An un­pre­dictable sci­ence

The Star Malaysia - Star2 - - SCIENCE -

With great un­cer­tainty, ge­ol­o­gists try to pre­dict the chance of a big quake strik­ing. By OLIVEr MOr­rI­SON Prague, Ok­la­homa, in 2011, which caused around US$ 10mil ( RM42mil) in dam­age and sent sev­eral peo­ple to the hos­pi­tal.

But sci­en­tists at the USGS have been un­will­ing to rule out the pos­si­bil­ity of a mag­ni­tude- 7 quake.

One rea­son is that the lat­est earth­quakes have been ac­ti­vat­ing old fault lines, some of which they didn’t know ex­isted, ac­cord­ing to Ge­orge Choy, a re­search geo­physi­cist at the USGS in Colorado.

Sedg­wick County’s own haz­ard anal­y­sis plan from 2011 points out that a 300- mil­lionyear- old un­der­ground moun­tain range, the Nemaha Ridge, runs right through Sedg­wick County, from ap­prox­i­mately Ok­la­homa City to Omaha.

Nemaha is thought to have been the source of the largest recorded earth­quake in Kansas just out­side Man­hat­tan in 1867.

And no mat­ter the strength of the earth­quake, there is rea­son to be­lieve the lo­cal area is par­tic­u­larly vul­ner­a­ble.

One rea­son is that earth­quakes in the Mid­west can be felt far­ther away than many coastal earth­quakes, ac­cord­ing to Hal­i­han, the pro­fes­sor at Ok­la­homa State.

The soil in the Mid­west tends to be stiffer than that on the coasts, ac­cord­ing to Hal­i­han. It’s like drop­ping a rock on con­crete ver­sus in mud – the sound waves are go­ing to travel much fur­ther when it hits the con­crete.

And most of the quakes in Kansas and Ok­la­homa are rel­a­tively shal­low, he said, mean­ing they don’t have to travel as far to reach the sur­face and their force won’t dis­si­pate as much.

“Usu­ally the folks from Seat­tle go, ‘ What are you guys com­plain­ing about? It’s just a 4.7,’” Hal­i­han said. “4.7’ s here are a hell of a ride.”

In 2015, the Kansas Cor­po­ra­tion Com­mis­sion lim­ited the amount of waste­water that oil com­pa­nies are al­lowed to dis­pose of deep into the earth in Harper and Sum­ner coun­ties. More than a half year af­ter th­ese changes came into full ef­fect, the com­mis­sion re­ported that there is some ev­i­dence the num­ber and sever­ity of earth­quakes orig­i­nat­ing in Kansas may have fallen in the se­cond half of 2015.

The fall in the price of oil the past two years, could con­tinue to mit­i­gate the chances for more Kansas quakes. Many of the new wells that com­pa­nies tried drilling far­ther northwest into Kansas were not that pro­duc­tive even be­fore the price of oil dropped, ac­cord­ing to Buchanan, di­rec­tor of the Kansas Ge­o­log­i­cal Sur­vey.

“A lot of the wells didn’t work and pro­duce enough oil for the amount of wa­ter they were pro­duc­ing,” Buchanan said. “Wa­ter is heavy and it’s ex­pen­sive to bring it to the sur­face, es­pe­cially if you have to in­ject it back to the deep sub­sur­face.”

But the Sierra Club has filed an in­tent- to­sue let­ter, hop­ing to re­quire a more am­bi­tious re­duc­tion in the dis­posal of waste­water from frack­ing, which would in­clude Ok­la­homa.

Buchanan of the Kansas Ge­o­log­i­cal Sur­vey said that while he doesn’t know any­one who would rule out a mag­ni­tude- 7 quake, he hasn’t heard any­one talk­ing of a quake with a mag­ni­tude larger than 6, in part be­cause the largest one recorded since the re­cent earth­quakes started in Ok­la­homa so far has been a 5.6.

But he said there also are ques­tions about the im­pact of smaller quakes.

