A mag­ni­tude 6.5 quake could hit, ex­perts say

Ottawa Citizen - - FRONT PAGE - TOM SPEARS

The walls start sud­denly to shake and groan.

First, it’s a dull rum­bling sound, like a heavy truck where no truck should be. Then comes a bang­ing and clang­ing that threaten to rend the walls and the ceil­ing of your of­fice.

Out­side, fall­ing plates clat­ter along the ground of the Sparks Street pa­tios.

Over on Bank Street, walls bulge out­ward. Bricks from the older stores fall to the side­walk and to the street.

In Sandy Hill and down in the ByWard Mar­ket, some walls of old brick homes and stores give way. The city’s old­est stone and brick churches, which have stood since the 1800s, shift omi­nously.

Up on Par­lia­ment Hill, the mas­sive stone blocks trem­ble and over­head light fix­tures rat­tle, but noth­ing col­lapses.

Wel­come to Ot­tawa’s great earth­quake. It’s an imag­ined sce­nario, a tale of “what if?”

But that doesn’t mean it couldn’t hap­pen.

We know the Ot­tawa area could face a sub­stan­tial earth­quake be­cause it has hap­pened be­fore: In Corn­wall in 1944, when a mid­night earth­quake dam­aged hun­dreds of build­ings; in Témis­cam­ing in 1935; in Mon­treal in 1732. All these cities are part of our “seis­mic zone,” mean­ing we share com­mon fault lines in Earth’s crust.

And none of those earth­quakes was as strong as the kind ca­pa­ble of hit­ting Ot­tawa. The ear­lier three were in the range of mag­ni­tudes 5.6 to 6.2.

The quake that rat­tled the cap­i­tal in 2010 — which was cen­tred in Val-des-Bois, Que. — was smaller still, at 5.0.

This re­gion, say the ex­perts, could have an earth­quake of mag­ni­tude 6.5 or so.

(Quake fact: That’s a big dif­fer­ence, be­cause the mag­ni­tude scale is log­a­rith­mic: A mag­ni­tude 7 is 10 times greater than a 6, which is 10 times greater than 5, and so on.)

Of the 47 types of pos­si­ble dis­as­ters on an On­tario emer­gency plan­ning list, Ot­tawa con­sid­ers earth­quakes one of the five most se­ri­ous threats, based on our ge­ol­ogy and types of build­ings.

That puts it on the same risk level as another ice storm, or a se­vere sum­mer storm (which can bring tor­na­does.)

“It re­ally wouldn’t take much” to cause big trou­ble, says Pierre Poirier, the city’s chief of se­cu­rity and emer­gency man­age­ment.

“An earth­quake of (mag­ni­tude) 6.5 in this city could be dev­as­tat­ing. It doesn’t have to be a 9.2.”

And the his­toric land­slides scar­ring our re­gion show that truly mas­sive shak­ing has hap­pened in the past.

So, what would hap­pen if we had the Big One to­mor­row?

Kate Ploeger was in her back­yard in Or­léans in June 2010 when she heard a deep rum­ble. Thun­der, she thought. But the sky was blue. A low air­plane? She couldn’t see one. Then the ground shook. Her first thought? “I’ve got data!” Ploeger stud­ies earth­quakes. In 2010, she was just be­gin­ning her PhD.

To­day, she teaches at the Univer­sity of Ot­tawa, but as a stu­dent it was her job to an­a­lyze what a big earth­quake would do to cen­tral Ot­tawa based on the same two vari­ables that Poirier cites: What kind of build­ings are there, and what kind of ground is un­der them?

