EARTHQUAKE AREAS.

New Zealand Herald, Volume LXVI, Issue 20309, 17 July 1929, Page 8

EARTHQUAKE AREAS.

GREAT FAULT LINES.

NELSON TO WESTPORT,

MATAKITAKI AND MARUIA.

BY N. D. COCHRANE. No. I. Long beforo the white man settler] in New Zealand the Maoris had noted and could point out the line of weakness in the earth's crust extending more or less south-west from White Island to Tonga* riro—a striking tribute to the observant character and sagacity of our noble native race. But that line of weakness was quite distinct from the earthquake happenings we have had of late. Tbe.se latter, as has already been pointed out by Professors Park, Bartrum and Speight, are more connected with the earth movements on the great fault lines, and are not the effect of volcanic action. These fault lines of great magnitude run, however, more or less in the same lino throughout tho middle portions and tlio West Coast of the South Island of New Zealand. < The extent of such faults may be only 100 yds., or they may extend 100 miles and over, and their displacement from next to nothing to several thousands of feet. One, such great dislocation runs through the city of Wellington. Standing oil the roof of the house of the late Alexander McKay, Government geologist, some 25 years ago, he pointed out to me, along the base of the hill, the line of tlio fissure which occurred in one of the two great earthquakes of early days in Wellington— 1848 and 1855. The line was still clearly to be seen running from the diieclion of tho late Dr. McGregor's house along the base of the hill to Petone, and, no doubt, if not obscured by the buildings can still be seen. It was said that one side of Jhe fissure was elevated nine feet by the earthquake, and during (no night depressed for some five feet, leaving a diffeience of four feet, though I have seen that stated lately as only two feet. This displacement by the gradual weathering will now be much less marked than it has been. At the same time, at road used for driving cattle to the \\airarapa, round the harbour was being raised to avoid its being blocked at times of high tides, but the same earth forces so elevated it that the work was not gone on with. Coal Seam Displaced. The question was only dealt with bv Professor Cotton a few years ago. These faults extend right across Cook btiait the South Island. One large one traverses Nelson, and the side of tho Waimea Plains; another is found m the Clarence Valley in Marlborough; others run down the West Coast, mostly more or less parallel but with many cross faults or dislocations. In Westport, in particular, the coalmine situated on the hill at Denniston at a-n elevation of 2000 ft has the coil seain displaced outside the ,„t Company s ground .lon* w..h. to oilier rocks; and it occurs agan 2000 liplow at Waimangaroa. with the co. taTmmo ov less ™d involved m tlTta.lt, and still dij.pi.ig rt~P'y '<«• ncatll tlio low level of tlio raiklkls. At Reefton. great faults occur, and nes Grevmouth there is one faultthat , s said to be between 4000 ft, and 5000 ft..in displacement. Whether this great displacement has had any effect in lessening the disturbance by relief of strain in that district, it is too early to say. Dredges in State of Decay. The town of Nelson used to be frequently shaken by earthquakes in the early days, and many years ago the question of building in brick was consl^ but thought not advisaole in case of the rpturn of the tremors of the eaily dajs. Matakitaki, to the southward, stands in a fairly open little pain at the confluence of the Matakitaki and Buller Rivers. Proceeding up the Matakitaki Valley for a few miles, the valley narrows in with small but beautiful alluvial flats, and a quarter of a century aRO , •,! remains of dredges which had been built and operated at the time of the dredging boom were clearly to be seen in a state of decay. They had worked some, little time, but the results were not sufficient to warrant continuation, although it, was contemplated at one time to dredge away the river flats. Further up tho river and tributaries, alluvial mining has gone on in the past, at some places quite extensively, but all the easily-got gold for regular individual mining ahs been won, and any deposits remaining are in such positions or elevations that even although payable for sluicing, with large quantities of water, the cost would bo too great under present conditions. Still further up the valley wo come to the Mammoth Hotel, famed for the laudlordships of May and O'Rourke. (^' 10 former was the "king" of the "lost tribe§." Further on still, the road ascends the Maruia Saddle, a sidling cutting, and descends on tho other side to the Maruia Plain, but before this the Matakitaki branches off to tho east, and near its source, among the very high and precipitous mountains, I have been told, more than once, of strange "boomings" « rarely heard. If&answer to my queries, the possibility of thunder or great distant landslides were not considered the cause, but rather earthquake rumblings. Why not stay and investigate? In those days, times were hard and strenuous, the work in hand requiring every minute.

Swampy and Alluvial Ground. The Maruia Plain, far beyond the region of the lost tribes, extends in a beautiful valley, a considerable height above the Maruia River, and some miles right ahead are tho hot water springs which, no doubt, will come into much greater prominence at some future date. From Murchison to Lyell the road rtiris along the side of tho rugged and beautiful Buller Gorge, with an occasional alluvial flat. Lyell itself is built on the steep road sidling above Lyell Creek. Soino four miles beyond it tho former United Alpine mine was situated, and for many years paid handsome dividends. Tho country is exceedingly steep, and ono has almost to hold on in going down the cut steps to some of the smaller mines, which worked leaders 3in. or 4in. in thickness, but which paid the individual owners well, with a return of about 13 ounces to the ton. From this, onward to the luangaluia Junction, tho gorge, after passing tho bridge, opens out. Nevertheless, that seems to have been the site of great disturbances. From Inangahua to Westport tho road runs along the side of the famous Buller one of the most beautiful gorges in the world. It crosses the Buller at tho nine-mile, and runs along tho alluvial flats to Westport, tho scene of the sovere disturbances of late. It can be taken for granted that as Westport stands on swampy and aliuvial ground, it would suffer from earthquake movements severely.