Hi All,

Regarding our afternoon session which was on the topic of historic earthquakes, the lectures which were given focused on using records available at a time when no seismic instruments were available. They used any personal accounts that were available including diaries, newspaper reports and in some cases generational reports. They used these accounts and tried to fix magnitudes of earthquakes using the Mercalli scale. Along with trying to discern the length of rupture, they also wanted to determine whether huge segments of failure occurred or only partial segments in cases where there was no surface rupture. In using this form of data for earthquakes occurring in the 1600's for instance, they can determine if there is a potential for future earthquakes in the area and to what magnitude those quakes might be. In some of the material presented it was difficult to determine if some the earthquakes which had been thought to be in the 8.0M range were actually lower, such as a 7.2M and they were able to do a very good job using this method.

While the earthquake locations were in various countries, the greatest knowledge which one can derive from the lecture series is how to discern the information once you have it. As Roger Musson pointed out, if the residents lived in a high seismic risk area and had experiences with many quakes, their sensitivity to these events would be less than in Wales where there are very few earthquakes. Thus one would report feeling an infrequent quake with much more emphasis on the event, than perhaps someone who lived in the California area over a hundred years ago, but had earthquake experiences frequently.

This information to me comes at a fortuitous time in my research of the Russian occupation of the West Coast of America and looking for historical accounts of earthquakes during that time, if and when I should come across some information I will have a better understanding in evaluating the magnitude of the earthquakes based on the Mercalli scale and how people themselves weigh the experience.

Petra