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Home , 1660s, Charlevoix, Charlevoix Seismic Zone

A new analysis of the magnitude of the 1663 at Charlevoix,

Author: J. E. Ebel

Persistent link: http://hdl.handle.net/2345/bc-ir:107016

This work is posted on eScholarship@BC, Boston College University Libraries.

Published in Bulletin of the Seismological Society of America, vol. 101, no. 3, pp. 1024-1038, 2011

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THE SEISMOLOGICAL SOCIETY OF AMERICA 400 Evelyn Ave., Suite 201 Albany, CA 94706-1375 (510) 525-5474; FAX (510) 525-7204 www.seismosoc.org Bulletin of the Seismological Society of America, Vol. 101, No. 3, pp. 1024–1038, 2011, doi: 10.1785/0120100190

A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec by John E. Ebel

Abstract This paper presents a new and comprehensive analysis of the magnitude of the 1663 Charlevoix, Quebec, earthquake. Based on a modified Mercalli intensity scale (MMI) of about VI from reports of damage to chimneys and a masonry wall in Roxbury and Boston, Massachusetts, the best estimate of the moment magnitude of this earthquake is M 7.3 to 7.9 from MMI attenuation relations. Using ground-motion attenuation relations and the threshold for chimney and masonry damage from fragility curves for seventeenth- and eighteenth-century dwellings in Boston, the mag- nitude of the 1663 earthquake is at least M 6.9 if the damage occurred on very soft soil conditions and is M 7.3 to M 7.7 if the damage took place on firm soil or bedrock. Both the best estimate of a length of 73 km for the most active section of the Charlevoix Seismic Zone and an estimated fault area of 73 km × 25 km for the 1663 earthquake are consistent with an earthquake of M 7.3 to 7.6 based on scaling relationships. Also, in the 1811–1812 New Madrid earthquake sequence only the 7 February 1812 shock, the largest of the sequence, caused chimney damage beyond about 600 km. The 7 February New Madrid event is thought to have taken place on the Reelfoot fault, for which the length of the recent earthquake activity and of the suspected 1812 rupture is less than that of the active seismicity zone at Charlevoix. These observations suggest that the 1663 Charlevoix earthquake was approximately comparable in magnitude to or even larger than the largest of the 1811–1812 New Madrid and therefore was at least M 6.8. When put together, the several lines of analysis in this study indicate that the best estimate of the size of the 1663 earthquake is M 7:5  0:45.

Introduction The accurate assessment of the seismic hazard of a Madrid seismic zone (NMSZ). Johnston (1996) argued that region requires a detailed understanding of the past seismi- the largest earthquake of this sequence, with moment mag- city of that region. One important element of seismic hazard nitude M 8.1, was the strongest known historically in the assessment is a determination of the maximum earthquake intraplate region of and perhaps the strongest that is possible in each seismic source zone without a con- known historically from all stable cratonic regions. Later, sideration of when such an earthquake might occur. In most Hough et al. (2000) estimated that the largest of the 1811– parts of central and eastern North America, the estimation of 1812 earthquakes was M 7.4–7.5, whereas Bakun and the maximum earthquake is difficult because there is no cer- Hopper (2004) reported that the 1811–1812 earthquakes tainty that the largest possible earthquake has been observed ranged up to M 7.8. Recently, Hough and Page (2010) in the different seismic source zones of the region during the argued that a maximum magnitude of about M 6.8–7.0 in past four centuries for which there is historical information the NMSZ can reconcile the repeating seismicity of that zone on the earthquake activity. Furthermore, with a few excep- with a strain rate due to postglacial rebound, and is also at tions no paleoseismological evidence of earlier strong - the low end of the magnitude range inferred from a recent quakes has been found so far. At the present time, for each analysis of consensus intensities from the largest events in seismic source zone one only can put a lower bound on the the 1811–1812 earthquake sequence. While clearly large maximum possible earthquake by determining the largest earthquakes, the magnitude of the largest of the 1811–1812 earthquake that has taken place in the historic record. seismic sequence still has an uncertainty of at least several It is well known that there was a series of very strong tenths of a magnitude unit. earthquakes that took place in the midwestern United States Also known, but much less well studied, is a strong earth- in 1811–1812 (Fuller, 1912) in what is known as the New quake that took place in eastern Canada in February 1663,

1024 A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec 1025 which was probably centered somewhere in the Charlevoix probably was about M 7.5 and was similar in magnitude to seismic zone (CSZ) along the St. Lawrence River in Quebec. or larger than the largest of the 1811–1812 earthquakes in According to the Canadian earthquake catalog (see the Data the NMSZ. and Resources section), this earthquake was about magnitude 7.0, although the source of this magnitude assignment is Summary of the Historic Accounts of the 5 February unclear. Gouin (2001) included this earthquake in his study 1663 Earthquake of historic earthquakes of eastern Canada, and he argues that It has long been known from the lore of eastern North this earthquake is mLg 6:5  0:5 based on the area where it was felt. Clearly there is some uncertainty concerning the America that a very strong earthquake was experienced along magnitude of this historic earthquake, due in large measure the St. Lawrence River in Canada in 1663 (Brigham, 1871). The mainshock took place about 5 p.m. local time on 5 Feb- to the paucity of data for this event because it took place during ruary on the Gregorian calendar, which was in use in New the early days of European settlement of North America at that time. Figure 1 shows a map from Gouin (2001) This paper presents a new and comprehensive analysis of that summarizes from historic reports the locations where the the magnitude of the 1663 Charlevoix earthquake. The mag- earthquake is known to have caused damage or been felt. nitude of this earthquake is estimated based on analyses of In Canada, the most detailed and notable accounts of the damaged structures reported in the Boston, Massachusetts, strongest effects due to the earthquake were sent by Catholic area as well as on the modern seismicity that is routinely missionaries such as the Jesuit Fr. Jerome Lalemant, S.J. reported from the CSZ. Comparisons are also made between back to their superiors in Europe (Jesuit Relations, 1663). – the 1663 earthquake and the largest events from the 1811 Ebel (1996) and Gouin (2001) present comprehensive sum- 1812 New Madrid earthquake sequence. The major conclu- maries and transcriptions of the reports of this earthquake. sion that is reached in this paper is that the 1663 earthquake Hodgson (1928) summarizes the reports of landslides along

