Department of the Interior 

U.S. Geological Survey

ON THE MODIFIED MERCALLI INTENSITIES AND MAGNITUDES

OF THE 1811/1812 NEW MADRID, 

CENTRAL UNITED STATES, EARTHQUAKES

by 

Susan Hough 1, John G. Armbruster^ Leonardo Seeber2and Jerry F. Hough3

OPEN-FILE REPORT 99-565

This report is preliminary and has not been reviewed for conformity with U.S. Geological 

Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, 

product, or firm names is for descriptive purposes only and does not imply endorsement 

by the U.S. Government.

1. U.S. Geological Survey 2. Lamont-Doherty Earth Observatory 3. Duke University 

525 S. Wilson Ave Palisades, NY 10964 Durham, NC 27706 

Pasadena, CA91106

1999
Figures, Tables and Appendices

Figure 1. Original Intensity map ................................ p 21

Figure 2. Histogram of original and revised intensities............... p 22

Figure 3a. Reinterpreted MMI values, 12/16/1811, subjective contouring . p 23 

Figure 3b. Reinterpreted MMI values, 12/16/1811, least-squares ....... p 24

Figure 3c. Reinterpreted MMI values, 12/16/1811, Boolean contours .... p 25

Figure 4a. Reinterpreted MMI values, 1/23/1811, least-squares contours p 26 

Figure 4b. Reinterpreted MMI values, 1/23/1811, Boolean contours..... .p 27

Figure 5a. Reinterpreted MMI values, 2/7/1812, least-squares contours. . p 28 

Figure 5b. Reinterpreted MMI values, 2/7/1812, Boolean contours ..... .p 29

Figure 6. Comparison of magnitude results ........................p 30

Table 1. Locations of available felt reports ........................ p 31

Table 2 . MMI assignments for 12/16/1811 event................... p 34

Table 3. MMI assignments for 1/23/1812 event.................... p 36

Table 4. MMI assignments for 2/7/1812 event..................... p 38

Table 5. Summary of magnitude results...........................p 40

Appendix 1. Sample sources from compilation of Street (1984)........p 41

Appendix 2. Original sources not included in previous studies ........ p 43
1 Abstract

Few debates in seismology have been as persistently vexing as that concerning the magnitudes of the principal earthquakes of the great New Madrid sequence of 1811-12. While 

many lines of indirect evidence suggest moment magnitudes of « 7 for the three largest 

events, Johnston (1996) obtained values of w 8 by comparing the isoseismal areas determined by Nuttli (1973) with those from other large stable continental region earthquakes 

worldwide. In this study, we reexamine the original felt reports analyzed by Nuttli (1973) 

and Street (1984) to determine revised isoseismal maps for the largest three events. In 

many cases we interpret lower values than those assigned by the earlier studies. In some 

cases the revisions result from an interpretation of original felt reports with a modern 

appreciation for site response issues. More generally, the earlier studies had assigned 

MMI values of V-VII to a substantial number of reports that we conclude do not describe damage (and other effects) commeasurate with intensities this high. Isoseismal 

contours are rather poorly constrained by the revised MMI values, for the second and 

third mainshocks especially. For the first event (2:15 a.m. local time, 12/16/1811) we use 

three methods to draw contours: one subjective, one based on a least-squares optimization approach, and one based on a Boolean regression scheme. All three approaches yield 

areas that, given the area-moment regressions of Johnston (1996), imply Mw in the range 

of 7.1-7.6 for the December event. We conclude that, given the likely site response biases, 

the data are most consistent with Mw 7.2-7.3. Data are considerably more sparse for the 

second and third large events, which occurred at approximately 8:00 a.m. on 1/23/1812 

and approximately 3:45 a.m. on 2/7/1812. We do not consider the data sufficient to 

determine isoseismal areas as well as is possible for the first event. However, the relative 

sizes of the events can be established directly from the accounts. Consistently, the second 

and third mainshocks are reported as having been slightly smaller and somewhat larger, 

respectively, than the first. Based on the available information for the February event, 

we conclude that Mw of approximately 7.4-7.5 is most consistent with both the felt reports and the established geometry of the Reelfoot fault (which all evidence suggests to 

have been the causative structure). We note that, in many cases, the inference of lower 

magnitudes for the New Madrid events implies that site response may play a significant 

role in controlling seismic hazard along river valleys in the central United States and 

coastal areas in the east.

2 Introduction

The earthquake sequence that struck the New Madrid region of the Mississippi Valley in 1811-1812 had, without question, remarkably far-reaching effects [Mitchill, 1815; 

Bradbury, 1819, Fuller, 1912; Nuttli, 1973; Penick, 1981; Street, 1984; Johnston, 1996]. 

Contemporary accounts document three principal events: approximately 2:15 a.m. local 

time on 12/16/1811; around 8:00 a.m. on 1/23/1812, and approximately 3:45 a.m. on 

2/7/1812 (henceforth NM1, NM2, and NM3, respectively). All three events were felt
throughout much the central and eastern United States. Additionally, a large aftershock 

to NM1 occurred near dawn on 12/16/1811. Substantial aftershock activity following all 

events was also documented, with felt events persisting throughout the 1810's [Fuller, 

1912; Penick, 1981].

Because paleoseismic investigations have suggested a repeat time on the order of 

400-500 years for the New Madrid events [e.g., Tuttle and Schweig, 1996; Tuttle et a/., 

1999], the magnitude of the earthquakes becomes a critical issue for an understanding of 

intraplate earthquake processes. That is, the low strain rate inferred by geodetic studies 

[e.g. Newman et al, 1999] and general geomorphic considerations imply that if the New 

Madrid earthquakes were extremely large (Mu w 8) and the repeat time estimates are 

correct, the seismicity rate must be highly non-stationary.

The New Madrid earthquakes are of considerable societal as well as scientific importance. A repeat of the 1811-1812 sequence would clearly have a tremendous impact on 

the present-day mid-continent region. The New Madrid Seismic Zone contributes a nontrival component of seismic hazard for relatively far-flung midwestern cities such as Saint 

Louis, Missouri, and Cincinnati, Ohio [Frankel et al, 1996]. Yet the 1811-1812 sequence 

has remained vexingly enigmatic because of several factors: 1) The lack of instrumental 

data; 2) Our generally limited knowledge of intraplate earthquakes, and 3) The geology of 

the New Madrid/Mississippi Embayment region, which effectively obscures most surface 

expression of faulting.

Because an evaluation of the magnitudes of the 1811-1812 events is so critical to a 

determination of long-term seismic hazard in the region [e.g. Frankel et al., 1996] tremendous effort and ingenuity has been invested in gleaning quantitative information from the 

limited available data. Available data include: 1) Paleoliquefaction features preserved by 

the sediments within the Mississippi embayment [e.g. Tuttle and Schweig, 1996]; 2) The 

present-day distribution of seismicity in the New Madrid Seismic Zone, which is assumed 

to illuminate the principal fault zones [e.g., Gomberg, 1993; Johnston, 1996], 3) Modern 

estimates of the long-term deformation/strain accumulation in the region [Weber et al., 

1998; Newman et al, 1999] and 4) Contemporary first-hand reports ("felt reports") of 

the shaking and/or damage caused by the events over the central/eastern United States 

[e.g., Nuttli, 1973, Street, 1984],

Determination of magnitudes for the 1811-1812 mainshocks hinges on the felt reports 

and their interpretation for MMI intensities, which provide arguably the only direct 

constraint on magnitude. Nuttli (1973) drew isoseismal contours based on his compilation 

of approximately 40 felt reports. He determined nib = 7.2, 7.1, and 7.4 for NM1, NM2, 

and NM3, respectively, based on a relationship between ground motion and intensities 

from smaller and more recent instrumentally-recorded earthquakes in the central United 

States. With an exhaustive archival search, Street (1984) greatly expanded the number of 

reports (to approximately 100 for NM1) and assigned them intensity values. Street (1982) 

used these new data and the same method used by Nuttli (1973) to obtain ra{,=7.1 and 7.3 

for NM2 and NM3, and M7.0 for the 08:15 (local time) aftershock of December 16, 1811. 

Street (1982) determined these values by assuming the m^ value for NM1 determined by 

Nuttli (1973) and comparing the relative isoseismal areas of the other events. The new
macroseismic data determined by Street (1984) have not previously been interpreted with 

isoseismal contours.

Johnston (1996) carried out a comparison between intensity distribution and moment 

magnitude, Mw for large earthquakes in stable continental regions worldwide. He compared areas within isoseismals of discrete intensities with instrumentally measured moment magnitudes. On the basis of this calibration, he assigned 8.1+/ 0.31, 7.8+/ 0.33, 

and 8.0 + / 0.33 for NM1, NM2, and NM3, respectively. In this calculation, Johnston 

(1996) used the only available intensity contours; those determined by Nuttli (1973). 

Thus the current widely accepted magnitude determinations for the New Madrid mainshocks were derived from one set of isoseismal contours drawn subjectively based on less 

than half of the available data.

Both interpretation of felt reports and contouring of MMI data are inevitably highly 

subjective, especially with sparse and/or old reports. Although no one interpretationincluding the one that we will present-can claim to be unique and definitive, we argue that 

a revisitation of the original data is timely and appropriate given both the importance 

of the issue and our current appreciation for the the dramatic role that site response can 

play in controlling ground motions at regional distances.

We address the magnitude determination for the New Madrid mainshocks in two 

ways. First we reconsider intensity assignments for the reports compiled by Nuttli (1973) 

and Street (1984) (Table 1). In our reinterpret at ion, we focus on two types of information 

that are considered relatively objective: the extent to which people were woken up by 

events NM1 and NM3, and descriptions of damage to structures. The former information can provide important differentiation between moderate Modified Mercalli Intensity 

values, III-V [see Richter, 1952; Stover and Coffman, 1983]. The latter, in turn, can 

help differentiate between MMI values of V-VII. We focus on data away from the immediate New Madrid region, in an attempt to better constrain the isoseismal contours for 

moderate MMI values IV-VII.

Using the reinterpreted MMI values, we then draw new isoseismal contours using 

subjective as well as systematic approaches. Uncertainties are explored using a bootstrap 

technique. We use our new isoseismal contours to obtain moment magnitude estimates 

following the procedure and calibration established by Johnston (1996).

In the following section we discuss a suite of representative examples of original felt 

reports that we have interpreted differently than Nuttli (1973) and/or Street (1984).

3 Intensity Reports

3.1 Original Sources

All of the MMI values used to construct the original isoseismal maps [Nuttli, 1973] are 

presented in Table 2 and shown in Figure 1. MMI assignments from Street (1984) are 

also included in Table 2. In our reading of the felt reports, we find the original MMI 

assignments to be too high for two basic reasons: a general bias in the interpretation of
reports whose drama is belied by low levels of actual damage reported, and a failure to 

take site response issues into account.

