Seismic source identification data

DOE-STD-1022-94

investigation of the site. Additionally, Senior Seismic Hazard Analysis Committee (1997c) provides a

methodology for characterizing seismic sources linked to completing a probabilistic seismic hazard

analysis (see DOE-STD-1023-1995). If such a study clearly shows that the near site features dominate

the hazard, more extensive site investigations should be made in the near field. McConnell et al., (1992)

provides an iterative approach for identification of the regions to be investigated to identify fault

displacement hazards and seismic hazards at a geologic repository in the Western United States (WUS)

based on a review of the pertinent literature, relevant field investigations, and consideration of alternative

tectonic models. For investigations of sites containing facilities with SSCs in Performance Category 4

such as nuclear reactor safety, U.S. NRC Regulatory Guide R.G. 1.165 (USNRC, 1997) provides

guidance for identification of the regions to be investigated:

Regional investigations using literature reviews and geological reconnaissance should generally be

conducted for a radius of 320 km (200 miles) from the site, unless clearly justified.

Geological, seismological, and geophysical investigations should be carried out for a radius of 40 km (25

miles) from the site to identify and characterize the seismic and surface deformation potential of seismic

sources, or to demonstrate that such structures are not present.

Detailed geological, geophysical, seismological, and geotechnical (GGSG) investigations should be

conducted for a radius of 8 km (5 miles) from the site to determine the potential for surface tectonic and

non-tectonic deformations in the site vicinity.

The area of detailed GGSG investigations may be larger than a 5-mile radius in regions of late Quaternary

earth movements or historical seismic activities, or where a site is located near a fault zone, or complex

geology.

2. Type of investigations. There are several acceptable types of investigations to identify seismic sources.

Different techniques are required depending on the geologic setting and tectonic environment. In most

cases, more than one approach must be used and the reliability of the results depends on the experience

and competence of the investigators for synthesizing and interpreting various types of geological,

seismological, and geophysical data. Types of investigations include:

Analysis of aerial photographs and other remote sensing imagery

Geologic, including stratigraphic and structural, reconnaissance and mapping

Geomorphic analysis (e.g., fault scarp morphology, terrace profiling, geodetic land surveys)

Analysis of local and regional geophysical data (e.g., seismic reflection, seismic refraction,

aeromagnetics, gravity, etc.,)

Subsurface investigations of suspected fault traces (e.g., trenching, geophysical investigations, borings)

Age dating techniques including radiometric (e.g., carbon 14, thermoluminescence), chemical (e.g.,

pedogenic soils), biological (dendrochronology), and evolutionary (palynology)

Listing of all historically reported earthquakes (including instrumentally recorded data) that are associated

with seismic' sources, any part of which is within a radius of 320 km (200 miles) of the site, and

seismicity analysis, including date of occurrence, earthquake sizes (intensity and/or magnitude), epicentral

locations, focal depths, and focal mechanisms

Correlation of seismicity with geologic structure

Interpretation of stress orientation from focal mechanisms, geologic indicators, field experiments (e.g.,

hydrofracturing, borehole breakout investigations), and geodetic data

3. Source zones. In the stable continental region of the Eastern U. S. (EUS), away from tectonic plate

margins, it generally has not been possible to associate seismicity with specific geologic structures