Ploeger knew the vary­ing types of build­ings re­act to shak­ing very dif­fer­ently: Un­re­in­forced ma­sonry, or build­ings with a main struc­ture of brick, stone or con­crete blocks, do very poorly. Their walls are good at hold­ing up weight, but they break apart when the ground shakes side-to-side. Ploeger’s sur­vey found that 45 per cent of Ot­tawa’s his­toric core is made of these types of build­ings. Out­side the core, they are more rare, be­cause mod­ern build­ing codes don’t al­low this kind of con­struc­tion any­more. Be­fore the 1970s, how­ever, there were no such rules. Build­ings with a wood frame (even with brick on the out­side) are much stronger. The wood flexes like a tree branch in the wind. “So en­ergy (from the earth­quake) is ab­sorbed by yield­ing, flex­ing and by dam­ag­ing com­po­nents in the struc­ture,” says Mu­rat Saat­cioglu, who teaches earth­quake en­gi­neer­ing at the Univer­sity of Ot­tawa. “If it’s brit­tle, like brick, you can’t de­form (i.e. bend) a brick. They re­sist forces un­til they fail,” and then they break apart com­pletely. The wood struc­ture acts a lit­tle like the shock ab­sorber on your car, he says, with one im­por­tant ex­cep­tion: The car’s shocks are “elas­tic,” mean­ing they spring back to their orig­i­nal shape. A wood-framed wall, once bent, will stay bent un­til you fix it. But it gen­er­ally won’t fall down. Cal­i­for­nia’s ex­pe­ri­ences with se­ri­ous earth­quakes have shown that wood-framed build­ings per­form well, he said. “Of course, the ex­te­rior façades came down, but I don’t think in Ot­tawa that the mag­ni­tude and shak­ing would cause fail­ure of wood con­struc­tion.” Mod­ern of­fice or apart­ment tow­ers also do well, as their steel frames can bend without break­ing. The Par­lia­ment Build­ings are in a very lucky class by them­selves. Saat­cioglu says their lo­ca­tion will pro­tect them: “It is stone ma­sonry, so it is sup­posed to be vul­ner­a­ble, but it is sit­ting on a rock, so that will save it.” Call it ge­o­log­i­cal good luck: The seat of gov­ern­ment stands on bedrock, not soft soil. “If the same build­ings were on soft soil, the ef­fect would am­plify,” be­cause deep soil shakes around more than the un­der­ly­ing rock does. Imag­ine a big bowl full of Jell-O, he says. If you shake the bowl back and forth, the Jell-O wob­bles and moves more than the bowl it­self. If you put a tiny house from a Monopoly game on top of the Jell- O, it will be shaken more than the same tiny house in a bowl alone. Soft clay, which is all over Ot­tawa but es­pe­cially in its eastern half, wob­bles like Jell-O. The bedrock shakes only lit­tle, by com­par­i­son.

“If we had a (mag­ni­tude) 5.5 earth­quake right un­der­neath the city of Ot­tawa, my guess is the old brick build­ings in the Mar­ket area would suf­fer sig­nif­i­cant dam­age. Newer build­ings — re­in­forced con­crete built af­ter the 1980s — will not,” Saat­cioglu said.

“In terms of sin­gle-fam­ily homes, they will be OK. The out­side wall may just fall on the street, but it won’t be as crit­i­cal as load-car­ry­ing mem­bers (struc­tural pieces) com­ing down.” Western Univer­sity’s Gail Atkin­son agrees: “The real hazard in a city like Ot­tawa, and the same is true in Mon­treal, is a lot of older build­ings. Think of all those old, un-re­in­forced ma­sonry build­ings, the old brick build­ings that you see in down­town Ot­tawa. The ByWard Mar­ket, all of those build­ings that are kind of one- to five-storey walk-up build­ings.

“You might see some of those build­ings col­laps­ing.”

As a city, Ot­tawa de­pends on its bridges, both over the rivers and for high­way over­passes.

Bridges, like build­ings, vary in age and strength.

Older bridges, gen­er­ally speak­ing, can ex­pe­ri­ence fail­ures of the ver­ti­cal col­umns that hold up the “deck” — the part we drive on. But a sec­ond rea­son bridges can col­lapse is odder: The beams that hold up the deck, and which sit in turn on top of col­umns, may not stretch out widely enough.

Shak­ing can jos­tle them side­ways un­til they top­ple over the edge of the sup­port­ing col­umn like a cof­fee cup set too close to the edge of a ta­ble. If that hap­pens, a sec­tion of bridge comes down, too.

Saat­cioglu says that un­til Hur­ri­cane Ka­t­rina, the great­est eco­nomic dam­age from a nat­u­ral dis­as­ter in the United States came from the col­lapse of bridge sec­tions that sev­ered High­way 5 in Cal­i­for­nia, the state’s main north-south high­way and an eco­nomic life­line. That was a re­sult of the Northridge earth­quake (mag­ni­tude 6.7, plus af­ter­shocks) back in 1994.


“Ot­tawa is an area of mod­er­ate seis­mic hazard,” notes Claire Sam­son of Car­leton Univer­sity’s earth sci­ences depart­ment. “Cer­tainly we do ex­pect ev­ery decade or few decades to get a mag­ni­tude five-ish earth­quake, like the one that was felt in 2010.”

Over a pe­riod of “hun­dreds to 1,000 or so years, you ex­pect to get a re­ally large earth­quake, mag­ni­tude 6 or greater.” One very to close 1,000 years ago caused mas­sive land­slides where the Quyon River meets the Ot­tawa River, and about nine other land­slides east along the Ot­tawa for 50 or 60 kilo­me­tres.

The Ot­tawa and St. Lawrence val­leys are ge­o­log­i­cally sep­a­rate, but they’re re­lated.