Many of the accounts simply do not appear to support values as high as those 

originally assigned. In St Louis, Missouri, Fuller (1912) describes reports (from the 

Louisianna Gazatte, 12/21/1811) of people having been woken up by NM1, and furniture 

and windows having been rattled. He notes that "several chimneys were thrown down," 

and a few houses, "split." The interpretation of word "split" is open to interpretation, 

but it seems to have been used in a couple of contemporary accounts to mean "cracked" 

rather than destroyed. Consistently, as in the above example, the phrase "thrown down" 

is used to describe more complete damage to either chimneys or entire houses. The 

Louisianna Gazette account goes on to note that "no lives have been lost, nor has the 

houses sustained much injury." Based on these reports, we conclude that a MMI of VI-VII 

is more appropriate than the value of VII-VIII that Nuttli (1973) assigns for NM1.

At many locations, including Columbia, South Carolina; Detroit, Michigan; Washington DC; Knoxville, Tennessee; Lebanon, Ohio; and Norfolk, Virginia, event NM1 is 

generally reported as having been "distinctly" (often the word "sensibly" is used) felt, 

but with no reports of damage. Instead, reports describe the rattling of washing stand 

pitchers, glass, china, and furniture.' Reports from these locations also generally indicate 

that "many" were woken up by the event. Such descriptions are consistent with an MMI 

value of IV-V.

In Ft. St. Stephens, Louisiana, the only report of disturbed objects states that the 

event "shook fowls off of their roosts," but one might fairly suppose the fowls relocated 

of their own volition.

In Appendix 1, we present four representative original sources (quoted verbatim 

from Street, 1984) that were interpreted with MMI values of VI or V-VI. Although the 

ringing of a church bell (Milledgeville) and the unsteadiness of people standing (Edenton) 

are listed as effects of MMI VI, the reports do not describe the overall effects consistent 

with this intensity level, which include damage to plaster, broken dishes and windows, 

and overturning of furniture. In previous studies of intensity data from eastern U.S. 

earthquakes, MMI values of VI are reserved for locations at which multiple instances of 

plaster/chimney damage are documented [e.g. Gordon et a/., 1970].

Reports from Charleston, South Carolina, do describe the ringing of church bells, 

some cracking of walls, and the agitation of water in wells by the second major event of 

the sequence at approximately 8:00 a.m. local time on 12/16/1811. This report stands 

apart from many others (at comparable distance) in that it does document effects beyond 

the rattling of objects/houses.

In one critical instance, it appears that Nuttli (1973) was simply mistaken in his 

reading of the original sources. While Nuttli assigns an MMI of VI to the city of Arkport 

in western New York for NM1, the Pennsylvania Gazette account reports clearly that 

the observations of ground motion were made around sunrise (which corresponds to the 

time of a large aftershock). There is no mention of the 2:15 a.m. event having been 

felt at all in Arkport, implying a MMI of perhaps II-III (i.e., not felt at night) for NM1. 

Moreover, the shaking described for the sunrise event is a fairly gentle swinging/rocking

6
felt by individuals at rest, also more suggestive of MMI III than VI.

It also appears that a transcription error might have been responsible for the MMI 

value of VII that Nuttli (1973) assigns for Lexington, Kentucky for NM1. Fuller (1912) 

does not mention damage in Lexington at all, and the only original source included in 

Nuttli's compilation mentions the earthquake having done "some inconsiderable injury 

to several dwellings." The compilation of Street (1984) includes a report in the Kentucky 

Gazette of 12/17/1811 that describes windows having been shaken "equal to what they 

would have been in a hard gust of wind." This account goes on to note that no material 

injury was sustained in the area. However, two of the original sources included in the 

Nuttli compilation-the New York Post of 3/11/1812 and the Lexington Reporter-relay a 

letter that was written to an individual in Lexington, from an individual who had been 

in New Madrid at the time of the earthquake. Nuttli (1973) ascribes his assigned MMI 

value to the "2/11/1812 New York Post." However, only two letters from this issue of 

the Post are included in the compilation, neither of which describe damage in Lexington. 

(Only one of the letters even mentions Lexington, and then only briefly). There is also 

no account of effects at Lexington in the 2/11/1812 issue of the Post, which we reviewed. 

Based on the Kentucky Gazette account, we assign a MMI value of V for Lexington, KY.

In addition to the reassignments discussed above, a number of our MMI "downgrades" derive from a more complete understanding of site response than was available 

at the time of the earlier studies. As a first-order observation, the intensity data are 

strikingly sparse and concentrated along rivers and other bodies of water. The latter 

observation is no surprise; it reflects the distribution of the overall population in the 

more sparsely-populated parts of the central and southeastern U.S. in the early 1800's. 

Because the New Madrid sequence predates the construction of railroad lines into the 

mid-continent, settlements tended to remain clustered in proximity to waterways. As 

documented by the Missouri Historical Review of 1911, westward expansion followed the 

major rivers and virtually all early 1800's settlements in Missouri (the extent of the western frontier at that time) were within a few miles of the Mississippi River. New Madrid 

was built so close to the bank that, even before the earthquakes, parts of the town regularly gave way under the continued assault of river currents [Penick, 1981]. Much of 

the "bootheel" of Missouri was known as the Great Swamp, and was generally flooded 

at least part of the year [Shortridge, 1980]. One of the other sizable Missouri settlements 

of the time, Sainte Genevieve, had been moved to higher ground approximately a mile 

from the river after a flood in the late 1700's resulted in substantial erosion of the river 

bank upon which the town had originally been built [Brackenridge, 1817].

However, intensity data from river bank and other coastal regions will almost certainly reflect a significant site response resulting from the amplification of seismic waves in 

unconsolidated (and often water-saturated) sediments. The importance of site response 

in controlling earthquake ground motion has been understood for over a century [Milne, 

1898]. However, the potential magnitude of site amplifications at regional distances was 

perhaps not been fully appreciated until it so dramatically demonstrated in a number of 

destructive earthquakes in recent years [e.g., Singh et a/., 1986; Hough et a/., 1990].

Recent dramatic examples of site response have tended to involve lake beds, valleys or
basins, and coastal regions such as the San Francisco Bay Area. Significant site response 

along river valleys has been documented [e.g., Stover and von Hake, 1982] but is relatively 

uncommon, perhaps because of modern settlement patterns. That is, in modern times, 

relatively few people live on the very poor soils that are often found immediately adjacent 

to river banks. (The town of Sainte Genevieve never did expand back towards the river 

bank). Such settlements were common in earlier times, and isoseismal maps obtained for 

events such as the M6.6 1895 Charleston, Missouri earthquake clearly show substantial 

elongation of MMI contours along major river valleys in the central United States [Nuttli 

et al. , 1979; Hopper and Algermissen, 1980].

One should note, however, that very few substantial earthquakes have occurred in 

the central and eastern United States during the twentieth century. It is therefore unclear 

how strongly modern cities along major river valleys will be affected by site response.

A close reading of original sources reveals that the role of site response in controlling 

ground motions from the New Madrid events is documented in several contemporary 

accounts of the events. For example, Fuller (1912) quotes an account by Daniel Drake of 

Cincinnati, Ohio:

[Event NM1] was so violent as to agitate the loose furniture of our rooms, 

open partition doors that were fastened with falling latches, and throw off the 

tops of a few chimneys in the vicinity of the town.

It was this account that apparently prompted Nuttli to assign a MMI value of VI-VII 

for Cincinnati for NM1, yet Drake goes on to write:

It seems to have been stronger in the valley of the Ohio [River] than in the 

adjoining uplands. Many families living on the elevated ridges of Kentucky, 

not more than 20 miles from the river, slept during the shock; which can not 

be said, perhaps, of any family in town.

This account-in particular the fact that many people away from the river slept 

through the event-suggests a MMI value of perhaps IV, certainly not as high as V. 

Considering reported effects from the river valley and those from higher ground, one 

obtains a MMI range of IV-VI for Cincinnati, or an average of V. Or, equivalently, this 

approach corresponds to separate assignments for river valley and hill sites at Cincinnati. 

(In the absense of location direction of the ridge sites, we assign both values to the same 

location; see tables 1-3).

Another report, from the Western Intelligencer newspaper of 1/24/1812 [see Street, 

1984] reports:

...it appears that [the earthquakes] were scarcely noticed at Chillicothe 

[Ohio], except along or near the banks of the largest streams.

This report provides a cautionary illustration of the potential biases associated with 

intensity data given a very sparse population density and substantial site response. That
is, the damage reported in a town like Chillicothe may not be representative of shaking 

anywhere except along the riverbanks, but, in the absence of specific information such as 

the above, there is no choice but to assign an overall intensity level based on the available 

report.

Of the felt reports from the New Madrid sequence, site response is explicitly documented in a number of cases: Cincinnati, Ohio; Chillicothe, Ohio; Newark, New Jersey; 

Asheville, North Carolina; and Brownsville, Pennsylvania. In each instance, shaking 

and/or damage is reported to have been worse within a valley or along a riverbank than 

on adjacent higher ground. Where such information is available, we assign distinct MMI 

values for river bank/valley sites and "hard rock" sites away from the waterways. Where 

the reports do not explicitly document relatively higher shaking along shorelines, we 

generally do not attempt to correct the MMI values for site response.

However, in some cases, it appears that high intensity values were assigned based 

solely on riverbank effects; we do downgrade some of these values. Along the Mississippi 

River the felt reports document a number of instances of riverbank slumping and even 

collapse of islands following NM1. One example is Vicksburg, Mississippi, where a MMI 

value of VII was assigned, apparently based on a report from one island (Island No. 94) 

near the city:

In the night the earthquake came and next morning when the accompanying 

haziness disappeared the island could no longer be seen. It had been utterly 

destroyed as well as its pirate inhabitants.

Although dramatic, we suggest that the assignment of VII for the city of Vicksburg is problematic in several respects: 1) An MMI of VII involves "considerable damage in poorly built or badly designed structures; some chimneys broken." Yet there 

are no reports of significant damage from the city itself in the compilations of Mitchill 

(1815), Fuller (1912), or Street (1984). Also, 2) It appears virtually impossible to know 

the geology of Island No. 94, the effect that earthquake-generated river disturbances 

(waves/currents) might have had on its demise, or even the ultimate fate of the "pirate 

inhabitants." Fuller does describe the overturning of canoes elsewhere along the river 

in the same vicinity, and original felt reports describe large and sustained disturbances 

in the Mississippi river currents caused by event NM1. At a point along the river then 

known as Devil's Race Ground (120 miles below New Madrid), one account reports,

...our boat appeared as if alternatively lifted out of the water, and again 

suffered to fall. The banks above, below, and around us were falling every 

moment into the river...

Clearly, differentiating between the effects of river disturbances along the Mississippi 

and ground shaking is difficult, if not impossible.

In the final analysis, we conclude that some level of bias will inevitably remain in 

our reinterpreted MMI values. However, we conclude that, in many cases, the available

9
data are sufficient to assign a more representative regional MMI level based not on the 

maximum effects reported, but on a full consideration of all available reports.

