Download EARTHQUAKES ALONG THE WASATCH FAULT

Duckworth Report 1
EARTHQUAKES ALONG THE WASATCH FAULT
What are the odds?
Fig 1
Wasatch Fault
Source: Google Earth. Web. 22 Feb. 2012
Abstract
The local earthquake threat here in Utah causes many anxieties among locals living in or near the
Salt Lake Valley. In attempts to quell their worries, research has been done to determine the
odds of a large earthquake occurring along the Wasatch Fault within the next five years. Using
several sources, it has been discovered that the central portion of the fault is about 50-250 years
overdue for a large earthquake. It was determined that there is no possible way of determining
how soon or where the next large earthquake will hit in Utah. The conclusion is that it is more
important to prepare for the event rather than worrying about when or if it is going to happen any
time soon.
Introduction
Defining Earthquakes
Our Earth is covered by crust, broken into several pieces called plates. When these plates move
around, the ground can become very unstable as it shakes. This is called an earthquake.
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Sometimes, these plates have breaks in them that like to move around called faults. Utah just
happens to have a fault line running right through it called the Wasatch Fault. Part of that fault
line, the Salt Lake City segment, runs straight down through the east side of the Salt Lake
Valley. An earthquake along this fault could be deadly to thousands of people living in or near
Salt Lake (Keller 25-48).
Size and Intensity
Not all earthquakes are dangerous. They can greatly vary in size and intensity. Different size
earthquakes are categorized by their magnitude (M), or energy released. For example, an M 7.0
earthquake is much stronger and more destructive than an M 6.0 earthquake. Both, however, can
destroy whole cities if not prepared. The next large earthquake to hit Utah is projected to be an
M 7.0 or greater, along the Wasatch Fault (Keller 51-93).
The Wasatch Fault
What is the likelihood of a big earthquake actually hitting the Salt Lake Valley? According to
the Utah Geological Survey, “The Wasatch fault has been active for at least 15 million years as
the earth's crust has stretched across the eastern Basin and Range Province” (Eldredge 12). Since
the fault is considered active, there will definitely be earthquakes here in Utah, but will there be
an earthquake that could leave the city in ruins? Will it be any time soon?
Hypothesis
In this report, the goal is to determine how likely Salt Lake is to get hit by an M 7.0 or greater
earthquake within the next five years or so. The hypothesis is that a large earthquake will hit, but
not in the next five years. If it has gone hundreds of years without having a quake that large, it
may wait a little longer.
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Results
Recent Earthquakes Worry Utahns
Back in 2010, during Earthquake
j
Fig 2
Preparedness Week, many Utahns were
worried about an earthquake hitting, due to
the recent earthquakes around the world.
This caused Richard Piatt, a reporter for
KSL TV, to write an article discussing the
potential hazard for Salt Lake Valley. He
mentioned that Utah's largest earthquakes
Source: University of Utah Seismograph Stations.
N.p., N.d. Web. 22 Feb. 2012
recorded included an M 6.6 in Hansel
Valley, just north of the Great Salt Lake, in
shows some of the damage that was caused due
1934, and an M 6.5 near Richfield in 1901
to the earthquake in Hansel, which has Utah
(Recent Earthquakes). Neither of these
residents wondering how much damage will
quakes caused major damage. Figure two
occur when the next one hits.
Earthquakes
were on the Saltand
LakeUtah
segment of the
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Wasatch
The
UtahFault.
Geological Survey often supplies
earthquake happens somewhere on the fault.
pamphlets addressing different issues of
For each individual segment, though, the
concern. In 1997, they supplied a very
interval is longer - from about 1,200 to
interesting pamphlet called “Earthquakes &
2,600 years on the central segments, and
Utah. The educational pamphlet explained,
about 10,000 years or more on the distal
"Approximately every 350 years a large
segments. These intervals are
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approximations only" (6). The Wasatch
here are not clear, however, on how soon it
Fault is divided into 10 segments, which
could hit. The survey makes it very clear
means that a large earthquake occurs
that, "Earthquakes cannot be predicted and
somewhere on one of those segments
an economically devastating, destructive
approximately every 350 years.
earthquake could happen today, next week,
The survey also indicated that, "The
largest earthquakes expected in Utah are in
or hundreds of years from now. Therefore,
earthquake preparedness is vital" (6). It
the magnitude 7.0-7.5 range” (1). This
seems that more important than if or when it
means that the Wasatch Fault is expected to
will strike, is to make sure we are prepared
have a large earthquake around M 7.0 or
for it.
greater sometime in the future. The results
Scientists Try to Predict Earthquakes
j
For many years now, PBS has been
minute, wham" (Deadliest Earthquakes).
producing a documentary program called
Even with today’s technology, scientists are
NOVA, which discusses many different
still unable to determine how soon an
topics of interest. In this particular episode,
earthquake will hit. The best they are able
they are teaching about earthquakes, and
to do is make an educated guess determined
how scientists are trying to harness the
by looking at the past.
ability to more accurately predict when and
As scientists continue to develop
where an earthquake will happen. During
new technology, they may be able to unlock
the episode, it mentions, "We can't see
the key to predicting earthquakes in a
earthquakes coming. That's the problem.
reasonable time frame, but as is stated in the
One minute, they're not there. The next
episode, "Until seismologists make a
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breakthrough in prediction, communities
would not be able to predict an earthquake
must be ready for the unexpected, because
much further in advance than a week or two.
the next quake could strike at any time"
It goes on to say, “Earthquake prediction is
(Deadliest Earthquakes).
still a complex problem. Even if reliable
According to Keller and DeVecchio,
“Unlike a forecast, a true earthquake
prediction specifies a relatively short time
precursors can be identified, dependable
short-range predictions are many years
away” (83). By the time we are able to
period (days to weeks) in which the event is
successfully predict short-range earthquakes,
likely” (82). This would mean that one
the big one may have already it Utah.
