The Ml 4.5 in southeastern Colorado is extremely unusual as previously stated. It was
followed by another Ml 3.7 aftershock. NEIS claims responsibility for detecting
earthquake in Colorado. Several small local networks have been installed (by
USBR in the Paradox Basin area) and by University of Colorado (in the Boulder Valley
area). but generally funding is poor since it assumed that such simply duplicate
NEIS efforts (which of course, they do not). The result is that Colorado is a black
hole where small earthquakes are generally not recorded at the same rate as for
the rest of the U.S. It is the nature of the governmental beast and appropriations
that the big dog gets the bone.
As for the Montrose area, there have been 11 earthquakes recorded with Ml>=4
within 100 km of Montrose since 1944. The largest of these was a Ml 5.5 which
occurred on October 11, 1960. The earthquake was felt over approximately
10,000 square miles. There was slight damage such as crack chimneys,
windows and plaster. Foundations were cracked at Montrose and sidewalk
buckling was observed. At Ophir there was a cracked chimney and broken windows
were observed at Placerville and Powderhorn. Plaster fell from walls at Lake City
and there were cracked walls at Telluride.
This is a particular beautiful section of the Colorado Rockies. I have taken several
bicycle trips through the area and never get tired of the beautiful scenery. I guess
that occasional earthquake are part of what causes this natural beauty. As a
native Coloradan ( I was born about 10 km from where these earthquakes are
occurring) I will not say anything negative about this state.