Surface Trace of the 1855 Earthquake
[Read before the Wellington Branch, October 9, 1934; received by the Editor, March 2, 1943; issued separately, September, 1943.]
The Wellington. (N.Z.) earthquake of the 23rd January, 1855, was described on the 16th June, 1856, to the Geological Society of France by Sir Charles Lyell, who got his information from conversing in London with three men who had been present in New Zealand at the earthquakes, Edward* Roberts, of the Royal Engineers, Walter Mantell, and Frederic A. Weld; and the account of the meeting was published in the Bull. Soc. Geol. France, August, 1857, expressly as a preliminary account. But Lyell never made his promised, more detailed report, though the later editions of his Principles of Geology contain a translation of the above. Mr Edm.* Roberts of the Royal Engineers contributed his account of the earthquake as appendix “F” of Richard Taylor's Te Ika a Maui (1855, pp. 471-2). Except for a short letter in the third Rep. Austral. Ass. Adv. Sci., 1891, from Mr S. Vennell of Tauherenikau and an article in Wairarapa Daily Times for 24th September, 1932, by Mr. B. Iorns, of Masterton, no further information has been published.† While doing the regional geology of Eketahuna Subdivision in 1933–4, the writer recognised the fault-trace and mapped it for 25 miles south of Mauriceville. Later, with Mr. C. Bannister, of Masterton, and Mr. B. Iorns, he followed the part that runs north of east from Mauriceville, and later again, directed by Mr. C. Benton, of Featherston, and Mr. Eglinton, of Palliser Bay, and accompanied by Dr. C. E. Adams and Dr. L. Bastings, he followed two other parts of the fault-trace. On the 1935 excursion of the Geological Section the Featherston and Palliser Bay parts were again examined, and in December, 1935, with the assistance of Mr. M. Gage, the fault-trace was followed from Mauriceville east and then north through Alfredton, across Makuri River to near Makuri Village, where it was lost, apparently through its dying out.
As little is known of the earthquake, and as Taylor's book and Lyell's publications have long been out of print, Roberts's account in the former is here quoted:–
“The shock was of the greatest violence in the narrowest part of Cook's Straits, a few miles to the S.E. of Port Nicholson; but it was felt over the whole of the islands and by ships at sea 150 miles away from the coast; the whole extent of the area over which the convulsion was felt must have been 360,000 square miles.
“Its effects were most violent in the immediate vicinity of Wellington, where a tract of land of 4,600 square miles in extent was elevated to a height varying from one to nine feet, the greatest elevation being a range of hills called the Rimutaka (a spur from the Tararua Mountains), which terminates abruptly at the sea coast in Cook's Straits.
[Footnote] * One report gives Edward, the other gives Edm.; probably Edm. should be Edw.
[Footnote] * One report gives Edward, the other gives Edm.; probably Edm. should be Edw.
[Footnote] † J. C. Crawford described some of these 1855 earthquake features in 1870, Trans. N.Z. Inst., vol. 2, p. 345.
“This range, which appears to be have been in the direct line of the subterranean action, was elevated nine feet, while the whole country as far as Wai-nui, about two miles northward of the foot of the road leading down the Pari-pari, was elevated with it, though the elevation at the last named point was on the sea coast very slight. On the eastern side of the range is the valley of the Wairarapa, the centre of which is occupied by a lake. This valley and plain remain on the same level as before, the range of hills having gone up along a perpendicular precipice of nine feet in height, which has been traced to a distance of ninety miles inland.
“The valley of the Wai-rau, on the middle island (which appears to have formed part of a continuous basin with the Wairarapa), together with parts of the adjoining coast, subsided, during the shock, about five feet; so that now the tide flows eight miles further into the Wai-rau River than it formerly did.
“The harbour of Port Nicholson, together with the valley of the Hutt, is elevated from four to five feet, the greater elevation being on the eastern side of the harbour, and the lesser on the western.
“A rock, known as the ‘Ballet Rock,‘a short distance from one of the points of Evan's Bay, which was formerly two feet under water at the lowest tides, and over which was placed a buoy to mark its position, is now nearly three feet above the surface at low water.
“Very little tide now enters the Hutt River, in consequence of the elevation.
“The Rimutaka Range was very much shaken in its elevation, and a great many large slips occurred, laying bare the western side as well as on the eastern.
