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An evaluation of the geological seismological hazard was conducted at the St. Stephen Powerhouse Project, which is part of the cooper River Rediversion Project in South Carolina. The project is located about 60 km North of Charleston, SC, and consists of a reinforced concrete powerhouse structure founded on rock, flanked by rolled fill earth embankments, founded partially on rock and partially on alluvium. For the purposes of this study, the alluvium is assumed to be competent, not susceptible to liquefaction. The Maximum Credible Earthquake (MCE) is estimated to correspond to a magnitude 7.5 event, 55 km from the site, resulting in peak ground accelerations at the site of 0.32 and 0.35 g. The Operating Basis Earthquake (OBE) is estimated to correspond to about a magnitude 5 event, resulting in a peak ground acceleration of 0.04 to 0.05 g at the site. The Newmark sliding block analyses indicate deformations in the maximum section under the MCE will be negligible, less than 1 cm. However, deformation under retaining walls and embankments founded on natural ground may be on the order of 15 to 35 cm.

The purpose of this investigation is to define the maximum potential for earthquakes and to provide peak horizontal ground motion for earthquake shaking which night occur at J. Strom Thurmond Dam. Results of this study are for use in the engineering-seismic evaluation of J. Strom Thurmond Dam and associated structures. The dam is located on the Savannah River in the Piedmont Physiographic province of Georgia and South Carolina (see Figure 1). This investigation includes both geological and seismological analyses and consists of the following parts: (a) a review of the regional and local geology, including an evaluation of faulting in the area, (b) a review of historical seismicity in the study area and its relationship to the geology, (c) determination of the maximum earthquake(s) that could effect the dam as well as a determination of the attenuated peak ground motions at the dam.

A seismic zoning was developed for eastern Pennsylvania and adjacent states based on the geology and the historic seismicity. Floating earthquakes were assigned to those zones in the absence of identifiable active faults. At the Prompton and Francis E. Walter Damsites, motions were far field, Modified Mercalli VI, acceleration 0.12g, velocity 7 cm/sec, and 3 sec bracketed duration or = 0.05g. Accelerograms and response spectra appropriate to these parameters were selected.

The region in which Barkely Dam is located was divided into four seismic source zones. Zone 1, the new Madrid source, was seen to provide the severest shaking at Barkley damsite. The maximum earthquake is m sub b = 7.5 and is attenuated 118 km. The Santa Barbara record for the 1952 Kern County, California, earthquake was scaled to an acceleration of 0.24 g, a velocity of approximately 35 cm/sec, and a duration (= or 0.05 g) of approximately 60 sec. Contents: Earthquake Zones; Earthquake Motions; Review of Earthquake Sources; Review of Earthquake Motions; Earthquakes and Geology of the Barkely Dam area in Relation to the New Madrid Earthquake Region to 1977, with Supplementary Earthquakes to 1981; Earthquake Motions and Recommended Acclerograms for the Barkley Damsite, Based on Zones I, II, and III; Earthquake Motions for the Barkley Damsite Based on the Wabash Valley Zone (Zone IV).

The large dispersion of data for components of earthquake motion requires that the spread be appraised in design applications. Instrumental data also must be related to historic records of intensity. The near field and the far field contribute greatly to differences in peak motions. Site conditions, soil versus rock, affect duration. With these considerations, and with geological studies and the probability of recurrence, peak values can be specified from parameters of motions related to Modified Mercalli intensities. These peak values can be used for rescaling selected strong motion records or alternatively for the generation of synthetic seismograms. The procedure incorporates the wide variability in ground motions that have occurred during earthquakes. (Author), See also Rept. no. 6, AD-A040 870.

No evidence of active faults is present in the general area of the damsite. It is concluded that the faults which are present are all ancient ones and are inactive. Present day tectonism indicates that moderate earthquakes occur in the Piedmont and adjacent regions. Severe earthquakes are restricted to a narrow band along the Summerville to Charleston, South Carolina area. Motions attenuated from Summerville-Charleston band to the damsite are low. A probability of recurrence study showed that the operating earthquake has an acceleration of 0.075g (0.01 annual risk). The operating basis earthquake is generally more moderate than the maximum earthquake. It is selected on a probabilistic basis from regional and local geology and seismology studies as being the largest expected to occur during the life of the project; in this case, 100 years., Original contains color plates: All DDC reproductions will be in black and white.

The purposes of this investigation were principally to assess the duration and spectral content of strong-earthquake accelerograms and, indirectly, to consider their applicability in earthquake design. Correlations of duration with MM intensity for the near and far fields and for Richter magnitude have been obtained. Difference in durations for soil and rock sites was determined. A set of relations between the duration and distance for soil and rock sites was established from records of the San Fernando Earthquake of 9 February 1971 (magnitude of 6.5). Values for other magnitudes were extrapolated. Duration is taken to be the time interval between the first and last peaks of acceleration equal to or greater than 0.05 g. The spectral content in the range of 0.1-10 Hz for strong-motion records in western United States for acceleration level equal to or greater than 0.05 g processed with the modified Nigam and Jennings' response spectra computer programs., See also Rept. no. 7, AD-A048 309.

