EARTHQUAKES OX THE PACIFIC COAST -17 



April 24,1906, 1:25 a. ni., slioit. 

 " " 1:32 a. m., tremors. 



1:14 p. 111. 



April 25, 1906, 4:30 a. m. 



3:17:10 p. ni.. double waves recorded on scisiiiograph. 



April 27,1906, 1:07 p. in. 



April 29,1906, 4:09 p. m. 



April 30,1906, 1:57:30 a. m. 



'' '' 1:59:40 a. in., single swing. 



" " 7:10 a. m. 



Xumerous shocks, mostly light, occurred in May, especially during 

 the first two weeks. 



The initial disturbance on April 18, from 5:13:05 to 5:13:45(?) a. ni.. 

 consisted of heaving, throwing, and racking motions sufficiently 

 intense to dislodge cornices, crack walls, break chimneys, and 

 wrench solid masonry. On made ground and in alluvial soil, 

 crevices and cracks of varying width were opened. While the 

 destruction was great and considerable debris filled the streets, 

 it was noticed that buildings on the hills apparently suffered less 

 than those on lowlands; also that the steel buildings, known as 

 Class A, as well as heavilj^ built stone buildings, were practically 

 intact after the shock. At the office of the Weather Bureau, on 

 the tenth floor of the Mills building, the instruments there and 

 on the roof (12th floor) were examined before 7 a. m. and found 

 to be all in working order, except that the anemometer support 

 had been shaken down. The thermograph on the roof and the 

 telethermograph and barograph in the office showed a displace- 

 ment of the pens of about 0.75 of an inch on each side, or 1.5 

 inches in all. Within a few minutes after the shock fire broke 

 out in many parts of the city. For four days the fire raged. 

 About 520 city blocks, or 3,000 acres, were burned, 25,000 build- 

 ings were destroyed, one-half of which were residences, ninety- 

 five square miles were devastated, and more than 100,000 people 

 rendered homeless. The financial loss has been estimated at 

 $350,000,000. The insurance loss was estimated at $235,000,000. 

 About 400 lives were lost. 



The earthquake was felt distinctly at Eureka and as far south as 

 Los Angeles.* The line of greatest intensity appears to be 

 along one of the old faults running from Mussel Eock southeast 

 through Lake San Andreas, Crystal Springs, Stevens Creek. Camp- 

 bell Greek, Wrights and Skyland. This is generally known as 

 the San Andreas fault. Dr. John C. Branner, of Stanford Uni- 

 versity, fortunately made an extensive and detailed survey of 

 the Santa Cruz section shortly before the slip, and has been able to 

 promptly resurvey this section of greatest dislocation. He is 

 of the opinion that the slipping of the fault is plainly shown by 

 surface conditions, especially by tree destruction. Near Loma 

 Pricta he found along the line of the fault marked destruction 

 of trees. ''The forest looked," he says, "as though a swath had 



* A shock was felt at San Diego at 4:30 p. m., April 18, but was probably an after shook. 



