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Geologists try to date latest shaking from Stateline Fault
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JONATHAN CARTER/COURTESY OF WANDA TAYLOR
A trenching operation that UNLV geologists launched west of Pahrump is aimed at finding out when the Stateline Fault last moved and how large an earthquake it could deliver. The geologists in January began digging three 10-foot-deep trenches in the fault zone's clay.
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Geosciences professor Wanda Taylor discusses the Stateline Fault during an interview Tuesday at the University of Nevada, Las Vegas. Gary Thompson/LAS VEGAS REVIEW-JOURNAL » Buy this photo
LAS VEGAS REVIEW-JOURNAL
The Stateline earthquake fault slumbers like a giant deep in the rocks west of Pahrump, and geologists wonder when it will wake up again and unleash a ground-shaking jolt toward the Las Vegas Valley 50 miles away.
They don't know the last time the fault moved, but a team of geologists led by University of Nevada, Las Vegas professor Wanda Taylor is trying to find out.
Taylor and student geologists including Jonathan Carter, who is writing a master's thesis on the subject, set out in January to dig three 10-foot-deep trenches in the fault zone's clay.
"The reason we're doing the research is we really don't know much about the fault," Taylor said. "Although we've known about it for decades, we're recognizing it has the potential for a larger earthquake than we thought before."
Whether the fault last ruptured a few centuries ago or tens of thousands of years ago, narrowing down the answer through clues left in the crust will help them estimate how much strain is building up along the fault to the point that it could snap.
Such an event would cause deep rock layers to slide against each other, similar to how the San Andreas Fault makes the Pacific tectonic plate slip northwestwardly against the North American Plate.
Taylor said the Stateline Fault, which was first mapped in the 1930s, could cause a powerful earthquake on the low end of a scale for what geologists consider to be large earthquakes.
"We don't think if the whole thing broke it would be a magnitude 9. Geologically that's unlikely," Taylor said last week at her office on the UNLV campus.
"We think it would rupture in segments with a most credible earthquake of about magnitude 7."
For comparison, an earthquake in the Indian Ocean in 2004, which had a recorded magnitude of between 9.1 and 9.3, sent out a series of tsunamis and was one of the deadilest natural events in history, killing more than 225,000 people.
Closer to the magnitude that the Stateline Fault could unleash was the 1989 Loma Prieta earthquake on the San Andreas Fault, which struck south of the San Francisco Bay Area.
The 7.2 magnitude Loma Prieta quake caused widespread damage and killed 57 people.
This year, the catastrophic earthquake that hit Haiti in January was magnitude 7, and the one that struck Chile in February was rated 8.8 magnitude.
Magnitude is a measure of the strength of an earthquake, or the energy from strain that's released from it.
An increase in one unit of magnitude, from 4.6 to 5.6, for example, equals a 10-fold increase in the amplitude, or size of waves.
That translates to a 30-fold increase in the amount of energy released for each magnitude.
Certainly if significant movement occurred on the Stateline Fault, seismic waves would impact the Las Vegas Valley.
"If it has a magnitude 7, Vegas is shaking," Taylor said.
Just how much damage would occur depends not only on the magnitude and distance involved but also the structural integrity of buildings and the type of soils beneath them.
Building codes for homes, businesses and resorts have been beefed over more than a decade to reduce the hazard from ground shaking and amplified ground motion caused by fine, soft sediments in some parts of the Las Vegas Valley.
However, Taylor said, "If your home is older than 1996, you need to check to be sure the water heater is strapped down."
At least 11 faults either cross the valley's floor or are located outside of it that are each capable of producing a substantial jolt.
The California Wash Fault, 50 miles northeast of Las Vegas, near Valley of Fire State Park, could deliver a magnitude 7 earthquake. It was one of the faults that Hoover Dam was designed to withstand.
Some faults in eastern California and in the Death Valley fault systems are also capable of producing ground motion that could shake Las Vegas.
Evidence of the Stateline Fault was found in two of three trenches from 70 meters to 100 meters long that Taylor's team dug a few miles west of Pahrump.
"The zone is several meters wide, and we know it has a little bit of a normal component, meaning that extension across it pulls it apart," Taylor said.
Soil from the trenches was collected in hopes that it contains enough pollen, charcoal or carbon remnants that can be age-dated based on the measured, radioactive decay of the isotope carbon-14 from the samples.
By comparing the dated soils on each side of the fault, the team will then have an idea when it last moved.
In addition, UNLV's Cathy Snelson conducted seismic reflection studies of the area, and researchers under Barbara Luke from the Civil and Environmental Engineering Department will collect ground-shaking data from a 100-meter-deep bore hole in the fault zone.
They also will evaluate the stiffness of sediments from core samples that were extracted.
"We'll be able to take all the data together and have a good package," Taylor said. "To have three sets of data is rare."
