Seismic Reflection Studies of Sediment 
Thickness Around the Hawaiian Ridge 1 
Loren W. Kroenke 
During the spring and summer of 1964, 
seismic profile surveys of sediment thickness 
were made on board the Research Vessel "Nep- 
tune I” around the Hawaiian Ridge. The seis- 
mic-reflection profiling techniques were based 
on a shallow explosive sound source of V 2 -lb 
blocks of TNT. The recording equipment was 
a modified facsimile drum recorder similar to 
that described by Ewing and Tirey (1961). 
The detector was an array formed with eight 
hydrophones enclosed in an oil-filled polyvinyl- 
chloride tube. 
1 Hawaii Institute of Geophysics Contribution No. 
93. 
The positions of seven tracks along which 
data were obtained are shown in Figure 1. The 
data obtained are presented in Figures 2, 3, 
and 4 in the form of profiles, with the vertical 
scales showing two-way travel time in seconds 
and the horizontal scales indicating position 
time for the vessel in hours. No corrections 
have been made for variations in the velocity 
of sound in sea water. 
Because sedimentary velocities are not well 
determined for the area around the Hawaiian 
Swell, an average velocity of 2 km/sec has been 
assumed, based on available data from refrac- 
FlG. 1. Chart showing tracks of R/V "Neptune I," with 2-hourly positions, during seismic reflection 
profiling cruises. 
335 
