Contemporary newspaper accounts of the 1811-1812 Mississippi Valley earthquake sequence are used to construct a generalized isoseismal map of the first of three principal shocks of the sequence, that of December 16, 1811. The map is characterized by an unusually large felt area, with MM intensities of V as far away as the southeast Atlantic coastal area.
By correlating the isoseismal map with that of recent earthquakes for which ground motion data are available, the body-wave magnitude of the December 16, 1811 earthquake is estimated to be 7.2. The other principal shocks, on January 23, 1812 and February 7, 1812, had estimated mb values of 7.1 and 7.4, respectively. The total energy released by the principal shocks and their larger-magnitude aftershocks is estimated to be equivalent to that of an mb = 7.5 (or Ms = 8.0) earthquake.
The anomalously large areas of damage and of perceptibility of the principal shocks result from both the surficial geological conditions of the Mississippi Valley and the relatively low attenuation of surface-wave energy in eastern North America.
Estimates of the vertical component of ground motion, for an earthquake of mb = 7.2 occurring in eastern North America, are given. These include values for particle velocity, displacement, and acceleration at frequencies of about 3, 1 and 0.3 Hz.
[1]
O. Nuttli,et al.
Seismic wave attenuation and magnitude relations for eastern North America
,
1973
.
[2]
San Fernando rupture mechanism and the Pacoima strong-motion record
,
1972
.
[3]
Rayleigh waves from a moving thrust fault
,
1972
.
[4]
Wilbur I. Duvall,et al.
Blasting Vibrations and Their Effects on Structures
,
1971
.
[5]
William Stauder,et al.
Seismic studies: South central Illinois earthquake of November 9, 1968
,
1970,
Bulletin of the Seismological Society of America.
[6]
Robert B. Herrmann,et al.
The south-central Illinois earthquake of November 9, 1968: Macroseismic studies
,
1970,
Bulletin of the Seismological Society of America.
[7]
James N. Brune,et al.
Seismic moment, stress, and source dimensions for earthquakes in the California‐Nevada region
,
1968
.
[8]
O. Nuttli,et al.
The Earthquake of October 21, 1965 and Precambrian Structure in Missouri
,
1965
.
[9]
J. Wiggins.
Construction of strong motion response spectra from magnitude and distance data
,
1964
.
[10]
Charles F. Richter,et al.
Earthquake magnitude, intensity, energy, and acceleration(Second paper)
,
1956
.