United States Earthquakes, 1933 Page: 76
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COAST AND GEODETIC SURVEY
granite surface of the fault block slopes northward due to the tilting
of the block between the bounding faults. The water table is about
100 feet below the surface.
Strong-motion seismograph in subbasement and on twenty-eighth floor
The Shell Building is on the northwest corner of Battery and Bush
Streets. It is 29 stories high, constructed of reinforced concrete
throughout with some terra cotta facing and is about 68 feet square
at the twenty-eighth floor. The foundation is built on caissons ex-
tending approximately 140 feet beneath the subbasement to bedrock.
The southeast caisson is deeper than the others due to sloping of the
bedrock in that direction.
The material immediately beneath the building is unconsolidated
material, probably estuarine deposits and fill. The nature of the
underlying rock, at one hundred and forty or so feet in depth, is
unknown, though it perhaps is the same as that constituting the
exposed rock in the city. See report on the Southern Pacific Building
for regional geology.
SOUTHERN PACIFIC BUILDING
Accelerograph, displacement meter, and strong-motion seismograph in basement; also
strong-motion seismograph on twenty-eighth floor
The building is on Market Street between Steuart and Spear Streets,
facing northwest. The building is 10 stories high. The construction
is concrete built about steel framework with brick facing throughout.
It is E-shaped with long outer wings, and inside wing extending
several stories above the other sections. The ground floor is 275 by
210 feet. The foundation is built on piles driven into water-soaked
sediments. The piling extends to a depth at which driving became
difficult at the time but not necessarily to firm ground. The deepest
pile is about 110 feet; the average, about 90 feet. The main in-
strument room is in the basement beneath the ticket office. The
auxiliary station is in the blue print room on the eleventh floor of the
The earthquake geology of the San Francisco peninsula is described
by Dr. H. O. Wood in Bulletin VI of the National Research Council
on Physics of the Earth Series, and the general geology by Andrew
Lawson in the United States Geological Survey, folio 193. The bulk
of the bedrock belongs to the Franciscan series assigned to the Jurassic.
The series contains cherts interbedded with sandstones and intruded
by serpentines. The strip of land traversed by lower Market Street
and including the Southern Pacific Building is largely man-made fill.
In the early days the bay extended to the foot of Montgomery Street
which includes the present site of the Shell Building.
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United States Earthquakes, 1933, report, 1933; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc40326/m1/79/: accessed December 15, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.