Figure 1. Map of the area affected by the earthquake of 5 February 1663 (Gregorian calendar), modified from Gouin (2001). The proposed epicentral region near is indicated, as are localities where landslides were reported due to the earthquake. Localities for which Gouin (2001) has felt reports are indicated by closed circles (where an intensity assignment was made by Gouin, 2001) and plus signs (where no intensity assignment was made by Gouin, 2001). Open circles were added to show additional localities where the earthquake was reported felt. 1026 J. E. Ebel the banks of the St. Lawrence, and he quotes the writings this earthquake is a line in a letter dated 7 1663 of Francis Mercier in 1665: “Two highly trustworthy from Jeremias van Rensselaer of Rensselaerswijck in New Frenchmen, who have traversed the whole coast of Malbaye Netherland to his brother Jan Baptist in in the (down to is indicated) made the assertion that . The letter contains a line that can be translated the Relations of the year 1663 (Lalemant) had only half from the original Dutch as (J. Jacobs, personal com- described the ravages wrought by the earthquake shocks mun., 2009) in that region.” Aftershocks were numerous in Canada for months afterward (Gouin, 2001). Since at least the publica- There is not much news to tell except that last winter we tion of the report of Hodgson (1928), the epicentral area of had an earthquake which was very strong further inland this earthquake has been assigned to what is today known as and did a lot of damage to the houses of the French. the Charlevoix seismic zone of Quebec (Fig. 1). Not only does this report show that an earthquake was felt in The 1663 mainshock and several of its immediate in the winter of 1662–1663, but it indicates aftershocks were also experienced in Boston, Massachusetts, that this was the same earthquake that caused damage in New and nearby communities. As noted by Ebel (1996),New France. Thus, the evidence in this report supports the idea was using the at this time, so the that the 5 February 1663 earthquake was felt throughout mainshock is reported in the local records there as being the New Netherland colony. on 26 1662 or 1662–1663 (since the new year on the Other New Netherland sources also attest to an earth- Julian Calendar did not begin until 25 ). Ebel (1996) quake in 1663, although they give less information than does published a church record entry by the Reverend S. Danforth van Rensselaer. Peter Stuyvesant, the last Dutch governor of from Roxbury, Massachusetts (today Roxbury is part of the , wrote in his annals that (Abbott, 1873) city of Boston). According to Reverend Danforth, the people of Roxbury felt the mainshock at about 6 p.m. local time on 26 The year 1663 was a year of many disasters. Early in the January as well as aftershocks about midnight and once or year an earthquake shook severely the whole of New twice the next morning. On the morning of 28 January at about Netherland and of the adjacent regions. 10 a.m. local time yet another event was felt. During the main- Joannes Nevius reported that during the year 1663 there shock, the ground shaking at Roxbury was so strong that the was an earthquake (Honeyman, 1900). O’Callaghan (1865) tops of several chimneys were thrown down (Danforth, 1880; reports in his annals for 1663 an earthquake in New Ebel, 1996), and objects were thrown from shelves. Netherland. A later report by Fiske (1899) states, There is another report of damage in Boston due to this 1663 earthquake. Porter (1887) contains a description of a An earthquake shook the valley of the Hudson, all the building at Ship (later North) Street and Clark Street in way from Beverwyck down to Fort Amsterdam, and sent Boston that was called the Ship Tavern. The building had reverberations far into Canada and . been torn down about 20 yr before Porter (1887) was pub- Beverwyck is now Albany, New York, and Fort Amsterdam lished (therefore it was probably destroyed about 1867). In stood in what is currently the financial district of New York writing about the Ship Tavern, Porter (1887) states, City (Fig. 1). None of these reports indicate any damage in It was originally two stories high, and built of English New Netherland due to the 1663 earthquake, but they state that the earthquake was felt throughout the entire Dutch brick, laid with shell and clay mortar. There was an old colony. crack in the front wall, said to have been caused by an New Netherland is the farthest south that the 1663 earthquake in 1663, “which made all New England earthquake from Canada is known to have been felt. So far, tremble.” Internet searches by the author have failed to turn up any felt The crack in the brick wall must have come early in the his- reports from Maryland, Virginia, or the Carolinas or from tory of the building, because Boston itself had only been farther south or west. The 1925 M 6.2 Charlevoix earthquake founded in 1636. Furthermore, the crack from 1663 must (Bent, 1992) was felt in Virginia and North Carolina have been quite notable because its cause was remembered (earthquakescanada.nrcan.gc.ca/histor/20th‑eme/1925/ for more than two centuries. This structure would also have intensitew‑eng.php); the 1663 earthquake should also have experienced potentially damaging shaking in the later 1755 been felt in these areas if it was at least as large as the 1925 Cape Ann earthquake, which was known to have caused earthquake. much masonry damage throughout Boston. Even so, the To the east, the earthquake was reported felt in Acadia, nineteenth-century author (Porter) did not attribute the crack which is now Nova Scotia (Gouin, 2001; Fig. 1) and at Percé at in the Ship Tavern wall to the better-known 1755 earthquake, the eastern tip of the Gaspé peninsula. Gouin (2001) cites the but rather he ascribed it to the earlier 1663 event. description of the 1663 earthquake written by Nicolas Denys Other felt reports for the 1663 earthquake come from the in Acadia that was published in Ganong (1908). According to New Netherland colony of North America, comprising what is Denys, the earthquake was a “small” affair that nevertheless today southern New York state. The most direct evidence of was made up of three distinct shocks that rattled cooking A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec 1027 utensils and tableware. Gouin (2001) states that Denys was Mercalli intensity (MMI) of about VI based on the chimney probably at what is now St. Peters, which is located on Cape damage and cracked masonry wall. One can argue that the Breton Island in eastern Nova Scotia, but curiously Gouin early colonials in Massachusetts could only produce very (2001) does not show that location on his map of felt locations weak mortar for their chimneys, and so perhaps the true main- of the 1663 earthquake (Fig. 1). A. Ruffman (personal com- shock intensity was somewhat less than VI, such as V.5 or mun., 2009) also believes that St. Peters was the likely loca- perhaps even V. On the other hand, if the very sparse existing tion of Denys in February 1663, so this evidence suggests that accounts do not report the full extent of earthquake damage the 1663 earthquake rattled dishes in eastern Nova Scotia. that was experienced throughout the Massachusetts colony Some other sources that give less believable reports due to the 1663 ground shaking, then perhaps the MMI there of the felt area of the 1663 earthquake have been found. might have been somewhat larger than VI, such as VI.5. Kingsford (1887) states, An estimate of the magnitude of the 1663 earthquake The movement extended from Labrador to the Ottawa, can be made from the MMI value at Boston using published passing thence to New York and New England. intensity-attenuation relations if the epicentral distance is known. Two intensity-attenuation relations that are applic- The statement that the earthquake was felt in Labrador has able to earthquakes in northeastern North America, those not been confirmed by any primary accounts or independent of Klimkiewicz and Pulli (1983) and Bakun et al. (2003), sources. No colonial settlements in what today is Labrador are used in this analysis. Figure 2 shows the location of are known from 1663, and at that time all of the area that Boston compared with that of the zone of high earthquake drained into Ungava Bay was considered Labrador (M. Sta- activity that is called the Charlevoix seismic zone. At its veley, personal commun., 2009). Thus, this statement from closest, the CSZ is about 560 km from Boston, and its farthest Kingsford (1887) cannot be used to confirm how far to the point is about 640 km from Boston. Thus, the mean distance northeast this earthquake was felt. of the CSZ is about 600 km from Boston. In addition to the strong earthquake in Quebec on 5 Feb- Table 1 summarizes magnitude estimates for the 1663 ruary 1663, there was also a strong earthquake probably earthquake using the Klimkiewicz and Pulli (1983) and centered along the west coast of Mexico on this same day. Bakun et al. (2003) intensity-attenuation relations. The Some sources apparently link these two seismic events into a Klimkiewicz and Pulli (1983) intensity-attenuation relation single earthquake. For example, Perley (1891), in describing m et al. the 1663 earthquake, states, is based on b, whereas the Bakun (2003) intensity- attenuation relation is based on M. To allow a direct compar- Although New England was more or less shaken, the ison of the magnitude values in the table, the mb values were country on either side of it suffered more. It extended as far north as Canada, and south to Mexico, probably being felt farther in both directions. The historic earthquake catalog of Garcia and Suarez (1996) gives a brief description of an earthquake on 5 February 1663 in Mexico. As part of their description, they cite M. Iluet, who states in his Manual de Geografia “…estos sacudimientos se extendieron desde las costas del Ecuador hasta el Canada” [trans., …the shaking extended from the coasts of Ecuador to Canada].

