162 



area north of the shelf projection has been down-faulted, or 

 tilted to the south. 



The geologic structure of the bay is not considered to 

 be unique and faults are probably as numerous as on land. In 

 addition, it is likely that fatilting is as active in the bay 

 as elsev^ere in the southern California region. Although 

 there is no topographic expression of faulting on the shelf, 

 data strongly suggest one or more major faults. It is not 

 known whether the outfalls cross active subsurface faults. 

 However, since there is no surface expression of faulting 

 along the proposed outfall route, it may be prestiraed that no 

 vertical displacement will occur even if the faults are now 

 active. 



Earthquakes resulting from movements along active faults, 

 either within the bay or elsewhere in the region, should be 

 regarded as probable. A long rigid outfall on unconsolidated 

 sediments may then be subjected to considerable stresses. 



