great cracks were formed in the 

 streets, and these cracks were twisted into all shapes. 

 The houses, before they were destroyed by fire, were 

 also seen to be out of alignment. 



Outside San Francisco many towns are known to 

 have suffered severely, especially San Jose, Santa Cruz 

 and Santa Rosa ; others less seriously, from Mendocino 

 on the north to Monterey on the south. With our 

 present information (and the absence of news from 

 neighbouring places, and especially from the Lick 

 Observatory, is disquieting), the meizoseismal area 

 is a band extending along the coast and parallel to 

 th? Coast Range, about three hundred miles in length 

 and not more than fifty miles in width. The extent 

 of the disturbed area will remain unknown until 

 inquiries have been made, but it is curious how few 

 details on the subject have yet been published. Los 

 Angeles (only 350 miles S.E. of San Francisco) does 

 not seem to have been affected to any extent by the 

 principal earthquake, though the shock was felt 

 severely throughout the whole of the neighbouring 

 State of Nevada, and there are vague reports of more 

 distant observations. 



Position of the Epicentre and Seismic Sea-Waves. 



If the line drawn so as to bound the known area of 

 destruction be even approximately correct, there can 

 be no doubt that the epicentre was submarine and 

 situated some little distance from the coast. The fact 

 that the shock was felt at San Francisco two or three 

 minutes after the epicentral time implied by the seismic 

 records is also in favour of this conclusion. The 

 chief difficulty in accepting it lies in the absence 

 of any very great sea-w-aves. Much of San Fran- 

 cisco is only about twelve feet above high-water 

 mark, and would have been submerged by any con- 

 siderable wave. There seems, however, to have been 

 some disturbance of the sea. Many vessels, it is said, 

 were washed ashore with each disturbance, and washed 

 out again by the receding waters. There are also 

 unconfirmed reports that Terminal Island, a seaside 

 resort about twenty miles from San Francisco, has 

 been destroyed by a sea-wave, and that other places 

 on the Californian coast have also been swept away. 

 At present it is probable that the first decisive 

 evidence of sea-waves, if any existed, will come to us 

 from the eastern shores of Japan, which would be 

 reached by them in about ten and a half hours after 

 the earthquake. 



NO. I904, VOL. 73] 



Geological Relations of the Earthquake. 



The earthquakes of California have been studied for 

 some years by Messrs. Holden and Perrine, of the 

 Lick Observatory, and the geology of the State is 

 being revealed through the labours of Messrs. Russell, 

 Diller and Lawson ; while an admirable summary 

 of their relations was recently presented in M. de 

 Montessus' valuable work on " Geographie seismo- 

 logique " (pp. 404-412). Between the Rocky Moun- 

 tains and the Pacific are the parallel chains of the 

 Sierra Nevada and the Coast Range. Among the 

 Rocky Mountains earthquakes are few and slight ; on 

 the eastern slopes of the Sierra Nevada they are more 

 frequent, and sometimes, as in the Owen's Valley 

 earthquake of 1872, of considerable severity. The 

 western portion of the Sierra Nevada, the Cascade 

 Range, is remarkably free from earthquakes, though 

 it is worth noting by those who see an intimate rela- 

 tion between volcanic and seismic actions that it con- 

 tains the recently extinct cones of Shasta, Mount Hood 

 and Mount Rainier. Again, the Coast Range, and 

 especially the districts surrounding San Francisco and 

 Los Angeles, is one of the great seismic regions of 

 the globe. Lastly, to the west of California the sea- 

 bed deepens rapidly, the contour of 4000 metres lying 

 onlv a short distance from the land, and from this 

 region many of the strong Californian earthquakes 

 are known to proceed. 



Recent studies have established a close connection 

 between these earthquakes and the geological 

 structure of the district. Whether the earthquakes 

 take place under the Coast Range or beneath the 

 adjoining ocean, the longer axes of the isoseismal 

 lines are either parallel or perpendicular to the sub- 

 oceanic contour-lines, the crust-folds of the Coast 

 Range and the long lines of fault of the Pacific sea- 

 board. It is difficult to resist the conclusion that in 

 the western United States we are presented with 

 mountains in four successive stages of growth. In 

 the Rockies we have ranges so ancient that they have 

 almost ceased to grow; in the Sierra Nevada to the 

 west another which is approaching old age ; the Coast 

 Ranges are in the stage of youthful, vigorous growth, 

 with the possibility of a long and active life before 

 them; while, still farther 'to the west and not yet risen 

 above the ocean, there seems to lie an embryonic 

 range, of which the San Francisco and other earth- 

 quakes are the birth-throes. 



The Unfelt Earth-Waves. 



In all parts of the world delicate seismographs 

 soon afterwards recorded the occurrence of a violent 

 earthquake. The first waves reached Victoria (B.C.) 

 at 1. 16 p.m.; at Washington the movement was so 

 strong that the pen passed off the recording sheet. In 

 a quarter of an hour the seismographs of Great 

 Britain took up the tale, large disturbances being re- 

 corded at Shide, Bidston, and Edinburgh ; at Birming- 

 ham the pointer of the Omori horizontal pendulum 

 swept three times off the drum. Passing over to the 

 Continent, they set to work the instruments at Berlin, 

 Heidelberg, Vienna, Laibach, Turin, Rome, and many 

 other places. The pendulums at Florence shared the 

 fate of those at Washington and Birmingham. The 

 seismograph at Cape Town also registered the move- 

 ment, while those in Japan were disturbed by the 

 waves proceeding in the opposite direction across the 

 Pacific. Only the scantiest details are as yet made 

 known, but, if we may judge from the diagram at 

 Birmingham, the complete series of records will be 

 one of great interest and value. 



The first series of preliminary tremors reached Bir- 

 mingham at ih. 25m. 3s. p.m. (G.M.T.); they were 