Buchanan said he has been talk­ing with the state trans­porta­tion depart­ment about the po­ten­tial ef­fects of the kind of “re­peated, low- level shak­ing” the state has al­ready seen.

It’s not clear what re­peated low- level shak­ing might do to wa­ter lines, roads and build­ings, he said, adding: “That ques­tion is re­ally in its in­fancy.” – The Wi­chita Ea­gle/ Tribune News Ser­vice LORI Lawrence said she was stand­ing in the hall­way of her home near Cen­tral and Hill­side in Kansas on Jan 6 when the bed­room door started rat­tling.

It was, she said, the sixth earth­quake she’s felt in the past two years.

Friends filled up her Face­book feed with com­ments about the lat­est quake, which was ac­tu­ally two back- to- back quakes, the largest of which had a mag­ni­tude of 4.8.

It was in­tense enough that the city of Wi­chita, for the first time, sent out a team to ex­am­ine whether any of its in­fra­struc­ture had been af­fected by an earth­quake.

Re­ports had al­ready been com­ing in about three wa­ter lines that had burst around the time of the quake. Af­ter a day of in­spec­tions, a few more po­ten­tial cracks had turned up, in­clud­ing one at a waste­water treat­ment plant.

In the past two years, Lawrence has be­come one of the lead­ing or­gan­is­ers for the Kansas chap­ter of the Sierra Club try­ing to doc­u­ment lo­cal dam­age from earth­quakes. In Novem­ber, the le­gal non- profit Pub­lic Jus­tice posted on be­half of the Sierra Club, a no­tice of its in­tent to sue four of the largest frack­ing com­pa­nies in Kansas and Ok­la­homa to pre­vent them from con­tin­u­ing to in­ject waste­water that many sci­en­tists say is prob­a­bly caus­ing the earth­quakes.

But even as Lawrence and oth­ers are try­ing to doc­u­ment pos­si­ble dam­age from low- level shak­ing, sci­en­tists are es­ti­mat­ing the like­li­hood of a much larger earth­quake in the area.

Be­tween 2003 and 2012, there were three earth­quakes in Kansas, but since then, there have been 579.

This num­ber doesn’t in­clude more than 900 quakes in Ok­la­homa in 2015 alone, or the 70 quakes in the first week of 2016.

Ok­la­homa’s earth­quakes have been creep­ing far­ther north, un­til in 2013, they reached the Kansas state line.

In 2014, Kansas ex­pe­ri­enced the largest earth­quake recorded orig­i­nat­ing within the state. But the two most in­tensely felt re­cent earth­quakes in Wi­chita, in Novem­ber 2015, and on Jan 6, orig­i­nated in Ok­la­homa.

Be­cause of the in­crease in the num­ber and sever­ity of earth­quakes, the US Ge­o­log­i­cal Sur­vey ( USGS) has had to change how it maps earth­quake risks and de­vise new ways of mea­sur­ing risk lo­cally.

The new mea­sure­ments sug­gest a po­ten­tial for an earth­quake much more se­vere than what most struc­tures in south­ern Kansas have been built to with­stand.

But the new pre­dic­tive mod­els may not be any­where near as ac­cu­rate as the ones along tra­di­tional seis­mic plates, ac­cord­ing to Todd Hal­i­han, a pro­fes­sor of ge­ol­ogy at Ok­la­homa State Univer­sity.

“The pre­dic­tions kind of suck,” Hal­i­han said. “We’re some­where be­tween a cou­ple of liquor bot­tles fall­ing off the shelf and com­plete Ar­maged­don. And that’s not par­tic­u­larly com­fort­ing or use­ful, so you should prob­a­bly take some steps to pre­pare peo­ple for what to do that is log­i­cal in a case of un­cer­tainty.”

The USGS makes what are called “haz­ard maps” that re­flect how likely an area of the coun­try is to ex­pe­ri­ence a large earth­quake that could cause cat­a­strophic dam­age.