Apparently, Iluet learned of reports of the strong earth- quake in Canada and perhaps of an earthquake in Ecuador on this same day, and he used these reports to argue that the 5 February 1663 earthquake was felt from the coast of Ecuador all the way to Canada. Clearly, no single crustal earthquake could have been felt over such a large area.

Estimation of the Magnitude of the 1663 Earthquake from the MMI at Roxbury and Boston, Massachusetts Figure 2. Seismicity map for the time period 1975 to 2009. The box shows the location of the Charlevoix seismic zone. The The reports from Roxbury and Boston in Massachusetts distances from the ends of the CSZ to Boston are indicated. The for the 1663 earthquake are consistent with a modified color version of this figure is available only in the electronic edition. 1028 J. E. Ebel

Table 1 1663 Magnitude Estimates Based on the MMI at Boston*

Intensity-Attenuation Relation MMI V at Boston MMI V.5 at Boston MMI VI at Boston MMI VI.5 at Boston Assuming an Epicentral Distance of 560 km Klimkiewicz and Pulli (1983) 7.0 (mb) (6.9 M) 7.2 (mb) (7.4 M) 7.5 (mb) (7.8 M) 7.8 (mb) (8.3 M) Bakun et al. (2003) 6.7 (M) 7.0 (M) 7.3 (M) 7.6 (M) Assuming an Epicentral Distance of 600 km Klimkiewicz and Pulli (1983) 7.0 (mb) (7.1 M) 7.3 (mb) (7.5 M) 7.6 (mb) (7.9 M) 7.9 (mb) (8.4 M) Bakun et al. (2003) 6.8 (M) 7.1 (M) 7.3 (M) 7.7 (M) Assuming an Epicentral Distance of 640 km Klimkiewicz and Pulli (1983) 7.1 (mb) (7.2 M) 7.4 (mb) (7.6 M) 7.7 (mb) (8.1 M) 7.9 (mb) (8.5 M) Bakun et al. (2003) 6.9 (M) 7.2 (M) 7.5 (M) 7.8 (M) *The Klimkiewicz and Pulli (1983) magnitudes were converted to moment magnitudes using the relation between M and ˆ Mn of Atkinson and Boore (1995) under the assumption that mb Mn. assumed to be equivalent to mn values, and the conversion covered near Providence, , in the late 1660s and formula from Mn to M of Atkinson and Boore (1995) was near Newburyport, Massachusetts, in the late 1690s. For this used in Table 1. Because the epicenter of the 1663 earth- reason, large brick or stone structures that used lime-based quake is not known, magnitude estimates were computed mortars were rare until the 1720s in Massachusetts, although based on the closest distance, the average distance, and the the historical account cited previously indicates that the Ship greatest distance of Boston from the CSZ. The best estimate Tavern in Boston was constructed of a lime mortar made of the MMI at Roxbury and Boston is VI, which yields mag- from shells. Jenison (1976) notes that mortars made from nitude values of mb 7.5 (M 7.9) using the Klimkiewicz and shells and mortars made from limestone undergo exactly Pulli (1983) relation and M 7.3 using the Bakun et al. (2003) the same chemical reactions, and so they presumably have relation for an epicentral distance of 600 km. Magnitude the same strength. estimates computed using MMI V, V.5, and MMI VI.5 are also Ho (1979) carried out an analysis of the ground motions computed in Table 1 to show the range of magnitude esti- that would lead to chimney damage in a typical early mates based on possible variations in the MMI values that eighteenth-century house in eastern Massachusetts. The struc- were experienced at Roxbury and Boston. ture he studied was a two-story heavy timber-frame dwelling with a brick chimney made from clay and shell mortar that had Estimation of the Magnitude of the 1663 Earthquake been built about 1638. He considered a wide range of chimney from Chimney and Masonry Damage at Roxbury strengths because there were no standard construction prac- and Boston, Massachusetts tices during the seventeenth and early eighteenth centuries. Another way to estimate the magnitude of the 1663 Ho (1979) determined that the natural period of the entire earthquake is to directly use the observation of chimney structure was about 12 Hz and that damage to the weakest 0 015 damage at Roxbury and a cracked masonry wall in Boston. chimneys would occur in ground motions between : g 0 04 While the analysis in this section effectively is based on the and : g. In another study Whitman (2002) determined same data as in the previous section, the analysis methods fragility values for typical eighteenth-century masonry con- between the two sections are quite different. In the previous struction in Boston. Ebel (2006) used the Whitman (2002) fra- section the analysis was based on relationships involving gility values and the Kircher et al. (1997) fragility curves for predictions of MMI values as a function of event magnitude unreinforced masonry structures to estimate the fragility and epicentral distance that were derived directly from inten- curves for the chimneys of eighteenth-century New England sity data, whereas the analysis in this section makes use of houses. Ebel (2006) argued that the threshold for chimney da- modern ground-motion attenuation relations that have been mage in eighteenth-century structures is 0:01g for peak determined using instrumental recordings and simulations of ground acceleration (PGA) and 0:03g for pseudospectral ac- instrumental ground-motion data with no input of earthquake celeration (SA 0.3 s period) and that the natural period of the intensities at all. structures is about 0.3 s. The Ho (1979), Whitman (2002), and According to Jenison (1976) during the first half of the Ebel (2006) studies together can be used to bracket the ex- seventeenth century in New England, there was no known pected range of minimum ground motions that were required source of limestone for making cement; most chimneys were to cause damage to seventeenth-century chimneys and laid with clay or mud mortar on their interiors with just an masonry walls in eastern Massachusetts. exterior application of lime-based mortar to make the struc- In this analysis of the 1663 earthquake it is assumed that ture watertight. Only small amounts of mortar could be made the ground motions at Roxbury and Boston in 1663 were at during this time by burning shells that were collected from least equal to the threshold damage values to explain the coastal areas. Economic limestone deposits were only dis- reported chimney damage and masonry damage. Modern A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec 1029 ground-motion attenuation relations can be used to estimate experienced soft rock or hard-soil ground motions. Buildings the magnitude of the earthquake in the CSZ necessary to in seventeenth-century Roxbury on unconsolidated alluvium cause a damaging level of ground motion in Roxbury and may have experienced National Earthquake Hazard Reduc- Boston. In this study, four attenuation relations are applied, tion Program (NEHRP) class C or possibly D soil conditions. namely those of Somerville et al. (2001; the intraplate rift The Ship Tavern in Boston was located on one of the glacial relation), Campbell (2003), Tavakoli and Pezeshk (2005), drumlins that comprise much of Boston’s original Shawmut and Atkinson and Boore (2006). peninsula (Woodhouse et al., 1991; Brankman and Baise, Table 2 summarizes the magnitude estimates for the 2008), and this most likely corresponds to soft rock or hard- 1663 earthquake using these four attenuation relations and soil site conditions. the threshold ground-motion values in Roxbury and Boston. In Table 2 ground-motion values for each of the four All of the ground-motion attenuation relations in Table 2 are attenuation relations were computed for M 7.0, 7.3, and based on moment magnitude M and use the closest distance 7.6 for soil site conditions (NEHRP class D soil conditions) to the fault as the distance parameter. As noted previously, for PGA, SA 0.1, and SA 0.3 at a distance of 560 km from the the distance from Roxbury and Boston to the closest part of 1663 rupture. Also shown in Table 2 for each ground-motion the current active seismicity zone at Charlevoix is approxi- parameter is the estimated minimum ground motion that was mately 560 km, so that is assumed in this analysis to be the needed to cause damage to chimneys or masonry in seven- closest distance to the 1663 rupture, a value that is needed for teenth-century Roxbury and Boston based on the work of Ho the attenuation-relation computations. The site conditions in (1979), Whitman (2002), and Ebel (2006). The last column Roxbury where the damage occurred are unknown because in Table 2 shows for each attenuation relation the M value the locations of the structures with the chimney damage are where the predicted ground motion for hard-rock site condi- not given in the existing reports about the earthquake. In tions is to equal that of the threshold for chimney or masonry 1663 most buildings in what was then called Roxbury prob- damage. The values in Table 2 can help bracket the magni- ably were located on glacial till, glacial outwash deposits, or tude of the 1663 mainshock. bedrock (Woodhouse et al., 1991; Brankman and Baise, From the analysis of Ho (1979), it appears that the SA 2008), although a few structures may have been built on un- 0.1 ground motions are the most important for determining consolidated alluvium along the local rivers and drainages. the possibility of chimney damage at Roxbury in 1663. If the Bedrock is probably no deeper than a few tens of feet below 1663 damage occurred to weak chimneys (with a damage the surface beneath much of the original seventeenth-century threshold of 0:015g) that were located on thick soft soils, Roxbury settlement (Woodhouse et al., 1991). Buildings on then, depending on the attenuation relation, an earthquake bedrock would probably have experienced hard-rock ground as small as M 6.9 to 7.2 would have been sufficient to motions, while buildings on glacial till or outwash likely damage the Roxbury chimneys. On the other hand, if the