The At­lantic Ocean formed once long ago, but closed up as con­ti­nents shifted. Then more shift­ing of con­ti­nents caused it to form again, says Western’s Atkin­son.

The first time, “It caused a lot of deep-seated faults as the plates were torn apart. Then they all got shoved back to­gether again and the At­lantic Ocean opened in a new place far­ther off to the east.”

Old, deep faults from that ini­tial open­ing run along the Ot­tawa and St. Lawrence val­leys. In ad­di­tion, an old vol­canic hot spot be­neath the Western Que­bec zone (Mon­treal to Témis­cam­ing) may have fur­ther weak­ened the Ot­tawa Val­ley’s faults.


One tool for in­ter­pret­ing our earth­quake risk is the new abil­ity to find ev­i­dence of big quakes dat­ing back thou­sands of years, or “pa­le­oearthquak­es.”

Sam­son works with Gre­gory Brooks of Nat­u­ral Re­sources Canada, a ge­o­mor­phol­o­gist who has de­vel­oped a new tech­nique. He looks un­der­wa­ter.

Brooks be­gan in lakes in north­west­ern Que­bec and has moved close to Ot­tawa with the tech­nique. Work­ing on Lac de l’Argile, or Clay Lake, north of Notre-Dame-de-laSalette.

Last sum­mer, he and a stu­dent from Car­leton did a study in­ves­ti­gat­ing the bot­tom of the lake by bounc­ing acous­tic pulses off it. It maps the dif­fer­ent lay­ers on the bot­tom, which were laid down at dif­fer­ent times in the past.

They found one layer where the en­tire lake had been dis­turbed.

“All around the lake, mas­sive land­slides oc­curred at once,” Sam­son said. The lake is sev­eral kilo­me­tres long. It’s still a jump to say this is proof of a ma­jor earth­quake, so more field work is re­quired, and the group also hopes to ex­pand the project to two other lakes nearby and take sed­i­ment cores for dat­ing and anal­y­sis. In the mean­time, they are pre­sent­ing their re­sults so far to a meet­ing of the Cana­dian Geo­phys­i­cal Union next month.

Ploeger cau­tions that each earth­quake is dif­fer­ent, and that there is no one-size-fits-all es­ti­mate of the dam­age. It de­pends es­pe­cially how far away the earth­quake is: “Nat­u­rally, you would see more dam­age as you ap­proach the epi­cen­tre,” which is the heart of the earth­quake, the place where the deep rock shifts sud­denly.

Nonethe­less, Ploeger’s over­views of­fer some ideas of what dam­age we could ex­pect here in Ot­tawa, if the Big One hit.

“You will likely have more dam­age in his­tor­i­cal neigh­bour­hoods, so ByWard Mar­ket, Sandy Hill, Cen­tre­town, Glebe. You would also likely see more dam­age on pock­ets of deep, soft clay. A deeper sed­i­ment of clay would usu­ally am­plify an earth­quake wave as it ap­proaches the sur­face,” mak­ing the sur­face shake more.

“With a (mag­ni­tude) 6.5 close to Ot­tawa, you would likely have some col­lapsed build­ings.”

“You would likely see some build­ings with ex­ten­sive dam­age that is beyond re­pair. In some cases, it prob­a­bly could be re­pairable,” ex­cept that the build­ings around have fallen and fur­ther dam­aged the build­ing that could have sur­vived. That hap­pened a lot in Christchur­ch, New Zea­land (a mag­ni­tude 6.3 in 2011.)

There will be “out-of-plane fail­ures.” This means a wall that used to be a straight ver­ti­cal sur­face now bulges out dan­ger­ously. This hap­pens with brick walls, and this can lead to col­lapse. “We’ve seen it ex­ten­sive in Cal­i­for­nia earth­quakes (and) Christchur­ch.”

Even if the build­ings are stand­ing, their “guts” can be badly dam­aged. “You see burst pipes, gas leaks, fires within min­utes af­ter an earth­quake oc­cur­ring. Prob­a­bly power out­ages, and even fail­ures of the backup power. We’ve seen this in Cal­i­for­nia, where there’s a main power fail­ure and the backup sys­tems weren’t ad­e­quately tied down, or de­signed or main­tained for earth­quakes.

“The other in­ter­est­ing one is elec­tri­cal arc­ing and elec­tro­cu­tion. Be­cause you can have the wires just be dis­lodged a lit­tle bit and it can cause fires, or if there’s a burst wa­ter pipe and arc­ing then you have elec­tro­cu­tion.”

