Canada's Earthquakes

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Geoscience Canada

Canada’s Earthquakes: ‘The Good, the Bad, and the Ugly’ J. F. Cassidy, G. C. Rogers, M. Lamontagne, S. Halchuk and J. Adams

Volume 37, Number 1, January 2010 Article abstract Much of Canada is ‘earthquake country’. Tiny earthquakes (that can only be URI: https://id.erudit.org/iderudit/geocan37_1art01 recorded by seismographs) happen every day. On average, earthquakes large enough to be felt occur every week in Canada, damaging earthquakes are years See table of contents to decades apart, and some of the world’s largest earthquakes are typically separated by intervals of centuries. In this article, we provide details on the most significant earthquakes that have been recorded in, or near, Canada, Publisher(s) including where and when they occurred, how they were felt, and the effects of those earthquakes. We also provide a brief review of how earthquakes are The Geological Association of Canada monitored across Canada and some recent earthquake hazard research. It is the results of this monitoring and research, which provide knowledge on ISSN earthquake hazard, that are incorporated into the National Building Code of Canada. This, in turn, will contribute to reduced property losses from future 0315-0941 (print) earthquakes across Canada. 1911-4850 (digital)

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Cite this article Cassidy, J. F., Rogers, G. C., Lamontagne, M., Halchuk, S. & Adams, J. (2010). Canada’s Earthquakes:: ‘The Good, the Bad, and the Ugly’. Geoscience Canada, 37(1), 1–16.

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they occurred, how they were felt, and aging earthquakes have struck Canada the effects of those earthquakes. We because, typically, they occur decades also provide a brief review of how apart, often located in offshore or earthquakes are monitored across remote, unpopulated regions. It is even Canada and some recent earthquake easier to forget that some of the hazard research. It is the results of this world’s very largest earthquakes have monitoring and research, which pro- struck within, or adjacent to, our coun- vide knowledge on earthquake hazard, try. These huge (magnitude (M) 8 or 9) that are incorporated into the National earthquakes are typically centuries Building Code of Canada. This, in apart, and are often located in remote turn, will contribute to reduced proper- areas. In this article, we summarize ty losses from future earthquakes Canada’s ‘good’, ‘bad’, and ‘ugly’ earth- Canada’s Earthquakes: across Canada. quakes. We define ‘good’ earthquakes ‘The Good, the Bad, and as those that either: the Ugly’ SOMMAIRE • have been widely felt, and there- Un bonne partie du Canada est un fore have made people more aware ‘pays de séismes’. De petits séismes of (and perhaps better prepared J.F. Cassidy1, G.C. Rogers1, M. 2 3 (que seuls les séismographes peuvent for) future earthquakes; or Lamontagne , S. Halchuk , and J. enregistrer) s’y produisent quotidien- • those that are large enough to be Adams3 1 nement. En moyenne, un séisme assez ‘scientifically useful’−they teach us Geological Survey of Canada fort pour qu’on le ressente s’y produit about the potential impact of PO Box 6000 à intervalle d’une semaine; assez fort future earthquakes in Canada. Sidney, BC, Canada, V8L 4B2 pour causer des dommages s’y produit ‘Bad’ earthquakes are those E-mail: [email protected] à intervalle de quelques années à that have caused significant damage quelques décennies; alors que l’inter- (including landslides, structural dam- 2 Geological Survey of Canada valle de récurrence des plus grands age, and other effects) in Canada, and 615 Booth Street séismes est de l’ordre des siècles. Dans ‘ugly’ are some of the world’s largest Ottawa, ON, Canada, K1A 0E9 le présent article on trouvera des earthquakes (larger than M 8). The détails sur les plus importants séismes purpose of this article is twofold: 3 Geological Survey of Canada s’étant produits sur ou à proximité du 1. To summarize the effects of Cana- 7 Observatory Crescent territoire canadien, incluant le lieu et le da’s most significant earthquakes Ottawa, ON, Canada, K1A 0Y3 moment, leurs manifestations et leurs (reminding us that destructive répercussions. On y décrit sommaire- earthquakes have struck Canada in SUMMARY ment les moyens de détection déployés the past, and will do so again in Much of Canada is ‘earthquake coun- sur le territoire canadien ainsi que the future); and try’. Tiny earthquakes (that can only be quelques-unes des recherches récentes 2. To highlight new earthquake recorded by seismographs) happen sur les risques sismiques. Ce sont les resources that constitute valuable every day. On average, earthquakes résultats des efforts de surveillance et tools for education and earthquake large enough to be felt occur every des recherches sur les tremblements de preparedness. This includes the week in Canada, damaging earthquakes terre qui ont été intégrés dans le Code new and updated ‘Earthquakes are years to decades apart, and some of national du bâtiment du Canada. Et Canada’ website the world’s largest earthquakes are typi- cela aidera à amoindrir les répercus- [http://www.earthquakescanada. cally separated by intervals of cen- sions des séismes à venir sur la pro- ca] and the updated list of signifi- turies. In this article, we provide details priété. cant Canadian earthquakes (Lam- on the most significant earthquakes ontagne et al. 2008). that have been recorded in, or near, INTRODUCTION Canada, including where and when It is easy to forget that large and dam- 2

Figure 1. Map of earthquakes with magnitude ≥2.5 in Canada (1660−2009). The red ellipses and article highlight some of the areas discussed in the text.