Table 2 1663 Magnitude Estimates Based on the Chimney Damage at Roxbury, Massachusetts

Magnitude Mw 7.0 7.3 7.6 M Threshold for Rock PGA (g) Soil Site (D) Conditions* Atkinson and Boore (2006) 0.008 0.011 0.015 8.0 Campbell (2003) 0.008 0.011 0.014 7.7 Somerville et al. (2001) Rift 0.006 0.009 0.014 7.7 Tavakoli & Pezeshk (2005) 0.010 0.014 0.019 7.4 SA at 0.1 s (g) Soil Site (D) Conditions† Atkinson and Boore (2006) 0.016 0.021 0.028 7.7 Campbell (2003) 0.015 0.020 0.027 7.5 Somerville et al. (2001) Rift 0.012 0.018 0.027 7.5 Tavakoli & Pezeshk (2005) 0.013 0.017 0.023 7.7 SA at 0.3 s (g) Soil Site (D) Conditions‡ Atkinson and Boore (2006) 0.020 0.026 0.033 § Campbell (2003) 0.008 0.011 0.015 9.2 Somerville et al. (2001) Rift 0.006 0.011 0.019 8.2 Tavakoli & Pezeshk (2005) 0.019 0.027 0.037 7.9 *Threshold for chimney/masonry damage ˆ 0:01g †Threshold for chimney damage ˆ 0:015g to 0:04g ‡Threshold for chimney/masonry damage ˆ 0:03g §Attenuation relation does not allow a rock ground-motion value as large as 0:03g. 1030 J. E. Ebel chimney damage occurred to structures that were located on Ebel et al. (2000) that aftershock zones in intraplate regions bedrock, then the magnitude of the 1663 event must have can be observed as long as a couple thousand years after a been M 7.5 to 7.7. If the damaged chimneys were part of mainshock. Support for this idea comes from the NMSZ, structures situated on glacial till or outwash deposits, then where the active lineations in the modern seismicity are the 1663 mainshock magnitude was probably M 7.3 to interpreted to show the locations of the major earthquake 7.5. It is unlikely that any structures at that time were built ruptures in the 1811–1812 sequence (e.g., Johnston and on alluvium deposits, because those structures would have Schweig, 1996; Hough et al., 2003). been prone to flooding during strong coastal storms. For this Figure 3 shows the spatial extent along the St. Lawrence reason, it is considered most probable that the Roxbury struc- River of the CSZ. The length along the river of the highest tures that sustained chimney damage in the 1663 earthquake seismicity zone is about 73 km, although arrows on the figure were located on glacial outwash, till, or bedrock. show alternate interpretations that are about 54 km and The SA 0.3 and PGA values can also be used to estimate 100 km. Outside of this zone of highest seismicity there are the magnitude of the 1663 mainshock based on the ground elongated belts of much lower seismicity that stretch south- motions that may have been experienced in Roxbury and at west to and northeast past the confluence of the the Ship Tavern in Boston. If the chimney and masonry with the St. Lawrence. Following the reason- damage occurred to structures on soil site conditions, the ing of Ebel et al. (2000), the central zone of highest seismi- SA 0.3 ground-motion estimates from Atkinson and Boore city is taken as an estimate of the fault segment that ruptured (2006) and Tavakoli and Pezeshk (2005) are consistent with in the 1663 earthquake. – M about 7.4 7.5, while the other two ground-motion rela- Focal mechanisms of the largest earthquakes in the CSZ tions suggest a magnitude above M 7.6. Rock or hard-soil since 1924 generally show thrust faulting on northeast- site conditions for the chimney masonry damage would sug- southwest striking nodal planes (Bent et al., 2003), suggest- gest a moment magnitude close to or above M 8.0. In the ing that this may have been the focal mechanism of the 1663 case of the Atkinson and Boore (2006) attenuation relation earthquake. The modern microseismicity at Charlevoix dips for SA 0.3, the predicted ground-motion value does not reach southeast from near the surface to a depth of about 25–30 km 0:03g for any magnitude value, presumably due to nonlinear (Lamontagne and Ranalli, 1997), which indicates a south- effects at large ground motions. The estimated magnitude east-dipping fault plane for the 1663 earthquake. The dimen- values from the PGA threshold for soil site conditions at sions of the modern seismicity at Charlevoix (73 km long Roxbury and Boston are somewhat lower than for SA 0.3 and 25 km wide) can be used to estimate the magnitude for almost all of the attenuation relations: about M 7.0 using of the 1663 earthquake under the assumption that the zone Tavakoli and Pezeshk (2005), M 7.3 from Atkinson and of modern high seismic activity delineates the 1663 rupture. Boore (2006) and Campbell (2003), and M 7.4 from Somer- Using the Wells and Coppersmith (1994) scaling relations for ville et al. (2001).ForPGA, rock, or hard-soil site conditions thrust earthquakes, one finds that both a surface rupture for the Roxbury chimney damage and for the damage and the masonry wall at the Ship Tavern in Boston mean that the length and a subsurface rupture length of 73 km are consis- magnitude of the earthquake is between about M 7.3 tent with an earthquake of M 7.3. In addition, if one takes 73 25 and M 7.7. fault dimensions