Amchitka Research Articles

Secular strain measurements before and after the CANNIKIN nuclear test

abstractSecular earth-strain measurements have been made in the central Aleutian Islands during the years 1970 and 1971. An annual variation of about 3 × 10−6 is evident on all records. A residual deformation of less than 3 × 10−6 per year is detected on most records. The state of strain near Amchitka Island, Alaska, at the time of CANNIKIN, November 6, 1971, differed from the state of strain at the time of the MILROW test, October 2, 1969, by less than 1 × 10−5. The strain records also contain novel episodes of large size (1-3 × 10−6) and high strain rate (1 × 10−7 / hr).

Strain and tilt records of the CANNIKIN nuclear test

abstract During the CANNIKIN underground nuclear test of November 6, 1971, nearsurface earth deformations were observed by a total of 26 strainmeters and eight tiltmeters at nine sites in the Aleutian Islands at distances of 10 to 1125 km from ground zero on Amchitka Island. Permanent strain steps were observed at all stations. The size of strain steps observed at about 10 km (> 10−4) implies that the zone of nonelastic behavior extended to more than 10 km from ground zero. The size of strain steps observed at 295 and 1125 km (< 10−8) indicates that the residual strains at these distances were not as large as the amplitude of the daily earth tide. The permanent steps exhibit a pronounced directional assymmetry but, at five stations, are in reasonable agreement with predictions based on the work of Wideman and Major (1967). Redundant observations of areal strains at two stations yield values of −29.5 × 10−9 versus −24.2 × 10−9 and −2.1 × 10−7 versus −3.2 × 10−7.

Hydrological effects of the CANNIKIN event

abstract The hydrological effects of the underground nuclear explosion, CANNIKIN, were monitored by a network of streamflow stations and ground-water boreholes located on Amchitka Island. Continuous records were obtained from six surface-water stations that range from 1.50 to 14.07 km from surface ground zero (SGZ). Confined fluid pressures in boreholes were recorded at five stations with slant distances ranging from 2.14 to 14.11 km from ground zero (GZ). Fluctuations of water level were measured in one open hole 6.42 km from GZ. The stream system draining the CANNIKIN site lost 96 per cent of its flow within hours after the explosion. Lakes formed near SGZ remain low in stage and appear to be providing infill water for the rubble chimney. Measurements in boreholes also showed that the ground-water gradient was toward the explosion site. The response of confined fluid pressures was recorded in a number of boreholdes, and a relationship between maximum fluid pressure, P, and slant range, Rs, has been established as P = 920 Rs−2.10.

Source Time Functions and Spectra for Underground Nuclear Explosions

The model of Haskell for explosion source time functions and spectra fails to satisfy data in the short-period band recorded teleseismically from the three Amchitka Island underground nuclear tests: LONG-SHOT, MILROW, and CANNIKIN. A more recent model due to Mueller and Murphy satisfies the data quite well. The difference in the two models is basically in the fall-off at high frequencies. A simple revision of Haskell's model produces waveforms and spectra nearly identical to ones from Mueller and Murphy's model. This revision requires velocity waveforms to have a rise time of extremely short duration at the elastic boundary, a premise validated by actual near-field measurements. Waveforms are derived from the revised Haskell model and the Mueller and Murphy model and illustrated for pressure at the elastic boundary, reduced displacement potential at the elastic boundary, and far-field displacement. Corresponding spectra are derived and illustrated.

Close-in ground motion from the MILROW and CANNIKIN events

abstractMotion of the ground induced by the CANNIKIN and MILROW nuclear explosions beneath Amchitka Island was observed at vertical arrays of subsurface stations in borings offset 90 m from the shot holes and at surface stations at distances ranging from surface zero to about 10 km. Acceleration, particle velocity, and displacement time histories were obtained: vertical components only in the vertical arrays and three orthogonal components at surface stations.MILROW results indicate Rayleigh waves in records from a horizontal range of one-half shot depth and beyond. Analysis showed the initial spall depth near 110 m, with later spallation below 150 m and between 30 and 90 m. Surface data indicate spallation extended laterally to four times shot depth. CANNIKIN data were trucated at about 1.8 sec by power circuit malfunction. Peak motion was recorded at all but the most remote CANNIKIN station before loss of power. Comparison of CANNIKIN data with those from MILROW indicate greater peak motions from the more energetic CANNIKIN explosion, but scaled peak motions from these events are similar.

