QUAKE AREAS

Taranaki Daily News, 29 April 1931, Page 12

QUAKE AREAS

WORLD’S UNSTABLE BELT SCIENTIST’S REVIEW. MINIMISING DISASTERS. How the great earthquake belt of the world has been mapped by geologists, and the continual crumpling of the earth’s crust gradually brought under scientific observation, is told in the following article in the “Manchester Guardian” by Professor J. W. Gregory. He believes that the disastrous effects of earthquakes will be minimised in the future by the acquisition of greater knowledge of the changes in the earth’s surface.

In striking contrast to the four months’ seismic truce in the early part of 1930 has been the world-wide series of volcanic and earthquake disasters of the end of that year and still in progress. The middie and latter parts of last year were marked by a series of earthquakes which began in the East Indies and gradually spread westward through Burma, Northern India, Persia, and Southern Europe. This series continued to extend westward, and on January 11 caused the most violent earthquake experienced in Mexico since 1911. It overthrew the city of Oaxaca, with a loss of 40 lives.

It is significant that this disaster happened to the west of the isthmus of Tehuantepec, where the structural grain of Mexico runs west and east and the coast of Central America projects into the Pacific, owing doubtless to a former subsidence of the land to the south. This earthquake was preceded on January 2 by two submarine earthquakes under the Pacific about 1200 miles west of Oaxaca and in the same line. ' In Europe the disturbances on this o-reat east-to-west earthquake belt from Central America through the Mediterranean and across Southern Asia to the East Indian Archipelago, have been renewed by the serious earthquake at Corinth, by a shock on January 28 which destroyed 600 houses at Koritz in Albania, and by seven shocks on January 21 in Central Java. This succession of earthquakes shows that some stress on the earth’s crust is producing numerous fractures on the unstable o belt, which runs roughly parallel to the equator, and to the_ north of it all around the world. This belt lies across the Pacific from the East Indies, includes the huge volcanoes of the Hawaiian Islands, and passes through Southern Mexico, and the oft shaken West Indies and across Southern Europe and Asia. From this belt three other earthquake zenes branch off southward almost at right angles. One of these leaves the east-west belt at Hawaii and passes through the two remarkable submarine rift valleys known as the Tonga Deep and Kermadec Deep, and farther south on the same line is the eastern coast of New Zealand, which is constantly disturbed by small earthquakes and is bordered by a series of great volcanoes, some still active and others extinct, gome of the earthquakes along this coast are famous.

That of January 23, 1855, near Wellington, and along the shores of Cook Strait, which separates the two. larger of the New Zealand islands, is well known as one of the first in which an earthquake was proved to have been accompanied by a widespread uplift and tilting of the land. The official surveys demonstrated that an area about equal to Yorkshire had been uplifted from on© to nine feet. . This earthquake is the best known of those in New Zealand, as it happened near the capital, but many others along the eastern coast had been recorded. Sir Charles Lyell concluded that “in no country, perhaps, where the English language is spoken, have earthquakes . . . been so active in producing changes of geological interest as in New Zealand.” Many of the earthquakes are along fractures, and are due to the land” on the one side being moved horizontally. The extent of this movement has been often shown by the displacement of fences, which are snapped across and one side shifted several yards.. In some cases the movements produce long open fissures, such as one 60 miles long and 18 inches wide formed in 1848. VOLCANIC ERUPTIONS. That the long and relatively straight eastern coastline of New Zealand, from East Cape, at the north-eastern corner of the North Island, to Long Point, at the south-eastern corner of the South Island, is due to earth movements has long been recognised. This coast cuts across the grain of the rocks, showing that it has broken across the folds and the former eastward extension of the country. Along this line the most conspicuous projection, Banks Peninsula, beside Christchurch, is an extinct volcano. In the North Island the main volcanic eruptions have been to the west of the mountain chain behind the eastern coast. They have formed a triangular band of volcanic rocks that run inland from the Bay of Plenty past Rotorua, famous for its hot springs and geysers, and Tarawera, notorious for the explosion in 1886, which blew 11 P the exquisite pink and white terraces and left a ten-mile explosion rift under their site, and includes the basin of Lake Taupo. While the inner part of the North Island lias been the scene of longcontinued volcanic activity, the mountain chain between it and the Pacific has been affected by numerous earthquakes, due, no doubt, to the continuation of the processes by which the former eastward extension of the land has foundered beneath the Pacific. Along this line have occurred some of the most powerful of New Zealand’s earthquakes, such as the long series on the Kaikoura Hills, which McKay called attention to the lateral displacement of the land long before it had been established by the San Francisco earthquake. FOLLOWING THE, LINE. This eastern series is most pronounced along a line which passes from the East Cape down the eastern coast to Gisborne, where there was a serious earthquake in October, 1914. The line crosses Hawke’s Bay to Napier and then runs inland parallel to the coast between the coastal range and the main mountain axis of the North Island, which runs through the Raukumara range of the East Cape peninsula, the Huirau range behind Hawke's Bay, and the Ruahine range inland from Hastings to the Tararua range which projects into Cook Strait west of Pa Hiser Bay. The continuation of this line beyond Cook Strait passes the front of the Kaikoura Hills and the coast town of Cheviot, which had a fatal earthquake in November, 1901. | The recent shock was of world-shak-ino- severity, for it was recorded on the seismographs at Kew and West Bromwich. The seismograms at each showed that it originated at so great a distance that such strong disturbance of the instruments indicates a shock of the highest intensity. The fact that this

disaster can be correlated with the scries that has been happening along the West Indian-Mediteivauean-East Indian belt encourages the hope that with an increased number of earthquake recording stations it may be possible to follow the stresses which creep through the earth's crust along the earthquake zones, and thus recognise the danger spots. In this earthquake, aS in so many others, much of the damage has beei/ due to fires, which could not be checked, because of the breaking of the water-pipes. And though foreknowledge could not lessen the actual oscillation of the ground it could minimise the fatalities and devastation.