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

Because of the long duration of most seismic cycles with respect to thehistory of seismological instrumentation,seismograms from the first half of the 20th century constitute an invaluableresource, allowing significant constraints on the regional chronologyof earthquake occurrence as well as the modern quantification of their sizethrough the calculation of seismic moments. This is especially true in theSouthern 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 July2014 a pilotproject, administered by IASPEI, to test the feasibility ofphotographically scanning records of the Wiechert and Bosch instruments operatedat the Jakarta (ex-Batavia) station since 1910 and archivedat the BMKG regional office in Ciputat. We used a 24 MP SONY alphaNEXT 7 camera with a nearly distortion-free wide angle lens mounted on a copystand with underside light-table illumination. We encounteredmany 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 systemis effective in providing well-resolved waveforms, and reaped more than 500digital copies of seismograms of earthquakes earmarked for theirglobal or regional importance, going back to 1910.Including the compilation of metadata necessary for futuresearch 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 complementsimilar endeavors, especially in the critically important Southern Hemisphere,either ongoing (e.g., at Canberra, Silverton), or desirable (e.g., at Lower Hutt,La Paz).