I feel a little like I'm on vacation, out on a boat in the
middle of Lake Tahoe famous deep blue waters on a calm beautiful
day. But I'm actually here with a team of seismologists on a
serious mission. They're looking for clues about when the
next big earthquake could strike the Lake.
I'm sure a lot of beachgoers this summer would have a hard
time imagining a devastating earthquake churning up these placid
waters. But as Graham Kent who heads up University of Nevada at
Reno's seismological lab explains calm waters belie a violent
past.
Graham Kent: "We're heading right for the largest fault in
the basin, the west Tahoe fault ruptures about every four to five
thousand years. It's last rupture was 4500 years ago. So
obviously there's some concern because we're at the end of that
earthquake cycle. Doesn't mean it's gonna happen
tomorrow. But it wouldn't be a surprise if it
did."
At least three faults run underneath the lake: the
Stateline, the Incline Village and the West Tahoe. Now it
looks like there is one more.
Graham Kent: "Yesterday we discovered there's a
smaller fault in between the West Tahoe and the
Stateline. So that's one of the things we just found out
yesterday."
To help get answers like that, Kent is deploying a cutting
edge tool he and his team developed. It looks like a small yellow
submarine, which is submerged alongside the boat. It's
called the CHIRP.
"chirp, chirp, chirp."
And you might think that's because of the bird like sound it
emits. But actually it stands for compressed high intensity radar
pulse. The CHIRP sends a signal to a computer monitor right on the
boat giving the seismologists a detailed view of the complex
topography under the lake.
Graham Kent: "On land that field of study is called
Paleoseismology. But they tend to use backhoes, and backhoes don't
work so well in the water. So this CHIRP profiler is a
acoustic backhoe. So as you saw out on the lake today, you get
unbelievable pictures in real time of what the sediments look like
and how they're warped and deformed and faulted. So we go out there
and make maps to understand the history of those ruptures and that
gives us a sense of when the next big one in the Tahoe Basin might
occur."
The CHIRP profiler is helping unravel all kinds of mysteries.
For instance, Kent says we now know that that the faults sometimes
erupt together, creating earthquakes as large as 7.0-7.5.
And a quake that big would mean a potentially deadly tsunami
up to thirty feet high.
Graham Kent: "Since I also run the Nevada
Seismological laboratory, I would be remiss to remind people
that the biggest story in Japan is the fact that the number of
people that didn't die, and it's because of preparedness.
Ultimately, preparedness trumps everything else. If you know
anything about Japan, they prepared for this day, even though the
tsunami was larger than they thought, they prepared for that day,
and you can see it in the YouTube videos - people by and large were
on a move in a way that wouldn't happen in the U.S.
today."
So what should you do if your Tahoe summer vacation gets
interrupted by an earthquake on Lake Tahoe. Kent recommends
you duck and take cover waiting out the shaking and then, in a
reasoned way get as high as you can.
Kent says he is working with officials in California and
Nevada and hopes to see tsunami warning signs on the lake in the
not too distant future.