Figure 1 presents a histogram of MMI values for NM1 obtained in this study compared to those determined by Street (1984). Overall, we have assigned significantly more 

MMI 4-5 values and significantly fewer 5-7 ones, although in a few instances our MMI 

assessments for a given location are higher than those of Street (1984).

A final map of reinterpreted MMI values is shown in Figures 3-5 and tabulated in 

Tables 2-4. These results include MMI values based on data from the following sources: 

Mitchill (1815), Fuller (1912), Nuttli (1973), Street (1984). Additional data are obtained 

from the Chillicothe Fredonian (1811-1812) and the Raleigh Star (1812) [see Appendix 2]. 

Tables 2-4 also includes brief exerpts from original reports that were considered pivotal 

in the assignment of MMI values.

4 Isoseismal Areas

The reinterpreted MMI values are considerably more spatially variable than those determined by Nuttli, (1973). Considering the data shown in Figure 3a, it is clear that 

isoseismal contours are not well-constrained. To obtain magnitude estimates using the 

equations derived by Johnston (1996), however, one must estimate isoseismal areas.

We use three different approaches to contour the data from NM1. In the first, the 

contours are drawn by eye (Figure 3a), a procedure that is entirely subjective but for 

which there is considerable precedence in previous intensity studies.

The second approach (Figure 3b) is based on a modification of the least-squares 

minimization scheme presented by Seeber and Armbruster, 1987 [see also Armbruster and 

Seeber, 1987]. The data are contoured with a suite of best-fitting ellipses, with degree of 

ellipticity determined by the data. Least-squares residuals are calculated between each 

data point and the predicted intensity at that distance.

In the third approach (Figure 3c), the MMI values are treated as Boolean data. If a 

data point falls within the appropriate isoseismal area (e.g., a value of 4 that falls between 

the MMI 4 and 5 contours) the residual is zero. If a data point is outside the appropriate 

contour, the residual is equal to the (whole number) difference between the observed 

and calculated values. This approach was designed to reproduce the usual conventions 

applied when intensity data are contoured subjectively. That is, isoseismals are generally 

drawn to outline areas of equal intensity.

In both regressions, the starting model for the fall-off of intensity with distance is 

derived from the empirical equations of Johnston (1996). The inversion schemes then 

allow for iteration away from this model based on the distance decay of the data.

Using the regression approaches, the treatment of the "not felt" (NF) reports becomes a critical issue. Because NM1 and NM3 occurred at times when people can be 

assumed to have been asleep, we assume that a NF report implies a bound of MMI < 

4 (the shaking level at which "some" people are awakened; [Stover and Coffman, 1993]. 

For NM2, which occurred around 8:00 a.m. local time, a NF report is taken to imply a

10
bound of MMI < 3.

We do not attempt a subjective contouring of the data for events NM2 and NM3. 

Given the sparsity of the data for these events, we also fix both the ellipticity and 

the shape of the distance-decay to match that determined for NM1. The decision to 

fix ellipticity is a pragmatic one; allowing another free parameter with the sparse data 

results in solutions that we consider unstable.

Figures 3-5 present the results of the least-squares and Boolean regressions for all 

three events. We estimate Mw values from each individual isoseismal contour using the 

equations derived by Johnston (1996). For MMI of 6 and below, we use the regression 

results derived specifically from eastern North American data. For MMI 7 and 8, we 

use the regression results derived by Johnston (1996) from a global data set of stable 

continental region earthquakes.

Johnston (1996) presents so-called western correction factors for extrapolation of 

isoseismals from the New Madrid sequence to the west. Johnston (1996) uses the 1843 

Marked Tree, Arkansas earthquake to derive correction factors for NM1 and the 1895 

Charleston, Missouri, earthquake to derive a different set of factors for NM2 and NM3. 

We apply these same correction factors to our results.

The Mw values implied for each isoseismal (MMI 4-8) from each event are summarized in Figures 6a and 6b. To obtain an average Mw for each regression, we estimate 

seismic moment, M0 using the standard formula

log(M0 ) = 1.5MW + 16.05 (1)

and compute an average M0 value that we then translate to Mw using equation (1) 

(Figure 6). The variability of the results for NM2 and NM3 (with isoseismal level) are a 

direct result of the western reduction factors, which vary substantially with MMI level. 

If one instead applies the set of reduction factors derived by Johnston (1996) for NM1, 

the inferred magnitude estimates from individual isoseismal levels are more consistent, 

but not significantly different on average.

To investigate the uncertainties associated with each regression, we apply a bootstrap 

analysis in which isoseismals are fit using 50 randomly resampled sets of data points. For 

each intensity, the five most extreme results are discarded and bounds are estimated from 

the remaining 45 sets. The uncertainty ranges resulting from the bootstrap analysis are 

shown in Figures 6a and 6b.

5 Interpretation

For NM1, the range from both regressions is approximately 0.3 units. For NM2 and 

NM3, ranges of 0.35-0.7 are inferred. However, considering the range of results from 

both the Boolean and least squares approach for each event, one obtains uncertainties of 

approximately a full magnitude unit for all three events.

We suggest, though, that the available data do constrain the magnitude of each 

event to better than +/ 0.5 magnitude units. Returning to the Boolean contouring

11
results for events NM1 (Figure 3c) and NM3 (Figure 5b), we argue that the isoseismal 

contours are contradicted by a key subset of the observations: for both events, the MMI 

4 contour extends to the northeast well beyond the limits of the (positive) felt reports for 

both events. The northeast was the most densely populated part of the country at the 

time. If the MMI 4 contour for NM3 truly bisected Massachusetts, then surely the event 

would have been felt throughout southern New York and New England. Similarly, the 

Boolean MMI 4 contour for NM1 suggests that this event would've been felt throughout 

eastern Pennsylvania.

The MMI 4 contours from the least-squares regressions for both NM1 and NM3 are, 

we suggest, considerably more reasonable. For both events, the MMI 4 contours nicely 

separate the felt from the NF reports. Although the data from NM2 are more ambiguous, 

the MMI 4 Boolean contour for this event does include a number of MMI 3 values in the 

northeast.

We conclude that while the Boolean approach would be preferred given a sufficiently 

complete set of felt reports, it is yielding over-estimates of isoseismal areas for the New 

Madrid events because of the significant remaining site response biases. The least-squares 

regressions, on the other hand, result in contours that are closer to what one would draw 

subjectively based on one's assessment of site response. Although the isoseismal contours 

for NM2 are less well constrained than the other two events, we consider it likely that 

the data would be biased by the same factors that bias the data from the other events.

We therefore consider the least-squares results for events NM2 and NM3 to be our 

preferred magnitude estimates. For event NM1, our preferred estimate is the one resulting 

from the subjective contouring. Although we do not consider it possible to quantify the 

uncertainties precisely, we conclude that the bootstrap results do provide a good general 

indication of the appropriate error bars. Our final, preferred estimates for the three events 

are, respectively as follows: MW 7.2 7.3, Mu w 7.0, and MW 7.4 7.5, with uncertainties of 

approximately 0.3 units in each case. Interestingly, as shown in Table 5, these estimates 

are quite close to the ra& values originally determined by Nuttli (1973).

Given a prolonged sequence of events, one might suppose that the damage from 

NM2 and NM3 was exacerbated by the pre-existing damage from the earlier event (s). 

However, damage to weakened structures would only be reflected at MMI levels large 

enough to cause damage (l V), and there is no evidence that the larger MMI values are 

disproportionately elevated for the second and third events.

In addition to inferences drawn from the intensity data from each event, the above 

magnitude and uncertainty estimates are also guided in part by a consideration of the 

relative shaking levels reported for the different events. That is, intensities for NM2 are 

somewhat-but not enormously-smaller overall than for NM1. The January event was 

described as being stronger than NM1 at some locations, which may have reflected 1) 

the more northerly epicenter of NM2 and 2) the fact that NM2 happened during daylight 

hours, when people's perceptions were likely to have been more keen. Based on the overall 

intensity fields, we conclude that NM2 was somewhat smaller than NM1, although, as 

the bootstrap uncertainties show, this magnitude estimation is the least certain of the 

three. (A significant cold spell in the weeks preceding NM2 reportedly slowed boat traffic

12
into the mid-continent and may have served to impede reporting of this event more than 

the others).

NM3, on the other hand, is widely described as having been the largest event, in 

terms of both amplitude and duration of ground motions. Although this event was also 

farther north than NMl, we consider it unlikely that the modest difference in location 

would have accounted for the documented differences in shaking as far away as Ohio, 

Pennsylvania, Virginia, and South Carolina. It is tempting to speculate that, as the one 

thrust event, perhaps NM3 was of comparable magnitude to NMl (assumed to be a strikeslip event) but had a higher stress drop. Clearly, we cannot conclude with certainty that 

this was not the case. However, the felt reports are remarkably consistent in describing 

NM3 as having had the longest duration of shaking, which suggests the event had a larger 

magnitude-rather than, or in addition to-a larger stress drop than the other events.

5.1 A Note on Demographic Issues

An important consideration in the interpretation of sparse felt reports is the population 

density of the towns from which the data are derived. Fortunately, such data are available 

in the 1810 Federal Census, which included both states and territories. Unfortunately, 

the data are incomplete in some instances, with population tallied only by county or 

district, not by individual town.

The total population of the United States was approximately 7,000,000 in 1811, 

including sizable numbers in Tennessee, Kentucky, and the territories, including presentday Missouri and Louisiana.

The 1810 Census documents the population for several districts for which felt reports are considered, including the District of Saint Louis (pop. 5667), Natchez (10,002), 

Cincinnati (2540), New Orleans (24,552), and Detroit (2227). What is noteworthy about 

these figures is that they are comparable to, or in some cases greater than, the populations of districts for which damage from NMl is documented: Cape Girardeau (3888), 

Louisville (1357), and New Madrid (2103).

Although present-day Missouri was relatively sparsely populated in 1811, available 

contemporary accounts [e.g. Bradbury (1819); Brackenridge (1817)] provide a fairly thorough documentation of demographic and related information. These sources reveal that 

cities such as Saint Louis and Sainte Genevieve were far more than simple villages by 

1811, with solidly constructed houses appearing by the turn of the century. In Sainte 

Genevieve, Anderson (1937) describes the typical house of the time as being a one-storied 

dwelling with plastered walls and front and back porches. The oldest brick building west 

of the Mississippi was built in Sainte Genevieve in 1804. This house, and approximately 

50 others that predate the New Madrid sequence, are still standing today.

Moreover, while the New Madrid sequence predated even telegraph communications, 

a perusal of the contemporary sources reveals that news did circulate between towns. A 

weekly Saint Louis newspaper, the Louisiana Gazette, printed over a dozen separate reports on the New Madrid earthquakes between 12/21/1811 and 5/2/1812. These reports 

included observations from various midcontinent locations. Additional information was

13
carefully compiled by the naturalists and historians of the time: Mitchill, Brackenridge, 

Bradbury. We conclude that, had there been substantial damage in towns such as Saint 

Louis, Sainte Genevieve, or Cincinnati, it would have been documented.

