Gravity and Magnetic Fields Over the Proposed 
Moho Hole Site North of Maui 1 
John C. Rose and John C. Belshe 
During 1964 the Hawaii Institute of Geo- 
physics carried out two marine surveys of the 
area north of Maui. These surveys provided the 
gravity, magnetic, and bathymetric data which 
will be discussed in this paper. The first survey 
was made by J. C. Rose on the Bureau of Com- 
mercial Fisheries ship "Charles H. Gilbert,” 
using a LaCoste-Romberg shipboard gravimeter 
loaned by the University of California at Los 
Angeles. The second was conducted under a 
cooperative program with the U. S. Coast and 
Geodetic Survey on the hydrographic survey 
ship "Surveyor,” under the command of Cap- 
tain R. Jones with Mr. Kenneth Culler repre- 
senting the Hawaii Institute of Geophysics. 
Position points along the tracks of these opera- 
tions are shown in Figure 1. 
Subsequently, there have been two magnetic 
measuring cruises on the Hawaii Institute of 
Geophysics vessel R/V "Teritu.” 
PREVIOUS STUDIES 
Many earlier studies have been made of the 
gravity and magnetic fields in the vicinity of the 
Hawaiian Islands. Most of the early work was 
confined to submarine gravity measurements, 
starting with the pioneer round-the-world trip 
of Vening Meinesz in 1925 and continued by 
the Lamont Geological Observatory in the years 
immediately following World War II. The 
operations made on the U. S. submarines "Capi- 
taine,” SS 336; "Sea Dog,” SS 401; "Bugara,” 
SS 331; and "Rock,” SS 274 were by various 
observers, but mostly by Dr. J. L. Worzel. The 
subsequent surface ship operations involving 
both gravity and magnetic observations were 
made by the "Argo,” operated by the Scripps 
Institution of Oceanography, which carried out 
local surveys during cruises Monsoon and Dodo 
while on her way to participate in the Interna- 
1 Hawaii Institute of Geophysics Contribution No. 
98 . 
tional Indian Ocean Expedition. One of the 
authors (Belshe) was aboard during both of 
these operations, and the other participated in 
the second. Measurements have also been made 
by the "Rehoboth” operated by the U. S. Navy 
Oceanographic Office, and by the "Surveyor” 
and the "Pioneer” operated by the U. S. Coast 
and Geodetic Survey. During the spring 1964 
operation of the "Surveyor,” Dr. P. Dehlinger 
of Oregon State University was in charge of the 
gravity program. The authors are indebted to 
all these groups for their cooperation in mak- 
ing available the information from these cruises. 
Most, but not all, of the gravity information 
from these earlier studies has been used in the 
gravity analysis presented in the paper in this 
issue by Strange et al. (p. 381 in this issue). 
It can be seen from Figure 2 that detailed 
coverage in the area of immediate interest 
(centered on 155°28'W, 22°22'N) is not as 
good as one might wish, although probably ade- 
quate for present purposes — the determination 
of the gross field and any significant abnormali- 
ties in the crust or mantle in the general area 
of the proposed Moho Hole site. 
narration of the "gilbert” operation 
Arrangements were made in May 1964 be- 
tween the Hawaii Institute of Geophysics, the 
Office of Naval Research, and the University of 
California at Los Angeles, for the loan of a 
LaCoste-Romberg sea gravimeter S3 for two 
weeks. 
Through the cooperation of the Bureau of 
Commercial Fisheries, the ship "Charles H. Gil- 
bert” was made available for the survey. The 
ship conducted underway gravity and bathy- 
metric observations between 0445Z, May 30, 
and 1400Z, June 4, 1964. Position points for 
the ship’s track during observations are shown 
on Figure 1. Because of the relatively small size 
of the ship and the prevailing sea and wind di- 
374 
