The following article appeared in the Rocky Mountain News (Saturday,
8 September = p 8b) It might help clear up some questions we
have been discussing on the Coloradoa earthquake sequence.

In Trinidad, rumors fly about earthquakes

No evidence town faces the Big One

By Jim Erickson
News Science Writer

Trinidad -- Depending on which rumore you believe, this scenic
border town is about to be washed away by an epic flood or leveled by
the big one.
There's no evidence to support either claim, but that doesn't stop the
rumormongers in this town rattled by eight magnitude 3.4 to
3.4 earthqaues since Aug. 28 (note - there was another Ml 3.4
today about 1:30 p.m. MST - so much for these earthquake happening
only in the morning hours).
Some Las Animas County residents are convinced that the earthen
dam that holds back Trinidad Lake, three miles upstream form Trinidad
is about to burst, sweeping away the town.
Others say the quakes are Mother Nature's payback for pumping too
much natural gas -- and bigger quakes may be coming. Since 1995, more than
1,300 permits to drill for methane gas have been issued here.
"I'll bet nine out of 10 people here think that it's the gas
companies sucking the stuff out of the ground that's causing it,"
said said filmmaker Mark Hutto, co-owner of HBL films in Segundao,
a few miles west of Trinidad.
Though the U.S. Geological Survey's naational seismic network
has recorded eight quakes in the area (now nine) since Aug. 28,
Hutto said he's felt at least 25 during that time (so there are
small events, they just aren't being reported by USGS, and since
no local seismic networks cover the region, it is a black hole
as was suspected by members of this board). He owns a century-old
brick house and and adobe store in Segundo; walls in both
structures cracked during the magnitude 4.5 quake Wednesday, he said.
Magnitude 2.5 to 3 quakes are the smallest generally felt
by people. Magnitude 4 quakes can cause moderate damage. There have been
no injuries in the tremors.
To pinpoint the source of the quakes and to help determine why
they're happening, the Geological Survey is installing seven portable
digital seismographs in the area.
There are no mapped faults in the Trinidad area, Before the current
quakes, the last tremors recorded there by the U.S. National Seismic
Network occurred in 1973 said Geological Survey geophysicist Mark Meremonte.
"There was no activity for 28 years. Then, all of a sudden, there is a
flurry of activity, a swarm of activity," Meremonte said, "For some
place along the San Andreas Fault that may not be unusual, but for
this area it's unusual."
Preliminary analysis of data from the quakes suggests there may be
a previously unknown fault west-soutwest of Trinidad, running from the
northeast to southwest. Early data suggest it may be a "normal" fault,
a type of fracture produced by tensional stess.
There is no indication that the recent quakes are precursors
to a larger one, Geological Survey researchers say.
The Trinidad-area earthquakes appear to be originating about 3 miles
beneath the surface, but that too is preliminary finding, said Anthony
Crone, assistant chief scientist on the Geological Survey's geologic
hazards team in Golden.
The portable seismographs should help agency researchers get a
clearer picture.
But one gas company official seized on the 3-mile-deep figure
Friday as evidence that natural-gas extaction and the quakes are
unrelated (a little learning is a dangerous thing - the 3-mile
depth is 5 - km a default depth to make the computers run faster -
and has no basis in reality).
Denver-based Evergreen Resources operates more than 600 wells
in the Trinidad area - more than any other company.
Evergreen uses a process called coalbed methane pumping ro
remove natural gas from coas seams embedded in sandstone and shale.
Evergreen's wells are 1,500 to 2,500 feet deep, so it's "a near
impossibility" that they are responsible for quakes occurring
miles beneath the surface, said Stephanie Basey, Evergreen's
operation manager in the Trinidad area (too bad she doesn't
know about default depths in earthquakes!!)
At Trinidad Lake, the U.S. Army Corps of Engineers has stepped
up inspections of the 6,860-foot-long earthen dam above the town.
Some inspections that were done weekly or monthly are now done
daily, said reservoir manager Key Merchant.
No damage and nothing unusual has been observed at the dam since
the quakes started, Merchant said Friday.
Nevertheless, some residents believe the structure is about to
fail and wipe out the town of 10,000 residents.