Digital Filming of the Seismograms Held in the Jakarta Archives: A Pilot Program

Monday, 15 December 2014
Emile A Okal, Northwestern University, Evanston, IL, United States and Stephen H Kirby, U. S. Gelogical Survey, Menlo Park, CA, United States
Because of the long duration of most seismic cycles with respect to the
history of seismological instrumentation,
seismograms from the first half of the 20th century constitute an invaluable
resource, allowing significant constraints on the regional chronology
of earthquake occurrence as well as the modern quantification of their size
through the calculation of seismic moments. This is especially true in the
Southern hemisphere which hosted few seismic stations before the 1930s.

In this context, the preservation of seismograms in a digital format allowing their seamless exchange is an important challenge to the scientific community.

Under funding from the Earth Observatory of Singapore, we initiated in July
2014 a pilot
project, administered by IASPEI, to test the feasibility of
photographically scanning records of the Wiechert and Bosch instruments operated
at the Jakarta (ex-Batavia) station since 1910 and archived
at the BMKG regional office in Ciputat. We used a 24 MP SONY alpha
NEXT 7 camera with a nearly distortion-free wide angle lens mounted on a copy
stand with underside light-table illumination. We encountered
many challenges, including the fragility of acidic paper,
serious dark-brown age-toning of the paper, as well as many missing records.
However, this pilot test showed that this inexpensive system
is effective in providing well-resolved waveforms, and reaped more than 500
digital copies of seismograms of earthquakes earmarked for their
global or regional importance, going back to 1910.
Including the compilation of metadata necessary for future
search capability, 15 to 20 seismograms can be scanned per hour.
Following successful capacity building through on-site training of BMKG Staff,
it is hoped that this project can be pursued at BMKG, and complement
similar endeavors, especially in the critically important Southern Hemisphere,
either ongoing (e.g., at Canberra, Silverton), or desirable (e.g., at Lower Hutt,
La Paz).