Seamount Reflections from the CANNIKIN Underground Explosion

Hydroacoustic signals were recorded from the five megaton Amchitka Island underground explosion (code name CANNIKIN) of 6 November 1971. SOFAR depth hydrophones of the Missile Impact Location System (MILS) off the islands of Midway, Wake, and Oahu in the Central Pacific were used as detectors. In the low-frequency (<20 Hz) band, the main signal was followed by reverberations that persisted for several hours after the shot. Arrival times of some of these reverberations were correlated with those computed for reflections from seamounts in the Emperor Seamount Chain and the Hawaiian Arch. Reverberations from more distant reflectors were separated by quiet periods or “windows” of several minutes duration. The azimuthal and temporal distribution of the “windows” versus the reverberation maxima is investigated in relation to low-frequency ambient noise in the ocean.

Seismological evidence for a lithospheric tearing beneath the Aleutian arc

Travel times have been studied from the Longshot underground explosion detonated on Amchitka Island on October 29, 1965. The travel-time residuals of P waves at stations in azimuths from N10°E to N30°E around the source, are, on the average, larger by 1 to 2 sec than those at stations in adjacent azimuths. This observation suggests the existence of a low-velocity region having a limited spatial extent; a P-velocity contrast of 0.3 to 0.6 km/sec is estimated. This low-velocity region can be explained in terms of a lithospheric tearing beneath the Aleutian arc and of a subsequent intrusion of low-velocity material from the underlying asthenosphere. The lithospheric tearing is considered to have been caused by bending of the oceanic lithosphere at a markedly curved portion of the Aleutian arc.

Seismic reflection evidence supporting underthrusting beneath the Aleutian Arc near Amchitka Island

Two seismic reflection records were obtained across the Aleutian trench south of Amchitka Island. Horizontal strata up to 1.6 km thick partially fill the trench, and in one crossing some of the turbidite layers adjacent to the insular trench wall appear to be deformed. Along the southern margin of the trench, traces of pelagic sediments can be seen draped conformably over the rough acoustic (oceanic) basement. This deep-sea sediment blanket becomes indistinct as it plunges under the trench fill, but the oceanic basement reflector continues northward 2–7 km beyond the base of the northern trench wall. The records can be interpreted in accord with the theory of plate tectonics and can be used to support the hypothesis of a large shear zone or mega-thrust fault at the base of the trench.

Analysis of Teleseismic Signals from Underground Nuclear Explosions Originating in Four Geological Environments

A comparison of Yellowknife records of the short-period teleseismic P codas of underground nuclear explosions with synthesized records enables us to differentiate between the primary signal and anomalous signal-generated noise. By primary signal we are referring to the P coda generated by a symmetric point source in a layered crust; both source and receiver crusts satisfy the requirements of the Haskell-Thomson matrix theory. For epicentral distances for which multipathing in the upper mantle does not occur, the large-amplitude phases in the first several cycles are dominated by the primary signal. Complexities in the next portion, which consists of smaller amplitude phases, are probably due to signal-generated noise resulting from the presence of lateral heterogeneities near the source such as faults and perturbations in layer thickness and composition. Finally complexities in the latter portion of the P coda may, in some cases, be due to explosion-generated noise resulting from the presence of topographical irregularities at greater distances from the source. Of the four geological environments studied, the events from Amchitka Island appear to have the smallest complexity factor and the event from Novaya Zemlya, the largest. The complexity of the events from the E. Kazakh site and the Nevada Test Site lie in between these two values.

Explosion Effects and Earthquakes in the Amchitka Island Region

Microearthquakes were monitored by a network of seismographs located on Amchitka and nearby islands; the nature of earthquake activity in this region was found to be consistent with the hypothesis of underthrusting of the Aleutian arc by a rigid lithospheric plate. Seismic effects of the nuclear explosion Milrow were small, of short duration, confined to the region immediate to the explosion, and were apparently independent of this geotectonic mechanism.

Concerning the phaeophycean genera Analipus and Heterochordaria

Abstract Evidence is presented to include the phaeophycean genus Heterochordaria Setchell et Gardner (1924) in Analipus Kjellman (1889) (Chordariales, Chordariaceae). On the basis of recent collections made at Amchitka Island, the Aleutians, Analipus japonicus (Harv.) Wynne comb. nov. [=Heterochordaria abietina (Rupr. ex Farl.) Setch. et Gardn.] is recognized in addition to the type species, A. filiformis (Rupr.) Papenf.