CAUSES OF EARTHQUAKES IN An average of approximately 50 earth- types are sometimes also referred to as CANADA quakes are felt across Canada each megathrust, or great earthquakes. Just Each year in Canada, approximately year. to the north of Vancouver Island, the 4000 earthquakes are detected by seis- The largest and most frequent Pacific and North America plates slide mologists at Natural Resources Cana- earthquakes occur along the west coast, past one another along the Queen da. The earthquake distribution (Fig. 1) and most are associated with plate Charlotte Fault (Canada’s ‘San can largely be explained by tectonic motions and active faults (Fig. 2). In Andreas’). This seismically active fault setting (Fig. 2); for example, most of southwestern British Columbia (BC), zone produced Canada’s largest historic the earthquakes occur along the active the oceanic Juan de Fuca and Explorer earthquake − a M 8.1 event just west plate boundaries off the west coast. plates are subducting beneath the of the Queen Charlotte Islands in However, there is also significant activ- North American Plate at a rate of 2−4 1949. This fault extends north to the ity throughout the Cordillera (particu- cm/yr (Riddihough and Hyndman Yakutat region of Alaska, where colli- larly in the Yukon and Northwest Ter- 1991). This subduction process pro- sional tectonics (including a subduction ritories), along the Arctic margin, in duces three types of earthquakes: zone to the west that generated a M the Ottawa and St. Lawrence river val- those within the subducting plate (typi- 9.2 earthquake in 1964) again domi- leys, in the northern Appalachians, and cally at 30−60 km depth), those within nates. along the eastern offshore margin. The the North American Plate (down to 30 The seismicity in the Richard- fewest earthquakes occur within the km depth), and giant subduction earth- son and Mackenzie mountains of the stable craton (including the plains of quakes along the interface between the Yukon and Northwest Territories (Fig. Saskatchewan and Manitoba; Fig. 2). latter two plates. The last of the three 1) results from crustal stress being GEOSCIENCE CANADA Volume 37 Number 1 March 2010 3

Figure 2. Major tectonic features of Canada. Inset shows the active tectonics along Canada’s west coast, including the Queen Charlotte Fault and the subduction zone. transferred from the Yakutat collisional continent transition, and may be relat- (Adams and Basham 1991). zone to reactivate shallow thrust faults ed to the reactivation of Mesozoic rift In eastern Canada, earth- within the foreland fold and thrust belt faults. Seismicity within the Labrador quakes are believed to be primarily of the Mackenzie Mountains (Mazzotti Sea is concentrated on the extinct caused by a northeast-to-east oriented et al. 2008) and strike-slip faults within spreading ridge and associated trans- compressive stress field reactivating the Richardson Mountains (Cassidy form faults associated with the zones of crustal weakness − either and Bent 1993). The seismic zones breakup of Pangea. Concentrations of failed rifts or old fault zones (Kumara- along the eastern Arctic margin seismicity near Baffin Island and across pelli and Saull 1966; Adams and (including a M 7.2 earthquake in Baffin the Boothia and Ungava peninsulas Basham 1991). The most active zones Bay in 1933) are situated at the ocean− may be caused by postglacial rebound are located at the mouth of the St. 4

Lawrence River, near La Malbaie in Charlevoix County, in western Québec/eastern Ontario, and in the northern Appalachians. Charlevoix (Fig. 1) is the site of five large earthquakes (M >6) since 1663, the most recent being in 1925. The offshore Atlantic margin (southeast of New- foundland) experienced a magnitude 7.2 earthquake in 1929.

EARTHQUAKE MONITORING IN CANADA Earthquake monitoring began in Cana- da in the late 1800s. The first known, instrumentally detected earthquake in Canada was the March 23, 1897 M~5 Montreal-area event, recorded on a 3- component seismograph at McGill University in Montreal, Québec (QC). The first continuously operating seismographs in Canada were located in Toronto, Ontario (ON) (installed Sep- tember, 1897) and Victoria, BC (starting September 3, 1898). These were low-gain Milne seismographs (most Figure 3. The CNSN and POLARIS seismic stations operating in Canada in 2009. sensitive to large, distant earthquakes), which were a part of the global net- ning in 1991, the Canadian National These instruments are designed specifi- work established by the British Associ- Seismograph Network (CNSN) was cally to record the very strong shaking ation for the Advancement of Science. completely modernized (North and associated with large earthquakes Additional low-gain seismographs were Beverley 1994), with digital data from (when the ‘standard’ seismographs may deployed across Canada (e.g. Ottawa, approximately 80 sites being continu- be off-scale), thereby providing infor- Halifax, St. Boniface and Saskatoon) ously transmitted in real-time (via satel- mation critical for engineering purpos- during the first two decades of the lite links, dedicated phone lines, and es. As of 2009, the GSC operates 123 1900s. For a detailed description of the UHF radio links) to data processing strong-motion instruments in Canada early history of earthquake recording centres in Sidney, BC and Ottawa, ON. (Cassidy et al. 2007; Fig. 4a, b). Most in Canada, see Stevens (1980), Rogers Nearly half of the stations included of these instruments are modern (1992), and Basham and Newitt (1993). state-of-the-art three-component ‘Internet Accelerometers’ located in Significant upgrades in earth- broadband seismometers. This network the urban centres of southwestern BC quake monitoring capacity in Canada lowered the magnitude threshold in (Fig. 4c, d). These low-cost instru- occurred in the 1960s, 1970s, 1990s, most areas of Canada (except the far ments, designed at the Natural and most recently in the early 2000s. In north) to about M 3. In 2000, the Resources Canada (NRCan) office in the early 1960s, 24 ‘standard’ seismic POLARIS seismic network − a part- Sidney (Rosenberger et al. 2007), trans- stations (similar to the ‘World Wide nership of government agencies, Cana- mit data in real-time via the Internet. Standard Seismic Network’) were dian universities, and industry − began In addition, when triggered by strong deployed across Canada. These stations to be deployed across Canada. shaking, they send information on the contained ‘short-period’ as well as POLARIS deployed more than 90 shaking level via e-mail to key clients. ‘long-period’ seismographs (using pho- three-component broadband, digital tographic recording) and recorded seismic stations across the country, tar- CANADA’S EARTHQUAKE HISTORY both local and global earthquakes. geting specific research areas (including The known earthquake history of With this network, any earthquake larg- seismic hazard, mapping earth struc- Canada varies significantly across the er than about M 3.5 beneath the Cana- ture for the diamond industry, etc.). As country, largely because of the time lag dian landmass could be recorded. of 2009, there are more than 120 seis- associated with European exploration Starting in the mid 1970s and into the mic stations operating within the (and hence written records); this histo- 1980s, digital telemetered networks CNSN, and more than 100 POLARIS ry begins in the early-mid 1500s in with short-period seismometers were sites in operation (Fig. 3). eastern Canada, but not until the late installed in both southwestern BC and In addition to the CNSN and 1700s along the BC coast. Canada’s southeastern Canada. These networks POLARIS networks, the Geological first reported earthquake is based provided, for the first time in Canada, Survey of Canada (GSC) operates a largely on Huron oral tradition and real-time access to seismic data. Begin- ‘strong motion seismograph network’. describes an earth tremor felt at the GEOSCIENCE CANADA Volume 37 Number 1 March 2010 5