“In the lower part of the valley of the Hutt, numerous hillocks of sand were thrown up, forming cones, varying from two to four feet in height, and in many parts of the valley large fissures were formed, with partial subsidences in many places. In the plains of the Manawatu this was the case to a much greater degree.
“In places soft mud and slime were ejected, but this appeared more a mechanical effect than anything else, the liquid mud having pre-existed and been forced out at fissures formed during the vibration by superincumbent masses of more solid material.
“Upon the whole the province of Wellington will gain considerable advantage from the earthquake:–
“(1) Large portions of land can be easily reclaimed from the harbour for the extension of the town.
“(2) The main road to the Hutt and the interior formerly suffered occasionally from the action of the waves during high winds, and many parts had to be retained by a sea-wall; now it will escape the damage of the one and the expense of the other, and the whole of that valuable valley will be rendered, if possible, more healthy from greater facility of drainage arising from the elevation.
“(3) A much better coast road to the eastward is already formed for the temporary use of the colonists and the driving of cattle.”
In Lyell's report, nothing was added by Roberts to what he wrote to Taylor, but Lyell was told by one of his three informants that the quake was at half past nine in the evening. Weld supplied information about the Cape Campbell-Wairau Valley region, and Mantell added some points as follows:
“La masse soulevée consiste, d'après M. Walter Mantell, en argillite ancienne, non stratifiée, ayant la composition ordinaire du schiste argileux, mais sans présenter de schistosité. Cette roche forme, du côté de la mer, une falaise de plusiers centaines de pieds de hauteur, tandis que les couches marines tertiaires, qui sont à jour à l'est, le long de la éôté, forment une autre falaise, relativement basse, qui ne dépasse pas 80 pieds en hauteur. Ces couches tertiaires n'ont été nullement soulevées.…”
“La ligne de jonction des roches anciennes et plus modernes que nous avons décrites plus haut est marquée, dans l'intérieur de la contrée, par un escarpement continu qui suit la direction N–S tout le long des collines Rimutaka, dont le flanc est escarpé du côté oriental et domine la plaine de Wairarapa, formée de dépôts tertiaires. La direction de la faille produite par le soulèvement a été rendue visible par la formation d'un mur presque vertical qui porte la trace d'une récent rupture à 9 pieds de hauteur, et peut ětre suivi dans l'intérieur des terres sur l'étonnante longueur de 90 milles, suivant la témoignage de M. Borlase, colon qui habite la vallée Wairarapa, à peu près à 60 milles an N. dè détroit de Cook. La faille est, néanmoins, marquée en beaucoup d'endroits par une fissure ouverte dans laquelle les bestiaux sont venus tomber, sans qu'on ait pu, dans certains cas, les en retirer: quelquefois ces fissures, de 6 à 9 pieds de largeur, sont remplies çà et là de boue et de terre meuble.
These graphic accounts have all the freshness of the recent experience on which they were based, and naturally contain some mistakes. Mukamuka is referred to as being at the north-west corner of Palliser Bay, but is two miles south of the bay-head down the west side. Moreover, neither at Mukamuka nor at the north-west corner of the bay is there any fault between different formations as described and figured by Lyell. This fault is not along the west side of the bay and not along the flank of the mountains, but three-quarters of a mile east across the bay, where the west side is dark indurated crusted greywacke and argillite, probably Palaeozoic, and the east side is light loose river conglomerate, probably Pleistocene. And again, this fault is not on the line of the 1855 earthquake fault-trace; but lies well east of it. The 1855 scarplet, it is true, does not actually extend to the coast; it can be followed south definitely to a point a mile from the coast, where it appears as in Fig. 1. Thence south, it is not traceable on either side of Wharekauhau Stream; but on the spur south of that, it appears as a fault wedge with two breaks on each side as shown in Fig. 2. South of that no scarp could be found; but the line of it runs to the coast well west of the fault between the two formations. Accordingly Lyell's diagram in his Principles of Geology, tenth edition, vol. 2, p. 85, which he cautioned readers was merely explanatory of information received, does not represent the 1855 earthquake fault.
Again, Lyell described the fault as vertical, heading up to a fissure between horizontal beds forming a cliff 80 ft. high on the east and the old argillite several hundred feet high on the west. The fault between the formations is a low angle thrust, dipping less than 30°, and the lowest cliffs are not 80 ft. but 250 ft. high; and the 1855 movement was not on this fault.