The con­tents of a build­ing can also be dan­ger­ous, “prob­a­bly worse in Eastern Canada when you com­pare it to Western Canada” be­cause west­ern­ers are more likely to use wall brack­ets or spe­cial putty to keep tall, heavy ob­jects in place. They do this to pre­vent top­pling in a re­gion more prone to earth­quakes than ours.

It’s not just your grand­mother’s china col­lec­tion that will fall.

“The other things are those huge stor­age racks, the floor-to-ceil­ing stor­age racks in busi­nesses and in ware­houses that can go down like domi­noes.

“Chem­i­cal stor­age, with all the chem­i­cals fall­ing off shelves, whether it’s at a hard­ware store or a univer­sity chem­istry lab. With build­ing con­tent, we just think it’s an­noy­ing where we have to clean up glass, but it could be HAZ­MAT sit­u­a­tions.”

Roads can be blocked by de­bris or fires, es­pe­cially in dense his­tor­i­cal neigh­bour­hoods where com­mer­cial build­ings stand right at the edge of the side­walk.

Bridges — even if they’re still stand­ing — would likely be closed for in­spec­tion. Who wants to send buses across a bridge without know­ing how solid it is?

The city has an over­all emer­gency plan for all kinds of haz­ards, from ice storms to tor­na­does.

It lays out du­ties and com­mand struc­tures for dis­as­ters, gen­er­ally.

But there are sep­a­rate, de­tailed plans for par­tic­u­lar kinds of trou­ble, said Poirier, the city’s emer­gency man­age­ment chief.

“So, the para­medic ser­vice has an emer­gency plan, and part of (it) is to deal with the surge in call vol­ume.

“If there were, say, de­bris on the road, we would co-or­di­nate with Pub­lic Works to clear de­bris from the road. If we needed to house or shel­ter peo­ple, we would work with recre­ational, cul­tural and fa­cil­ity ser­vices to turn Ne­pean Sport­splex into a re­cep­tion cen­tre.

“These are the el­e­ments that all come to­gether.”

The city’s plan lays out a com­plex struc­ture of com­man­ders, strike teams, sit­u­a­tion units, ground sup­port units and more. It reads a lot like this. It’s a tad ... bu­reau­cratic.

“7.13 Emer­gency Op­er­a­tions Cen­tre Deputy Com­man­der

The Emer­gency Op­er­a­tions Cen­tre Deputy Com­man­der is re­spon­si­ble to sup­port the over­all man­age­ment of the Emer­gency Op­er­a­tions Cen­tre fa­cil­ity, as­signed re­sources within the Emer­gency Op­er­a­tions Cen­tre, and the pro­vi­sion of sit­u­a­tion sup­port. The Com­man­der and Deputy Com­man­der work to­gether to en­sure that the ob­jec­tives set by the Emer­gency Op­er­a­tions Cen­tre Con­trol Group are im­ple­mented op­er­a­tionally. The Deputy Com­man­der pro­vides lead­er­ship for the Emer­gency Op­er­a­tions Cen­tre Op­er­a­tions Group and may be del­e­gated as Com­man­der as re­quired.”

The Ot­tawa Hos­pi­tal lumps earth­quakes into the gen­eral cat­e­gory of any in­ci­dent with “mass ca­su­al­ties.”

The hos­pi­tal ex­plained by email that af­ter the shak­ing stops, “stag­ing ar­eas would be set up if units were un­safe and de­ci­sions to evac­u­ate man­aged ac­cord­ingly.”

De­pend­ing on the sever­ity of the event, The Ot­tawa Hos­pi­tal would ac­ti­vate its Emer­gency Op­er­a­tions Cen­tre (EOC) to as­sist first re­spon­ders in res­cue op­er­a­tions and to guide re­cov­ery ac­tiv­i­ties. No­ti­fi­ca­tion is sent to staff to ad­vise of the im­pacts and to stand by for de­ploy­ment. To meet the ca­pac­ity chal­lenges, units would then as­sess cur­rent staffing lev­els, call back staff and plan ac­cord­ingly to staff for long-term in­ci­dents.” ts­[email protected]­


Mur­ray, left, and Kelly James look at their de­stroyed house in cen­tral Christchur­ch, New Zea­land, a day af­ter a deadly 2011 earth­quake. The pos­si­bil­ity of a sim­i­lar nat­u­ral dis­as­ter strik­ing Ot­tawa, and the po­ten­tial dev­as­ta­tion that could re­sult, are wor­thy of ex­am­i­na­tion.


The Par­lia­ment build­ings stand on bedrock, which would help dampen earth­quake shock­waves.


The Royal Alexan­dra In­ter­provin­cial Bridge and other spans would likely be closed for in­spec­tion af­ter a quake, even if they did not col­lapse.

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