Wednesday, 12 June 2013

Earthquakes, dams and archives by Dr Roger Musson

Recently, the Engineering Group of the Geological Society started the preparation of a Special Publication to be called “Geological hazards in the UK: Their occurrence, monitoring and mitigation”. The intention is a one-volume reference work for the various geohazards in the UK, with each chapter in the book detailing a different hazard, and written by a relevant specialist in that field (several of whom are from BGS). I was asked to provide the chapter on earthquakes, and I recently completed the first draft.
Now, in the course of this, I needed to discuss the various sorts of damage that have occurred from British earthquakes, and not just to ordinary houses, but also special structures like dams. I have always said, in the course of talks, that there have been three cases of damage to dams from earthquakes in Britain: one in the English Midlands in 1957, and two in Scotland in 1839 and 1979. This is important information for the chapter, but the statement needed to be backed up with citations.
The first two cases were easy, as I knew of journal papers discussing them, but the last one was more problematic. I knew about it from remembered conversations back in the 1980s - but was there a written account of it anywhere?
My first step was a comprehensive internet search, which yielded precisely nothing. You would think the dam in question was never affected by any earthquake. The internet is a wonderful resource for many things, but it is not nearly as omniscient as some people would like to think. For some specialist areas it is particularly weak.
Secondly, I turned to conference proceedings. One of the characteristics of seismic hazard as a field of science, is that much of the scientific development is conducted as part of research projects conducted outside of academia. A consequence of this is that many important publications appear not in the high-impact journals so beloved of research assessment exercises, but in obscure reports and conference papers.
These are typically printed in small runs and can be very hard to access. Successive seismologists in BGS have carefully hoarded copies of these valuable documents, and in many cases, the copies preserved in BGS are the only copies in the country. Having ready access to copies of these plays an important part in the ability of BGS staff to undertake seismic hazard research to the standards required for support of the engineering industry.
Running through the BGS collection, I was able to find a paper that described the safety-related activities undertaken at the dam after the earthquake - but of the effects of the earthquake itself, there was no mention.
Failing to find a published account, even an obscure one, I finally turned to the seismological archives of the BGS, and a file of correspondence from the period. Here I soon found exactly what I was after - a contemporary letter from someone who had visited the dam immediately after the earthquake, and describing the damage. This is precisely what I needed: it had the details, and it was attributable.
This nicely demonstrates one of the important roles of a geological survey: to act as a permanent repository of archival data relevant to the earth sciences. It is easy to imagine that in a university department or commercial company, such information would be lost on the retirement of whoever collected it. Only in a geological survey can the long-term survival of such records be guaranteed. And such records, which might look on casual inspection to be just a bunch of old letters, may turn out, after the passage of many years, to be key documents relevant to safety from geohazards.

Dr Roger Musson

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