6 Discussion and Conclusions

The results presented in this study show that a plausible reinterpretation of the intensity 

data yields magnitude estimates nearly a full unit below those previously inferred. Our 

preferred estimates for the moment magnitudes of the three principal events are MW 7.2- 

7.3, w7, and 7.4-7.5, respectively.

Considerable uncertainly clearly remains in the assignment of magnitudes for all 

three of the New Madrid mainshocks because of uncertainties associated with both the 

assignment of MMI values and with the estimation of isoseismal areas. Interpretation 

of felt reports is inherently subjective. Our approach has been to assign MMI values 

based more on descriptions of damage and other specific effects, and less on vague qualifiers regarding the perceived severity of shaking. Ground motions-the long-period waves 

in particular-from large (M7+) earthquakes at regional distances can be surprisingly 

powerful without being damaging, presumably all the more so to people with no prior 

(first-hand) experience with earthquake ground motions. In some cases we also base our 

MMI assignment not on a single effect indicating the highest intensity, but rather on an 

overall assessment of effects described.

Because the isoseismal area-Mw regression results of Johnston (1996) were calibrated 

with similarly subjective data, the critical question is the extent to which our assignments 

are consistent with those on which the regressions were based. In general, there is some 

precedent for keying an MMI assessment on the most dramatic effects described, such 

as MMI values of VI for Edenton, N.C., because of the single report that people "could 

scarcely keep their feet" and for Milledgeville, GA, because the bell in the State House 

was set ringing (see Appendix 1, and associated discussion earlier in the text).

However, considering the MMI assignments made for the 1968 ra&5.3 South-Central 

Illinois earthquake [Gordon et a/., 1970] as an example, it is clear that an MMI of VI 

is typically assigned when there are multiple instances of the damage usually associated 

with this level of intensity: broken windows, cracked plaster, damage to brick chimneys, 

etc.

We also note, that, in some cases (including those from Edenton and Milledgeville), 

the specific report suggesting a high MMI value is one that suggests relatively long-period 

shaking effects. There is ample precedent for not assigning an MMI value based on such a 

report when the effects related to higher frequency shaking (i.e., toppling of small objects 

and furniture) indicate a much lower value [e.g., Armbruster and Seeber, 1987].

In general, there is a fundamental distinction between the 1811-1812 New Madrid 

events and those used by Johnston (1996) to derive the isoseismal area-moment magnitude regressions: the latter events are those for which instrumental magnitudes are 

available, which means they are from the 1900's (1925 onward). They are thus more re14
cent by upwards of 100 years than the New Madrid sequence, and so the collection of felt 

reports from the New Madrid sequence is considerably sparse than the others. Density 

of data depends on both the density of population and on the completeness of reporting. Both factors could conceivably bias the inferred intensity data, but no systematic 

bias-either positive or negative-has yet been documented.

However, systematic differences in spatial sampling can clearly introduce substantial 

biases. In 1811-1812, logistical constraints induced most of the population to live along 

river banks (or coasts), which are often characterized by alluvial near-surface geological 

conditions. Later in the 19th century, the introduction of ground transportation allowed 

settlement to shift to higher ground, away from potential flooding hazard. Sedimentinduced amplification is therefore much more likely to affect reports from the early part 

of the 19th century than those from the 20th century (or even the mid-19th century). 

Although we recognize this possible bias in the 1811-1812 intensity data, we do not correct for it systematically in our assignment of MMI values. We have, however, addressed 

the issue of site response in two ways: 1) by revising the MMI assignments where contemporary accounts do document significant site response, and 2) by using judgement in 

choosing preferred isoseismal contours. Nuttli et al. (1979) argued that "protuberances 

in the isoseismals are due to the enhancement of the intensity by surficial geology" and 

should not be used to constrain contours. We use this very consideration to reject the 

Boolean regression results in favor of the least-squares contours. The least-squares regressions essentially allow high MMI values (such as those along coastal South Carolina) 

to become outliers.

A systematic site response correction could be done via a careful consideration of 

intensity distributions from more recent data. Hopper et al. (1983) present a map of 

isoseismals expected from a repeat of a New Madrid mainshock in which site response is 

included implicitly. We note, however, that site corrections for the 1811-1812 data would 

require an very detailed analysis because settlement patterns changed so drastically in 

the decades following the New Madrid sequence.

We also note that the MMI values predicted in the Hopper et al. (1983) study 

are grossly inconsistent with our inferred values. For example, their MMI VII contour 

stretches well into Georgia and South Carolina. These contours result from their methodology, in which observed MMI data from smaller earthquakes are scaled up by maximum 

reported intensity of NM1. This equates to the assumption that the shape of the intensity 

fall-off is the same for earthquakes of all magnitudes (in a given source region), an assumption that is not necessarily valid. For example, a very large event might have a very 

steep decay with distance from MMI XI to VIII, as these intensities tend to be controlled 

by near-field effects, while the distance decay of MMI for a smaller, deeper event can 

be more gradual. However, if one were to use the shape of the intensity contours from 

Hopper et al. (1983), which do reflect expected site response patterns, with rescaling 

using our revised MMI values, the resulting isoseismal areas could be appreciably smaller 

still than those determined here.

We have focused on the moderate intensity contours because their isoseismal areas 

are the critical inputs to the area-based magnitude determination method of Johnston

15
(1996). Isoseismal contours for MMI levels IV-VII can be constrained by relatively objective reports of damage to structures and the perceptions of individuals who (it can 

generally be assumed) were asleep at the time of events NM1 and NM3. The felt reports 

closer to the New Madrid seismic zone are relatively incontrovertible in documenting the 

extent of damage and ground failure. However, as noted by Newman and Stein (1999) 

interpretation of these reports is greatly complicated by the vast extent of poorly consolidated and largely water-saturated sediments within the Mississippi embayment. And, 

once again, the natural settlement patterns would have resulted in a strong correlation 

between population density and proximity to the Mississippi River.

A MU of w 7.2 7.3 for NM1 is consistent with several other lines of evidence, including 1) an extrapolation of the currently observed seismicity distribution, given constraints 

on the repeat time as determined from paleoseismic studies; 2) the available area of the 

inferred causative fault as constrained by the extent of the southern limb of the New 

Madrid Seismic Zone and the observed depth of microseismicity [e.g., Gomberg, 1993]; 

and 3) a long-term slip rate recently inferred from GPS data to be less than 2 mm/yr 

[Newman et al. 1999]. That is, the low strain rate recently determined from GPS data 

is inconsistent with Mu of 8+ for the 1811-1812 events if they occur as often as has been 

inferred from paleoseismic data [e.g., Tuttle and Schweig, 1996], Newman et al. (1999) 

therefore argue that either the repeat time is longer than previously estimated or the 

magnitudes are smaller. Although interpretation of short-term GPS data is fraught with 

fundamental uncertainties regarding tectonic processes-in intraplate regions especiallyMW 7.3 is consistent with the most straightforward interpretation of both deformation 

and seismicity data.

The revised MMI contours obtained for event NM1 are not too different-perhaps 

20% larger-from those obtained for the largest earthquake to have occurred in eastern 

North America in the twentieth century-the 1929 MW 7.2 Grand Banks, Canada event. 

For this event, teleseismic data has been used to obtain an instrumental estimate of Mu 

as well as a finite fault rupture model [Bent (1995)]. The inferred model involves complex 

strike slip faulting, with an overall fault length of w 100 km. Gomberg (1993) infers a 

similar dimension for the southern limb of the New Madrid seismic zone. We therefore 

suggest that the Grand Banks and (first) New Madrid event were in fact fairly similar, 

with the latter perhaps a bit bigger than the former.

Event NM2 is difficult to analyze in any detail because the inferred causative fault, 

the northern strike-slip limb of the New Madrid Seismic Zone, is the least well-understood 

part of the zone. Also, although the hour of the event provided a better characterization 

of the low intensity (MMI 3-4) field, a strong cold spell in January had slowed boat 

traffic, and therefore the flow of information, in the mid-continent.

However, recent investigations have provided significant constraint of the Reelfoot 

fault, the thrust fault in between the two strike-slip limbs of the New Madrid seismic zone 

that is inferred to have produced NM3 [e.g., Russ, 1982; Kelson et al., 1992; Johnston, 

1996]. Structure of the Reelfoot fault has been elucidated in recent years with seismic 

reflection profiling. Odum et al. (1996) infer an overall fault length of at least 30 km and 

constrain the dip to be approximately 40 degrees.

16
Although no direct measurements of fault scarp height are available for NM3, contemporary accounts from boats on the Mississippi describe waterfalls forming on the 

river. As discussed by Odum et al. (1996), these observations correspond to points 

where the inferred fault rupture crossed the river. The height of these waterfalls is not 

well constrained, although some information can perhaps be gleaned from available reports. One observer by name of Mathias Speed described them as similar to the rapids of 

the Ohio, a 23-foot descent over a distance of 2 miles [Penick, 1981]. Another observer, 

W. Shaler, described a height of "at least six feet" [see Street, 1984]. In light of these 

reports and the established geometry of the Reelfoot fault, we assume an average slip of 

4-5 m. Further assuming a fault length of 30-40 km and a down-dip width of 28 km, one 

obtains a M^ of 7.3-7.5 for NM3.

The above rupture parameters are generally consistent with scaling relationships 

established using data from events worldwide [Wells and Coppersmith, 1994]. Their 

relation between rupture length and magnitude yields M6.9 for a rupture length of 40- 

km, but their relationship between average slip and magnitudes yields M7.5 for a slip of 

4.5 m, perhaps lending a measure of support to the hypothesis that the 2/7/1812 event 

was a high stress drop event.

As a final note, we address two arguments that have been made against "downgrading" the magnitudes of the 1811-12 events: 1) That if the New Madrid events were 

Mu;7.0-7.4 instead of 8, then the magnitudes of other large historic eastern events, such as 

the 1886 Charleston, South Carolina (and other smaller events in turn), must be reduced 

correspondingly; and 2) That a repeat of the ground motions from the 1811-12 sequence 

would be equally destructive whether they were M^S events with typical ground motions 

for their size or MJl events whose ground motions were anomalously high because of the 

regional near-surface geology.

We first note that the logic behind argument (1) is not necessarily valid. For one 

thing, it is possible that the magnitude of the other eastern events have also been overestimated. However, even by 1843 (the year of the M6.3 Marked Tree, Arkansas earthquake), 

the eastern United States was considerably more populated than it had been just 30 years 

earlier. Isoseismal contours for the 1886 Charleston, SC, and 1895 Charleston, MO, 

events are better constrained still. As mentioned earlier, increased population density 

(especially away from the immediate vicinity of waterways) would reduce site response 

biases by providing a more representative sampling of site conditions.

