The mean monthly numbers follow approximately the mean annual variation of atmospheric pressure in New Zealand. The total number of earthquakes reported felt in New Zealand, and the maximum intensities reported in each of the years to inclusive, were as follows:—. The figures in the above table, giving the number of reported earthquakes, require careful interpretation.
In years of major earthquakes, such as and , many of the numerous after-shocks are liable to be passed unnoticed, while during a period of quiescence there is a tendency for all shocks, however slight, to be reported. This leads to an undue emphasis being placed upon earthquake activity during a comparatively quiet period.
The great number of earthquakes reported in is due to the swarm of local shocks which occurred in the Taupo region in the latter half of that year.
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Also, although there was no major earthquake in , a large number of shocks occurred in that year, due mainly to the continuation of after-shocks of the Buller earthquake of 17th June, During the period the number of deaths recorded in New Zealand as due directly or indirectly to earthquakes was Of these, were due to the Hawke's Bay earthquake of 3rd February, A table giving details of the number of deaths due to earthquakes in New Zealand was published in the issue of the Year-Book.
Earthquakes in New Zealand are recorded by means of seismographs, and also by a system of non-instrumental reports. The main seismograph stations are located at the Dominion Observatory, Wellington, and the Magnetic Observatory, Christchurch. The Dominion Observatory acts as a central station for ten other subsidiary stations in New Zealand and one at the Chatham Islands. The subsidiary stations are operated by officers of other Government Departments, by Engineers of some of the Electric-power Boards, and by private individuals.
The station at Apia, Samoa, is under the direct control of Apia Observatory. The system of non-instrumental earthquake reports was inaugurated in At first it was confined to a selected number of telegraph-offices distributed throughout the Dominion, but in recent years more telegraph-offices have been added, and a number of lighthouse-keepers and several private observers have also taken up the work. There are at present non-instrumental reporting stations.
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This system of recording earthquakes depends entirely on personal observations. Special forms are used, on which information is required concerning the observed time of an earthquake, the direction and duration of the movement, and any other particulars likely to be of value in estimating its intensity.
The Dominion Observatory collects and summarizes all such reports of earthquakes felt in New Zealand. Information regarding earthquakes obtained from the seismograph records of all the New Zealand stations, and from the reports furnished by non-instrumental stations, is published in a monthly seismological bulletin.
This bulletin includes provisional earthquake epicentres in New Zealand and in the south-west Pacific generally. The New Zealand epicentres are determined solely from the records and reports of the New Zealand stations, while the determination of those in other parts of the south-west Pacific requires the use of additional data from Apia, Papeete, and the Australian seismograph stations. The Dominion Observatory also publishes special bulletins dealing with the results of research work in seismology. All seismological publications are distributed to the chief seismological stations and institutions throughout the world.
Seismic activity in New Zealand in was notable chiefly for a series of rather severe earthquakes towards the close of the year. Although the number of shocks felt was less than in , the maximum intensity reported R. The activity in may be summarized as follows:—. Occasional small shocks felt at Whakatane.
These may be due to volcanological activity on or near White Island; but no data are available from the island to confirm this. Periodic activity in Hawke's Bay region, with four prominent shocks during the year, two of which reached minor destructive intensity.
The first shock occurred on 18th January, and had an epicentre not far from that of the Pahiatua earthquake of The second shock occurred on 14th June, and originated near the point where the most recent work has placed the origin of the Napier earthquake of It indicates that the block which moved in is still undergoing seismic strain.
The shocks of 15th and 30th December originated close to the Mangatoro fault, along which traces of comparatively recent activity have been reported by the Geological Survey. These two shocks reached intensity R. A continuation of moderate activity in the Wanganui region, with a marked disturbance centreing round 23rd November.
Particulars of this disturbance are given below in the list of the most important earthquakes in The active zone centred near Wanganui has extended as far north as Whangamomona and Ohakune, and south into the South Taranaki Bight. It is possible that the shocks in this region are due to magmatic movements. A continuation of mild activity in north-west Nelson. About forty shocks were reported during the year, but none exceeded R. Two earthquakes, on 31st October and 1st November, are noteworthy on account of their focal depth, which was of the order of kilometres.
