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ABSTRACT
A 1959 March Scientific American article titled "Long earthquake waves",
contains the following statement: "Though experimental data are scanty,
the earth's free oscillations have intrigued mathematicians since the early 19th century. As a result, a considerable body of theory is ready
for the test of observation when that becomes possible." Data to assist the indicated theory have remained scanty for the four
decades since this article was written. Although long-lived, but infrequent eigenmodes of the free earth have been studied and
catalogued since then; the much more common short-lived modes remained without
notice until studies with an instrument invented by Dr. Peters (http://physics.mercer.edu/petepag/pend.htm#tiltmeter). The tiltmeter
which uses his patented symmetric differential capacitive (SDC) sensor is less an accelerometer and more of an earth shape sensor than the
conventional geoscience instrument. By monitoring the tiltmeter simultaneously with an SDC modified vertical seismometer
(WWSN Sprengnether), interesting new earth motions have been discovered just
in the month since these studies started (http://physics.mercer.edu/earthwaves/instr.html). A description of the
instrument will be provided, including the contrast between it and conventional instruments; and some results will be provided--including
material to be presented at the fall 2000 American Geophysical Union conference under the title: "Autocorrelation analysis of data from a
novel tiltmeter". |