The second argument is a more valid one. Assuming the paleoseismic constraints 

on repeat times for 1811-12 events to be correct, it makes an enormous difference for 

long-term probabilistic hazard assessment whether these events were Afw 7-7.4 or M^S. 

However, as others have noted, the hazard is a function of the expected ground motions, 

which, in the case of the New Madrid sequence, appear to have been significantly elevated 

in many cases by site response. An evaluation of site response may therefore be critical 

for seismic hazard assessment at many locations in the central/eastern United States, 

particularly those immediately adjacent to major rivers and the Atlantic seaboard.

17
7 Acknowledgments

We thank Jim Dewey, Hiroo Kanamori, Lucy Jones, Bill Bakun, and Jim Dolan for 

helpful comments and suggestions that greatly improved the manuscript; Research by L. 

Seeber and J. Armbruster was supported by USGS NEHRP grant 1434-HQ-98-AG-01946. 

Figures 2-5 were generated using GMT software [Wessel and Smith, 1991].

8 References

Anderson, H. M., Missouri, 1804-1828: Peopling a frontier state, Missouri Hist. 

Rev., 31, 150-180, 1937.

Armbruster, J. and L. Seeber, Seismicity 1886-1889 in the Southeastern United 

States: The aftershock sequence of the Charleston, S.C. earthquake, U. S. Nuclear Regulatory Commission, Washington, D.C., NUREG/CR-4851, 153pp, 1987.

Bent, A. A complex double couple source mechanism for the Ms7.2 1929 Grand 

Banks earthquake, Bull. Seism. Soc. Am., 1003-1020, 1995.

Bradbury, J., Travels in the interior of America in the years 1809, 1810, and 1811, 

Sherwood, Neely, and Jones, London, 1819.

Brackenridge, H. M., Views of Louisiana; containing geographical, statistical and 

historical notices of that vast and important portion of America, Schaeffer and Maund, 

Baltimore, 1817.

Prankel, A., C. Mueller, T. Barnhard, D. Perkins, E. V. Leyendecker, N. Dickman, 

S. Hanson, and M. Hopper, National seismic hazard maps: documentation, U.S. Geol. 

Surv. Open-File Rep., 96-532, 69 pp, U.S. Gov. Printing Office, Washington B.C., 1996.

Fuller, M. L., The New Madrid Earthquake, U.S. Geol. Surv., Bull. 494, 1912.

Gomberg, J. S. Tectonic deformation in the New Madrid Seismic Zone: Inferences 

from map view and cross-sectional boundary element models, J. Geophys. Res., 83, 

6639-6664, 1993.

Gordon, D. W., T. J. Bennett, R. B. Herrmann, and A. M. Rogers, The SouthCentral Illinois earthquake of November 9, 1968: Macroseismic studies, Bull. Seism. 

Soc. Am., 60, 953-971, 1970.

Hopper, M. G. and S. T. Algermissen, An evaluation of the effects of the October 

31, 1895 Charleston, Missouri, earthquake, U.S. Geol. Surv. Open-File Rpt, 80-778, 43 

pp., 1980.

Hopper, M. G., S. T. Algermissen, and E. E. Cobrovolny, Estimation of earthquake 

effects associated with a great earthquake in the New Madrid Seismic Zone, U.S. Geol. 

Surv. Open-File Rpt, 83-179, 94 pp, 1983.

Hough, S. E., R. D. Borcherdt, P. A. Friberg, R. Busby, E. Field, and K. H. Jacob., 

The role of sediment-induced amplification in the collapse of the Nimitz freeway during 

the October 17, 1989 Loma Prieta earthquake, Nature, 344: 1990.

Johnston, A. C., Seismic moment assessment of earthquakes in stable continental 

regions-Ill. New Madrid 1811-1812, Charleston 1886, and Lisbon 1755, Geophys. J. Int.,

18
126, 314-344, 1996.

Kelson, K. I., G. D. Simpson, R. B. VanArsdale, C. C. Haraden, and W. R. Lettis, 

Multiple Holocene earthquakes along the Reelfoot fault, central New Madrid seismic 

zone, J. Geophys. Res., 101, 6151-6170, 1992.

Milne, Seismology, first ed., London, Kegan Paul, Trench, Truber, 320 pp., 1898.

Mitchill, S. L. A detailed narrative of the earthquakes which occurred on the 16th 

day of December, 1811, Trans. Lit and Philosophical Soc. New York, 1, 281-307, 1815.

Newman, A. V., S. Stein, J. Weber, J. Engeln, A. Mao, and T. H. Dixon, Slow 

deformation and low seismic hazard at the New Madrid Seismic Zone, Science, 284, 

1999.

Nuttli, O. W. The Mississippi Valley earthquakes of 1811 and 1812: Intensities, 

ground motion, and magnitudes, Bull. Seism. Soc. Am., 63, 227-248, 1973.

Nuttli, O. W., G. A. Bollinger, and D. WL Griffiths, On the relation between modified 

Mercalli intensity and body-wave magnitude, Bull. Seism. Soc. Am., 69, 893-909, 1979.

Odum, J. K., W. J. Stephenson, and K. M. Shedlock, Near-surface structural model 

for deformation associated with the February 7, 1812 New Madrid, Missouri, earthquake, 

Geol Seism. Am. Bull, 110, 149-162, 1998.

Penick, J. L., Jr., The New Madrid Earthquakes, revised edition, University of Missouri Press, Columbia and London, 1981.

Richter, C. F., Elementary Seismology, W.H. Freeman and Co., San Francisco, 1958.

Russ, D. P., Style and significance of surface deformation in the vicinity of New 

Madrid, Missouri, in McKeown, F. A., and Pakiser, L. C., eds., Investigations of the New 

Madrid, Missouri, earthquake region, U.S. Geol. Surv. Prof. Pap., 1236, 95-114, 1982.

Seeber L. and J. G. Armbruster, The 1886-1889 aftershocks of the Charleston, South 

Carolina, Earthquake: a Widespread Burst of Seismicity, J. Geophys. Res., 92, 2663- 

2696, 1987.

Shortridge, J. R., The expansion of the settlement frontier in Missouri, Missouri 

Hist. Rev., 75, 64-83, 1980.

Singh, S.K., J. Lermo, T. Dominguez, M. Ordaz, J.M. Espinosa, E. Mena, R. Quass, 

The Mexico earthquake of September 19, 1985-A study of amplification of seismic waves 

in the Valley of Mexico with respect to a hill zone site, Earthquake Spectra, ^, 653-673, 

1988.

Stover, C. W. and C. A. van Hake, eds, United States Earthquakes, 1980, U.S Dept. 

of Int. and U.S. Dept. of Commerce, Golden, Co., 1982.

Stover, C. W. and J. L. Coffman, Seismicity of the United States, 1568-1989 (revised), U.S. Geol. Surv. Prof. Pap., 1527, 1993.

Street, R., A contribution to the documentation of the 1811-1812 Mississippi Valley 

earthquake sequence, Earthq. Notes, 53, 1982.

Street, R., The historical seismicity of the central United States: 1811-1928, U.S. 

Geol. Surv. Final Rpt, contract 14-08-0001-21251, Append. A., 316 pp., 1984.

Tuttle, M. P. and E. S. Schweig, Archaeological and pedological evidence for large 

prehistoric earthquakes in the New Madrid seismic zone, central United States, Geology, 

23, 253-256, 1996.

19
Tuttle, M. P., J. Collier, L. W. Wolf, and R.H. Cafferty, New evidence for a large 

earthquake in the New Madrid seismic zone between AD 1400 and 1670, Geology, 27, 

771-774, 1999.

Weber, J., S. STein, and J. Engeln, Estimation of intraplate strain accumulation in 

the New Madrid seismic zone from repeat GPS surveys, Tectonics, 17, 250-266, 1998.

Wells, D. L. and K. J. Coppersmith, New empirical relationships among magnitude, 

rupture length, rupture width, rupture area, and surface displacement, Bull. Seism. Soc. 

Am., 84, 974-1002, 1994.

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AGU, 72, 441-446, 1991.

20
Original MMI Values, Contours FmmNuttli (1973)

48° -

46° -

44° -

42° -

40° -

266° 268° 270° 272° 274° 276° 278° 280° 282° 284° 286° 288° 290 C

Figure 1. Original MMI values assigned by Nuttli (1973) for the 02:15 a.m. 

(local time), 12/16/1811 earthquake. Approximate original contouring is also 

shown

21
This Study

^u - ^ 15 

0

.a£10- 

^ 

Z 5

n

« 26

, MMI -6

< ... : : . 1

2 3 4 5 6 7 8 9 10 11 12

MMI

20

o

.Q

15 - 5 H

0

Street (1982)

J______I______I______I______I______I______I______I

36 

MMI 6

I I I I I T

4 5 6 7 8 9 10 11

MMI

12

Figure 2. Histogram binned by 0.5 MMI 

units showing distribution of assigned 

values for NM1 from this study (top) as 

compared to those of Street, 1984 (bottom). 

"Not felt" reports are included in the MMI 3.5 bin in both cases.
NF

NF

30CM<m

16 Decerrber 

SUBJ ECTI VE

181

Figure 3a. MMI values based on reinterpretation of original felt reports as 

documented by Nuttli (1973) and Street (1984). In some instances, MMI 

values are shifted very slightly for clarity. Also, in some cases where we 

have assigned an intermediate value or a range of values for a given site, 

only the average is shown. Half MMI units are denoted with "+" signs. 

Contours are drawn subjectively and yield Mw using the regression results 

and western correction factors from Johnston (1996).

23
I- 8

4 8 12 16 

PI STANCE ( DEGREES)

NF"

NF

(-----5---

NF

NF

4+\ 'NF

' \ ^^V \ /6+ 7° / * + 4

\ V-*> 5 / r

' 16 Decanter 181

LEAST/SQUARES

\v

44' 

43' 

42' 

41 = 

40' 

39' 

38' 

37' 

36' 

35' 

34' 

33' 

32' 

31' 

30'

Figure 3b. MMI data for event NM1; least-squares contouring results. 

Inset shows observed intensity values as a function of distance from 

the epicenter shown (symbols) and predicted values (smooth line). 

"Not felt" results are shown with inverted triangles; a report that the 

event was "felt" (i.e., with no other information) is shown with an upright 

triangle. Small circles show results from felt reports that include 

enough information to determine a numerical MMI value.

24
16/Decerrber 

BOOLEAN

1-81

Figure 3c. MMI data for NM1; Boolean contouring results. Inset 

plotting conventions same as in Figure 3b.

25
- 92° - 90 - 86° - &4 &2/ - 80° - 78° 76° - 74° - 72° - 70°

4 8 12 16 

Dl STANCE ( DEGREES)

300' km

23yJanuary 1812 

SQUARES

Figure 4a. Reinterpretted MMI data for event NM2; least-squares 

contouring. Inset plotting conventions same as for Figure 3b.