Th­ese maps draw on hun­dreds and thou­sands of years of his­tor­i­cal and ge­o­log­i­cal data about when earth­quakes have oc­curred in the past and where known fault lines are.

But when the USGS sci­en­tists were mak­ing the map for 2014, they re­alised that the thou­sands of small earth­quakes in Kansas and Ok­la­homa that were likely caused by hu­mans were throw­ing off their mod­els.

If they left in all the re­cent lo­cal earth­quakes, south- cen­tral Kansas and Ok­la­homa would sud­denly look like a rel­a­tively huge risk for a ma­jor earth­quake.

That’s be­cause in a typ­i­cal ac­tive fault zone, such as those found in Cal­i­for­nia, the num­ber of earth­quakes that have be­come a reg­u­lar event here would be an in­di­ca­tor of a po­ten­tially large fu­ture earth­quake.

But USGS stud­ies have in­di­cated that th­ese lo­cal earth­quakes prob­a­bly fol­low a dif­fer­ent pat­tern. Their like­li­hood in­creases the more waste­water is in­jected un­der­ground in some ar­eas, and the earth­quakes sub­side when the waste­water dis­rup­tions are low­ered or halted.

But that wasn’t a sat­is­fy­ing an­swer for peo­ple who wanted to know the short- term like­li­hood and dan­ger of earth­quakes in Ok­la­homa and Kansas.

So in April last year, the USGS be­gan cre­at­ing sep­a­rate, short- term haz­ard maps that es­ti­mated the chance of ex­pe­ri­enc­ing a cat­a­strophic quake here. Th­ese maps put the re­cent up­surge of lo­cal earth­quakes back into their model.

And, in­stead of ap­pear­ing light gray or dark gray, which im­plies a low level of earth­quake risk, south- cen­tral Kansas and a huge area of cen­tral and north­ern Ok­la­homa now ap­pear red and or­ange.

There are only three places in the Lower 48 states that ap­pear red on the USGS’ 2014 50- year haz­ard map.

One is the San An­dreas Fault in Cal­i­for­nia, which in­cludes San Fran­cisco, the site of the 1906 earth­quake, the largest in US his­tory out­side of Alaska. The 1906 quake killed around 3,000 peo­ple and de­stroyed most of the city.

An­other is the New Madrid Fault in far south­east Mis­souri, the site of the se­cond- largest quake in US his­tory. That quake, which oc­curred in 1811, was de­scribed by wit­nesses as a “dis­tant thun­der” that caused trees to crack and fall, rivers to over­flow their banks and the sky to turn black.

The red ar­eas of the maps are the places in which there is a 2% chance of one the most se­vere earth­quakes oc­cur­ring in the next 50 years. Th­ese are the dev­as­tat­ing kinds of quakes that do strange things, like make the Mis­sis­sippi River flow back­ward, as hap­pened in 1811, ac­cord­ing to Hal­i­han. Th­ese earth­quakes are rel­a­tively rare. In­stead of mod­el­ing over 50 years, the new USGS maps for Kansas and Ok­la­homa cover just one year. They show a 1% or less risk of a ma­jor earth­quake oc­cur­ring dur­ing the year.

If this rare event hap­pens, even the mostup- to- date build­ings would ex­pe­ri­ence earth­quake forces as much as or more than 20 times greater than what they were built to with­stand based on cur­rent build­ing codes.

Only the most south­ern Kansas coun­ties, such as Harper, are coloured red. But Sedg­wick County and Wi­chita are close enough that they would still ex­pe­ri­ence forces a num­ber of times greater than what build­ing codes dic­tate new build­ings should with­stand.

Many ge­ol­o­gists have been op­er­at­ing on the as­sump­tion that the largest mag­ni­tude earth­quake Kansas or Ok­la­homa might ex­pe­ri­ence would be around a 5.6. That was the mag­ni­tude of the largest re­cent quake in

Lawrence shows a new crack on her garage floor. She claims that the foun­da­tion of her 1917 brick home in Kansas was dam­aged by the re­cent earth­quakes. — TnS

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