Geophysical data collected in 1975 and 1976 reveal major
crustal and tectonic elements of the continental margin of southern
Baja California. Gravity, magnetic, seismic reflection and bathymetric data show seaward extension of the islands enclosing Magdalena
and Almejas Bays. A seismic reflection profile, oriented
approximately normal to the trend of...
Gravity, magnetic and seismic data indicate that the oceanic
crust is 9.7 km thick west of the Continental Borderland. The top
of the mantle is about 12 km deep under the Borderland, and deepens
to 27 km beneath the Peninsular Ranges of Baja California. The
mantle is about 20 km...
A free-air gravity anomaly map of the area between 10°-17°N and
90°-101°W shows distinctive positive and negative anomalies which
parallel the Tehuatepec Ridge. The positive anomaly approximately
overlies the topographic expression of the ridge. On the wide continental
shelf southeast of the Gulf of Tehuantepec a positive gravity
anomaly with...
Seismic refraction measurements along two unreversed lines
indicate that the earth's crust is 26 km thick in southeastern Alaska
and 30 km thick along the Inside Passage of British Columbia. The
crust in southeastern Alaska, north of Dixon Entrance, consists of
a layer 9 km thick with a seismic velocity...
Marine geophysical data from the continental margin of Baja
California and the Gulf of California, and geological and geophysical
data from the Baja California Peninsula and mainland Mexico, outline
the major geologic and tectonic features of the Baja California
Peninsula and the surrounding areas from 24.5° N. Lat. to 27.5°...
A free-air gravity anomaly map of the continental margin of
Peru between 12° and 18° S. Lat. shows a -110 to -220 mgl anomaly
associated with the Peru-Chile Trench, a -60 mgl anomaly over the
Pisco Basin on the continental shelf, and -120 mgl anomaly over the
Mollendo (or Arequipa)...
The thermal regime of a postulated descending lithospheric slab
is calculated. The gravity anomaly associated with such a structure
is large in amplitude and long in wavelengh. Observed free-air
gravity anomalies in the Pacific Northwest do not indicate a gravitational
effect due to a descending slab.
Two hypothetical compensation models...
In order to quantitatively examine the crustal structure of the
Panama Basin without the benefit of local seismic refraction data, the
following assumptions were made: (1) No significant lateral changes
in density take place below a depth of 50 km. (2) The densities of the
crustal layers are those of...
Gravity and seismic data obtained by the geophysical group at
Oregon State University on the R/V YAQUINA during 1969, 1971, and
1973 plus other available data over the area just west of Nicaragua
and Costa Rica indicate the tectonic complexity of the region. Gravity
measurements show negative free-air anomalies over...
Gravity and magnetic data from cruises by the R/V Yaquina in 1973
and the R/V Wecoma in 1975 provide new data that make possible the construction of a map of the free-air gravity anomalies at sea and simple
Bouguer anomalies on lano in Panama, western Colombia, and the eastern
Panama...