26
-92° -90° -88° -86° -84° -82° -80° -78° v-76° -74° \72° -70°

/ 300 km /

,-'23 January 1812 

A--'' BOOLEAN-''

\ . '

Figure 4b. Reinterpreted MMI data for event NM2; Boolean contouring 

results. Inset plotting conventions same as for Figure 3b.

27
-92*" -90° -88° -86° -84° -82° -80° -7-8° -76° -74° -70°

Figure 5a. Reinterpreted MMI data for NM3; least-squares contouring 

results. Inset plotting conventions same as for Figure 3b.

28
-92° -90° -88° -86° -84° -82° -80° -78° -76° -74° -72° -70°

0 4 8 12 16 20 

Dl STANCE ( DEGREES)

300 km/

/'7 February 181< 

BOOLEAN

Figure 5b. Reinterpreted MMI data for event NM3; Boolean contouring 

results. Inset plotting conventions same as for Figure 3b.

29
Regression Results, Bootstrap Uncertainties

2/7/1812 2/7/1812

8

7

t

8

7

/

8

7

/

i i 

M7.45 Least-squares _

...... .. . TT

I 4 6

1/23/1812

i

8

i i 

;_ M7.0 Least-squares

~~---TT

I 4 6

12/16/1811

-y8

i i 

M7.1 Least-squares

y---.-- t-t~H

246

- 4- - -:

i

8

8

7

y«

8

7

/

8

7

/

i i

- i i ._____,. .,._n_

Boolean

i.i.

I 4 6 

1/23/1812

i i

7 t 1 r... T .. T ._rr

Boolean

i.i.

I 4 6 

12/16/1811

i i

Boolean

i.i.

I 4 6

i

T:

M7.9 ~

i

8

i

. y . .:

M7.4 ;

i

8

i

M7.4 "

i

8

Figure 6

from ea

squares 

and Boo

for NM1 

and NM

triangles 

estimate 

bootstra

in value

resamp

extreme 
Table 1. Available Felt Reports

location

Abingdon, VA

Annapolis, MD

Alexandria, VA

Arkport, NY

Asheville, NC

Augusta, GA

Augusta, KY

Baltimore, MD

Beaufort, SC

Birdsville, KY

Boston, MA

Brownsville, PA

Cahokia, IL

Cape Girardeau, MO

Carlisle, PA

Carthage, TN

Charleston, NH

Charleston, SC

Charleston, WV

Chillicothe, OH

Cincinnati, OH

Circleville, OH

Clarksburg, OH

Clarksburg, WV

Clarksville, TN

Clinton Hill, IL

Columbia, SC

Columbia, TN

Concord, NH

Cooperstown, NY

Coshockton, OH

Dandridge, TN

Dayton, OH

Detroit, MI

Dorena, MO

Easton, MD

Edenton, NC

Fort Stephens, LA

Fort Wayne, IN

Frankfort, KY

Fredericksburg, VA

Georgetown, KY

Georgetown, SC

Germantown, PA

Goshen, IL

Hartford, CT

Henderson County, KY

Herculaneum, MO

Hodgenville, KY

Jamaica, NY

Jeffersonville, KY

Kaskaskia, IL

long

-82.00

-76.50

-77.03

-78.00

-82.53

-81.97

-84.00

-76.67

-80.69

-88.40

-71.03

-75.45

-90.18

-89.58

-77.40

-85.60

-72.30

-79.97

-81.60

-83.00

-84.52

-83.00

-83.15

-80.35

-87.37

-89.85

-81.12

-87.17

-71.50

-74.88

-81.90

-83.42

-84.22

-83.02

-89.24

-76.00

-76.50

-91.80

-85.14

-84.87

-77.47

-84.55

-78.78

-75.07

-89.97

-72.68

-87.60

-90.55

-85.74

-73.81

-87.72

-89.92

lat

36.90

38.97

38.85

42.60

35.53

33.37

38.77

39.18

32.42

37.20

42.37

40.00

38.57

37.23

40.30

36.35

43.20

32.90

38.37

39.35

39.16

39.90

39.51

39.27

36.55

38.55

33.95

35.63

43.20

42.67

40.60

36.02

39.90

42.42

36.62

38.75

36.05

31.25

41.08

38.19

38.30

38.21

33.38

40.30

38.80

41.77

37.80

38.30

37.57

40.69

38.18

37.92

NM1

Y

N

Y

Y

Y

Y

N

Y

N

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

N

N

Y

Y

Y

Y

Y

Y

Y

Y

N

N

Y

N

Y

N

Y

Y

Y

N

Y

Y

NM2

N

Y

Y

N

N

Y

N

Y

N

N

Y

N

N

Y

Y

Y

N

Y

Y

Y

Y

N

N

N

N

N

Y

N

Y

Y

Y

Y

Y

Y

N

N

Y

N

Y

Y

N

Y

N

N

N

Y

N

N

Y

Y

N

N

NM3

N

N

Y

N

N

Y

Y

Y

Y

N

Y

Y

N

Y

N

N

N

Y

Y

Y

Y

Y

N

N

N

N

Y

N

Y

Y

N

N

Y

N

N

N

N

N

Y

Y

Y

N

Y

Y

N

Y

N

N

Y

N

N

N

31
Table 1. (continued)

location

Knoxville, TN

Lancaster, OH

Lebanon, OH

Lexington, KY

Louisville, KY

Marietta, OH

Meadville, PA

Milledgeville, GA

Muhlenberg County, KY

Mortons Gap, KY

Nashville, TN

Natchez, MS

Newark, NY

New Bern, NC

New Bourbon, MO

New Haven, CT

New Madrid

New Orleans, LA

Newport, KY

New York, NY

Norfolk, VA

Nottingham, MD

Paris, KY

Philadelphia, PA

Piney River, TN

Pittsburgh, PA

Pittsfield, Mass

Raleigh, NC

Red Banks, TN

Richmond, VA

Rogersville, TN

Russellville, KY

Saint Louis, MO

Salem, NC

Savannah, GA

Sevierville, TN

South Union, KY

Springfield, TN

Suffolk, VA

Troy, OH

Uniontown, KY

Vicksburg, MS

Vincennes, IN

Washington DC

Washington, KY

Washington, MS

Waterford, PA

Wheeling, WV

White Bluff, GA

Wilmington, DE

long

-83.98

-82.60

-84.30

-84.50

-85.73

-81.45

-80.12

-83.24

-86.15

87.47

-86.68

-91.38

-74.17

-77.08

-90.05

-73.92

-89.40

-90.25

-84.49

-73.94

-76.20

-76.45

-84.26

-75.13

-86.35

-80.22

-73.26

-78.78

-86.40

-77.33

-83.01

-86.89

-90.38

-80.25

-81.20

-83.58

-86.66

86.88

-76.64

-84.22

-87.93

-90.90

-87.53

-77.03

-83.85

-91.30

-80.00

-80.70

-81.20

-75.53

lat

35.82

39.72

39.60

38.33

38.18

39.42

41.63

33.09

37.20

37.24

36.12

31.55

40.72

35.12

37.98

41.31

36.80

29.98

39.10

40.67

36.90

39.36

38.21

40.01

35.95

40.50

42.45

35.87

35.90

37.50

36.41

36.84

38.75

36.08

32.13

35.89

36.88

36.50

36.70

40.04

37.77

32.60

38.68

38.85

38.62

31.58

42.00

40.08

32.03

39.74

NM1 YYYYYYYYYYYYYNYYYYYYYNNYYYYYYYNNYYYYYYNNYYYYYYYYYYNM2 YNNYYYNNNNNNYNNYNYYYYYYYNNYYNYYNNYYYNNYNNNYYYNNYNYNM3 YYNYYYNNNNYNYYNYYYNYNNNYNYYYNYNYYNYNYNNYNNYYNNNYNY

32
Table 1. (continued)

location long lat NMl NM2 NM3

Worchester, MA

Worthington, OH

Yellowbanks, KY

York, Ontario

Zanesville, OH

-71.87

-83.02

-87.12

-79.63

-82.01

42.27

40.10

37.76

43.68

39.95

Y

Y

Y

Y

Y

Y

Y

N

Y

Y

Y

Y

N

Y

Y

City and State; longitude and latitude (decimal degrees) estimated from 

U.S. Census database for modern cities where available. Reports from counties 

assigned to approximate center of modern county; Y=report available; N=no 

information.

33
Table 2 MMI values, 12/16/1811 Event

location

Abingdon, VA

Alexandria, VA

Allegany County, NY

Arkport, NY

Asheville, NC

Augusta, GA

Baltimore, MD

Birdsville, KY

Boston, MA

Brownsville, PA

Cahokia, IL

Cape Girardeau, MO

Carlisle, PA

Carthage, TN

Charleston, NH

Charleston, SC

Charleston, WV

Chickasaw Bluffs, TN

Chillicothe, OH

Cincinnati

Circleville, OH

Clarksburg, OH

Clarksburg, WV

Clarksville, TN

Clinton Hill, IL

Columbia, SC

Columbia, TN

Concord, NH

Cooperstown, NY

Dayton, OH

Detroit MI

Dorena, MO

Easton, MD

Edenton, NC

Fort Dear borne, IN

Fort Massac, IL

Fort Pickering, TN

Fort Stephens, LA

Fort Stoddert, LA

Fort Wayne, IN

Frankfort, KY

Georgetown, SC

Goshen, IL

Hagerstown, MD

Henderson County, KY

Herculaneum, MO

Hodgenville, KY

Hopkins County, KY

Hudson, NY

Jefferson, KY

Kaskaskia, IL

Knoxville, Tenn

MMIN

N/R

N/R

N/

6

N/R

N/R

N/R

N/R

N/R

N/R

N/R

8-9

N/R

7

2-3

5-6

N/R

N/R

N/R

6-7

6

N/R

N/R

N/R

N/R

5-6

5-6

N/R

N/R

N/R

5

N/R

N/R

N/R

N/R

N/R

N/R

5

4-5

N/R

N/R

5

N/R

N/R

7-8

6-7

N/R

N/R

N/R

N/R

N/R

5-6

MMI

N/F

4-5

4-5

2-3

4-6

4-5

4

7-8

N/F

4

7-8

7-8

NF

7

3

5-6

NF

F

5

4-6

4-5

5

4-5

6-7

5

5-6

5

NF

NF

5

4

8

2-3

5-6

F

7

8

4

4

F

6-7

5

6-7

NF

6-7

7

5

6

4-5

7

7-8

4-5

report

furniture shaken; "no portentious effect"

objects visibly swung

2:15 event not felt

people awoken; "tanning vats displaced" ; worse in valley

family awoken; no damage described

"felt"

one wall (or possibly chimney) collapsed

not felt

"slight" shock felt

liquefaction; damage to brick structures

several houses damaged; chimneys damaged

not felt

threw bricks from chimneys; cracked brick foundation

reported as felt

church bells rung; clocks stopped

not felt

felt

widely felt; no damage

many familes on elevated ridges slept

many awoken; no damage

"sensibly felt"; no damage

felt

many chimneys injured

"violent shock felt" ; no damage described

many awoken; plaster fell at one location

many awoken; no damage

not felt

not felt

almost everyone awoken

distinctly felt in region; no damage reported

brick part of one house fell

morning aftershock felt but mainshock not reported

only report from persons on a warfe

"felt"

chimneys fell

liquefaction

many awoken; "shook fowls off roosts" ; no damage

felt by some "felt"

bricks thrown from chimneys

many awoken; ground at one site settled 1-2 in.

