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His efforts paid off. evidence of success came with the investigation
of the Santa Monica earthquake of 1930. the study was a joint effort by
Wood, Richter, and Beno Gutenberg—europe's premier geophysicist, newly
arrived at Caltech. the researchers “obtained an unusually large number of
observations on the action of the shock.” Indeed, more than three hundred
noninstrumental reports were supplied by “private individuals, postmasters
and other public officials, and representatives of corporations, co-operating
with the Survey.” these reports were, in fact, “more numerous and more
suitably and adequately distributed over the area of perceptibility than ever
before for a shock in Southern California.” Despite this auspicious start,
a critical note soon crept into their article for the BSSA. the information
available did not match what “has been available on some occasions in
other parts of the world.” this allusion to european seismology hints that
the voice was now Gutenberg's. the critique continued: “little of the data
is precise enough or explicit enough to permit critical study. On the whole
very praiseworthy, necessarily in most instances the reports were not made
by trained or expert investigators, and in many instances it is difficult to
judge which of two grades of intensity is indicated.” these lines depart radi-
cally from Wood's positive assessment of the felt reports in his letter to
Byerly that February. they sound like the opinion of an observatory scientist
with little previous experience in the use of nonexpert observations. the rest
of the article vacillated over the significance of the noninstrumental data.
Intensity values showed “inconsistencies” when plotted against a CGS map
of the region that displayed relief and drainage. these were attributed in
part to “the experience and psychology of the observers.” It seemed fruitless
to plot isoseismals, given the complexity of this intensity distribution. At
the same time, however, the map was also said to demonstrate “important
peculiarities.” For instance, the “spotted” character of the intensity distribu-
tion was likely due to the brevity of the shaking, which may have subsided
before producing stronger effects on humans or structures; thus the accelera-
tion had perhaps been higher than the visible effects suggested. Meanwhile,
“tentative isoseismals” seemed to display an interference pattern—was this
a real effect or an artifact? the article struggled to account for it in physical
terms and ultimately flagged it as a question for the future. In all, the article
hinted at disagreements among its coauthors about what could and could
not be learned from felt reports. 170
Wood continued to press ahead with his recruitment of citizen-observers,
even when others were ready to admit defeat. After a conversation with an
acquaintance who owned a small country newspaper, he drew up a request
to editors to print reports of each weak local tremor. Wood was confident
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