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

234 G. A. EabyFrom a seismic point of view the earliest years of the colony were unusually active.Within a few months of their arrival Wellingtonians experienced a strong earthquakeand the sequence of aftershocks that followed. In 1843 the newly-built houses ofWanganui were badly damaged, and in 1848 Wellington also suffered damage fromshocks centered across Cook Strait in Marlborough. New Plymouth chimneys fellin 1853, and two years later a magnitude 8 shock in southern Wairarapa was feltthroughout the whole country. Few Wellington buildings escaped damage, and partsof the northern shore of Cook Strait were lifted several metres. It is no surprise tofind these events well documented, and that even the occurrence of small shockslong continued to attract the notice of the press.In 1868, government climatological observers were appointed, and their dutiesincluded the reporting of felt earthquakes. Annual summaries were published, andthe possibility of making recording instruments was discussed. Milne sent detailsof his work in Tokyo, and in 1884 a horizontal pendulum based on his ideas beganrecording in Wellington. (Young, 1984; Young et al., 1984). None of its recordsare known to have survived, but descriptions of its indications are to be found inthe press. In 1898, the Government bought two Milne pendulums, which were setup in Wellington in 1900 and in Christchurch in 1901. Data were published by theSeismological Committee of the British Association for the Advancement of Science,and this is usually considered to be the beginning of instrumental seismology in NewZ e aland .The first two decades of the twentieth century mark a period of confusion duringwhich it is impossible to be sure that records are complete. Leading seismologicalpersonalities died or retired, patterns of government administration changed, andthe disruptions of the first World War included delays in publication. In 1921, however,the first of the “New Zealand Seismological Reports” appeared, and these havecontinued under the direction of what has now become the Seismological Observatory,Wellington, surviving a number of confusing changes in the Observatory’sname and its administrative control. The New Zealand Department of Scientificand Industrial Research has a statutory duty to carry out research “that is in thenational interest”, and the attention the Observatory can give to such matters ascompiling historical catalogues or conserving existing records is consequently limitedby political priorities.2. Earthquake CataloguesThe earliest attempts to make comprehensive lists of past New Zealand earthquakeswere prompted by a meeting of the Australasian Association for the Advancementof Science in Christchurch in 1891. The first (Hogben, 1891) lists 775shocks between 1848 and 1890, and is based upon reports found in leading newspapers,in lists of climatological observations published annually since 1868, andin a few minor sources. The other (Hector, 1891) summarises the climatologicalreports from 1868 to 1890 and appends some early listings of felt earthquakes.Neither provides any index of severity beyond the selection of a few shocks formore extended comment. These remain the major published lists of pre-instrumentalshocks, but there is much unpublished material in the Observatory’s files.R. C. Hayes’s “Catalogue of New Zealand Earthquakes up to and including theYear 1855” has been superseded by the published sections of my “Descriptive Catalogue”(Eiby, 1968a, 1973). Barnett’s “Catalogue of Non-Instrumental Earthquake