strong shaking; chimneys damaged in "American Bottom"

not felt

many chimneys destroyed (ambiguous report)

cracked or destroyed chimneys

widely felt; no damage reported

utensils thrown down; houses rattled

earthquakes felt frequenty staring in December

"felt very much as in Louisville"

liquefaction; damage to brick chimneys

many awoken; windows rattled

source

S1984

N1973, S1984

S1984

N1973

CF1811

S1984

S1984

S1984

S1984

S1984

S1984

N1973, S1984

S1984

F1912, S1984

N1973

F1912, S1984

S1984

S1984

S1984

F1912, S1984

F1912, CF1811

S1984

S1984

F1912

S1984

F1912, S1984

F1912, S1984

S1984

S1984

S1984

F1912; S1984

S1984

N1973

S1984

S1984

S1984

S1984

N1973

N1973

S1984

S1984

F1912

S1984

S1984

F1912, S1984

F1912

S1984

S1984

S1984

F1912

S1984

F1912

34
Table 2. (continued)

location

Lancaster, OH

Lebanon, OH

Lexington, KY

Louiville KY

Marietta, OH

Meadville PA

Milledgeville, GA

Muhlenberg County, KY

Mortons Gap, KY

Nashville, Tenn

Natchez, Miss

Newark, NJ

New Bourbon, MO

New Haven, CT

New Madrid, MO

New Orleans, LA

Newport, KY

New York, NY

Norfolk VA

Philadelphia, PA

Piney River, Tenn

Pittsburgh PA

Pittsfield, MA

Raleigh NC

Red Banks, Tenn

Richmond, VA

Saint Louis, MO

Salem, NC

Savannah, GA

Sevierville, TN

South Union, KY

Springfield, TN

Uniontown, KY

Vicksburg, Miss

Vincennes, Ind

Washington DC

Washington, LA

Water ford, PA

Wheeling, WV

White Bluff, GA

Wilmington, DE

Worchester, MA

Worthington, OH

Yellowbanks, KY

York, Canada

Zanesville, OH

MMIN

N/R

6

7

7

N/R

5

N/R

N/R

N/R

7-8

6

N/R

N/R

N/R

9

N/R

N/R

N/R

5

N/R

7-8

5

N/R

3-4

7

5

7-8

N/R

N/R

N/R

N/R

N/R

N/R

7

6-7

4-5

5-6

5

N/R

N/R

N/R

N/R

N/R

N/R

N/R

N/R

MMI

5

4-5

5

7

4-5

4-5

5

5

6

6-7

6

NF

7-8

F

9

4

7

NF

4-5

NF

6

4

NF

3-4

7

4-5

6-7

5

4

4

4-5

4

8

5

6

4

5

4-5

4-5

4

NF

NF

4

5

F

5

report

motion similar to rolling of ship

many awoken; no damage

"no injury sustained"

damage to gables and chimneys

widely felt; no damage reported

distinctly felt; many awoken

bell rung; no damage reported

general fear; no damage reported

crack in brickwork

"no real injury" ; fall of some chimneys

widely felt; minor damage

not felt

damage to chimneys

"barely felt"

pervasive ground failure and damage

felt (some accounts say not felt)

one chimney thrown down

not felt

doors swung; clocks stopped; no damage

morning aftershock felt; NM1 not felt

slumping along river

distinctly felt; many awoken

not felt

slight earthquakes were felt (no mention in Raleigh Star)

cracked or destroyed many chimneys

distinctly felt; bells rung

several chimneys thrown down

many awoken

rattling noise "like carriage on paved road"

felt; not noticed by all

felt; no damage described

felt by two who were awake at time

every brick chimney damaged/destroyed

Island No. 94 destroyed; no other damage reported

cracked chimneys

distinctly felt; furniture rattled

trees shaken; articles thrown

many awoken; no damage

creaked walls, windows

"felt sensibly", like ship on heavy swell

morning aftershock slightly felt; NM1 not felt

not felt

felt by some but "not generally noticed"

shaking felt; no damage reported

felt

many awoken; clocks stopped, "no injury done"

source

S1984

F1912

N1973, S1984

F1912, S1984

S1984

N1973

S1984

S1984

S1984

N1973, S1984

N1973, S1984

S1984

S1984

S1984

(various)

F1912, S1984

S1984

S1984

F1912, S1984

S1984

F1912

F1912, S1984

S1984

S1984, RS1811

F1912, S1984

F1912, S1984

F1912, N1973, S1984

S1984

F1912, S1984

S1984

S1984

S1984

S1984

F1912

F1912, S1984

F1912, S1984

S1984

N1973

S1984

N1973

S1984

S1984

S1984

S1984

S1984

S1984

City and State; MMIfj value assigned by Nuttli (1973); reinterpretted MMI value based on reports from towns; 

summary of firsthand reports on which MMI values are based; source of information (N1973=Nuttli, 1973; S1984 Street, 

1984; CFlSn=Chillicothe Fredonian, 1811; RS1811=JRaiez^/i Star, 1811; F1912-Fuller, 1912).

35
Table 3. 1/23/1812 Event

location

Alexandria, VA

Augusta, GA

Baltimore, MD

Boston, MA

Cape Girardeau, MO

Carlisle, PA

Carthage, TN

Charleston, SC

Charleston, WV

Chillicothe, OH (VAL)

Chillicothe, OH (HR)

Cincinnati

Columbia, SC

Concord, NH

Cooperstown, NY

Coshockton, OH

Dandridge, TN

Dayton, OH

Detroit, MI

Easton, MD

Edenton, NC

Fort Dearborne, IN

Fort Wayne, IN

Frankfort, KY

Georgetown, KY

Hartfort, CT

Hodgenville, KY

Jamaica, NY

Knoxville, TN

Lexington, KY

Louisville KY

Marietta, OH

Newark, NJ (VAL)

Newark, NJ (HR)

New Haven, CT

New Orleans, LA

Newport, KY

New York, NY

Norfolk, VA

Nottingham, MD

Paris, KY

Philadelphia, PA

Pittsfield, MA

Raleigh NC

Richmond, VA

Rogersville, TN

Salem, NC

Savannah, GA

Sevierville, TN

Suffolk, VA

Vincennes, IN

Washington DC

MMI

4

4-5

4

NF

7-8

NF

6-7

6

NF

5

4

4-6

6

NF

NF

6

4

5

3-4

4

F

F

F

5

F

F

5

F

4-5

4-5

7-8

5

3.5

2.5

3

4-5

5-6

F

4-5

3

5

NF

NF

3

5

4-5

F

4-5

4

4

6-7

4

Remarks

"distinctly felt"

comparable to NM1

felt like ship in heavy swell

not felt

stronger than NM1

not felt

nearly as severe as NM1

more severe than NM1; some cracks in masonry

not felt

"considerable shock felt"

"barely noticed except along river"

comparable to NM1

damage to plaster, worse than NM1

not felt

not felt

cracked chimneys

felt by almost all

worse than NMl, suspended articles swung

felt

"sensibly felt"; some pendulum clocks stopped

"felt" ; "no mischief done"

"felt"

"felt"

no damage described

"felt"

"sensibly" felt

"severe shock"; no damage reported

suspended articles swung

lighter than NMl; a few objects thrown from shelves

almost as severe as NMl

more severe than NMl; damage to chimneys

similar to NMl; like rolling of ship

"slight" shock felt

shock noticed by persons near river

gentle swinging of suspended objects

clocks stopped, glassware shaken lightly

strong shaking; no damage reported

felt

suspended articles shaken, clocks stopped

felt by some

suspended articles swung "violently", no damage reported

not felt

not felt

lightly felt

doors/windows "flapped", furniture shaken

like motion of ship at sea; no damage reported

felt

stronger than NMl, objects vibrated

rattled windows

felt by all; no damage reported

shook tops off several chimneys

felt by most, objects rattled

source

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

RS1812

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

36
Table 3. (continued)

location MM/ Remarks

Wheeling, WV

Wilmington, DE

Worch ester, MA

Worthington, OH

York, Canada

Zanesville, OH

4-5

NF

NF

4

4

5

nearly equal to NM1

not felt

not felt

felt, no damage reported

felt

as strong as NM1

S1984

S1984

S1984

S1984

S1984

S1984

City and State (VAL valley site; HR="hard rock"); reinterpreted MM I value based on reports from towns; remarks; 

source of information (81984= Street, 1984; CF1811=Chillicothe Fredonian, 1811; RSISU^ Raleigh Star, 1811.

37
Table 4. 2/7/1812 Event

location

Alexandria, VA

Augusta, GA

Augusta, KY

Baltimore, MD

Beaufort, SC

Boston, MA

Brownsville, PA (VAL)

Brownsville, PA (HR)

Cape Girardeau, MO

Charleston, SC

Charleston, WV

Chillicothe, OH

Cincinnati

Circleville, OH

Columbia, SC

Concord, NH

Cooperstown, NY

Dayton, OH

Fort Wayne, IN

Frankfort, KY

Fredericksburg, VA

Georgetown, SC

Germantown, PA

Hartfort, CT

Hodgenville, KY

Knoxville, TN

Lancaster, OH

Lexington, KY

Louisville KY

Marietta, OH

Nashville, TN

Newark, NJ

New Bern, NC

New Haven, CT

New Madrid, MO

New Orleans, LA

New York, NY

Philadelphia, PA

Pittsburgh PA

Pittsfield, MA

Raleigh NC

Richmond, VA

Russellville, KY

Saint Louis, MO

Savannah, GA

South Union, KY

Troy, OH

Vincennes, IN

Washington DC

Wheeling, WV

Wilmington, DE

Worchester, MA

MMI

4-5

4-5

4-5

4

6

NF

5

4

8

6

NF

6-7

6-7

5-6

6

NF

NF

5

F

6-7

5

5

4-5

NF

5-6

5

5-6

5-6

7-8

5

7

NF

5

4

10

4

F

4-5

5

NF

4

5

5

7

5

5

5-6

6-7

4-5

6-7

NF

NF

Remarks

similar to NM2

generally strongest shaking

more severe than earlier shocks

sensibly felt by several persons

more severe than earlier shocks

not felt

articles in cupboards rattled

"felt more sensibly along river bank"

stronger than NMl

longest duration, "quicker" motions

not felt

stronger than others, "sudden jerks"

one chimney toppled, "distinct" shocks

worse than others

damage to plaster, cracked chimneys

not felt

not felt

worse than NMl, "quicker", 2 shocks

"felt"

more violent than others

3 distinct shocks felt; most awoken

more violent; residents "generally awakened"

not felt by those sleeping

not felt

"severe shock"

stronger than NMl; shock furniture

rang bells; made other shocks seem "slight and feeble"

at least equal to NMl; some instances of cracked walls

at least as severe as NMl; damage to chimneys

stronger than NMl; no damage reported

strongest event; damaged chimneys

not felt

violent "rocking/jerking"; no damage reported

some awoken

knocked down houses

stronger than others; no damage reported

rattled cups and saucers; felt by many

felt by many; rattled doors

more sensibly felt than others

not felt

felt

stronger than others; many awoken

stronger than others; no damage reported

stronger than others; several chimneys toppled

felt by many; "no injury done"

"tremendous" ; no damage reported

stronger than others; little damage

shook tops off several chimneys

not felt by all

stone house and chimney cracked

not felt

not felt

source

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

CF1812

S1984

S1984

S1984

S1984

S1984

SI 984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

S1984

RS1811

S1984

S1984

S1984

S1984

S1984

S1984

SI 984

S1984

S1984

S1984

S1984

38
Table 4. (continued)

location MM/ Remarks source

Worthington, OH 

York, Canada 

Zanesville, OH

4-5 

4 

5-6

stronger than others; no material damage 

strong than others; no damage done 

stronger than others

S1984 

S1984 

S1984

City and State (VAL=valley site; HR="hard rock"; reinterpreted MM I value based on reports from towns; remarks; 

source of information (81984=Street, 1984; CF18ll=Chillicothe Fredonian, 1811; RS1811=Raleigh Star, 1811.