Freshwater Food Habits of "Salvelinus malma" (Walbaum) on Amchitka Island, Alaska

Freshwater Food Habits of SaZveZinus maZma (Wa1baum) On Amchitka Island, Alaska by John F. Palmisano, Master of Science Utah State University, 1971 Major Professor: Dr. William T. Helm Department: Wildlife Resources ix Stomach contents of 3,672 Dolly Varden char collected from September 1967 to November 1968 were examined to determine the food habits of this species. Of these, 3,100 (86%) had food in their stomachs. Aquatic invertebrates (Insecta and Crustacea) comprised over 90% of the diet. Food habits varied with habitat. Aquatic insects were most important in the diet of stream fish while aquatic insects and crustaceans were most important in the diet of lake fish. Food habits of lake fish were re1ated to lake bottom type and access to the sea. Fish in landlocked lakes fed primarily on aquatic insects, fish, and fish eggs. In lakes with access to the sea, crustaceans, followed by aquatic insects, were the major food items in those with firm bottoms adjacent to shore while aquatic insects, followed by crustaceans, were the major food items in those with muck bottoms adjacent to shore. As fish size increased, feeding activity decreased and aquatic insects became less important in the diet while crustaceans and fish became more important. During summer, feeding activity was highest for lake fish while it was highest during autumn and summer for stream fish. Aquatic insects were the dominant food item in summer while crustaceans and fish were dominant

Dynamics of Raptor Populations on Amchitka Island, Alaska

Hult6n, E. 1960. Flora of the Aleutian Islands. 2d ed. J. Cramer, Weinheim. 418 p. Hult6n, E. 1968. Flora of Alaska and Neighboring Territories. Stanford University Press, Stanford, California. 1008 p. Powers, H. A., R. R. Coats, and W. H. Nelson. 1960. Geology and submarine physiography of Amchitka Island, Alaska. U.S. Geol. Surv. Bull., 1028: 521-554. Shacklette, H. T., et al. 1969. Vegetation of Amchitka Island, Aleutian Islands, Alaska. U.S. Geol. Surv. Prof Paper 648. 66 p. Shacklette, H. T., and M. Rubin. 1969. Radiocarbon dating of ash deposits on Amchitka Island, Alaska. U.S. Geol Surv. Prof. Paper 650-B:81-83. Shear, J. A. 1964. The polar marine climate. Ann. Assoc. Amer. Geogr., 54: 310-317. Tamm, C. 0. 1953. Growth, yield and nutrition in carpets of a forest moss (Hylocomium splendens). Medd. Statens Skogsforskninginst. 43 (1) 1-140.

Spatial and Seasonal Distributions of Marine Algal Communities at Amchitka Island, Alaska

Studies on the benthic marine algae at Amchitka Island since July 1967 entailed considerable systematic effort since there have been no major phycological studies of the Bering Sea area since Kjellman (1889). A series of papers on various groups of benthic marine algae at Amchitka has been initiated (Wynne, 1970). Weinmann's (1969) study of the zonation of littoral algae provided a starting point for our ecological studies. More recently we investigated timedependent changes in the littoral biospace since a knowledge of these changes (or lack of them) will allow us to predict and differentiate to some extent natural and possibly man-induced changes. The major environmental factors affecting the distributions of littoral vegetation are terrestrial climate, sea temperatures, and wave action. The climate is maritime. Air temperature varies little, and sky cover and relative humidity are high throughout the year. These conditions are favorable for the development of littoral vegetation. Sea-surface temperatures range from 1 to 2 C in winter to 8 to 10 C in summer. Wave action can be consistently heavy, particularly in the winter. Dredging data indicate that waves of well over 100 m in wavelength are frequent.l Figure 1 shows the heavy wave action encountered at the Island. This condition would lead one to expect an extensive vertical range of littoral algae and an configuration of vegetation. This was not the case. In general, even on outer exposed points, the vertical range of macroscopic algae was less than 2 m above mean lower low water. This small vertical range is explained by the presence of extensive benches in the littoral. One of these benches is shown in O'Clair and Chew's Figure 1 (this symposium). Providing an unusually uniform habitat, these benches also act as buffers against the long-period waves approaching Amchitka. The outer edges of the benches generally rise abruptly in depth from 2 to 10 m. At these outer edges, most of the energy dissipates as the waves break (Fig. 2), and water piles on the benches, then flows landward and laterally, and eventually seaward via channels between the benches. The process is shown schematically in Figure 3. The buffering action at the benches must be the underlying cause of the absence of an configuration of littoral vegetation. Our first objective was to characterize the distribution of marine algae over This paper is based on work performed under AEC Contract AT(26-1)-171 for Battelle Memorial Institute, Columbus Laboratories. Contribution No. 330, College of Fisheries, University of Washington.

