EARTHQUAKES AND TIDES.

New Zealand Herald, Volume LXIII, Issue 19218, 6 January 1926, Page 7

EARTHQUAKES AND TIDES.

Sir, —Many years ago tho late Mr. ,T. T. Stevenson F.R.A.3. had a theory that wlien tho moon was nearest to the earth on the same day as new moon, earthquakes were highly probablo, as at new moon the sun and moon rise together and thus have a combined attraction on the same side of tho earth. For instance, Mr. Stevenson calculated the great Messina earthquake to within two days by this method. Tho nearest approach of tho mnon to tho earth is kno%vn in astronomy as tho perigee, and the greatest distance as the moon's apogee. The nearest point is given by Neison as 221,614 miles; tho greatest 252,972 miles, with a mean distance of 238,840 miles. It is not generally known that tho sun is 3,112,410 miles nearer to us every year on January 2, than on July 4 or 5, when it in at its extreme distance. This nearest approach of the earth to the sun every January 2 is known as the "Earth in Perihelion." Our distance on July 4 or 5 is called tho "Earth in Aphelion." On January 2 the sun is 91,240,745 miles distant; on July 4, 94,353,155 miles distant, while its mean distance is given as 92,796,950 miles. In January this year tho moon's perigee is only 17 hours after new moon, which occurs on January 14. In February tho moon's perigeo occurs less than five hours before new moon, which is on February 13. In March perigee occurs 27 hours 50 minutes beforo new moon, which is on. March 14. In April the difference begins to widen, perigee being 2 days 10 hours beforo new moon. Con-, ditions will be favourable for very high tides indeed, especially during January and February this year, as spirng tides are known to he about 20 per cent, higher if perigee occurs close to new moon. The conditions will also be most favourable for earthquakes, too. as the sun is only just beginning to recede from its nearest point. The sun s tide is equal to about five-elevenths of the moon's tide, but the sun alone shonjd raise a higher tide in January than My on account of its nearness. The* » W* ; n il, P ™»r ii the .indh fa " °H °Z Jnlncmsc »'b°nt f "<" responds to an .ncrrnse , i» »iso, ft. for' Auckland City in March, 1318, ow»S £ • , y Wraffio predi'cW *r»t mn.prts i oat .v ie( j closer to the sun than ''for Vbout 109 ~ years, that these condirions would be more favourable stll. the mi <* » n V h ° T/ men cement if 1926. According to Mr. «tevenson's theory severe earttoquanes ' should be highly probablo about new moon this month and next, and probacy in March and April to a lesser extent. Although the greatest earthquakes appear to have occurred in other months, the most favourable time would _ appear to be on January 2, if the perigee of the moon and new moon fell on that day. At | least the tides will be very high indeed j when this does occur. Stanley Si^-claire.