39
Table 5. Magnitude Comparison

Study NM1 NM2 NM3

Nuttli (1973) 7.2* 7.1* 7.4*

Street (1982) NI 7.1* 7.3*

Johnston (1996) 8.1 7.8 8.0

This Study 7.2-7.3 «7.0 7.4-7.5

Asterisk indicates mj,, otherwise, M^ values are shown. NI=no independent 

determination made.

40
1 Appendix 1. Sample Sources from compilation of Street, 1984 (S1984)

1.1 Lebanon, Ohio (from Mitchill, 1815)

"At Lebanon, in Ohio, the alarm was so great, that many persons forsook 

their houses. The vibration of the shocks seemd to be from east to west." 

(Assignment by S1984: VI; this study: IV-V)

1.2 Milledgeville, Georgia (from Poulson's American Daily 

Advertiser)

"The earthquake noticed in our last, says the Augusta (Georgia) Herald, was 

felt in every direction from this place as far as we have yet heard from. In 

Columbia, South Carolina, several successive shocks were felt in this place, 

and at about the same hours. In Milledgeville, the state House was shaken 

as to cause the clapper of the Bell in the Cupola repeatedly to strike. In 

Savannnah the shock was equally severe, as it was in different places in the 

country." (Assignment by SI984: VI; this study: V)

1.3 Newbern, North Carolina (Anonymous, 1812)

"At four o'clock yesterday morning, a strong and alarming shock of an earthquake was felt in this town. Its duration was, perhaps, two minutes: some 

think it continued much longer. The rocking, or rather jirking was often 

repeated and violent. It seemed as if some monstrous weight had rolled, or 

swung almost out of the power of force which was restraining it, and that 

that power by desperate tugs and efforts wrenched it back again. It went off 

with a trembling like the quivering of a vessel at sea, after it has sustained 

a rugged stroke from an enormous and impetous wave." (Assignment by 

S1984: V-VI; this study: V)

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1.4 Edenton, North Carolina (Chenango Weekly Advertiser, 1812)

"At Edenton, N.C. a warehouse on a warfe was so shaken that the persons 

working therein could scarcely keep their feet; and a new brig fitting at the 

warfe rolled so much that the hands at work on board immediately left her. 

The shock was felt in other parts of the town, the whole unattended by any 

noise." (Assignment by S1984: VI; this study: V-VI)

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1 Appendix 2

1.1 From the Raleigh Star (Raleigh), NC:

The paper makes no mention of earthquakes in issues between 1/17/1812 

and 2/7/1812. The 2/14/1812 issue reports that the "smart shock of an 

earthquake" was felt in Raleigh around 4 a.m. on 2/7/1812.

1.2 From the Chillicothe Fredonian 

12/18/1811

"On Monday morning last, between the hours of one and two o'clock, 

many of the inhabitants of this place were considerably alarmed by a sudden 

and violent trembling of their houses, which is supposed to have proceeded 

from an earthquake. The shock was so sensibly felt as to cause many to leap 

from their beds. About 8 o'clock the same morning, a similar shock was 

experienced, which continued for the space of half a minute -during which 

time the houses were considerably agitated. Neither shock was preceded or 

accompanied by any explosion."

1/26/1812

"On Thursday the 23rd instant, at a quarter past 9 in the morning [illegible] the violent shock of an earthquake was felt in this place. The trembling 

was so [illegible] as to shake coffee out of the cups [illegible] of some of the 

inhabitants who were at breakfast. The shock was much more terrible than 

either of those heretofore mentioned in our paper of the 18th (December)."

2/12/1812

"Several very severe shocks of earthquakes have been felt in this place 

since our last. That felt on Friday morning, at 45 minutes past 3, was, we 

believe, much more terrible than any of those which preceded or followed it. 

It was preceded by a rumbling noise like distant thunder, and the shaking 

continued with more or less violence for about three minutes."

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2/19/1812 - letter from John C. Edwards of Asheville, NC, dated 12/19/1811; 

reprinted in its entirety, transcribed verbatim

Gentlemen,-! take the liberty to transmit the following account of an 

earthquake which happened on the night between the 15th and 16th inst.

For several nights previous, the Aurora Borealis brilliantly illuminated the 

sky with its trembling corruscations; the late appearance of a splendid comet, 

and the blood-like color of the sun for several days, had alarmed a great many 

superstitious people. They talked of war; an when the news of Governor 

Harrison's dear-bought victory arrived, it brought to their recollection all 

those appearances which are still believed (as these are now) to have been 

the awful precursors of that bloody war by which we gained our independence.

On Monday morning, about one o'clock, the inhabitants were roused from 

their peaceful slumbers by a dreadful sound: some waggoners who were up 

the time it began, said it resembled, but was louder, than if 100 waggons 

were driven at full speed down the mountain. This gave us considerable 

alarm: the timid took to prayer, expecting every moment (as they say) to 

hear the sound of the last trumpet. The more courageous ventured to open 

their doors to discover what occasioned the noise. A sudden trembling of the 

earth caused fresh terror and alarm, from which we had not time to recover 

when we felt a violent shock which lasted about 3 minutes and was attended 

with a hollow rumbling noise, and ended with a dreadful crash leaving behind 

a strong sulphurous stench.

For the remainder of the night, all was still and calm, but was spent by us 

in trembling anxiety. When the wished for morning came, we were happy to 

find no lives were lost, but while some of us were in the street, congratulating 

each other on our happy escape, we were again alarmed by a much louder 

noise than any we had heard before. It was quickly followed by a more violent 

shock, which gave the earth an undulating motion resembling the waves of 

the sea. Two of those who were standing with me, were thrown off their 

feet, the rest of us with difficulty kept from falling, while two or three cows 

that were near us were unable to stand, and testified their fear by their loud 

bellowing, which with the cries of the women and children, and the terror 

that was depicted in the countenances of the men, presented a scene of terror 

I am uanble to describe.

It is somewhat strange that its effects were more violent in the vallies than 

on the mountains: a tan yard, in a valley near this place, had several vats

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displaced-the edges of some were raised 3 feet above their former level, and 

others were moved partly round, and left in a zig-zag manner. It would far 

exceed the bounds of this letter to describe all of the phenomena produced by 

this awful convulsion of nature: rocks moved, hills shook, houses shattered, 

&c.

A wonderful change has taken place in the manners of the people. I 

believe so many fervent prayers never were put up in this place as were on 

that fearful night and morning. I think what has been done may be termed 

a revival in religion.

I have just seen a gentleman from Knoxville, who passed Sunday night 

with Mr. Nelson at the warm springs: from his account his situation was 

more terrifying than ours. For several hours previous to the shock, a most 

tremendous noise was heard from the neighboring mountains. At intervals 

it was quiet, but would begin with so much violence, that each repetition 

was believed to be the last groan of expiring nature. The shock at that 

place did but little damage, except to a few huts that were built near the 

springs for the accomodation of invalids. The fulminating of the mountains 

was accompanied with flashes of fire seen issuing from their sides. Each 

flash ended with a snap, or crack, like that which is heard on discharging an 

electric battery, but 1000 times as loud. This induced him to believe that 

the earthquake was caused by the electric fluid.

In the morning it was observed that a large stream of warm water (temperature Fah. 142 degrees) issued from a fissure in a rock on the side of 

the mountain, which had been opened the preceding night. While they were 

examining it, another shock was felt which lasted two minutes. Although 

perfectly calm, the tops of the trees appeared to be greatly agitated, the 

earth shook violently, and the water of the warm springs, at that time overflowed by French Broad River, was thrown up several times to the height of 

30 or 40 feet.

Several masses of stone were loosed from their ancient beds and precipitated from the summits and sides of the mountains. One in particular, well 

known to western travelers by the name of the Painted Rock, was torn from 

its base and fell across the road that leads from hence to Knoxville: it has 

completely shut up the passage for wagons. A great many people who were 

moving westwardly, are in a pittable situation at this inclement season, being 

unable to proceed until a new road is made round the rock (no easy task): 

in this they are cheerfully assisted by their neighbors.

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I have been for three months in those dreary regions, examing a mine 

of Cobalt. The ore is rich: it abounds with arsenic. In May we intend to 

calcine the orre and prepare it for exportation, or perhaps manufacture it 

into smalt. The mine is within a few miles of Mackeysville.

John C. Edwards

Note:

John Clarke Edwards achieved a measure of infamy with a second letter 

that was published in the Pennsylvania Gazette on 2/19/1812. In this letter, 

Edwards describes an actual volcano-a "western Aetna"-in considerable and 

outlandish detail. The Gazette later printed a retraction. This curious chapter of the New Madrid story is explored in more detail in a separate study 

[Hough and Hough, in prep.]. Although Edwards credibility is clearly open 

to question, we conclude that several factors do lend credibility to his initial 

observations: 1) his initial report from the warm springs area clearly does 

not stem from pre-conceived notions of volcanic eruptions, and 2) Supposing 

the residents of Asheville were awoken by noise (rather than the shaking) 

of the P-wave, the timing the first perceived shaking is consistent with the 

expected S-P time at that distance. The quick subsequent arrival of a second, stronger shake is also consistent with the S-Lg time. Moreover, as of 

December 19th, it is highly unlikely that Edwards was able to fabricate his 

account based on reports from elsewhere, as news at that time moved only 

at the speed of boats and horses.

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