10:30 AM - 10:45 AM
[S05-2-01] Historical seismograms: Preservation efforts for an endangered species
invited
The long recurrence times characteristic of major earthquakes (typically one
to several centuries) result in severe undersampling of the Earth's seismicity
as documented by digital seismic networks (at most 40 years old), or even
their immediate predecessor, the WWSSN (55 years old). For this reason,
historical seismograms (typically from 1900 to 1962) are
absolutely crucial to the understanding of seismic cycles, notably at major subduction zones.
Yet, these precious datasets are often perceived by administrative stakeholders as
antiquated, obsolete and of little value, and are thus threatened with disposal and
irreversible destruction. This situation is aggravated by the aging and eventual
disappearance of the older generations of seismologists who were trained in the techniques allowing
the modern processing of such records.
We present a review of typical analog datasets of historical seismograms
and of the techniques available for their preservation through transfer to digital supports.
We focus on the Northwestern University Seismogram Archive Facility, which presently holds an
estimated 5 million seismograms on photographic support, including a rich WWSSN collection,
and complete archives of the Pasadena/Southern California network for 1923-1962, as well
as significant holdings of records from the former Soviet Union, Japan, and other critical
stations.
to several centuries) result in severe undersampling of the Earth's seismicity
as documented by digital seismic networks (at most 40 years old), or even
their immediate predecessor, the WWSSN (55 years old). For this reason,
historical seismograms (typically from 1900 to 1962) are
absolutely crucial to the understanding of seismic cycles, notably at major subduction zones.
Yet, these precious datasets are often perceived by administrative stakeholders as
antiquated, obsolete and of little value, and are thus threatened with disposal and
irreversible destruction. This situation is aggravated by the aging and eventual
disappearance of the older generations of seismologists who were trained in the techniques allowing
the modern processing of such records.
We present a review of typical analog datasets of historical seismograms
and of the techniques available for their preservation through transfer to digital supports.
We focus on the Northwestern University Seismogram Archive Facility, which presently holds an
estimated 5 million seismograms on photographic support, including a rich WWSSN collection,
and complete archives of the Pasadena/Southern California network for 1923-1962, as well
as significant holdings of records from the former Soviet Union, Japan, and other critical
stations.