To date the savYeys of South Branch of Scripps Canyon show a total 

 of five deepenings at an a.verage interval of nine months » Only one of 

 these occurred at the time of an earthquake despite ihe fact that four 

 earthquakes have been felt during this periodo However >, "New Valley" was 

 first developed at the tiine of one of the other earthquakes « Two of 

 the slides in South Branch occurred after a period of very rapid fill. 

 Four of the slides in South Branch were accompanied by smaller deepening 

 in the two gullies leading into Stmimer Branch but the fitth showed only 

 a fill in the adjacent branches. Both fill and deepening in "New Valley" 

 have occurred entirely independent of those of the other branches o 



Multi-Sock Sediment Trap 



Collections of sediment using the multi-sock sediment trap re- 

 ferred to in previous progress reports (I'JoSo 9, 10 and ll) are being con- 

 tinued. Four traps of this type have been constructed^ and it is planned 

 that they be used for simultaneous observations at four different depths. 

 This should give the relative iraportaxice of suspension at various depths 

 under any given wave conditions « 



Orbital Guirent Meter 



The faulty units in the amplifier output circuits of the orbital 

 current meter mentioned in the last report have been replaced. Laboratory 

 experiments to evaluate more accurately the virtual mass^, lag, and response 

 time of the system^ are in progress. 



Observations Using Self -Contained Diving Gear 



During June two rods^ each three feet longj, were forced into the 

 sand bottom of La Jolla Bay at a point wtere the water is about 30 feet 

 deepo The rods were placed vertically with appi'oximately two feet buried in 

 the sand and one foot exposed. If the rods reraain stationary^ repeated 

 measurements of the exposed length should result in accurate measurements 

 of the change in level of the sando A dive two weeks later showed no 

 appreciable change in the exposed portion of the rods. In addition to ttie 

 obvious advantage of this direct means of measuring changes in sand levels , 

 once the method is perfected^ it is intended that it be used to evaluate 

 the accuracy of the more rapid fathometer surveyso 



Observations of bottom features during conditions oi low waves 

 indicate the importance of bottom-dw'Jlling organisms in reworking sandy 

 sediiaents. On 15 July 1952 in 75 i'eet of vjater (on "D" Range) on the 

 shelf between La Jolla and Scripps submarine canyons ^ divers reported the 

 bottom was entirely lacking in the ripple marks viiich had been found pre- 

 viously at this depth. Tlrie bottom appeared tC' be completely reworked by 

 burrowing organisms and was very huiTuiiocky and irregular. Large mounds and 

 depressions were formed. The low wave conditions during tiie preceding weeks 

 appear to account for the lack of ripple marks^, and gave the bottom-dwelling 

 organisms a chance to rework and destroy the piB--existing ripple marks. 