of km × km to estimate the fault area Taken together, the ground-motion values in Table 2 of the 1663 rupture, one also computes M 7.3 from the Wells suggest an estimated magnitude value of at least M 6.9 to and Coppersmith (1994) magnitude versus fault area rela- M 7.0 for the 1663 earthquake if all of the damaged struc- tionship. On the other hand, if the fault area versus moment tures were on very soft soils and if the damaged chimneys magnitude relation of Somerville et al. (2001) is used, then a 73 25 in Roxbury were of weak construction. It is more likely that fault with dimensions km × km yields M 7.6. the damaged structures in Roxbury and Boston were con- Uncertainty in the estimated fault length can be explored structed on glacial till or wash deposits, which correspond by testing different rupture length scenarios for the 1663 to firm soil or soft-rock site conditions. For this case, the earthquake, such as those in Figure 3. For example, if the estimated magnitude of the 1663 earthquake falls in the 1663 fault rupture was only 54 km, the estimated magnitude range of about M 7.3 to M 7.7, even for weakly constructed using Wells and Coppersmith (1994) is M 7.1, and a fault chimneys. area of 54 km by 25 km also yields M 7.1. If the 1663 rupture extended farther to the southwest than the edge of the most Estimation of the Magnitude of the 1663 Earthquake active earthquake belt (such as for a total fault length of about 100 km as indicated in Fig. 3), then the estimated magnitudes from the Spatial Extent of the Modern Seismicity 100 25 in the Charlevoix Seismic Zone based on a fault area of km × km are both M 7.4 using Wells and Coppersmith (1994) and M 7.7 using Another way to estimate the magnitude of the 1663 Somerville et al. (2001). Thus, if the modern microseismicity earthquake is to assume that the spatial extent of the modern delineates the 1663 fault rupture, then this seismicity sug- seismicity shows the configuration of the aftershock zone of gests that the 1663 earthquake may have been as small as the 1663 earthquake. This idea builds on the suggestion of M 7.1 but more likely had M 7.3 to 7.6. A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec 1031

It is interesting to compare the modern seismicity in the than that along the Reelfoot fault segment of the NMSZ, sug- CSZ with that in the NMSZ (Fig. 3). The Reelfoot fault gesting that the 1663 earthquake was approximately compar- segment of the NMSZ is a northwest-southeast striking thrust able in magnitude to or perhaps even larger than the largest of fault that connects two active northeast-southwest striking the 1811–1812 New Madrid earthquakes. Using the smallest strike-slip faults (Johnston and Schweig, 1996). Unlike the estimate of the magnitude of the largest of the 1811–1812 rather steep dip of the CSZ down to 25 km or more in depth earthquakes proposed by Hough and Page (2010), the spatial (Lamontagne and Ranalli, 1997), the modern seismicity on extent of the CSZ when compared with that of the Reelfoot the Reelfoot fault ranges in depth between about 5 km and fault indicates that the 1663 earthquake was at least M 6.8. 15 km, with dips between 30° and 45° on the deeper parts of the fault and ranging up to 80° on the shallower parts of the Comparisons of Chimney Damage between the 1663 fault (Mueller and Pujol, 2001). The Reelfoot fault zone is Charlevoix Earthquake and the 1811–1812 thought to have failed in the 7 February 1812 earthquake New Madrid Earthquakes (Johnston and Schweig, 1996; Hough et al. 2003). As can Another way to estimate the magnitude of the 1663 be seen in Figure 3, the total length of the seismicity along earthquake is indirectly by comparing its intensity pattern Reelfoot fault thrust segment of the NMSZ is about 61 km to that of each of the three largest of the 1811–1812 New (Mueller and Pujol, 2001), somewhat shorter than the length Madrid earthquakes. Specifically, the occurrence of chimney of the active seismicity of the CSZ. Kinematic considerations damage at Roxbury, Massachusetts, in the 1663 earthquake of the interaction of the strike-slip and thrust segments of the at a distance of 560–640 km from the causative fault gives a NMSZ may have limited the length of the 7 February 1812 basis of comparison with the New Madrid earthquakes. thrust segment to only about 40 km (Mueller et al., 2004). According to Kochkin and Crandell (2004), chimneys in The magnitude estimates of the 7 February 1812 earthquake the area of the midwestern United States at the time of by Johnston (1996), Hough et al. (2000), Mueller and Pujol the 1811–1812 earthquakes were generally made of brick (2001), and Bakun and Hopper (2004) are M 8.0, M 7.4–7.5, or stone and were constructed using locally sourced lime M 7.2–7.4, and M 7.8, respectively. The modern active seis- and sand mortar. In this analysis it is assumed that the mid- micity zone at Charlevoix is somewhat larger in spatial extent western chimneys and masonry structures in 1811–1812