Figure 4. Maps of strong-motion seismographs in a) western Canada, b) eastern Canada, and c) the dense network in greater Vancouver; d) a photograph of a strong motion ‘Internet Accelerometer’. southeastern end of Georgian Bay, affected…” (Jackson 1990). an Earthquake Epicentre File database. ON, “prior to 1637” (Gouin 1994). During historic time In most cases, this is either a ‘moment The first reported earthquake in west- (1660–2009), more than 621 earth- magnitude’ (Mw) or ‘surface wave mag- ern Canada is described in Captain quakes of M >5 (i.e. earthquakes capa- nitude’ (Ms) which are the best magni- George Vancouver’s journal. He wrote ble of causing damage in populated tude scales to use for large (M >5) that, “on February 17, 1793, a very areas) have occurred in, and adjacent, earthquakes. severe shock of an earthquake had to Canada. Some of these are been felt” at the Spanish settlement at described in more detail in the follow- Potentially Damaging (M 5.0−6.4) Nootka on the west coast of Vancou- ing sections. In many cases, additional Earthquakes (‘The Good’) ver Island (Rogers 1992). There are information (including damage photo- For the purposes of this article, ‘good’ also numerous first nations’ oral tradi- graphs) on the earthquakes listed earthquakes are defined as those that tions associated with earthquakes, below can be found on the ‘Earth- were widely felt (thereby providing a described later in this article. In north- quakes Canada’ website [http://earth- ‘friendly reminder’ to people that ern Canada, the first reported earthquakescanada.nrcan.gc.ca] under the earthquakes occur, and often prompt- quake in the Yukon Territory was heading of ‘Historic Events’. Note that ing them to become better prepared described in the journal of Robert throughout this document the generic for future earthquakes), and scientifi- Campbell of the Hudson’s Bay Com- term ‘magnitude’ is used. There are cally useful for understanding and bet- pany. He wrote that at Fort Selkirk many different types of ‘magnitude’ ter assessing hazards associated with (west-central Yukon) on December 27, scales; however, all define the size of future, potentially larger earthquakes. 1850 “an earthquake was felt here for an earthquake, and are related to the However, these earthquakes are not the space of one minute. It was very amount of energy released. We use the ‘good’ in the generally accepted sense, severe and the houses were visibly preferred magnitude from the Canadi- as, in some cases, they seriously fright- 6

