Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

450 G. A. Eiby2.3. Arapuni (ARA)A Milne pendulum operated from 1930-49, and a Wood-Anderson seismometerfrom 1949 November until 1950 October, when the station was closed becausevibration from the near-by power station greatly reduced the usefulness of itsrecords.2.4. Auckland (AUC)A Milne-Shaw instrument was installed in 1941. The station was seriously affectedby tilt, and overlapping traces sometimes make the time-signals difficultto distinguish and the clock correction uncertain, but many teleseisms are wellrecorded.2.5. Roxburgh (ROX)Three-component classical Galitzin instruments began recording in 1957, butcalibrations are uncertain. A Willmore short-period vertical was added in 1962.2.6. Tongariro (TON)A short-period Jones vertical geophone recorded with some interruption from1952 until 1962, when it was replaced by a Wood-Anderson. During its operationthe Jones was probably the most effective instrument in New Zealand for recordingthe P-phases of teleseisms. Some records from this station were destroyed by fire,and others axe badly charred at the edges.2.7. Chatham Islands (CIZ)A Milne instrument operated with frequent and often long interruptions between1932 and 1941.2.8. Raoul Island (RAO)This station is strategically placed with respect to Tonga-Kermadec seismicity,but is troubled by a high background of microseisms and intermittent volcanictremor. The short-period Willmore vertical began operation in 1957. Instrumentalbreakdown caused an interruption from 1958 April until December.2.9. Other New Zealand StationsThe following stations operating before 1963 were equipped with Wood- Andersoninstruments. The dates are those when recording began: Chateau (CNZ), 1961;Cobb River (COB), 1949; Gebbies Pass (GPZ), 1956; Kaimata (KAI), 1942; Karapiro(KRP), 1951 (replaced by Willmore vertical, 1958); New Plymouth (NPZ),1931; Onerahi (ONE), 1954; Tuai (TUA), 1939 (A Jaggar shock-recorder operatedfrom 1932-39, The Wood-Anderson was replaced by a Willmore vertical in 1961).