Earthquake fault creeping up on Fish Spring Flat

It's been a very interesting week with the moon's total eclipse, the Navy's shooting down the spy satellite, the big snowstorm here and the 6.0 earthquake near Wells, Nevada. That might not sound like a very powerful earthquake but it was big enough to severely damage many of the old historic buildings from the 1860s.

We didn't feel the shaking here in Fish Springs but it was reported to be felt even in Southern California. The little town of Wells has a population of 2,300 and apparently only a few residents were injured. Lucky for that with all the old brick buildings falling down. There's probably some after-shocks still happening around that area of I-80.

Over the years there have been a lot of major earthquakes in Nevada. Alaska and California are the most active states for earthquakes and Nevada is the third most seismically active. Our beautiful alternating mountains and valleys were, and continue to be, formed by the process of faulting and sometimes it seems like Nevada is pulling apart.

Back in 1989, I was hiking up the hill behind our house when I first saw it. A large crack that was 2 inches wide and a whole lot deeper than my walking stick had torn open the earth's surface. I followed the mysterious crack for half a mile. It ran horizontally about one-third up the hillside on the northwest edge of Fish Spring Flat. I called various agencies to report the unusual phenomenon and a geologist from the Nevada Bureau of Mines and Geology came out to investigate. He directed a large backhoe to dig a trench 30 feet long, 5 feet wide, and 15 feet deep into the hill. The crack was directly on top of a previously unknown earthquake fault.

The fault goes deep - miles deep - into the earth. It is a creeping scarp-type fault and curiously, there was no earth shaking when it opened back in 1989. As it creeps, the east side, which is the lower part of the fissure, has moved down and it stretched the dirt on the surface, pulling it apart. The deep trench that was dug through the fissure showed a dramatic difference in soil color exactly where the fault line runs. One side was a light tan-white color, and the other side was a reddish-brown. They are totally different geological features. Some kind of tectonic stress may have caused this fault to quietly open up.

Creep is very common on earthquake faults of this particular type. There are two schools of thought about a creeping fault. One is that the energy is gradually released and thereby relieving the built-up pressure slowly as opposed to a sudden, violent movement. The other is that creeping indicates an active fault, with a larger earthquake in its future.

My belief is that the energy is gradually being released, but to play it safe, we are planning for a possible earthquake, just in case. Think positive - but store water.

-- Linda Monohan may be reached at 782-5802.


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