south to Kentucky and Virginia (more than 1100 km from the epicentre). In Témiscaming, about 80% of all chimneys were damaged. In addition, cracks developed in some solid brick walls. In Mattawa and North Bay (both about 70 km from the epicentre), many chimneys were thrown down. In the epicentral region, minor rockfalls were observed as well as cracks in the gravel and sand at the edges of islands and borders of lakes. In the months that followed the earthquake, numerous aftershocks were felt in Témiscaming and Kipawa. The day following the earthquake, it was observed that the water of Tee Lake close to the epicentre was discoloured by shaking caused by the earthquake. Near Parent, QC (300 km away from the epicentre), 30 m of railroad embankment slid away. Témiscaming continues to be seismically active. Residents were reminded of this on New Year’s Day, 2000, when a M 5.2 earthquake struck the region; Figure 5. Location of all ‘good’ (M 5.0–6.4) earthquakes in Canada (1660–2009). this caused some minor damage in Those highlighted in red are discussed in the text. Témiscaming and was felt as far as Toronto. For additional details, see ened people and caused millions of Charlevoix–Kamouraska area (Fig. 5). Hodgson (1936), Hodgson (1945), and dollars in damage. Typically, these Shaking from this earthquake was felt Bruneau and Lamontagne (1994). earthquakes range in magnitude from across much of eastern North Ameri- about 5.0 to 6.4 (Fig. 5). In total, 561 ca, to distances of 1000 km. This 1944: M 5.6, Cornwall, Ontario earthquakes within this magnitude earthquake caused considerable dam- This M 5.6 earthquake occurred just range have occurred within or adjacent age near the epicentre along the St. after midnight on September 5, 1944. to Canada between 1660 and 2009 (Fig. Lawrence River. The cracked walls, fall- It was felt from New York to Boston 5). Details on ten ‘good’ earthquakes en chimneys and broken windows to Québec City and Toronto. It caused are provided below. reminded local inhabitants that they considerable damage (estimated at $2 live in an active seismic zone that has million) in Cornwall, ON (where about 1920: M 5.5, Gulf Islands, British experienced 5 major earthquakes since 2000 chimneys were damaged), and Columbia 1663. In addition to homes, some very Massena, New York (where 90% of This earthquake struck at 11:10 p.m. important structures were damaged by the chimneys were damaged or local time on January 24. It was cen- the quake: the church in Saint-Urbain, destroyed). Most of the damage tred beneath the Gulf Islands and was the railway terminal (Gare du Palais) occurred in areas underlain by the felt across much of southwestern BC and port installations in Québec City, Leda Clay (ancient glacial lake sedi- and northwestern Washington State to and a church as far away as Shawinigan ments) of the St. Lawrence River val- distances of at least 150 km. There (about 250 km from the epicentre). In ley. For additional information on this were numerous reports of minor dam- the weeks that followed, dozens of earthquake, see Hodgson (1945) and age. At Bellingham and Anacortes, aftershocks continued to shake the Bruneau and Lamontagne (1994). Washington, brick walls were cracked; area, keeping the inhabitants living in in Vancouver, some bricks fell from fear. For additional details, see Bent 1982: M 5.7, Miramichi, New chimneys; at Victoria, plaster cracked (1992) and Bruneau and Lamontagne Brunswick and dishes fell; at Brentwood, the con- (1994). Just before 9 a.m. on January 9, 1982, a crete chimney and wall of an electric M 5.7 earthquake struck near power plant were cracked; and on 1935: M 6.2, Témiscaming, Québec Miramichi, New Brunswick (NB). This Mayne Island, the metal chimney at a On November 1, 1935, just after 1 a.m. event came as a shock to local resi- lighthouse was damaged (Milne 1956). a M 6.2 earthquake struck about 10 km dents who were unaccustomed to east of Témiscaming, QC. This earth- earthquakes, as did the M 5.1 after- 1925: M 6.2, Charlevoix, Québec quake was felt west to Thunder Bay, shock that struck 3½ hours later. On February 28, 1925, at 9:19 p.m., a ON, east to the Bay of Fundy, across These earthquakes were felt across the M 6.2 earthquake struck the the northeastern United States, and Maritime provinces, eastern Québec GEOSCIENCE CANADA Volume 37 Number 1 March 2010 7 and the New England states, to dis- a foreshock of M 4.7 on November 1997: M 4.7, Georgia Strait, British tances of about 350 km from the epi- 23, 1988. It was felt as far away as Columbia centre. People in highrises in Ottawa Detroit, Boston, Halifax, and southern At 7:40 a.m. on June 24, 1997, a M 4.7 and New York City felt swaying from Labrador. Damage in the sparsely pop- earthquake struck southwestern BC. the surface waves generated by this ulated epicentral area was modest, lim- This earthquake, located beneath the earthquake. Fortunately, because the ited to cracked or fallen un-reinforced Strait of Georgia midway between the immediate epicentral area was unpopu- masonry walls; however, eleven land- population centres of Vancouver (30 lated, damage was very slight: a few slides were attributed to the earth- km to the east) and Nanaimo (30 km hairline cracks but no structural dam- quake. Damage outside the epicentral to the west), was felt across most of age in buildings up to 100 km away. area was correlated with underlying Vancouver Island and east as far as Although there was no evidence for unconsolidated sediments; for example, Abbotsford (100 km away). Minor rupture at the surface, high-quality dig- nearly 350 km from the epicentre, the damage included broken glass in Van- ital data and monitoring of aftershocks former Montréal Est City Hall (built couver and a broken water pipe in showed a very clear ‘image’ of a west- on 17 m of clay) suffered severe dam- North Vancouver. This earthquake dipping rupture zone (fault) just below age to its masonry cladding. Detailed triggered a rush on purchases of earth- the surface. For more information, see analysis of seismic data from this quake preparedness kits in the region. Basham et al. (1982) and Basham and earthquake by a large number of Detailed analysis of this earthquake Adams (1984). researchers (e.g. Hough et al. 1989; and its aftershock sequence (Cassidy et Boore and Atkinson 1992; Boatwright al. 2000) provided the first ‘image’ of 1986: M 5.4, Prince George, British and Choy 1992; Somerville et al. 1990) an active fault in southwestern BC. For Columbia has provided valuable insight into the details, see Cassidy et al. (2000) and On March 21, 1986 at 3:56 p.m. a nature of moderate earthquakes in Mosher et al. (2000). widely felt M 5.4 earthquake occurred eastern North America. For example, in an area of low historic seismicity the strong ground motion recordings 2001: M 5.3, Near Dawson Creek, just west of the Rocky Mountains in exceeded predicted levels, which Had- British Columbia east-central BC (Fig. 5). The epicentral don (1992) attributed to the direction At 8:20 p.m. on Friday, April 13, 2001, region is sparsely populated and only and focusing of seismic energy, where- residents of northwestern Alberta minor damage (mainly to older mason- as other researchers (Boore and Atkin- (AB) and northeastern BC were sur- ry chimneys) occurred, although the son 1992) related it to the earthquake prised by a M 5.4 earthquake, the earthquake was felt strongly in Prince source properties and directional dif- largest ever recorded in that ‘seismical- George, 70 km to the west. Within 48 ferences in how seismic waves attenu- ly quiet’ region; the epicentre was hours of the main shock, portable ate. located 40 km to the northeast of short-period seismographs were Dawson Creek, BC. This earthquake deployed in the epicentral region and 1989: M 6.3, Ungava, Québec was felt in Edmonton, AB (500 km to operated for eight days. The few after- On December 25, 1989 a M 6.3 earth- the east), Prince George, BC (300 km shocks that were recorded were con- quake occurred in the remote area of to the southwest) and Fort Nelson, BC fined to a depth range of 9 to 16 km, Ungava, in northern Québec. Only (340 km to the northwest). Although and the largest was M 2.5. No fore- weakly felt at distant villages along there were no reports of structural shocks were detected by the CNSN. Ungava Bay, this was one of the most damage, items were knocked from The occurrence of this earthquake and significant earthquakes of the century, shelves, and, like the 1986 Prince several other moderate-to-large earth- as it provided the first historical evi- George earthquake, it served as a quakes in the northern and central dence for surface faulting in eastern ‘friendly reminder’ of earthquake haz- parts of the eastern Cordillera raises North America (Adams et al. 1991). It ards in the Cordillera. the question of the level of seismic also allowed, for the first time in east- hazard in the more populated southern ern North America, an opportunity to Damaging (M 6.5–7.9) Earth- section of the eastern Cordillera. For compare the extent and magnitude of quakes (‘The Bad’) additional details on this earthquake surface faulting and regional deforma- A total of 57 ‘bad’ earthquakes in the see Rogers et al. (1990). tion with waveform modelling of the M 6.5–7.9 range have occurred across rupture process (Bent 1994) and after- (or near) Canada since 1660 (Fig. 6). 1988: M 5.9, Saguenay, Québec shock distribution. The surface effects Most of these were either off the west On Friday, November 25, 1988 at 6:46 also indicate the type of evidence to be coast or in remote areas. Here we high- p.m. the largest earthquake in eastern sought from prehistoric ruptures. The light (in chronological order) the top North America in 53 years occurred 35 observation of surface faulting, and 10 of the ‘bad’ events, mainly those km south of Chicoutimi, QC and comparison with modelling from the that caused significant damage (high- about 150 km north of Québec City seismic observations, was a major leap lighted in red in Figure 6). (North et al. 1989). The epicentre was forward in constraining seismic hazard located in a relatively ‘seismically quiet’ in eastern North America. 1663: M~7.0, Charlevoix, Québec area, and had a deep focus (29 km This earthquake, with a magnitude esti- beneath the surface). Few aftershocks mated at M ~7.0, most probably were recorded, but it was preceded by occurred in the Charlevoix region of 8

quake was felt from Ketchikan, Alaska, 450 km to the north, to Terrace and Skeena, BC, nearly 400 km to the east. The strongest shaking was reported on the Queen Charlottes: at Masset (300 km distance), houses shook violently; at Queen Charlotte City and Skidegate, dishes were broken and a 1 m local tsunami was reported; at Sandspit, 500 feet of beach was reported to have dis- appeared into the sea; and at Rose Harbour, chimneys toppled. For more details, see Milne (1956), and Rogers (1986).

