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proceedings of this meeting were summarized in a report to UNESCO in March,
1983, which was included in Lee et al. 1988 (pp. 11-13).
In August 18-19, 1983, the Working Group convened a workshop in conjunction
with the IASPEI General Assembly in Hamburg, Germany. This Workshop was or-
ganized to discuss the status of historical seismic data for Latin America and Europe.
It was divided into six sessions with a total of 29 presentations from representatives
of 19 countries and 4 international organizations. The proceedings of this meeting
were summarized in a report to UNESCO in October, 1983, which was included in
Lee et al. 1988 (pp. 13-15).
In addition to microfilming pre-1963 seismograms, the Working Group was
actively engaged in organizing auxiliary earthquake information (such as station
bulletins), and promoting research in studying instrumental and pre-instrumental
earthquakes. Consequently, the name of the Working Group was changed to “His-
torical Seismograms and Earthquakes”. The status of the Historical Seismogram
Filming Project was presented by Glover and Meyers (1988) and appeared earlier in
more detail in Glover et al. (1985). In brief, over 500,000 seismograms and station
bulletins from 450 stations around the world were microfilmed. Countries that par-
ticipated include China, Egypt, Germany, India, Japan, Philippines, Peru, USA, and
USSR.
Unfortunately, the main source of funding to microfilm seismograms worldwide
was terminated by the U.S. Geological Survey at the end of 1985, and no other
funding source was found to replace it. The Working Group came to a halt and was
disbanded after a topic describing this effort was published (Lee et al., 1988).
4 Scanning WWSSN Seismograms
The World-Wide Standardized Seismograph Network (WWSSN) was fully opera-
tional in 1963 under the auspices of the U.S. Coast and Geodetic Survey (USCGS).
Each WWSSN station consisted of 3 short-period (SP) and 3 long-period (LP)
seismometers, recording apparatus, radio-synchronized crystal clock, and calibra-
tion controls (WWSSN 1964; Oliver and Murphy 1971). Typically, six 300 mm
×
900 mm seismograms were produced each day (3 SP and 3 LP). Data were originally
recorded on photographic paper mounted on rotating drums, and later (1980s) on
heat sensitive paper. The rotation rate of the SP drums was one revolution every
15 min, resulting in a 60 mm/min chart speed (1 mm/s). The rotation rate of the LP
drums was one revolution per hour, resulting in a 15 mm/min chart speed. Note that
some of the LP records in the early 1960s were recorded at 30 mm/min. There are
minute marks on the records (an offset in the traces of 2-s duration every minute).
The time marks were recorded using the NIST WWVB broadcast signal, and typi-
cally have an accuracy of better than 100 milliseconds. Hours are marked with a 5-s
offset, with no offset on the 0, 6, 12, and 18 h UTC.
The original photographic records were photographed using 70 mm film and
stored by station and year on 70
×
120 mm film chips (one seismogram per film
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