Figure 3. (a) Seismicity map for the time period 1985 to 2010 in the vicinity of the Charlevoix seismic zone from the Earthquakes Canada database. The spatial extent of this modern active seismicity is about 73 km and is indicated by the bold arrows. Short narrow arrows show a possible minimum extent of the CSZ of about 54 km; long narrow arrows show a zone that extends from the northeastern end of the most active zone to the southwestern end of the most concentrated small earthquake activity, a distance of 100 km. (b) Seismicity map for the time period 1985 to 2010 of the NMSZ from the CERI database at the University of Memphis. The total spatial extent of this modern active seismicity of the Reelfoot thrust segment of this zone (bold arrows) is about 61 km from Mueller and Pujol (2001), although kinematic considerations may have limited the 12 February 1812 rupture to about 40 km (Mueller et al., 2004; narrow arrows). The color version of this figure is available only in the electronic edition. 1032 J. E. Ebel were of comparable strength to those in Massachusetts soft soil conditions, M 7.3 and M 7.5 for very firm soil/soft in 1663. rock site conditions, and between M 7.5 and 7.7 for hard- Figures 4a,b,c show intensity maps for the three largest rock conditions (ignoring the larger hard-rock values in of the 1811–1812 New Madrid earthquakes from Hough Table 2). From the analysis of the dimensions of the modern et al. (2000), who used the areas within the MMI IV, V, VI, seismicity, the best estimate of the 1663 magnitude is M 7.3 VII, and VIII contours to estimate the magnitudes for each of to 7.6. Taking all of these analyses together, the estimates all these events. Each of these maps has been modified to show overlap in the range between M 7.4 and M 7.6. The center of those locations where chimney damage was reported, and this overlap region, M 7.5, is taken in this study as the best each map also contains a circle of 600 km radius centered estimate for the magnitude of the 1663 earthquake. on the center of the fault that is thought to have ruptured in The uncertainty in the best estimate of M for the 1663 that event. For the 7 February 1812 shock (M 7.4–7.5 earthquake can be found from the total range R of estimated according to Hough et al., 2000), chimney damage was M values found in all of the analyses in this paper, using the reported at an epicentral distance exceeding 600 km, while rule of thumb that the standard deviation is approximately for the 16 1811 event (M 7.2–7.3 according to R=4 (Mendenhall et al., 2009). There is a wide range of mag- Hough et al., 2000), there was chimney damage as far away nitude estimates presented in the previous sections of this as Cincinnati, close to 600 km from the causative fault. For paper, with the extremes being as low as M 6.7 to as large the 23 January 1812 event (M 7.0 according to Hough et al., as M 8.5 from the MMI analyses (again ignoring the M 9.0 2000), the greatest distance at which chimney damage is values in Table 2). This range of magnitude estimates sug- reported is about 400 km. It must be mentioned that Hough gests that the standard deviation of M for the 1663 earth- and Page (2010) have made arguments that the largest of the quake is about 0.45 magnitude units. Thus, the estimated New Madrid earthquakes was no more than M 6.8 to 7.0 to magnitude of the 1663 earthquake is M 7:5  0:45, and there reconcile the observed repeat times of the large New Madrid is a 95% probability that the magnitude of the event is earthquakes with the current regional strain release data. between M 6.6 and M 8.4. The magnitudes in this paragraph from Hough et al. (2000) are higher than the magnitudes favored by Hough and Page (2010). Discussion Hough et al. (2000) note that the chimney damage that was reported at Cincinnati occurred on soft ground and that The 1663 event is one of several strong earthquakes that the ground shaking was considerably reduced on the upland have been centered in the CSZ since the European settlement areas away from the Ohio River. In Roxbury the site condi- of northeastern North America. From the evidence presented tions in 1663 for most structures were probably glacial till or in this study, it confirms that the 1663 earthquake was larger bedrock; so the 1663 earthquake ground shaking at Roxbury than all of the subsequent Charlevoix events. Instrumental was probably comparable to the ground shaking in the records of the earthquake of 1 March 1925 were studied by upland areas away from the rivers of the Midwest in the Ebel et al. (1986) and Bent (1992) to estimate the source 1811–1812 earthquake sequence. From these comparisons, parameters for the event. Bent (1992) found that the 1925 6 2  3 6 5  4 it appears that the chimney damage report at Roxbury in event had M 6.2, Ms : : , and mb : : . She reported 18 1663 at an epicentral distance of about 560 km to 640 km a seismic moment of 3:1  2:5 × 10 N-m, which gives a means that 1663 earthquake was comparable in size to or range of M from 5.8 to 6.5. Ebel and Hart (2001) reported perhaps even larger than the largest of the New Madrid earth- on observations of the shaking effects of the 1925 earthquake quakes on 7 February 1812. This qualitative comparison in Boston and vicinity from newspaper accounts. While the supports the conclusion in the previous section of this paper earthquake was felt strongly enough that many people ran that the 1663 earthquake in Quebec and the 7 February 1812 out of buildings that were heavily shaken, no damage was earthquake in the had approxi- reported in Boston. Thus, the masonry damage reports in mately comparable magnitudes. Roxbury and Boston for the 1663 earthquake suggest that the 1663 event was larger than the 1925 event, and hence Best Estimate of the Magnitude of the 1663 larger than M 6.2. According to Ebel et al. (2011), the 1870 Charlevoix Earthquake earthquake at Charlevoix was about M 5.8, although it is rated at M 6.5 by the Canadian Geological Survey (Lamon- The previous sections of this paper present estimates of tagne, 2008). An examination by Ebel et al. (2011) of the magnitude of the 1663 earthquake based on several accounts in The Boston Evening Transcript newspaper of different analyses. From the MMI analyses, the best estimate the 1870 earthquake reveals that this event did not damage of the magnitude of the 1663 earthquake is M 7.3 from the chimneys or crack brick walls in Boston (which included the Bakun et al. (2003) relation and M 7.9 from the Klimkiewicz Roxbury section of the city), and thus the extant evidence and Pulli (1983) relation. From the chimney damage suggests that the 1663 earthquake generated stronger ground analyses, the best estimate of the 1663 earthquake magnitude shaking in Boston than did the 1870 earthquake. Thus, at appears to be in the range between M 6.9 and M 7.2 for very Boston the ground shaking in the 1663 earthquake appears A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec 1033

Figure 4. (a) Isoseismal map of the M 7.4–7.5 New Madrid earthquake of 7 February 1812, showing the locations where chimney damage was reported. (b) Isoseismal map of the M 7.2–7.3 New Madrid earthquake of 16 December 1811, showing the locations where chimney damage was reported. (c) Isoseismal map of the M 7.0 New Madrid earthquake of 23 January 1812, showing the locations where chimney damage was reported. On all three maps, a star shows the center of the fault on which the earthquake is thought to have taken place, and a dashed circular arc is drawn at an epicentral distance of 600 km. Intensity reports where chimney damage was reported are circled. An inset on the upper left corner of each figure shows the observed MMI values plotted as a function of epicentral distance in degrees. The arrows on these inset graphs indicate an epicentral distance of 600 km. All three maps are modified from those in Hough et al. (2000), and the magnitudes given in this figure caption are those of Hough et al. (2000). The color version of this figure is available only in the electronic edition. (Continued) 1034 J. E. Ebel