1929: M 7.2, Grand Banks, New- foundland This M 7.2 earthquake struck at 5:02 p.m. on November 18, 1929. It was located about 250 km south of New- foundland, along the southern edge of the Grand Banks and was felt as far away as New York (nearly 1500 km to the southwest) and Ottawa (nearly 1500 km to the west). On land, dam- Figure 6. Location of all ‘bad’ (M 6.5–7.9) earthquakes in Canada (1660–2009). age caused by shaking was limited to Those highlighted in red are discussed in the text. Cape Breton Island, where chimneys were overthrown or cracked and where Québec (Fig. 6). It was felt over the quake (Bakun et al. 2002). some highways were blocked by minor entire eastern part of North America landslides. This earthquake is most (an area of about 2 million km2; Gouin 1918: M 6.9, Vancouver Island, notable for the devastating tsunami 2001). At the time, most of the popu- British Columbia that was generated by a large subma- lation of New France lived in Québec This large, M 6.9, earthquake occurred rine slump (estimated at 200 km³ of City, Trois-Rivières and Montreal (all just after midnight local time on Friday, material) triggered by the earthquake more than 100 km away from the epi- December 6, 1918. It occurred near shaking (Fig. 7). The tsunami killed 28 centre), which may explain why no loss the west coast of Vancouver Island, people in Newfoundland, and was of life was reported and damage was and was felt very strongly at Estevan recorded along the Atlantic seaboard confined to a few cracked and broken Point lighthouse and at Nootka light- of the US and across the Atlantic in chimneys and items being tossed from house on the southern tip of Nootka Portugal. The underwater slump also shelves. The earthquake triggered Island. There was damage to the Este- ruptured 12 transatlantic cables in mul- large landslides over a vast area, includ- van Point lighthouse (rendering it inop- tiple locations. For more details on this ing the Charlevoix region and along erable) and to a wharf at Ucluelet. This earthquake, see Bent (1995) and Ruff- the St. Lawrence, Shipshaw, Betsi- earthquake awakened and frightened man and Hann (2006). amites, Pentecôte, Batiscan, and Saint- people all over Vancouver Island and Maurice rivers. in the greater Vancouver area. It was 1933: M 7.3, Baffin Bay, Nunavut felt in northern Washington State and This earthquake is the largest instru- 1872: M 6.8, Northern Washington at Kelowna, more than 500 km to the mentally recorded earthquake to have State, USA east in the interior of BC. The earth- occurred along the passive margin of This M 6.8 earthquake (Bakun et al. quake occurred within the North North America and is also the largest 2002) was located about 250 km south- American plate, and was followed by at known earthquake north of the Arctic east of Vancouver, BC. It occurred least 14 aftershocks (including one as Circle. In spite of its intensity, the 1933 within the North American Plate, and large as M 5.6). For more details see earthquake did not result in any dam- was felt from Quesnel (nearly 600 km Cassidy et al. (1988). age because of its offshore location to the north) to Eugene, Oregon (500 and the sparse population of the adja- km to the south). Strong shaking was 1929: M 7.0, Queen Charlotte cent onshore regions (the closest com- reported in Victoria, where items were Islands, British Columbia munities were more than 200 km knocked from shelves and people ran This M 7.0 earthquake occurred on away). For more information see Bent out into the streets (Milne 1956). May 26, 1929, along the Queen Char- (2002). Numerous aftershocks were felt for lotte Fault, about 50 km south of the more than a year following this earth- Queen Charlotte Islands. The earth- GEOSCIENCE CANADA Volume 37 Number 1 March 2010 9

1946: M 7.3, Vancouver Island, British Columbia This earthquake, Canada’s largest recorded onshore earthquake to date, was a M 7.3 event that occurred at 10:15 a.m. on Sunday, June 23, 1946. The epicentre was on central Vancou- ver Island, just to the west of Courte- nay and Campbell River. This earthquake caused considerable damage on Vancouver Island (Fig. 8), and was felt as far away as Portland, Oregon (about 500 km to the south), and Prince Rupert, BC (about 600 km to the north). The earthquake knocked down 75% of the chimneys in the closest communities, Cumberland, Union Bay, and Courtenay (including the Courte- nay School; fortunately, the earthquake occurred on a Sunday morning so no Figure 7. Photograph of a house that was washed 1–2 km out to sea by the tsuna- children were at their desks) and did mi resulting from the 1929 Grand Banks earthquake. Photograph courtesy of the considerable damage in Comox, Port Provincial Archives, Government of Newfoundland and Labrador. Alberni, and Powell River on the eastern side of Georgia Strait. A number of chimneys were shaken down in Vic- toria and people in Victoria and Van- couver were frightened, many running into the streets. More than 300 landslides were triggered by the earthquake (Mathews 1979), and there were numerous instances of liquefaction, particularly along the east coast of central Vancouver Island (Rogers 1980). Two deaths resulted, one from drown- ing when a small boat capsized in an earthquake-generated wave, and the other from a heart attack in Seattle. For additional information see Hodg- son (1946) and Rogers and Hasegawa (1978).

1970: M 7.4, Queen Charlotte Islands, British Columbia This M 7.4 earthquake occurred on June 24, 1970, at 6:09 a.m. It was felt with Modified Mercalli Intensity IV Figure 8. Damage to the Bank of Montreal building in Port Alberni, BC, resulting (i.e. rattling dishes, windows and doors) from the M 7.3 earthquake of 1946. throughout the Queen Charlotte Islands and was felt to a distance of about 350 km on the adjacent main- sis of seismic data revealed that this quake relative to the great 1949 earth- land and on northern Vancouver was the first earthquake in the region quake to the north (see next section on Island (Horner et al. 1975). The epi- to show a significant component of ‘Destructive Earthquakes’) reveals the centre was beneath the ocean about 30 thrusting, which is consistent with the existence of a ‘seismic gap’ along the km south of the southernmost point convergent motion between the Pacific Queen Charlotte Fault that has not of the Queen Charlotte Islands. and North American plates. A slight ruptured in the past century (Rogers Observed aftershocks indicate it rup- swell was observed in Tasu Harbour, 1986). tured the Queen Charlotte Fault in a 100 km north of the epicentre and southerly direction for about 35 km. about 10 minutes after the earthquake, 1985: M 6.9, Nahanni, Northwest The faulting mainly involved right lat- but no tsunami was observed on tide Territories eral strike-slip motion; however, analy- gauges. The position of the earth- The M 6.9 Nahanni earthquake of 10

Destructive (M >8) Earthquakes (‘The Ugly’) Some of the world’s largest earthquakes have occurred in, or adjacent to, Canada. All have occurred along the active plate boundaries off the west coast (Fig. 10).

