Stratigraphy and Geologic Structure at the Chemical and Metallurgy (CMR) Building, Technical Area 3, Los Alamos National Laboratory
Nine shallow (c70 ft), closely spaced core holes were continuously cored in the upper units of the 1.22 Ma Tshirege Member of the Bandelier Tuff at Technical Area (TA)-3 of the Los Alamos National Laboratory. The goal of the investigation was to identify faults that may have potential for earthquake-induced surface rupture at the site of the Chemistry and Metallurgy Research (CMR) building, a sensitive Laboratory facility that houses nuclear materials research functions. The holes were located from 25 ft to 115 ft from the building perimeter. Careful mapping of Lithologic sequences in cores, supplemented with focused sampling for geochemical analyses, yielded high confidence in the accuracy of delineating buried contacts within the Tshirege Member. Geologic analysis and investigation of the trends of surfaces interpolated from contacts in the core holes using commercially available software helped infer minor faulting in the strata beneath the building. Results show that gently north-northeast-dipping beds underlie the CMR building. The tilted beds are faulted by two small, closely spaced, parallel reverse faults with a combined vertical separation of approximately 8 ft. The faults are inferred from lithologically and geochemically repeated sections of core at about 55-ft depth in hole SHB-CMR-6. The data from nearby core holes SHB-CMR-2 and SHB-CMR-3 permit the extension of the faults, albeit with decreasing separation, toward the southwest beneath the CMR building. The fault trend is consistent with mapped lineaments from aerial photography and with nearby mapped structure, but direct evidence of the faults' orientations is lacking. No other faults were detected beneath the CMR building by this drilling and analysis method, which can detect faults with greater than about 2 ft separation.
- Research Organization:
- Los Alamos National Laboratory, Los Alamos, NM
- Sponsoring Organization:
- USDOE Office of Defense Programs (DP)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 1682
- Report Number(s):
- LA-13522-MS; ON: DE00001682
- Country of Publication:
- United States
- Language:
- English
Similar Records
Geology, drilling, and some hydrologic aspects of seismic hazards program core holes, Los Alamos National Laboratory, New Mexico
Geology of the Western Part of Los Alamos National Laboratory (TA-3 to TA-16), Rio Grande Rift, New Mexico