Lyell described the earthquake fissure as running north along the east face of the Rimutakas for 90 miles. The fissure is, broadly speaking, at the base of the mountains; but in many places it is out in the lowlands to the east. It runs 25° east of north not for 90 but for 60 miles, thence nearly east for 3 miles, 25° east of north for 17 miles and nearly east for 3 miles, where it joins the Mangatoro fault that trends 30° east of north for 20 miles and extends along faulted country to Hawke's Bay 75 miles to the north.
The letter of Mr. S. Vennell, of Tauherenikau, Wairarapa, published in 1891 in the third Rep. Austral. Ass. Adv. Sc., added a little information. He mentioned earthquakes occurring in 1834 or 1835 near Auckland, two, in 1840 and 1848, which he experienced himself, and “the most fearful of all” in 1855. It should be noted that he did not mention one in 1832. He recorded that the Wairarapa alluvium opened and closed along fissures and parts of it sank and that “the mountain near Masterton was literally rent in twain and remains to be seen this day,” “and the whole of the country was upheayed many feet.” This last statement is directly contradicted by the evidence of Roberts, that Wairarapa was not uplifted at all. The mountain described as “rent in twain” is Mount McLeod, nine miles north of Masterton, the first mountain that rises to the north of the Wairarapa Plain. It is undercut on its west side by the Ruamahanga River in a steep, high cliff. Part of this cliff broke away and slipped into the river, leaving a pond in the depression behind it as shown in the photo. No. 3. This is not a fault feature, but a land-slide initiated by the quake. It is not on the fault, but half a mile west of it.
This information of Mr. Vennell's was not known to Mr. Iorns when he published in the Wairarapa Daily Times for Sept. 24th, 1932, his account of the Wairarapa earthquake crack, which differs in several points from Mr. Vennell's., Mr. Iorns wrote, “Perhaps the most noticeable result of the shake was a fault or crack along the whole of the western side of the Wairarapa Valley.… Bruce's Lake, north of Masterton, was a result of the same shake.” Bruce's Lake is the one behind the slip in Mount McLeod, “the mountain rent in twain” described by Mr. Vennell, so Mr. Iorns and Mr. Vennell were describing the same earthquake; but, whereas Mr. Vennell, from personal experience, placed it in 1855, Mr Iorns, from information derived from the Maoris, placed it in 1832. Also, as Roberts had informed Lyell that this erack was formed in 1855, and as he was making a road round the coast at the time and had his work rendered unnecessary by the uplift, there seems no doubt that it was formed in 1855.
Mr. Iorns described the run of the fault trace from Mauriceville for 25 miles to the south by giving the names of the owners of the properties it crosses and supplied many details of its exact location.
Although the fault-trace has not been followed from end to end, it has been followed so far and picked up at so many other points that there is little doubt that it is continuous. At Palliser Bay it cannot be recognised at the actual coast line. Followed from the north it was plain to within a mile of the coast, as shown in Fig. 1, recognisable in the first spur south of Wharekauhau Stream, and not evident south of that. From Featherston north to Mauriceville it is well marked out to the east of the eastward-trending piece. There it was lost and picked up again north of the Mangamahoe Road, trending again N. 70° E. This stretch is gapped northward to Alfredton, where it is again strongly marked for five miles to beyond Tiraumea River. Thence it is not traceable for two miles, but again for the next half mile it is marked by a 3 ft. step. The next three miles shows no evidence of movement, but beyond that it is marked very strongly trending N. 70° E. for two miles and a half by a trench a chain wide and 20 ft. deep. Beyond this it was not found in several visits to Makuri-iti Stream. Here the Mangatoro Fault runs between the Te Aute limestone dip-slope on the toe of Puketoi Range on the east and the Jurassic greywacke scarp of the Waewaepa Range on the west; but no late movement was detected along this fault.