1700: M 9.0, Offshore Vancouver Island, British Columbia At 9 p.m. on January 26, 1700, a massive ‘megathrust’ earthquake struck off the west coast of Vancouver Island. It ruptured the Cascadia subduction fault from northern Vancouver Island to northern California (Fig. 10), causing very strong ground shaking for several minutes and spawning a tsunami that travelled across the Pacific. This earthquake was likely similar, in many ways, Figure 9. Rock avalanche triggered by the October 5, 1985 Nahanni earthquake to the 2004 Sumatra M 9.2 subduction (Horner et al. 1987). Photograph by R. Horner. earthquake (Cassidy et al. 2005). The Cascadia earthquake of 1700 occurred December 23, 1985, is not just a single Boore and Atkinson 1989). Deploy- prior to European exploration and set- earthquake, but part of a remarkable ment of seismographs to record the tlement of the area, although the event series of earthquakes that struck the hundreds of aftershocks revealed that was recorded in the oral traditions of northern Canadian Cordillera over a the earthquake sequence involved First Nations peoples on Vancouver three-year period (1985-1988). The thrusting along a shallow, 50 km-long Island. These oral reports describe the sequence began with a surprising M 6.6 by 15-km wide, west-dipping fault collapse of houses (because of land- event on October 23, 1985 (surprising (Wetmiller et al. 1988). slides) in the Cowichan area, shaking because the largest known earthquake that was so severe that people could in the immediate area prior to this was 2001: M 6.8, Nisqually, Washington not stand, and so prolonged that it about M 5), and continued for several State, USA made them sick. They also describe the years after, including a M 6 event in On February 28, 2001, a M 6.8 earth- destruction of a winter village on the 1988. The 1985 earthquakes were felt quake occurred between Seattle and west coast of Vancouver Island near to distances of about 1500 km. Olympia in the state of Washington, present-day Pachena Bay (Rogers Because no community is closer than about 150 km southeast of Victoria, 1992). Numerous other First Nations 100 km to the epicentres, no major BC. This earthquake, like the similar- oral histories in Washington and Ore- structural damage was reported. At sized events in the same area in 1949 gon are likely related to this event Wrigley, about 115 km north of the and 1965, was centred within the Juan (Ludwin and Smits 2007). Japanese epicentre, residents reported seeing the de Fuca plate about 60 km beneath the records of the tsunami triggered by the ground roll. Vehicles bounced on the surface. It resulted in widespread dam- earthquake (Satake et al. 1996) indicate road and trees and power lines age (more than $2B U.S. in Washington that it struck at about 9 p.m. and had a whipped back and forth. Sections of State), including structural damage to magnitude of 9. Geological evidence the banks of the Mackenzie River buildings (especially to unreinforced from Vancouver Island to California slumped into the water. Inside homes, masonry) and bridges, and liquefaction demonstrates that M 9 earthquakes furniture moved, dishes fell from cup- and landslides that impacted trans- occur, on average, about every 500 boards, doors swung open and shut, portation routes. In Canada, the earth- years along the Cascadia fault, and that and walls flexed. One of the largest quake was felt all across southwestern the interval between earthquakes varies rock avalanches ever recorded in Cana- BC, from northern Vancouver Island from 250 to 850 years). In addition to da (Fig. 9) was triggered by the Octo- to the Okanagan Valley. There was large tsunami and liquefaction, they ber 5 earthquake. A 70-m scarp result- some minor damage (including broken can also cause sudden coastal subsi- ed from the landslide, which was esti- windows, pipes and chimney damage) dence (Atwater et al. 1995). mated to displace 5 to 7 million m3 of in Victoria and greater Vancouver, BC rock. Recordings of shaking for this (Molnar et al. 2004). Studies of the 1899: M 8.2, Alaska Panhandle earthquake were the strongest ever earthquake provided important new Region recorded in Canada and provided information on the hazards associated During September of 1899, the Yaku- important information on ground with these deep, oceanic plate earth- tat Bay region of Alaska, near the motion processes and earthquake haz- quakes (Frankel et al. 2002; Atkinson Yukon/BC border, was shaken by a ards (Choy and Boatwright 1988; and Boore 2003; Kao et al. 2008). series of major earthquakes. The GEOSCIENCE CANADA Volume 37 Number 1 March 2010 11

street was described as “like being on the heaving deck of a ship at sea”. In Prince Rupert, windows were shattered and buildings swayed. The earthquake was felt from the Yukon Territory to Washington State. Based largely on the distribution of hundreds of aftershocks that occurred in the months after the earthquake, the rupture zone is estimated to have extended along a 500-km long section of the fault (Fig. 10), and average displacement was about 5 m (Bostwick 1984).