As is usual in deep-focus shocks, some interesting anomalies in surface intensity were recorded. The epicentres of both shocks were to the north-east of Taupo, and, although the first and stronger one was felt generally in the eastern districts of the North Island and on both sides of Cook Strait, it was not reported felt at several places comparatively close to the epicentre, such as Taupo, Rotorua, and Tauranga.
The second shock was reported felt only at Waipawa and Paraparaumu. After a long period of comparative quiet, the south-west portion of the South Island was shaken by a powerful disturbance on 17th December, the maximum intensity reported being R. The origin of this shock was deeper than normal, and an intensity of R. It was followed by numerous aftershocks during the latter half of December, some activity continuing well into the following year. One hundred and seventy-five shocks were recorded on the Jaggar seismograph at Monowai up to the end of December, The following list gives some particulars of the most important New Zealand earthquakes in —.
A total of shocks was reported felt during , 80 of which were felt in some part of the North Island and 60 in some part of the South Island. Eight shocks were felt in both Islands. The maximum intensity was R. The following is a monthly summary of earthquakes reported felt during —.
The following article on the climate of New Zealand was prepared by the late Dr. Kidson, O. Aviation-service stations are established also at Auckland and Christchurch Wigram Aerodrome. General weather forecasts based on observations at 9 a. District forecasts are telegraphed at midday to certain of the principal seaports, where they are displayed at the post-offices, and are provided, also, to the leading newspapers. The evening forecast is published by the newspapers on the following morning.
Weather reports intended primarily for aviators are transmitted from Station 2YA of the National Broadcasting Service at 6. With the 1 p. District forecasts are broadcast at 1 p. In the late afternoon a special Dominion forecast for farmers is issued from each of the main centres.
In the evening the Dominion forecast is broadcast once or twice from the four main centres, followed by district forecasts. The first issue from 2YA during the news session, which commences at 7 p. Rainfall data from approximately four hundred stations are printed monthly in the New Zealand Gazette. New Zealand lies wholly within the Temperate Zone, and it is also wholly and at all seasons within the zone of prevailing westerly winds though they are stronger and more persistent farther southward.
Owing to its isolation and its narrowness in the direction of the prevailing winds, its climate is predominantly marine in character. Nevertheless, the modifications due to the height and continuity of the main ranges and the general high relief of the country are quite considerable, especially in the South Island. There is, for example, a very great variation in the rainfall from the western to the eastern side of the Southern Alps, and for so narrow a country, features of a continental type are rather strongly developed in the interior of the South Island.
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By breaking up the prevailing winds and causing the air at different levels to mix, mountains tend, also, to prevent the stratification of the air into layers of different density. Consequently very extensive and persistent cloud-sheets are seldom experienced. New Zealand therefore enjoys a high percentage of sunshine, a factor of great importance in the climate of a country with so high a rainfall. The principal current in the surrounding ocean waters is from south-west to north-east. Off the west coast of the South Island, however, the current divides, one branch turning southwards to Foveaux Strait, while others pass through Cook Strait and round the northern extremity of the Dominion.
The rather small range in climate from north to south is probably accounted for by this current. According to the widely accepted classification of climates developed by W. Under the same formula are classified southern Victoria and Tasmania and parts of southern Chile in the Southern Hemisphere, much of Europe, Japan and Korea, and a strip of the west coast of North America in the Northern Hemisphere.
Generally, however, it is a climate characteristic of the ocean rather than the land areas of the Temperate Zone. Tables 1 to 10 appearing in the following pages relate to varying, but usually lengthy, periods. In Table 11 the duration covered by the respective averages for that table is given.
Of all the climatic elements, probably the one that exerts the greatest influence on our lives is rainfall. It causes us much personal discomfort, but the production of the food by which we live depends directly on the availability of moisture from this source. Maps showing the distribution of mean annual rainfall appeared in issues of the Year-Book prior to The controlling influence of topography on rainfall in New Zealand is very conspicuous. Areas exposed to the westerly winds have heavier rains than those protected from them by mountain ranges.
Next, the greater the altitude the greater in general is the precipitation. There must be a limit beyond which precipitation begins to decrease again with altitude, but this has not yet been determined in this country. The indications are that precipitation is heaviest between 3, ft. The annual total varies from about 13 in. The distribution of the precipitation throughout the year is little less important than its total amount, the effect of rainfall in winter, for example, being very different from that in summer.