The project is funded by the Department of Energy as part of a $3 million, six-year effort with state and federal earthquake programs to better understand hazards in Southern Nevada.
Contact reporter Keith Rogers at krogers@reviewjournal.com or 702-383-0308.
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I care, natural gas comes across that valley in a very big pipe. I also want to know if the hospitals and bridges are being built to stand after what ever this can throw at it!
"Ready wrote on May 09, 2010 06:06 PM: What a great example of tax and spend on diddle."
Uh, "Ready", nobody cares if you think that undestanding earthquake threats is not worth "diddle". You're just not that important.
"Harry stop spending my money on holes in the ground."
Uh, "Harry" was nowhere mentioned. How come you're not whining "Honest John Ensign and Gim Jibbons, stop spending my money on holes in the ground"?
Why indeed.
"Where's the RJ on this?"
Obviously not with the drama queen idiots like "Ready".
"How can this funding meet anyone's approval except a tax-funded waste-my-tax-money again liberal issue!"
Earthquakes don't care if you're a Republicon or not.
"This isn't a shove-ready project. It's a vomit-ready issue!"
What a DRAMA QUEEN.
And these teabaggers and town hall psycho screamers want to be taken seriously.
The information that most of you posters know the least about is science. That's just not their "trip." Now, I'm sure you know a lot about union laws, strippers, tippers, best cocktails in town, NASCAR winners, the Hooters menu, wagers, betting and bingo . . . BUT science is really NOT your forte. Leave the science to the scientists, get a life, and quit meddling with things you know nothing about!
@ Joe
Could be. Bush certainly looks old enough! (LOL)
But on the other hand, how could it be Bush's fault when we all know that everything is Obama's fault?
Actually, for those who do not already know, this type of scientific research is some of the best there is, in terms of "bang for the buck."
All it takes is a little backhoe time to dig the trenches, and a little money to rent safety equipment if you don't already own it (such as trench shoring and trench plates). Other than that, all it takes is graduate student time.
Which, as we all know, is some of the cheapest slave labor around!
Last time this fault went was it Bush's fault too?
From the LVRJ:
"Every time stories about building issues arise, reporters and columnists hear from people who don't like Clark County Director of Development Services Ron Lynn, who inflated his academic credentials in a trade magazine article he wrote in 1998. In Building Standards, a publication for the International Conference of Building Officials (now the International Code Council), Lynn wrote he obtained a bachelor's degree in structural engineering and a master's in geochemistry. He didn't.
When it was exposed by the Review-Journal in 2001, Lynn was the building department's assistant director and up for a job as director. Thom Reilly, county manager at the time, pulled his recommendation for Lynn's promotion.
Lynn's defense then about puffing himself up to his peers: "I was wrong, and I wish it had never occurred. I allowed a misrepresentation to be put into print, but I never applied for a job with a misrepresentation and I have never obtained any position through a misrepresentation."
Despite the lies, Lynn in June got the director's job with the support of County Manager Virginia Valentine, who said he was the best-qualified candidate. Commissioners approved it unanimously, although Rory Reid was absent. The résumé issue didn't come up."
CORRUPT since the day he LIED to get his job. RON LYNN.
Watch the finger pointing when the Harmon hits the Strip.
When the dust settles, Las Vegas will be TOAST.
News Flash! Breaking News! The Harmon Tower has construction defects!
Must be nice to have your head jammed in the sand all day. I bet you still see Dr. Desai for your weekly colonoscopy.
In case you haven't heard:
"CityCenter believes that it has significant claims against the general contractor related to its role in connection with the Harmon Hotel construction, which construction was halted by local building inspectors due to construction defects." NEED MORE?
It actually wasn't halted by the building department. It was halted by an Engineer who went for a walk. If not for his attentive eye, THE ENTIRE DISASTER WOULD HAVE BEEN COVERED UP.
Just like ALL of the other High Rises built on the Strip with construction defects. The SAFETY ASPECT OF EVERY ONE THEM has been compromised by a CORRUPT BUILDING and FIRE DEPARTMENT.
How did the Commissioners put it?
"Clark County officials last week described an audit of the county's building and fire safety inspections as "scathing," "shocking" and "disturbing."
So it bothers you to know there are High Rise Casinos and Hotels on the Strip that have construction defects?
Does it bother you to know that the Clark Building and Fire Inspectors were BUSTED falsifying paperwork to avoid Inspections? Do you know WHY they compromised the SAFETY of EVERYONE who sets foot inside CityCenter?
FREE STUFF. Bribes. Kickbacks.
The Harmon Tower is the FIRST to FAIL when Mother Nature decides it's time to bring Clark County Government Officials a wake up call. They CHEATED and got CAUGHT. I'm sorry you didn't know that.
Maybe you sould research the subject before you embarrass yourself again. Or... get a deeper sand box.