WSP04101

• File Number: 8080
• Description: Section D General Interstate Litigation - Rainbow Bridge Monitoring Program
• State: CO
• Basin: Statewide
• Date: 5/21/1964
• Author: DOI-BOR
• Title: Rainbow Bridge Monitoring Program - Reports 4 through 10
• Water Supply Pro - Doc Type: Report/Study

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6. Rock Mechanics

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7. Geologic Sections

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8. Seismic Monitoring Program

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The seismograph, installed January 28, 1976, and located about one
mile west of the Bridge on a high ridge, helps to confirm the loca-
tion ,and magnitude of local seismic events.

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Data collected from January 1, 1977, to June 30, 1977, has recently
become available and is reviewed in the report. In this six month
time period, a total of 123 local seismic events were recorded. .Two
earthquakes of small magnitude were identified about 125 plus miles
north of Glen Canyon. Ten events were so small that they could not
be located and the remaining events were located in the Black Mesa
region (51 events) and the Chuska Mountains (61 events). These
events are attributed to blasting in coal mining operations. Black
Mesa is located about 50 plus'miles southeast of Rainbow Bridge, and
the 'Chuska Mountains are about 120 plus miles southeast of the Bridge.

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In recent months, the station has been out of operation for a large
percentage of the time because of damages resulting from a bolt of
lightning and then a leaky battery. All further data collected will
be included in future status reports.

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All the data collected thus far indicates that no seismic events of
significance have occurred near Rainbow Bridge National Monument.

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9. Sedimentation Surveys

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Sedimentation studies conducted thus far have provided a good basis
for monitoring and evaluating the sedimentation process for Bridge
Creek Channel within'the Monument. The studies reflect not only
sedimentation patters due to reservoir action, but also the sedimen-
tation changing from flash floods draining into the Bridge Creek
Channel.

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Studies conducted during November 1977 reflected a significant shift
in sedimentation from earlier studies due to a series of flash floods
observed ahd reported on August 7, 1977. These floods shifted and