The trace of the fault differs from place to place and is not always definite, and besides the fault-trace, there are other features caused by the earthquake, such as land-slips and cracks, which are not along the fault. The principal evidence is to be seen in the trenches and steps that run straight for miles across hills and plains. From the way they join successive terraces it is evident that they are but the latest of many movements along the fault; and, of course, they are modified by erosion, in some cases so much so that it is difficult to say how much is due to the fault. In almost all places the surface is broken by a trench that interrupts the continuous slope in such a way that the downhill part is raised up forming a ridge with a notch above it. The figures show some of them. North of Makuri Gorge, for example, as shown in Fig. 4, the trench for a mile is from half a chain to a chain wide, and the ridge on the west and down-hill side is 20–30 ft. high; south-east of Alfredton in places the trench is a chain wide and the ridge on the west, the down-hill side, is up 10 ft. It is doubtful if the height of these ridges on the hills gives the measure of the movement. On the flats there are fewer disturbing factors. One of the best marked steps crosses the golf links at Alfredton, where the east side is up 6 ft. A mile to the north of this, west of the road, as shown in Fig. 5, the west side is up 6 ft. to 10 ft. These are on river flats; and though perhaps reduced by erosion evidently indicate the direction and amount of movement. On similar river terraces the movement is indicated, at Waiohine River 3–6 ft., at Mangatariri 6 ft., at Waingawa River 6–10 ft., at Waipoua River 4 ft., near Alfredton 6–12 ft., Tiraumea River 10 ft. The west side is up at all these points except Tiraumea River and the one at Alfredton.
In many places repeated movements along the fault are indicated by several terraces being cliffed by it. At Waiohine River, Fig. 6, for instance, the flat has a step in it 3 ft. high; and as this is followed
Fig. 3. Bruce's Lagoon, dammed behind a slip caused by the 1855 earthquake shaking down a high cliff underout by Ruamahanga River at the north of the [ unclear: ] Plain–the hill “rent in twann” mentioned by Mr. S. Vennell.
Fig. 7 View north of Warpona River at Mikimuki Road [ unclear: ] The 1855 earthquake formed the lower (5 ft) scarp the higher (40 ft) scarp marks an earlier earthquake Photo J. Morwah
Fig. 11 Looking south along the trace of the 1855 earthquake fault from near Warngawa River at Russell Trig, five miles west of Masterton. The fault has not hindered farming and development.
north away from the river it is joined by several terraces that trend south-east parallel with the river till they meet the fault trace which truncates them and steps up each terrace. The same thing can be seen at the Waipoua River, Fig. 7, where the 40 ft. step on the main road turns upstream 10 chains from the river as a 35 ft. terrace and leaves only a 5 ft. step trending along the fault on the lower flat.
In many places where the step along the fault is high, it can be seen to be composite, consisting of a fresher break about 6 ft. and older breaks forming a grassed step 20–50 ft. high. Examples of this can be seen in the north-west part of Tiffin Survey District a few miles west of Masterton, where the step is crossed by Dalefield, Jervois, and Joseph's Roads. Repeated movements along this fault connect the 1855 earthquake with the great structural fault running along the east of the Waewaepa Range.
Good examples of the breaks in the slope, the trenches and the ridges, are shown in the district west of Carterton, about five miles from town. Fig. 9 is a typical one and shows how the features vary, make, and die out. Fig. 10 shows similar features and also aligns the recent small movement with larger ones.
Perhaps the most interesting photo is Fig. 11, which not only shows the scarplet plainly but indicates that it provides no obstacle to settlement, roading, building, farming and general progress. No doubt earthquake architecture is called for; but that raises no great difficulty.
Mr. Benton, of Featherston, who pointed out the fault-trace at Featherston and told of it at Alfredton, has reported that another fresh fault trends north from the Tiraumea River six miles east of Alfredton towards Pongaroa; but so far this report has not be verified.
From the air, Mr. Pritchard, of the Public Works Department, located, besides other features, a line of swamps, ponds, depressions and ridges diverging from the main 1855 scarplet near Woodside and trending north-east through Clareville, near Carterton.
Apart from the fault trace other movements are indicated by land slides and cracked hills. The largest slip was the one on the north bank of Ruamahanga River at Mount McLeod, and the next on the north slope of a low hill in the north-west part of Puketoi S.D. half a mile east of Tiraumea River, where some 20 acres can be seen cracked into strips and moved down the slope in a set of steps. These do not indicate the measure of the shock but the readiness of the country to slip. In some places the hillside did not slip but opened along cracks. The best example of this is in the north-west part of Tiffin S.D., half a mile north of Carterton Bush. Trig. on the farm of Mr. T. Anderson, at Carrington, near Carterton. As shown in Fig. 12, the hill is trenched along three main cracks between the crest of the hill on the east and the earthquake fault-trace near the trees low down the slope.
The course of the fault trace is shown on the map. In all but two places the west side has been raised 3 ft. to 10 ft. and in two places the east side has been raised 6 ft. to 10 ft. In many places the latest movement is seen to be a repetition of earlier movements; and at the north the trace runs into the old fault, where the beds have moved thousands of feet.