EARTHQUAKE RESEARCH AND ADVANCES IN MITIGATION The best way to reduce future earthquake-related losses is to have robust seismic codes and standards in place to ensure that buildings and critical infra- structure will withstand future earthquakes. Structures designed according to code provisions can resist moderate earthquakes without significant damage, and major earthquakes without Figure 10. Location of all M >8 earthquakes near Canada’s borders. For each collapse. Earthquake research provides earthquake (see text) the rupture zone is shown in red. the fundamental building blocks that are used to develop and improve seis- sequence began on September 4, with by residents at Yakutat village. Ten or mic-hazard models, which are then a M 8.1 earthquake, followed by M 7.4 more earthquakes were felt at the included in seismic codes and stan- and M 8.2 events on September 10. Coast and Geodetic Survey camp near dards. Significant topographic changes result- the Copper River delta in Alaska, and The first seismic provisions in ed from this earthquake – a maximum several of them were violent. Several the National Building Code of Canada uplift of 14.5 m occurred on the west shocks were also felt on September 10 (NBCC) were put in place in 1953. coast of Disenchantment Bay, and in the Chugach Mountains near Prince These early seismic-hazard maps changes of 5 m or more affected a William Sound; five were reported included four ‘zones’, based on qualita- large area. Subsidence of as much as 2 about 300 km to the northeast on the tive assessment of historic earthquake m was observed in a few areas. Other Yukon River; and several were felt to activity. Significant updates to these documented phenomena included sur- the southeast at Juneau and Skagway. seismic-hazard maps were made in face faulting, avalanches, fissures, Details on this earthquake sequence 1970, 1985, and 2005, and some spouting from sand craterlets, and are provided by Plafker and Thatcher changes will be made in the 2010 code. slight damage to buildings. A destruc- (2009). The 1970 map (Milne and Davenport tive tsunami 11 m in height occurred in 1969) was the first national-scale prob- Yakutat Bay, and localized tsunamis 1949: M 8.1, Queen Charlotte abilistic seismic hazard map. It defined were observed at other places along Islands, British Columbia four zones based on peak acceleration the Alaskan coast. On August 22, 1949, a M 8.1 earth- at a 1% annual probability of The first earthquake was quake occurred on the Queen Char- exceedance (i.e. a 1-in 100-year event). strong enough to throw people off lotte Fault, the boundary between the The 1985 maps (Basham et al. 1985) their feet at Disenchantment Bay (near- Pacific and North American plates that included 7 zones, with both ‘accelera- ly 100 km from the epicentre). The follows the west coast of the Queen tion’ maps (for small buildings) and largest event on September 10 shook a Charlotte Islands off the west coast of ‘velocity’ maps (for taller buildings) mostly unsettled region, so the total BC (Fig. 2). The shaking was so severe based on a 10% probability of affected area is unknown. The event on the Queen Charlotte Islands that exceedance in 50 years (a 1 in 475-year was felt strongly in northwestern BC cows were knocked off their feet, and event). Most recently, the 2005 maps and southern Yukon, including White- a geologist working on the north end (Adams and Atkinson 2003; Adams horse. Prospectors camped on Disen- of Graham Island could not stand up. and Halchuk 2003; Heidebrecht 2003) chantment Bay felt over 50 shocks on Chimneys toppled, and an oil tank at provide location-specific uniform haz- September 10, two of which were Cumshewa Inlet collapsed. In Terrace, ard spectral acceleration levels at the strong. Two of the many shocks felt on the adjacent mainland, cars were 2% in 50-year probability level (a 1 in that day were also described as severe bounced around, and standing on the 2475-year event). A simplified seismic- 12

world, hazard maps will continue to evolve and improve, providing for safer structures, and safer and more resilient communities.

Sources of Seismic Risk Here we briefly outline some of the key aspects of seismic risk in Canada, as illustrated by historic Canadian earthquakes. For additional details on the geological and human effects of large earthquakes in southwestern BC, see Clague (2002). For additional details on significant earthquakes in eastern Canada, see Lamontagne (2002).

Pre-Building Code Buildings As demonstrated by large, historic earthquakes in both eastern and western Canada, many older, un-reinforced masonry structures built prior to modern building codes are extremely vul- nerable to earthquake shaking (Fig. 8). Some specific examples are provided in Figure 11. Simplified 2005 seismic hazard map for small (1–2 storey) structures. Bruneau and Lamontagne (1994) and a summary in Lamontagne (2009). hazard map from the 2005 NBCC is al. 1995; Clague 1997), searching shown in Figure 11. These maps use for active faults using modern Seismically triggered Landslides ‘firm-soil’ as a reference shaking level high-resolution techniques such as Seismically triggered landslides pose a (rather than ‘bedrock’ used in all previ- LiDAR, and precise location of significant threat and can hamper ous maps). Another significant change earthquake epicentres (Cassidy et recovery efforts after a major earth- in this map was incorporation of the al. 2000); quake by blocking transportation links. hazard associated with the rare (every 2. Ground motion studies in both In the mountainous areas of western ~500 years) Cascadia megathrust eastern and western Canada (e.g. Canada, strong ground shaking can earthquake on Canada’s west coast. It Atkinson 2005; Atkinson and trigger widespread landslide activity. was found that the megathrust event Boore 2006; Atkinson and Macias The 1946 Vancouver Island earthquake dominates the seismic hazard for com- 2009); (Mathews 1979; Rogers 1980) triggered munities along the west coast of Van- 3. Crustal deformation monitoring more than 300 landslides at distances couver Island. using Global Positioning Systems, exceeding 100 km from the epicentre. Updates to the seismic hazard which provides critical new infor- The 1985 Nahanni earthquakes trig- maps, and ultimately to the seismic mation to identify zones of strain gered massive landslides, as illustrated provisions in the NBCC, are driven by accumulation that indicate proba- in Figure 9. In eastern Ontario and earthquake monitoring and research ble locations of future earthquakes southern Québec, landslides triggered results (e.g. Adams and Atkinson 2003, (Mazzotti et al. 2003); by earthquakes have been observed in and other papers in the special volume 4. Better understanding of earth- the marine clays of the St. Lawrence of the Canadian Journal of Civil Engi- quakes in stable cratonic regions, and Ottawa river valleys (Aylsworth neering, Vol. 30, No. 2). particularly levels of activity and 2007). Samples of recent important maximum magnitudes (Mazzotti research activities (note that this list is and Adams 2005; Fenton et al. Liquefaction only a small sample) include: 2006; Atkinson and Martens Liquefaction caused by historic and 1. Subduction zone studies in BC, 2007); and prehistoric earthquakes in Canada has including GPS monitoring (e.g. 5. Better crustal models, and been observed on the Fraser River Hyndman and Wang 1995; Maz- improved understanding of wave delta of Vancouver (Clague et al. 1997; zotti et al. 2003), and investigation propagation and variation in earth- Clague 2002), and, in the case of the of Episodic Tremor and Slip (e.g. quake shaking with local geological M 7.3 Vancouver Island earthquake of Dragert et al. 2001; Rogers and conditions (e.g. Cassidy and Rogers 1946, to a distance of about 100 km Dragert 2003), marine mapping of 1999; Atkinson and Cassidy 2000). (primarily along the east coast of Van- the seafloor, paleoseismological As we learn more about earth- couver Island). Rogers (1980) reports studies (Adams 1990; Atwater et quakes across Canada and around the that liquefaction resulting from the GEOSCIENCE CANADA Volume 37 Number 1 March 2010 13