Figure 4. Continued. to have been greater than that in either the 1925 or the 1870 area does contain liquefaction features that might have been earthquakes. caused by the 1663 earthquake, these features do not directly One assumption that has been made in this study is that help constrain the magnitude of that earthquake. In addition, the 1663 rupture today is represented by the modern earth- quakes in the CSZ, which experiences the highest rate of small earthquake activity in northeastern North America. Ebel (2009) argued that in the rupture zones of past major earthquakes the modern earthquake activity of M ≥ 4 tends to cluster near the ends of those past ruptures. At Charlevoix, this appears to be the case. Figure 5 show the M ≥ 4 seismi- city in the CSZ and its immediate vicinity from 1985 to 2010. It is clear that most of the M ≥ 4 events during this time period took place at the northeast end of the active seismicity zone along with two M ≥ 4 events at the southwest end of the 1 zone. Stevens (1980) noted that the earthquake of M ≥ 4 2 from 1924 to 1978 also took place at the southwest and northeast ends of this seismicity zone. Thus, if these larger events since 1924 are indicative of the ends of the 1663 rup- ture, they support the idea that the 1663 earthquake had a rupture length of about 70 km. For many large earthquakes, another way to constrain their magnitude is by the size and distribution of liquefaction features, particularly sandblows, that were induced by the earthquake (Obermeier, 1996). In the Charlevoix area, Tuttle and Atkinson (2010) report young liquefaction features (less Figure 5. Map for the time period 1985 to 2010 in the vicinity than 540 yr old), although they do not know whether to of the Charlevoix seismic zone showing earthquakes of magnitude 4 and greater. The bold arrows show the same spatial extent of the attribute these to the 1663 earthquake or to one of the later most active seismicity as is indicated by the bold arrows in Figure 3. strong earthquakes that took place in the Charlevoix area, The color version of this figure is available only in the electronic such as those in 1870 and 1925. Thus, while the Charlevoix edition. A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec 1035

Tuttle and Atkinson (2010) found evidence for two earlier Newfoundland have yet been discovered from a search of the seismic events that were strong enough to cause the forma- Internet. tion of liquefaction features. One event dates to about Another indication of the size of the 1663 earthquake 5000 yr B.P., while the other took place approximately could come from finding the full distribution of sandblows 9770 yr B.P. Thus, the 1663 earthquake appears to have been and landslides that were caused by the event. Regarding one of a series of strong earthquakes centered in the CSZ liquefaction effects, Tuttle, Schweig, et al. (2002) reported during the past 10,000 yr, although the magnitudes of those that the major area of sandblows in the 1811–1812 sequence earlier events are unknown. extended out as far as about 100 km from the earthquake If the recent seismicity in the CSZ is aftershock activity faults, although smaller, more isolated sandblows exist as from the 1663 earthquake, then focal mechanisms of the seis- far as 240 km from the inferred epicenters (M. Tuttle, micity can be used to infer the focal mechanism of the 1663 personal commun., 2010). For the M 7.7 Bhuj, India, earth- earthquake. Lamontagne (1987), Bent (1992), Lamontagne quake of 26 January 2001, Tuttle, Hengesh, and Lettis (2002) and Ranalli (1997), and Bent et al. (2003) all report focal report widespread liquefaction within about 140 km of the mechanisms for earthquakes in the CSZ. The largest earth- epicenter and smaller, individual sandblows out to 240 km. quake analyzed, the 1925 M 6.2 earthquake, was a thrust Thus, if the 1663 earthquake had M 7.5, then it may have event with northeast-southeast nodal planes (Bent, 1992). caused liquefaction effects beyond 200 km from the fault Many of the other earthquakes in this seismic zone have zone. Finding such evidence may be quite difficult, because similar focal mechanisms. The recent seismicity at Charle- liquefiable areas are generally confined to river valleys in voix defines a pair of parallel, tabular zones that dip steeply northeastern North America and because the frozen ground toward the southeast (Lamontagne and Ranalli, 1997), which surface of midwinter when the earthquake took place may may indicate that this was the fault plane in the 1663 earth- have suppressed some liquefaction features from forming. quake. However, some of the earthquakes in the Charlevoix So far, all of the liquefaction features that can be attributed area have nodal planes that strike north–south or even directly to the 1663 earthquake have been found within northwest-southeast, similar to earthquakes in other parts 30 km of Les Eboulements in the CSZ (M. Tuttle, personal of Quebec (Bent et al., 2003). Thus, there may have been commun., 2010). a complicated pattern of faulting that took place during Landslides and land slumps can also be generated by the 1663 earthquake. strong ground shaking at large distances from strong earth- Analyses of modern geodetic deformations in Quebec quakes. Keefer (1984, 2002) analyzed the maximum distance suggest that an earthquake of M 7.5 and even larger is pos- from the epicenter and from the fault rupture of landslides sible in the Charlevoix area. Mazzotti et al. (2005) showed induced by earthquakes as a function of earthquake magni- from GPS evidence that the St. Lawrence Valley of Quebec is tude, and his analyses indicate that the greatest epicentral dis- shortening at an average rate of about 0:6  0:2 mm yr1, tance where a landslide would be expected for an earthquake with the rate in the CSZ being about double that of the entire of M 7.5 is about 200 km. Keefer (2002) noted that the 1988 St. Lawrence valley. From their analysis of the GPS data, they Saguenay, Quebec, earthquake caused landslides at epicen- argued that the maximum earthquake magnitude in the CSZ tral distances beyond what would have been expected from is about M 7:8  0:6 and that the recurrence time of M ≥ 7 the Keefer (1984) analysis, and so landslides at an epicentral earthquakes is 400–1300 yr. Thus, the magnitude of the 1663 distance beyond 200 km might be possible for an M 7.5 found in this study is consistent with the geodetic deforma- earthquake. Locat (2008) reviewed the observations of land- tions that have been observed in the Charlevoix area. slides and underwater sediment slumps that have been attrib- Mazzotti and Adams (2005) argued that the lack of signifi- uted to the 1663 earthquake. Landslides have been found at cant deformation markers in the Charlevoix area suggests several places in Quebec province, and submarine slumps that the local high strain rate may be a short-term transient have been found in the St. Lawrence estuary, the Saguenay that only lasts hundreds to thousands of years. Fjord, and several lakes on the . Also, some If the 1663 earthquake had a magnitude of M 7.5, it underwater slumps in a lake in the Appalachians of Quebec could have been felt over a significant part of eastern North may also have been caused by the 1663 earthquake. Based on America. Figure 6 shows theoretical MMI III isoseismals the landslide data, Locat (2008) favored an epicentral region computed with the two different intensity-attenuation rela- for the 1663 earthquake in the Saguenay region of Quebec tions that were used earlier in this paper. Figure 6 indicates and a magnitude M ≥ 7:6. The Locat (2008) epicentral that the 1663 earthquake should have been felt in Virginia region is at odds with the proposed 1663 fault rupture that and the Carolinas as well as in Newfoundland, and it might is favored in this study, but his magnitude agrees well with possibly have been felt in Florida. If felt reports of this earth- the size of the 1663 earthquake that is inferred in the analyses quake can be found in these far-flung localities, they would presented in this paper. Further work to find landslides and provide further evidence for the magnitude of the 1663 earth- underwater slumps that were caused by the 1663 earthquake quake that is argued for in this study. As noted previously, no could help refine the estimated magnitude and location of the felt reports of the 1663 earthquake from Virginia, Florida, or 1663 earthquake. 1036 J. E. Ebel

