TIDAL DYNAMICS
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By

Fergus J. Wood, Phd

(Review by Jim Berkland, MS)



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In this master work, Dr. Fergus Wood has combined his knowledge of oceanography, geophysics, astronomy, meteorology, and history to add a brilliant star to the firmament of scientific knowledge. In his position as Research Associate, Office of the Director, National Ocean Survey, this immense contribution was originally entitled, THE STRATEGIC ROLE OF PERIGEAN SPRING TIDES IN NAUTICAL HISTORY AND NORTH AMERICAN COASTAL FLOODING, 1635-1976, and was published by NOAA in 1978.
I wore out my original soft-cover copy from constant use, and am now working on the second edition.
In the forward by the Deputy Director of the National Ocean Survey, Gordon Lill commented: "As a research geophysicist, he has approached cautiously another aspect of the perigean spring situation--how it affects the solid earth. The same forces responsible for perigean spring tides in the ocean also create enhanced earth tides, the results of which are obscure. In the present state of knowledge, there seems to be no satisfactorily provable connection, for example, between perigean spring tides, earth tides and seismic events. But curious and openminded geophysicists are beginning to examine the connections, if any, between earth tides and earth movements, especially microseismic swarms. Perhaps this book will encourage them to look carefully at what, if anything, occurred in the solid earth on past occasions of perigean spring tides, notably of the ‘proxigean’ type..." (my emphasis...JOB)
I have been informed by senior members of the U.S. Geological Survey that Fergus Wood sent a copy of his book to the Survey with a plea to follow up on the possible tide/quake connnection. I was also informed that the Survey had essentially sat on these data until 1990, while I had been pursuing my own original investigations since 1974. Ironically, I had twice written to Dr. Wood prior to 1981 about certain complexities in his work and he had responded promptly and thoroughly to my concerns in an even-handed manner.Here I want to emphasize a particular aspect of his tables, which show a 600-year record of perigean spring tides betwen 1600-2200 AD. It is important to note that some years only contain two perigean spring tides, where a syzygy (new or full Moon) occurs on the same day as a perigee (closest monthly approach of the Moon to the Earth.) This relatively rare event takes place no more than five times per year during the 600 years tabulated. On pages 201-203, Wood points out that during those six centuries, the greatest tidal force exerted on the Earth by the Sun and Moon was January 4, 1912. On that date the Earth-Sun distance was at a minimum (perihelion); the moment of the Full Moon was only 6.5 minutes away from an extreme minimum perigee (a time separation I call "synchroneity"). Also it was also only two weeks after the heightened tidal effects of the winter solstice.
When I became aware of these extreme astronomical forces exerted upon the Earth on January 4, 1912, I naturally became curious as to what happened seismically around that time, during an ultimate Seismic Window. I turned to the listing of U.S. earthquakes, also published by the Department of the Interior, (EARTHQUAKE HISTORY OF THE UNITED STATES, Publication 41-1, Rev. Edition through 1970)
Only two quakes are listed for California/Nevada during 1912-1913. The strongest in those two years hit near the California-Nevada border, close to Bishop. It was felt at least 140 miles away at Bakersfield. No quake of anywhere near that strength was felt during 1912-1913 in Washington or Oregon.
Thus the strongest quake on the West Coast during 1912-1913 was the Bishop quake (about 5.5M), which occurred on January 4, 1912, the day of the maximum tidal forces in six centuries. I was told by my friends at the USGS that this was a mere coincidence. If that correlation is a coincidence, what IS corroborative evidence?

Jim Berkland, Geologist

13037

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