H.-34

92

The number of earthquakes recorded on the Milne-Shaw (north-south component) was 832. On the Milne-Shaw (east-west component) 930 earthquakes were recorded. Particulars of the numbers of the earthquakes registered on the two machines are given in the following table : —

Inequality in the number of shocks recorded on each seismograph is due to the following causes : — (1) The Milne-Shaw (N.-S.) component appears to be specially susceptible to disturbance by high winds ; therefore very small shocks are occasionally not traceable on the records. (2) A very few feeble shocks have been recorded on one Milne-Shaw machine only, possibly on account of directional effect. Officers of the Post and Telegraph and Marine Departments and private observers have given valuable assistance in the reporting of earthquakes felt by them in New Zealand. Four hundred and seventy-nine reports were received from the officers of the Post and Telegraph Departments, seventy-eight from the Marine Department, 175 from other observers, and 663 from the newspapers. An article on " Earthquakes in New Zealand " was prepared for and published in the New Zealand Year-book. Maps have been prepared showing in considerable detail the distribution and intensity of the earthquake-shocks felt in New Zealand. These are now being made ready for publication. The work in seismology has increased very considerably since the new Milne-Shaw seismograph has been running, and a further addition to the work has been caused by the installation of the second Milne-Shaw seismograph. In addition to the technical reports on earthquakes, contact prints are made of all important records and are sent to other observatories. The old Milne has proved its usefulness in a number of cases where the local shocks have been strong enough to throw the Milne-Shaw machines out of action. During the year 1929 earthquake reports have been received from sixty-three observatories. Steps are now being taken to obtain seismographs suitable for recording local earthquakes. By means of these seismographs it is hoped that some precise knowledge of the origins of New Zealand earthquakes may be obtained. Earthquakes in New Zealand, 1929. The outstanding seismic phenomenon of the year 1929 was the disastrous earthquake which visited the north-western portion of the South Island on June 17th. This shock was distinctly felt over the whole of New Zealand, and resulted in the loss of 14 lives, and serious damage to property in the Buller District, South Island. Table I gives a list of stations at which the shock reached, or exceeded intensity 8 on the Rossi-Forel scale : —

Table I.—Earthquake of June 17th, 1929.

Machine Machine T , i i929 - M ?N e i h r M (E n -w h r Earti^akes ' January . . .. .. 32 22 32 February . . .. .. 26 19 26 March. . . . . . . .. 38 34 38 April .. . . . . .. 24 23 24 May .. . . .. . . 30 32 32 June . . • • •• •• 444 379 444 July .. .. .. .. 122 125 125 August .. .. .. .. 57 56 57 September ,. . . . . 29 30 30 October . . . . . . 41 37 41 November .. .. .. 34 32 34 December . . . . .. 53 43 53 Totals for year .. .. 930 832 936

Station. fllT? Station " HUF) 7 Hawera .. .. . . 8 Murcliison . . .. . . 9-10 Wanganui . . .. .. 8 Lyell , . . . .. 9-10 Farewell Spit . . .. . . 7-8 Westport .. . . .. 9 Bainham .. .. . . 8 Inangahua . . .. .. 9 Kahurangi Point . . . . 8-9 Reefton . , .. . . 8-9 Nelson .. . . . . 8-9 Greymouth . . .. .. 8-9 Blenheim . . . . . . 7-8 Hanmer .. .. .. 7-8