Geoscience Reference
In-Depth Information
he was known to tell students, “an epicenter is a cross placed on a map
by a seismologist.”
161
Much as phenomenalism did for Mach (chapter 7),
for Byerly pragmatism collapsed the Kantian tension between the quest for
physical knowledge of the environment and the need for reflexive, critical
evaluation. Byerly's suspicion of claims to absolute truth made him toler-
ant of the uncertainties of macroseismic evidence. All his life he was a firm
believer in the value of felt reports.
Yet Byerly was discouraged by the results of his surveys. In 1930 he ad-
mitted to Wood that he was compelled to use an intensity scale with no
more than ten degrees: “from the kind of data which I get I cannot make
distinctions even as nice as the Rossi-Forel scale requires.”
162
By 1934, he
was forced to admit publicly that his analysis of a northern California
earthquake suffered from incomplete data. “the lists show that of the earth-
quakes recorded at more than one station 75 were not reported felt and
21 were reported felt. It seems certain that many of the 75 must have been
felt but were not reported. Also the fact that only two shocks of maximum
intensity I to III R-F were reported shows that observers are likely to allow
slight shocks to pass unnoted.”
163
By contrast, Wood expressed satisfaction with the observations he was
able to gather from the public in Southern California. “On the whole,” he
wrote to Byerly in 1930, “I think that this report form is working exceed-
ingly well, especially in respect to the percentage of replies received. If we
could receive reports from any adequate number of real enthusiasts, I would
prefer my own old more complete form, but I recognize the impracticabil-
ity of using this under present conditions or any likely to be encountered
for some time to come.”
164
Wood was learning what he could expect of the
local population.
Wood's papers at Caltech include a sampling of felt reports from this
period. Most observers simply crossed out or underlined the pertinent items
from Wood's list of common effects. But some added further descriptions,
along the lines of Wood's samples in his 1924 article. thus a Miss elizabeth
Connor sought to describe the course of the shaking more precisely than
the checklist allowed: “Following the first severe shock, when the observer
was out of doors, the earth seemed sometimes to heave, at other times to
jerk with a sideways motion. During the rest of the day, in the lighter shocks
which came at intervals, the earth seemed to tremble.” Another observer
added an unusual analogy: “P.S. earthquake similar to a large bird flying
into aerial of radio fastened to house. the same kind of vibration and jerk.”
the most consistent reporter was Mrs. Muriel Sweet of Pasadena, who had
been a member of the SSA since 1921.
165
She sent Wood a total of seven let-
