QUAKE CAUSES

Hokitika Guardian, 8 July 1935, Page 8

QUAKE CAUSES

LOCALITY OF ORIGIN DEFINED. LONDON, June 30. The recent Formosa disaster provides strong support for the belief that, th-. world’s major eathquakes occur in two well-defined belts, corresponding with the greatest mountain chains, states a scientific correspondent of the Morning Post, London. One of these belts, Wihch sprawls across the whole width of Europe and Asia, has been credited with 53 per cent out of a world catalogue of 160,000 earthquakes. It follows the line represented by the Pyrenees, the Alps the Himalayas and Malaya.

The other, which, according to the same survey, contributes 38 per cent of the world’s earthquakes, stretches in a semi-circle round the Pacific. Following the line of the Andes and the Rocky Mountains up thp west coast ot America, it passes ;through Japan. Formosa and the Philippine Islands. It then curves back east, and south across the Pacific until it reaches New' Zealand.

Many of the mountains responsible for this Pacific zone are partly or wholly submerged.. Japan owes most of her earthquake troubles to the Tuscarorn deep, off its Pacific coast, which reaches almost as far below sea level as Mount Everest towers above it. Formosa is in slightly dangerous proximity to the Philippine deep From the top of Nutakapama, the highest point of the island, the ground level drops no less than 31,600 ft. within 16 i miles, and the steepest part of the slope is relatively near Formosa. The rase of Tongan and Reminder Islands, between Samoa, and New Zealand, is even more striking. Each of these smaller groups rises sharpb from ocean deeps of the same names The greatest depth is about 30,000 ft. in both cases. ,

The theory is that a state of strain inevitably’ results from the uprearing of any big mountain chain. From this point of view it is immaterial whether the mountains are wholly or partly beneath the sea.

As the great mass of the mountain* gradually settles, the strain increases, until at some point or other breaking point is reached. There is a flight slipping of two rock surfaces and.tin* earth over a wide area is shaken to and fro, as the ends of a long stick vibrate when the stick is broken in the mid die.

In delation to the damage done the earth movement may be surprisingly small. A. moA’-ement ot less than a thousandth of an inch can be felt; and the greatest up-and-down move ment which has’ever taken place was' one of only four inches in the Japanese earthquake in 1891. During the same earthquake, the side movement reached 14in.