H.—34.

Astronomy. The establishment of the Carter Observatory early in 1939 relieved the Dominion Observatory of all astronomical work (except observations necessary for carrying on the time service). Arrangements were made for the astronomical section of the Dominion Observatory Library to be made available to the Carter Observatory, on loan. Certain astronomical equipment, such as telescopes, &c., and the radio apparatus of the two aurora stations in Southland, have also been taken over by the Carter Observatory, on loan. In accordance with regulations, the aurora radio stations ceased operating immediately on the outbreak of war. The Dominion Observatory tower room has been made available to the Carter Observatory, for use as a temporary library. Seismology. Seismic Activity in New Zealand in 1939. —Sesmic activity, on the average, showed a decline during the first six months of 1939. A slight increase occurred from July to November, after which a decline was again indicated. As compared with the previous year, more shocks were reported felt in the North Island in 1939, but slightly less in the South Island. In all, 157 shocks were reported felt in some part of New Zealand in 1939, as compared with 132 in 1938. On the other hand, the maximum intensity in 1939 was only R.-F. 7, as compared with R.-F. 8, in 1938. The activity in 1939 may be summarized as follows : — (1) Fairly frequent local activity extending from Whakatane to the Rotorua and Taupo regions, probably associated with volcanic activity. The strongest shocks occurred in June and reached a maximum intensity of R.-F. 5, at Whakatane. Some shocks, originating at depths of from 100 km. to 300 km., have been located beneath part of the thermal regions. Some of these shocks show very irregular distribution of surface intensity, being felt at isolated spots far removed from their epicentres. Although not considered to be directly connected with the volcanic activity, shocks at similar depths have been recorded beneath volcanic regions in other countries. (2) Occasional activity, centred in the Fjast Cape - Grisborne region, with a strong shock (R.-F. 6) on 4th July (No. 29 on map). (3) Fairly continuous activity in various parts of Hawke's Bay, with a particularly strong shock in the southern part of the district on 24th February. This shock reached intensity R.-F. 7, the fnaximum recorded in New Zealand during the year (No. 9 on map). (4) Activity in the Wanganui-Rangitikei region, concentrated around two dates—i.e., 13th May and 3rd November. On each occasion there was a group of shocks, the strongest of which reached intensity R.-F. 5-6 at Wanganui (Nos. 22, 23 ; and 49 -53 on map). (5) Some activity in the north-west Nelson and Buller regions, almost wholly confined to the first seven months of the year. The strongest shock (R.-F. 6) occurred on 10th February (No. 7 on map). (6) Very occasional shocks in Canterbury during the second half of the year, with a strong one (R.-F. 6 at Hanmer) on 26th July (No. 34 on map). (7) Activity in the south-western region of the South Island from January to April, and again from August to November. There were notable shocks on 11th February (No. 8), sth March, and Ist September (No. 41). Three shocks in this region reached a maximum intensity of R.-F. 6, while a large number of minor ones were recorded by the seismograph at Monowai in January. (8) A number of shocks originating in a submarine belt from 50 miles to 100 miles off the east' coast of the North Island. Most of these were recorded after the beginning of August, when a Wood-Anderson seismograph was installed at Tuai, in northern Hawke's Bay. It would appear, therefore, that the new seismograph at Tuai has revealed a considerable amount of activity in this submarine region, which was not evident before. Some of the shocks were sufficiently intense to be felt in parts of New Zealand. One on 15th May was felt with intensity R.-F. 5 at Opotiki and Tolaga Bay, and one on 31st December was extensively felt in the North Island, with maximum intensity R.-F. 5 (No. 59 on map). (9) Other minor activity occurred as follows : — (a) A slight shock reported from Cape Maria van Diemen on 22nd December. (b) A few slight shocks felt at Morrinsville. (c) Very occasional shocks in Taranaki, the maximum intensity being R.-F. 5. (d) Spasmodic activity in the Wairarapa-Wellington region. (e) Occasional shocks centred in Marlborough, the maximum intensity being R.-F. 5. The accompanying map shows the epicentres of earthquakes determined in 1939. The black circles, having an index number, represent epicentres determined from seismograph records. These are mostly correct within fifteen or twenty miles. The crosses indicate the approximate positions of small felt shocks, which could not be definitely located by instrumental records. Information regarding the felt effects of earthquakes has been supplied by officers of the Post and Telegraph Department, officers of the Marine Department, and several private observers. In all there are about 120 non-instrumental reporting stations.

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