Magnitude of Historical Earthquakes, from Macroseismic Data to Seismic Waveform Modelling: Application to the Pyrenees and a 1905 Earthquake in the Alps - Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes - page 364

Vallorcine. As this later earthquake has been well investigated from both local and
regional broad-band seismic networks, it provides an excellent opportunity to apply
our differential technique.
Intensities of the 1905 earthquake are taken in three catalogues: BCIS (Bureau
Central International de Sismologie (Christensen and Ziemendorff (1909)), BSSI
(Bollettino della Societa Sismologica Italiana (Palazzo 1907)), and ECOS. Intensi-
ties issued by BCIS and BSSI are given in the Rossi-Forel scale (De Rossi 1883),
while ECOS intensities are converted into the EMS-98. We have checked the de-
scription of the macroseismic effects published by BCIS with both the Rossi-Forel
scale and the EMS-98. Doing so, we conclude that for this event, intensities V of
the Rossi-Forel scale was intermediate between IV and V of the EMS-98, while VI
and VII are equivalent to V and VI of the EMS-98, respectively. Figure 5 shows
the isoseismals of the 1905 Chamonix earthquake where intensities are converted
into the EMS-98 with two possible interpretations for intensity V. Superimposed on
the 1905 map, we have drawn the isoseismals of the Vallorcine (2005) earthquake
by using, as previously, the same spatial grid for both the historical and the recent
events.
Figure 6 displays the distance-intensity curves D(I) for the pair of earthquakes
1905-2005, together with the curves corresponding to two recent magnitude M L ∼ 5

earthquakes located at distances less than 80 km from Chamonix. The moment mag-
nitude of the Vallorcine (2005) earthquake is well constrained to 4.5 from three
independent sources (SED in Zurich, INGV in Rome, and Geosciences Azur in

Fig. 5 Isoseismals and macroseismic areas for the Vallorcine (2005) and Chamonix (1905) earth-
quakes (EMS-98 converted)