the Pacific Ocean average (Von Herzen and Lee, 1969), but is in 

 excellent agreement with the mean value of 2.0 - 2.2 HFU found by 

 Watanabe and others (1977) in extensional marginal Pacific basins 

 formed in Early to Mid-Tertiary time. They attribute this anomalous 

 heat flow to significant differences in the properties and evolution 

 of the lithosphere below extensional basins, principally a thinner 

 lithosphere. 



Note that these measurements apply to extensional "back-arc" 

 basins (Karig, 1971) at island arc environs. The relevance of the 

 apparent analogous heat flow regime between the "back-arc" basins 

 studied by Watanabe and others (1977) and the Caroline Basin will be 

 evident in a later section on regional evolution. 



Earthquake Epicenters 



Figure 2 shows that the Caroline Basin is essentially aseismic, 

 at least within the ten year time frame (1961 - 1971) of the earth- 

 quake observations. Noting that there may be relatively large errors 

 in some of the earthquake locations, there are 3 shallow events in 

 the vicinity of the New Guinea Trench, but there is no indication of 

 a southward dipping seismic zone that would indicate any active sub- 

 duction. There are also shallow epicenters landward of the Manus 

 Trench, but again there is no seismic indication of a subduction 

 zone. 



An excellent summary of the focal mechanism determinations in the 

 area to the south of the Caroline Basin (Bismarck Sea; New Guinea) 

 is given in Hayes and Taylor (1978). The mechanisms found show a 



22 