The Dickey-Lincoln School damsites are less than 50 miles from an area along the St. Lawrence River which has experienced some of the most severe earthquakes in North America. A geological and seismological investigation was made of the region in order to determine the hazards from earthquakes at the damsites. No active faults were found in the general area of the damsites. The source area of potentially severe earthquakes was found to be restricted to a narrow band that follows the St. Lawrence River. This band was designated as Zone A. The boundary of Zone A is located 45 miles from the damsites. Zone B, with less seismic risk, borders Zone A and is 40 miles from the damsites. The damsites are situated in Zone C, which has the least seismic risk in the region. Zone D, with a level of seismic risk between that of Zones B and C, occurs 75 miles southeast of the damsites. The most severe ground motion at the damsites was interpreted to be from an earthquake in Zone A attenuated over a distance of 45 miles. Such movement is interpreted to have a peak acceleration of 0.35 g, a peak velocity of 65 cm/sec, and a peak displacement of 22 cm. The duration of shaking is estimated at 18 sec. Accelerographs are recommended for scaling in order to develop time histories of bedrock ground motion for dynamic analyses. (Author)

A review was made of major reservoirs of the Corps of Engineers with regard to their experiences with induced seismicity. The Corps has 24 large reservoirs, i.e. those with dams 60.96 m (200 ft) in height or greater, and with volumes of 1,233,500,000 cu m (1,000,000 acre-ft) or greater. Thirteen reservoirs were instrumented for monitoring microearthquakes. They range from large to small and are located in aseismic to highly seismic areas. Only one Corps reservoir, Clark Hill in Georgia-South Carolina, has experienced a felt earthquake, but the 21-year interval between impoundment and the occurrence of the earthquake is not typical of reservoir-induced earthquakes and a direct relationship appears improbable.

Laterization processes were studied and samples of laterite gravel collected at 40 sites in Thailand, Australia, Brazil, Ghana, Portuguese Angola, and Georgia (USA) to determine classification, field associations, genesis, and engineering properties important in road and airfield construction. Lateritic soils are self-hardening and may contain either laterite rock or nodular, laterite gravel. Tropical soils which are not self-hardening and which lack appreciable laterite rock or laterite gravel are called here tropical red soils. The soils studied in this report classify as sands and gravels in the Unified Soil Classification System. Generally they are poorly sorted, strongly fine-skewed, leptokurtic, and, on the average, contain approximately 12 percent fines. These soils have originated by the hydrolytic destruction of primary silicate minerals in warm, tropical to subtropical weathering environments which exhibit distinct wet and dry seasons, and are generally free draining. Laterite gravel is of primary importance in construction. Laterite rock requires crushing, and self-hardening laterite may be difficult to identify and thus may be confused with tropical red soils. Foreign engineers have found that two official U.S. specifications are too restrictive. They have developed base and subbase specifications suitable for road and airfield construction using laterite gravel.

A facility was designed and subsequently has been built for the utilization of californium-252 in research on moisture, density, and other properties of soil and rock in relation to their engineering characteristics. Preliminary testing shows good correlations between neutron radiation and the quantification and distribution of moisture both in soil slices and steel-encased undisturbed soil samples. Such data, when used in conjunction with X-ray studies, are valuable in furthering the knowledge and understanding of soil and rock behavior. Continued research will refine techniques for more detailed study of properties of earth materials. Detailed plans of the facility and its components are given in Appendix A.

Patoka damsite is in an area of appreciable past seismic activity. Activity along surface faults has not been determinable, so future seismic events must be postulated as likely to occur anywhere within certain zones. These zones were based on work by Professor Otto W. Nuttli and a review of seismic history. The most damaging earthquake with its peak recurrent ground motions is postulated as follows: magnitude, 6.1; acceleration, 0.11-0.44 g; velocity, 54 cm/sec; displacement, 26 cm; duration, 68 sec. If the earthquake occurred beneath the dam, it might contain high-frequency acceleration spikes at levels up to 0.9 g. The acceleration of 0.11 g (Nuttli) is presented as a lower limit; California experience shows that accelerations of 0.44 g are to be expected for earthquakes of comparable magnitude. In the absence of strong motion records in the central United States, the range is, therefore, 0.11 to 0.44 g. Velocities and displacements compare favorably with West Coast experience. Maximum duration is four times that of the West Coast value for earthquakes of comparable magnitude.

X-ray examinations of fine-grained soils from the Lower Mississippi Valley revealed numerous geologic features that are not visible to the unaided eye. These features include significant fracture patterns, details of planar bedding, cross-laminations and turbulence, secondary mineralizations, root penetrations and voids left by roots, the presence of disseminated organic matter and other details. These geologic features affect the strength properties of the soils in which they occur. Experiments with multiple specimens from single samples embodying different features demonstrated that many large variations in strength properties were not only directly dependent of these features but were predictable in a relative sense. Normally, these features are never identified during routine soils testing although the effects of these features contribute to erratic test results. Pretest radiographic examination is a potential means of avoiding these problems. (Author)

Film density measurements of X-radiographs can be interpreted into soil density measurements under suitable controlled conditions and with proper calibration curves. The method is nondestructive, and determinations can be made for a model during various stages of testing. The method needs to be supplemented to observe deformation and shear planes. (Author)

Atchafalaya Test Section VI is a 2000-ft-long portion of the Atchafalaya Basin Protection Levee System in south-central Louisiana. The soil in the area comprises fine-grained sediments laid down under shallow freshwater conditions. These backswamp deposits are underlain by a thick substratum of sands and gravels. The backswamp at Test Section VI is 100 to 110 ft thick where not consolidated by levee loading and 88 to 91 ft thick under the center line of the levee. Nine borings were made in Test Section VI for the purpose of interpreting the various depositional layers which compose the foundations soils and determining the effect of the levee fill upon the underlying soils at the site. An attempt was also made to define the extent and patterns of subsurface deformation which accompanied settlement of the levee. Samples from all nine borings were tested for engineering properties. In addition, undisturbed samples suitable for radiographic analysis were obtained from one of the borings. The backswamp deposit at Test Section VI was subdivided into layers A through H on the basis of sedimentary features revealed by radiography. Correlation sections were made between the nine borings at Test Section VI. Structure and isopach maps were constructed on the basis of these correlations. It was revealed that the structure of the levee had a pronounced effect on the pattern of settlement in the underlying soils.