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

2. New ZealandSeismograms Before 1963 in the South- West Pacific 457New Zealand possesses the largest and most complete collection of records madein the region. Most of them are to be found in the archives of the SeismologicalObservatory of the Geophysics Division of the government Department of Scientificand Industrial Research in Wellington. (P.O. Box 1320, Wellington, New Zealand).Most of the records are in good condition, but some of the early ones have becomebrittle, and others have suffered from poor photographic processing. Gaps in theseries are mainly the result of borrowers failing to return records, and seismogramsof some important teleseisms are missing. Most stations of the New Zealand networkwere primarily intended for the study of local earthquakes, and have only asingle short-period instrument. Before 1963 it was with few exceptions a horizontalcomponent. However, many large teleseisms have been recorded, and severalstations, including Wellington and Christchurch (the first to be established) wereequipped to record teleseisms. The history of the individual stations under NewZealand control and their instrumentation has been summarized by Smith (1981).2.1. Wellington (WEL)In 1884 an instrument built locally to designs supplied by John Milne beganrecording at the Colonial Museum (Young et al., 1984). No surviving records havebeen found. Records from a Milne pendulum erected in 1900 are to be foundin the DSIR archive, and in the files of the National Museum, but those datingfrom before 1915, when the instrument came under the control of the DominionObservatory, are incomplete and not readily identifiable. It is believed that someearly records were sent to Milne at Shide, and may still be found somewhere inEngland. In 1923 a Milne-Shaw instrument was installed. A second component wasadded in 1925, and a Galitsin-Wilip vertical in 1930. Wood-Anderson and othershort-period instruments came in 1931, including a Jones vertical geophone whichran from 1937-46. A short-period vertical Benioff ran from 1955-57, and World-Wide Standard Seismographs were installed in 1962 May. Timing in Wellingtonwas derived directly from the national time-sexvice, and is of very high reliabilityfrom the earliest years. Time was distributed throughout the country by telegraph,and radio time-signals were broadcast from about 1914, and were used to controltiming at other New Zealand stations. By the 1930s they were impressed on therecords by hand-key, and automatic recording was introduced in 1955.2.2. Christchurch (CHR)Regular operation of a Milne pendulum began in 1902, but records of someaftershocks of the large earthquake at Cheviot on 1901 November 16 exist. In 1930a three-component set of classical Galitzin instruments replaced the Milne, and aWood-Anderson was added the following year. In 1947 March the instruments weremoved to Wairiri (WAI), and returned about a year later, with some interruptionto recording. At the end of 1956 the Galitsins were moved to Roxburgh (ROX) andthe Wood-Anderson to Gebbies Pass (GPZ) and the station closed.