LOCAL EFFECTS OF SAN FRANCISCO EARTHQUAKE 315 



Francisco Bay, 9^ miles northeast of the fracture, there was a large 

 brick warehouse, with its ends parallel to the fault-line. The upper 

 half of each end toppled over, but the side walls, although badly 

 cracked, were left standing. 



The effects of this wave-motion have not been traced more than 

 12 miles from the fault-line, but it probably continued with dimin- 

 ished intensity to a considerable distance. In other districts, hav- 

 ing a different geological structure, the distances to which these 

 movements could be traced would undoubtedly vary greatly. The 

 wave-motion appears to have been more intense in the soft alluvial 

 deposits of the valleys than in the consolidated beds that form the 

 high ground, but there are not enough houses in the mountains 

 of this district to furnish conclusive evidence on this point. 



At Half Moon Bay the intensity of the earthquake was about 

 the same as at Stanford University; but as one goes down the coast, 

 and therefore away from the fault-line, the intensity decreases. At 

 Pescadero, which is about 12 miles from the fault-line, there was 

 scarcely any damage done, but there were no brick or stone buildings 

 in that village. 



In regard to the geological effects of the earthquake, there are 

 a few facts of general interest that might be mentioned. Most of 

 the landslides that occurred at this time were on the west side of 

 the Santa Cruz Range. This is probably to be attributed to the 

 greater rainfall on that side of the watershed. The springs and 

 streams on both sides of the range increased in volume after the 

 earthquake, and some creeks on the west side were nearly doubled. 

 All of the streams were muddy for several days after the earthquake. 



A marked effect was produced on the artesian belt near the 

 head of San Francisco Bay. Wells that had previously been dry 

 began flowing, and wells that flowed before the shock greatly increased 

 in volume and pressure. The following is one illustration out of 

 many that were recorded: A well near Alviso, at the head of the 

 bay, formerly required a wind-mill to pump the water. At the 

 time of the earthquake the casing was driven 2 feet out of the ground, 

 wrecking the pump, and since that time the well has been flowing 

 under a heavy pressure. In some of the lowlands small cracks 

 were formed, out of which water issued, bringing up mud and sand. 