The Probability of a Large Earthquake
j
Another pamphlet released by the Utah
evidence from previous earthquakes to
Geological Survey, “The Wasatch Fault”
determine the possibility of a big
was written by Sandra Eldredge. It
earthquake. Their research shows, "What is
discusses the Wasatch Fault, and what
the probability of the ‘big one’ happening on
accompanies living on or near by it. This
the Wasatch fault in our lifetime? Roughly
particular pamphlet proved to be an
13 percent during the next
abundant source of facts. It states,
50 years. In our grandchildren's lifetime?
"Although no surface-faulting earthquakes
Approximately 25 percent during the next
have occurred on the Wasatch fault since
century" (16). These results show that Utah
settlement in Utah, evidence of numerous
is more than likely to have a large
prehistoric events exists in the geologic
earthquake in the future, but just how near,
record" (13). Scientists were able to take
no one knows.
Duckworth Report 6
Discussion
After reading through the sources listed, the chances of an earthquake of M 7.0 or greater
occurring in the next five years are totally unknown. All of the sources seemed to come to the
same conclusion that no one could possibly know when it will hit. Although they cannot
determine when the next large earthquake will hit, they all seem to cohere with the fact that it
definitely will hit.
Fig 3
Source: Eldredge, Sandra N. "The Wasatch Fault." Public Information Series 40. Utah
Geological Survey. Department of Natural Resources, 1996. Web. 15 Feb. 2012.
As figure 3 shows, we only have about 6000 years of limited data from Utah’s earthquake
history, and “The 6,000-year record contains only a few earthquakes per segment. With this
inadequate data base, scientists do not know if Wasatch fault earthquakes occur in regular cycles,
if their timing is random, or if they occur in clusters" (The Wasatch Fault 16). Possibly, if we
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had a greater data base on Utah’s earthquake history, we would have a better idea on the odds of
an earthquake happening in the next 5 years.
The most recent large earthquake to hit the central portion of the Wasatch Fault happened
about 600 years ago or possibly 400 years ago. Since one is due approximately every 350 years,
then it would make sense to say that we are about 50-250 years overdue for an earthquake here
along the Wasatch Fault:
Collectively …how often a large earthquake has occurred on the central portion of
the Wasatch [F]ault, is approximately once every 350 years. The last large
earthquake happened about 600 years ago on the Provo segment, and possibly
earlier on the Nephi segment (…some researchers estimate an earthquake
occurred as recently as 400 years ago on the Nephi segment). (The Wasatch Fault
14)
Although we are quite overdue for a large earthquake along the central portion of the Wasatch
Fault that does not mean that it will be the Salt Lake section that will be hit next. The survey on
the Wasatch Fault indicates that the Brigham City segment may have a greater probability of the
next large earthquake hitting than other segments. On the other hand, "if earthquakes occur
regularly on segments, then the Salt Lake City segment may be next in line for a large
earthquake" (Eldredge16). It really is a toss-up regarding where the next quake will hit, as well
as when it will hit.
At the start of the research, the hypothesis was that the next large earthquake will not hit
Utah within the next 5 years. That turned out to be more of a pompous opinion resulting from
ignorance and a want for self-preservation. The truth is, that the only way to properly answer
this question would be to say that no one knows if or when the next big earthquake will strike
along the Salt Lake City segment of the Wasatch Fault.
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Conclusions/Recommendations
So, in determining that no one can accurately predict how soon the big one will hit Utah, we
should not focus so much on trying to decide when it will happen. What we should be doing is
preparing for it. Things that we can do to prepare for the next large earthquake along the
Wasatch Fault include but are not limited to: preparing a 72 hour kit, securing your water heater,
forming Community Emergency Response Teams, learning about the earthquake hazard, and
preparing a family disaster plan.
If we are properly prepared for the earthquake threat in Utah, then it won’t matter if it
happens when we’re around or not. It is better to learn from the past and from others
experiences, then learning from our own mistakes. Especially when our mistakes may prove to
be deadly. As I was taught all my life growing up, BE PREPARED.
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Works Cited
“Deadliest Earthquakes: Haiti and Chile.” NOVA. PBS, 4 Jan. 2012. Television.
"Earthquakes & Utah." Public Information Series 48. Utah Geological Survey. Department of
Natural Resources, 1997. Web. 15 Feb. 2012.
Eldredge, Sandra N. "The Wasatch Fault." Public Information Series 40. Utah Geological
Survey. Department of Natural Resources, 1996. Web. 15 Feb. 2012.
Keller, Edward A., and Duane E. DeVecchio. Natural Hazards: Earth’s Processes as Hazards,
Disasters, and Catastrophes, Third Edition. Upper Saddle River: Prentice Hall, 2012.
Print.
Piatt, Richard. "Recent earthquakes worry Utahns." KSL, ksl.com, 8 Apr. 2010. Web. 15 Feb.
2012.