FLOOD09139

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Federal Guidelines for Earthquake Analyses and Design of Dams
• Date: 3/1/1985
• Prepared For: State of Colorado
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

b. Conduc t a search of the historic seismological record to
determine the location, time of occurrence, and charac teristic s
(e.g., earthquake source parameters and wave propagation
effects) of previous seismic events within the area of
interest. Consideration should be given to the completeness of
the record and the locstion accuracy of individual events.

f

c. Conduc t a search of the instrument record to determine event
locations, frequency of occurrence of various event levels,
and characteristics of measured seismic activity within the
area of interest. Additional analysis of field monitoring may
be useful in areas where historic data are lacking.

d. Array the data for statistical analysis to develop frequency,
magnitude, and recurrence rela tionship s. Consider the
relationships between regional province-wide recurrence and
recurrence for individual faults or sources.

e. Display the developed seismic information by appropriate
tabulations and map presentations.

f. Review the historical records to develop information
rela ting to the surface effec ts of past earthquake events.

3. Seismotectonic Structures

Of primary importance to the earthquake analysis is the
identification and charac terization of faults and other
seismotectonic structures which may be the sources of the design
earthquakes. This effort may require literature searches in the
fields of tectonics, structure, seismology, and quaternary geology,
the documented seismic record, analyses of remote sensing imagery,
geophysical data, and field mapping and exploration programs to
veri fy and further define documented or suspec ted struc tures.
These activities should:

a. Document the type, location, areal extent, displacement, and
age of displacement of faults in the area of interest.

b. Characterize located faults by sense of movement, and degree
and age of activity. Potential for surface faulting in the
immediate vicinity of the dam should be addressed.

c. Charac terize other seismotec tonic struc tures which are not
correlative with surface features via the geophysical record,
regional geologic data, and seismicity characteristics.

d. Analyze recent historic earthquakes or data from
micro-earthquake monitoring to gain information on current
stress conditions.

Relationships may be established between identified faults and
other seismotec tonic features and the frequency of occurrence and
magnitude recorded from previous earthquake events by:

-9-