profiles, and with an airgun system in the case of the Lamont-Doherty 

 and University of Hawaii data. All references to "basement" are to 

 acoustic basement. In all cases, vertical units shown on both seismic 

 profiles and the isopach chart are seconds of two-way travel time. Data 

 may be converted to approximate sediment thickness by using a standard 

 sediment velocity of 2 km/s. The isopach chart (Fig. 13) was constructed 

 using values of two-way reflection time averaged over 1-2 hour periods 

 (15-40 km). 



Gravity 



Gravity data used in this report were furnished by the Defense 

 Mapping Agency Aeronautical Center, Gravity Services Branch. Gravi- 

 meters used were of the vibrating-string and gimbal suspended LaCoste 

 and Romberg types. Meters were referred to base stations in the western 

 Pacific established as part of the World Standard Gravity Net (Wollard 

 and Rose, 1963). Free air gravity anomalies were computed by subtract- 

 ing the theoretical gravity value, derived from the 1967 Geodetic 

 Reference System formula: g= 978.03185(1.0 + 0.00527889 Sin^ Lat. + 

 0.000023462 Sin Lat.), from the observed gravity value. Bouguer 

 anomaly valu^^s were computed using the density values 2.67 gm/cm and 

 1.027 gm/cm for crust and ocean water respectively. 



A detailed discussion of the accuracies of the gravity data, as 

 well as a free air gravity chart compiled from all available data in the 

 Caroline Basin area is to be found in Watts and others, 1978. 



