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

Seismological Measurement an Hong Kong 479Table 2. Available Pre-war HKC Seismograms on Aperture CardsYear Mon. Day Comp. Year Mon. Day Comp. Year Mon. Day Comp.1929 Jan 1213161720212430Feb 01142226Mar 060921232531Apr 08May 010205192126Jun 0203040912NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN1929 Jun 13151719232729Jul 0507142631Aug 08171819202128Sep 02111721Oct 0506161922N24 NN Nov 05 N1929 Nov 12141516171822Dec 060917181935 Jul 111936 Feb 12May 081937 May 12Aug 111938 Jan 18Feb 01Apr 14May 08Aug 18Oct 201939 Jun 13Jul 10Dec 201940 Jun 18NNNNNNNNNNNNNNEENEINNNNNEEINE,NE,NAll the post-war seismograms made by the Royal Observatory Sprengnether seismographs(1951-1976) were microfilmed in the form of aperture cards or 1Bmm rollfilm. The originals are no longer available.The Lamont seismograms from 1957 to 1976 were sent to the Lamont-DohertyGeological Observatory monthly without being microfilmed. After changing to electronicrecording in 1979, all the pen-and-ink records were microfilmed in 16-mm rollfilm. The original seismograms were disposed of after microfilming.The WWSSN seismograms were also sent away monthly since 1963. A copy ofthese seismograms from 1963 to 1977 was later obtained from the US. NationalGeophysical Data Center in 35-mm roll film. Beginning from 1978, the WWSSNseismograms were also microfilmed at the Royal Observatory and put on aperturecards before they were dispatched.All the seismograms of the three-station short-period network since its inceptionin November 1979 were microfilmed on 16-mm roll film before they were disposedof. Digital recordings of significant events within 320 k m of Hong Kong were kepton floppy disks. The first 25 seconds of these records were also plotted by a plotterusing an expanded time scale of 1 second per 5 mm and kept as permanent records.