The Dominion. FRIDAY, DECEMBER 27, 1907. ARE EARTHQUAKES' INCREASING?

Dominion, Volume 1, Issue 79, 27 December 1907, Page 4

The Dominion. FRIDAY, DECEMBER 27, 1907. ARE EARTHQUAKES' INCREASING?

!■.• : r-4 — : —- ■ ■■■/ ' It is probable that of late years many persons have asked themselves the question which constitutes the heading to this article. Owing to the non-existence of ' a historical earth-' quake catalogue from the very earliest times to the present, and including in its scope the whole world, this and similar queries cannot be answered by scientists. 'But Prof essor'John Milne, E.U.S., the noted seismic authority, considers that certain deductions can be drawn from the earthquake history of the best known parts of the .earth, and, of course, only, to apply to such parts. He says: "From observations at the', present time we know-that every year sixty world-shaking earthquakes are is to say); sudden yieldings_ take place in the process of rock-folding,: as, for example, ,in the. building of mountain ranges. The popular idea that this class' of,. earthquakes is on the increase is-simply, because. their origins have been in,: inhabited places. These repeated. shakings of the ground have often been regarded as a curse to humanity; but they may also be looked upon as blessings in disguise. Each' earthquake we feel.is.an announcement that rocky strata are being!;folded—that the ■'prustof our world is beha'ying like the bellow's of a' concertina : when' \ifc ■ is slowly closed." He goes "on to" show that if this process were not'in operation, as we know how many cubic miles of material stand above sea level, and how many cubic miles are carried by rivers and other agencies from land surfaces to be deposited in the sea, it would be easy to , calculate how many years it would take before every, land surface' would' be covered by the rising tides. But the "buckling crust," which is the earthquake, indicates that the world is not yet to be destroyed by inundation. In fact, the number of large or small earthquakes which occur every year is an index of the present vigour of our world's internal activity ; but about'the past our knowledge, says the Professor, is extremely vague. "We may say that about the time our coal seams (British) : were formed, which was many millions of years ago, and again in Miocene times, when a string of islands was probably joined up to form the Italian Peninsula, which was also some millions of years ago, the probability' is that earthquakes and volcanic 'eruptions were more frequent than they are at present." . ■ -. ■■ '-.-■'■ On the other hand Professor Milne states that if only tho?e earthquakes, are taken into account, which'have received historical record, because of : the great structural damage resulting, and attention,, is confined to, Europe and AVestern Asia, new results are reached in that a considerable increase in seismic activity up tp ; the present time is noticeable in certain areas. His own opinion is that this activity is always a fluctuating quantity. When, then, nations, or insurance companies, or individuals want to know the number of years that will elapse.before, a given district will again be devastated by earthquake, the Professor recommends a reference to the records of seismic activity in the , district in which special interest is taken. When this is done, in the case' of insurance companies, rates and risks may.be approximately apportioned. ' But much , will depend on local knowledge; a rate for one pprtion of a country might be absurdly high, and at the same time absurdly low for some other .part. Ratesi might even differ for different parts of a given city. In the case of a great country like Great Britain, having large financial interests in almost every portion of the world, the investigation of earthquake phenomena is almost a bounden duty. ■ The destruction of San Francisco necessitated British insurance companies meeting a bill of twelve million pounds sterling. It is no wonder that the shareholders would like to know if these earth convulsions are on.lhe increase, and if London will ever be shaken, and how many years will elapse before the next disaster takes place in California ? The only answer, however, that can bo giyen is that these seismic phenomena are fluctuating in their occurrence and recurrence; but that it were well to procure from every earthquake region—that is, from every known area subject to periodical seismic shocks— as detailed, a record of such shakes as can be procured, and going as far back, as is obtainable. From such record it may be that an average might be'struck affording some 'alight indication.as to probable periods safety and danger.