PERMFILE50024

• Permit No: M1988112
• IBM Index Class Name: Permit File
• Doc Date: 11/8/1988
• Section_Exhibit Name: APPENDIX B SEISMOLOGY STUDY
• Media Type: D
• Archive: No

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Grande Rift.
Rio Grande Rift seismicity is dominated by small earth-
quakes. In the entire historical record no earthquake larger
than ML= 6 has been recorded, and during the 15 year period
from 1962 to 1977 no earthquake larger than ML= 4 occurred
within the rift. In fact, although there are numerous young
faults distributed throughout the rift, none has micro-
earthquake activity associated with it, and the rift as a
unit can not be delineated on the basis of seismicity (Jaksha
and Sanford, 1986).
In nearly all respects, using seismicity, structural
style or tectonic history, the San Luis Valley is a mirror
reflecting conditions present in the rest of the Rio Grande
Rift. With the exception of the ratio of extension to uplift,
which may influence future earthquake size, there appears to
be good reason to expect the San Luis segment of the Sangre
de Cristo fault to behave the same as faults in adjacent
portions of the rift to the north and south, which have
been studied in more detail.
ACTIVE FAULTING POTENTIAL
Recent fault scarps of the Sangre de Cristo fau1= zone
adjacent to the Battle Mountain Gold property (San Luis
segment) have not been studied in detail to ascertain single
event fault displacenents, spatial segmentation or scarp
age relationships. Nevertheless, in nearly every respect
preliminary investigations by Kirkham and Rogers (1981)
indicate that this portion of San Luis Valley display:a the
same spatial and temporal tectonic style as the rest of the
Rio Grande Rift. There is every reason to expect that results
of detailed fault analyses to the north and south of i:he site
area, to be described below, in combination with the results
from Kirkham and Rogers (1981) in the site vicinity a<:curately
portray the future tectonic behavior in the site area..
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