Figure 6. Extents of the MMI III isoseismals for a magnitude 7.5 earthquake centered in the Charlevoix seismic zone. The solid line and the dashed line were computed from the intensity-attenuation relationships of Klimkiewicz and Pulli (1983) for mb 7.5 and of Bakun et al. (2003) for M 7.5, respectively. Towns far from the Charlevoix seismic zone (star) that were in existence in 1663 and where the earthquake might have been felt are indicated. The color version of this figure is available only in the electronic edition.

Conclusions February New Madrid event is thought to have taken place on the 61-km long Reelfoot fault, for which the length of the Several lines of evidence indicate that the 1663 earth- recent earthquake activity is somewhat smaller than that of 7 5  45 quake had M : : . One line of evidence is the MMI the modern active seismicity at Charlevoix. If the 7 February at Roxbury and Boston, Massachusetts, which suggests 1812 earthquake was M 7.4–7.5 (Hough et al., 2000)or the earthquake was M 7.3 to 7.9. A second line of evidence M 7.8 (Bakun and Hopper, 2004), then the magnitude is the masonry damage reported at Roxbury and Boston, 1663 earthquake equaled or exceeded M 7.4. On the other Massachusetts, which requires that the magnitude of the hand, if the largest of the 1811–1812 earthquakes was only earthquake at Charlevoix was probably M 7.3 to M 7.6 to M 6.8–7.0 (Hough and Page, 2010), then this comparison have caused ground shaking that was damaging to chimneys indicates that the 1663 earthquake was larger than M 6.8– and masonry in Massachusetts. A third argument is the 73- 7.0. Based on the results of all of the analyses of this study, km extent of the recent seismicity at Charlevoix, which is the maximum magnitude for the CSZ, and perhaps for other consistent with an earthquake of about M 7.3 to M 7.6 from sections of the St. Lawrence rift valley as well, is at least scaling relations of fault length or fault area as a function of M 7.5, the best estimate in this study for the magnitude magnitude. Finally, comparing the epicentral distance of the of the 1663 earthquake. chimney damage at Roxbury with that for each of the major – shocks in the 1811 1812 New Madrid earthquake sequence Data and Resources in the midwest United States suggests that the 1663 Charle- voix earthquake was roughly comparable in magnitude to, or All of the historical data used in this paper came from perhaps even larger than, the 7 February 1812 New Madrid published sources (primarily Ebel, 1996 and Gouin, 2001), shock, the largest event in that earthquake sequence. The 7 and all reports are given proper references in the text where A New Analysis of the Magnitude of the February 1663 Earthquake at Charlevoix, Quebec 1037 the historical reports are reproduced or described. In addi- Ebel, J. E. (2006). The Cape Ann, Massachusetts earthquake of 1755: A – tion, research on the Dutch accounts from New Netherland 250th anniversary perspective, Seismol. Res. Lett. 77, 74 86. Ebel, J. E. (2009). Using the Locations of M ≥ 4 Earthquakes to delineate was provided to the author by Jaap Jacobs in an unpublished the extents of the ruptures of past major earthquakes in intraplate report. That report is available from this author. All pertinent regions, Eos Trans. AGU 90, no. 52, Fall Meet. Suppl., Abstract historic accounts from the report by Jacobs have been S41A-1900. reproduced in this paper. The earthquake epicentral data Ebel, J. E., and K. A. Hart (2001). Observational evidence for amplification come from the earthquake catalogs at Weston Observatory, of earthquake ground motions in Boston and vicinity, Civil Engineering Practice 16, no. 2, 5–16. the Canadian Geological Survey, the University of Ebel, J. E., K.-P. Bonjer, and M. C. Oncescu (2000). Paleoseismicity: Memphis, and the Canadian earthquake catalog (http:// Seismicity evidence for past strong earthquakes, Seismol. Res. Lett. earthquakescanada.nrcan.gc.ca/histor/top10‑eng.php, last 71, 283–294. accessed December 2010). Ebel, J. E., M. Dupuy, and W. H. Bakun (2011). Assessing the magnitude of the , 1870 Charlevoix, Quebec earthquake, Seismol. Res. Lett. 82, 154. Acknowledgments Ebel, J. E., P. G. Somerville, and J. D. McIver (1986). A study of the source parameters of some large earthquakes of northeastern North America, I thank Tony Sewell for his efforts to locate reports of the 1663 J. Geophys. Res. 91, 8231–8247. earthquake in the New Netherland colony and Jaap Jacobs for his research Fiske, J. (1899). The Dutch and Quaker Colonies in America, Vol. 1, on this topic in documents in the Netherlands. Discussions with John Houghton, Mifflin and Co., Boston and New York. Adams, Allison Bent, and John Cassidy concerning my work on the Fuller, M. L. (1912). The New Madrid Earthquakes, U.S. Geol. Surv. Bull. 1663 earthquake are most appreciated. Comments on an earlier draft of this 494, Washington, D.C. paper by Martin Chapman, Maurice Lamontagne, Martitia Tuttle, and Rus Ganong, W. F. (1908). The Description and Natural History of the Coasts of Wheeler prompted me to make several improvements in the paper. My North America (Acadia), The Champlain Society, Toronto. appreciation goes to Mike Hagerty, who created some of the maps that Garcia, V., and G. Suarez (1996). Los Sismos en la Historia de Mexico, appear in the figures, and Luciana Astiz is thanked for her translation from Tomo I, Universidad Nacional Autonoma de Mexico, Ediciones Spanish to English. The helpful comments by two anonymous reviewers led Cientificas Universitarias, Mexico, D.F., Mexico (in Spanish). to many improvements in the analyses and presentation in the paper. Figure 1 Gouin, P. 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