Geoscience Reference
In-Depth Information
3.2 Historical Seismicity of the French Alps
In the 1990s, noticing that the Sirene database was not publicly available, we started
a study on the historical seismicity of the French Alps, particularly in the Grenoble
region. Special emphasis was placed on the study of small earthquakes, which had
not always been given sufficient attention in previous studies, despite Jean Vogt's
efforts in this regard. This led to the discovery of a large number of new primary and
secondary sources. The analysis of small earthquakes proved very useful in order to
assess epicentres with high precision. Evidence of an alignment of epicentres could
be obtained, that had not previously been visible (Thouvenot et al. 2003).
The list of earthquake dates found in the SisFrance database is usually rather
exhaustive, and we could scan local newspaper or literature to find new sources
improving the knowledge of events in this list. Nevertheless, both missing events
and false events still persist, and it is necessary to continue checking all known
catalogues as described above to complete it. As an example, we investigated a
hitherto unknown earthquake that occurred near Grenoble on 18 February 1909 at
10:13 a.m. Not less than eight descriptions were found in four regional newspapers
(Appendix 1). This earthquake was felt in the four villages, Vizille, Notre-Dame-de-
Commiers, Saint-Georges-de-Commiers, and La-Motte-d'Aveillans; its maximum
intensity can be evaluated as IV MSK.
The region of Grenoble is located in the
departement
of Isere (France is divided
into 96
departements
); we located no less than 36 local newspapers published in the
Isere between 1697 and 1945, and six historical scientific periodicals published in
Grenoble that contained data on earthquakes. Only a small percentage of these had
been exploited previously. Further north, in Savoy (France), historical sources are
located both in France and in Italy. Indeed Savoy has had a complex history, growing
from County to Duchy, and from Duchy to Kingdom, with its capital moving in
the mid XV century from Chambery (Savoy, France) to Torino (Piedmont, Italy).
The region was incorporated into France in 1860 and was divided from then on
into two
departements
with capitals in Chambery and Annecy. In the Haute-Savoie
departement
, 23 historical newspapers are available. For the Chamonix 1905 earth-
quake (Intensity VIII MSK), we found 14 new newspaper articles in the epicentral
region (Appendix 2). Collecting a list of newspapers titles, with publishing dates,
locations, and call numbers, is not an easy task. Often, library or archive depositories
do not maintain such lists, although this is gradually improving with the progress of
digital cataloguing.
4 Discussion
Often, seismic catalogues concentrate only on the largest damaging earthquakes
in a region, neglecting valuable information on foreshocks and aftershocks and
on smaller events. However, based on studies of present-day earthquakes with
temporary seismological networks, it is obvious that macroseismic epicentres can
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