1946 earthquake, caused extensive CONCLUSION localities intended for the 2005 damage to the wharf and cannery Large and damaging earthquakes have National Building Code of Canada: buildings at Kildonan, as well as ‘spec- struck Canada in the past, and will Geological Survey of Canada Open tacular downdrops and fountains of again in the future. We cannot predict File 4459, 155 p. blue clay that caked trees at Reid earthquakes at this time, and therefore Adams, J., Wetmiller, R.J., Hasegawa, H.S., Island’. Liquefaction effects have also and Drysdale, J., 1991, The first sur- our best defense against earthquakes is face faulting from a historical been observed for some earthquakes in to have modern earthquake codes and intraplate earthquake in North Ameri- eastern Canada (see Lamontagne 2002), standards, based on the latest earth- ca: Nature, v. 352, p. 617-619. including the deep (29 km beneath the quake research. In addition, scientists Atkinson, G.M., 2005, Ground motions for surface) 1988 Saguenay earthquake, need to continue to work with emer- earthquakes in southwestern British which caused extensive liquefaction- gency response organizations, planners, Columbia and northwestern Washing- related damage to local houses (Lefeb- and the public to maintain and raise ton: Crustal, in-slab, and offshore vre et al. 1991). awareness of earthquake hazards and events: Bulletin of the Seismological their potential impacts in Canada, and Society of America, v. 95, p. 1027- Tsunamis and Seiches help prepare for future earthquakes 1044 Tsunamis triggered by both distant and through improved monitoring, mitiga- Atkinson, G.M., and Cassidy, J.F., 2000, local earthquakes have affected Cana- tion of effects, and emergency plans. Integrated use of seismograph and da, as demonstrated by the 1929 New- One of the primary goals of strong-motion data to determine soil amplification: Response of the Fraser foundland tsunami, the 1964 tsunami this article is to provide a reminder of River delta to the Duvall and Georgia in Alberni Inlet on Vancouver Island Canada’s past earthquakes−the ‘good’, Strait earthquakes: Bulletin of the (generated by the M 9.2 Alaska earth- the ‘bad’, and the ‘ugly’−so that we can Seismological Society of America, v. quake) and the 1700 tsunami on Van- be better prepared for future earth- 90, p. 1028-1040. couver Island generated by a M 9.0 quakes. Atkinson, G.M., and Boore, D.M., 2003, Cascadia earthquake. For details, see Empirical ground-motion relations for Clague (2002). Seiches (standing waves ACKNOWLEDGEMENTS subduction-zone earthquakes and their set up in bodies of water such as lakes, The authors would like to thank our application to Cascadia and other rivers, bays, or even swimming pools) many colleagues who have deployed regions: Bulletin of the Seismological can be generated when seismic waves and operated seismograph stations Society of America, v. 93, p. 1703- from an earthquake (including waves over the years, and who have located 1729. from a very distant earthquake that thousands of seismic events each year. Atkinson, G.M., and Boore, D.M., 2006, Earthquake ground-motion prediction cannot be felt) pass through a region. We thank Richard Franklin for his equations for eastern North America: Several good examples of seiches gen- assistance with some of the graphics in Bulletin of the Seismological Society erated in western Canada by the M 6.9 this article. We gratefully acknowledge of America, v. 96, p. 2181-2205. Denali, Alaska earthquake of 2002 are Gail Atkinson, Ralph Currie, Sonya Atkinson, G.M., and Martens, S.N., 2007, described in Cassidy and Rogers Dehler, and Jane Wynne for their thor- Seismic hazard estimates for sites in (2004). ough review of this manuscript. This is the stable Canadian craton: Canadian GSC contribution number 20090113. Journal of Civil Engineering, v. 34, p. Variation in Ground Shaking 1299-1311. Soft soils and deep sedimentary basins REFERENCES Atkinson, G.M., and Macias, M., 2009, Pre- such as the Fraser River delta near Adams, J., 1990, Paleoseismology of the dicted ground motions for great inter- Vancouver can significantly alter Cascadia subduction zone: Evidence face earthquakes in the Cascadia Sub- ground shaking. 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J.F., 2007, The new real time reporting strong motion seismograph network in southwest BC: More strong motion instruments for less money: Proceed- ings of the 9th Canadian Conference on Earthquake Engineering, Ottawa, ON, Paper 1181, on CD-ROM. Ruffman, A., and Hann, V., 2006, The Newfoundland tsunami of November 18, 1929: An examination of the twenty-eight deaths of the ‘South Coast Disaster’: Newfoundland and Labrador Studies, Memorial University of Newfoundland, St. John’s, NL, v. 21, p. 97-148. CORPORATE MEMBERS Satake, K., Shimazaki, K., Tsuji, Y., and Ueda, K., 1996, Time and size of a giant earthquake in Cascadia inferred PATRONS from Japanese tsunami records of Jan- Alberta Geological Survey uary 1700: Nature, v. 379, p. 246-249. Anglo American Exploration Canada Somerville, P.G., McLaren, J.P., Saikia, Memorial University of Newfoundland C.K., and Helmberger, D.V., 1990, The 25 November 1988 Saguenay, Natural Resources - Government of Newfoundland and Labrador Quebec, earthquake: source parame- Northwest Territories Geoscience Office ters and the attenuation of strong ground motion: Bulletin of the Seis- SPONSORS mological Society of America, v. 80, p. 1118-1143. Northern Geological Survey Stevens, A., 1980, History of some Canadi- Royal Tyrrell Museum of Palaeontology an and adjacent American seismo- Yukon Dept. of Energy Mines & Resources graph stations: Bulletin of the Seismo- logical Society of America, v. 70, p. 1381-1393. SUPPORTERS Wetmiller, R.J., Horner, R.B., Hasegawa, Activation Laboratories Ltd. H.S., North, R.G., Lamontagne, M., Franklin Geosciences Limited Weichert, D.H., and Evans, S.G., IBK Capital Corp. 1988, An analysis of the 1985 Nahan- ni earthquakes: Bulletin of the Seis- Johnson GEO CENTRE mological Society of America, v. 78, p. SRK Consulting 590-616. UNIVERSITIES Received July 2009 Acadia University Accepted as revised December 2009 Institut national de la recherche scientifique (INRS) University of Calgary University of Geneve Université du Québec à Montréal University of Toronto University of Waterloo Utah State University