Large 19th Century Earthquakes in Eastern/Central North America: A Comparative Analysis - Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes - page 350

Fig. 6 The intensity distribution shown in Fig. 2, calculated using only those locations that are
within 10 km of a location for which there is an account of NM1. This illustrates what the
Charleston intensity distribution would have looked like, had the earthquake occurred in 1811
rather than 1886
intensity distribution might have looked like if the earthquake had occurred in 1811.
One still finds higher intensity values for NM1 at distances greater than 800 km, but
the winnowed values at closer distances are generally lower than the intensity values
for NM1.
One can further consider key indicators of the intensity field for NM1 versus
that for the Charleston earthquake: the maximum distance at which light damage
occurred, and the nature of shaking at hard rocks sites. The latter comparison is
difficult because so few observations are available from locations that are known to
be hard-rock sites. However, a few reliable observations are available. In Cincinnati,
Ohio, physician Daniel Drake described light damage in town along the river val-
ley, but noted that on the elevated ridges away from the river, many families slept
through the shock. (Drake went on to attribute this discrepancy to the fact that strata
in the river valley were “loose” compared to the nearby limestone hills, one of the
earliest observations of, and explanations for, site response (Drake, 1815)). This
indicates a MMI no higher than IV for hard rock sites, as V is the level at which
sleepers are generally awakened.
Another key hard-rock observation is available from Sainte Genevieve, Missouri,
which had been moved to higher ground approximately a mile from the river after a