Geographical Affinities and Migrations of the Avifauna on Amchitka Island, Alaska

sloughed into the sea), it is difficult to predict what will happen if much of the cliff and the eyrie site falls away. Possibly the pair will more to an adjacent cliff and start a new eyrie, although peregrines prefer certain cliffs and use these same cliffs generation after generation (White and Cade, 1971). On Amchitka, at least, bald eagles appear to have, or select, more alternate nesting sites than do falcons. About 30% of the eagle-nesting sites used one year are not used the following year. The eagles apparently move to adjacent (alternate) sites. Over 85% of the eaglenesting sites are on columns or of rock, termed sea stacks, separated from the main island. Sea stacks are, of course, very vulnerable to damage and destruction. In the event that stacks are destroyed, eagles would appear to be adaptable enough to shift to the main island for nesting. Future tests should not be conducted during the breeding season for fear of egg breakage.

Ecology of Threespine Stickleback "Gasterosteus aculeatus" Linnaeus on Amchitka Island, Alaska

Ecology of Threespine Stickleback "Gasterosteus aculeatus" Linnaeus on Amchitka Island, Alaska

Bioenvironmental Studies at Amchitka Island, Alaska

that would have to be supplied largely by air. The area considered in Central Nevada is about equi-distant from Las Vegas, Reno, and Salt Lake City. Its main limitations were ground motion effects on high-rise buildings in those cities and less vulnerable buildings in closer towns and ranches. Amchitka fit the criteria best. It has the great advantage of remoteness from human populations; it provides the ability for delivery of supplies by sea, as well as by air, at all seasons; and it provided repairable facilities and roads left from World War

The Coastal Zooplankton around Amchitka Island, Alaska

Investigations covered the continental shelf from about the 18-m to the 183-m bottom contour, in a region considered coastal. Its pelagic plankton is classified as neritic (Raymont, 1963). From the 200-m contour, the slope falls steeply into the abyssal depths and the pelagic fauna is oceanic. Waters south of the Aleutian ridge are dominantly influenced by the Alaskan Stream which is composed of water diluted by the freshwater runoff of the coastal areas adjacent to the Gulf of Alaska (Favorite, 1967). North of Amchitka lie the colder, more saline waters of the Bering Sea.

The Atomic Energy Commission's Interest in Bioenvironmental Research

The Atomic Energy Commission Nevada Operations Office is responsible for all of the United States testing of nuclear devices, whether for peaceful or military use. Predictions and evaluations of the radiological and ecological effects from nuclear detonation experiments are important in planning for these tests. These effects-evaluation studies have made the AEC one of this country's major sponsors of bioenvironmental research. How Amchitka Island was selected as a supplemental test site is described.

The Structure and Origin of the Organic Soil Cover of Amchitka Island, Alaska

The topographically low areas of Amchitka and many other islands of the western Aleutian chain are covered with a blanket of moss-lichen-sedge peat. A close relationship exists between the toposequence or drainage position of this peat, its chemical and physical characteristics, and the vegetation it supports. In terms of the U.S. Department of Agriculture's Histosol Supplement to the 7th Approximation, the organic soils of Amchitka can be separated by the relative proportions of the three decomposition states of the peat and the position of the soil in the drainage hierarchy. Those peats, which occupy the areally small, least well-drained positions in the toposequence such as drainage channels, are composed almost entirely of little-decomposed, coarse, fibrous (Fibric) peat several meters thick. The peat is strongly acid and contains >80% organic matter. Field moisture values frequently exceed 2000%. In slightly better drained, topographically higher positions in the toposequence, or on broad interfluve flats, are the areally extensive Blanket bogs. These bogs contain 1 to 2 m of both coarsely fibrous (Fibric) peat and peat of intermediate decomposition state (Hemic). These highly organic and strongly acid peats have an average field moisture of 650%. A thin gelatinous layer is just below the lichen-dominated vegetation. Traction applied to the surface of these soils can cause extensive and probably irreversible damage. It results in a tearing of the vegetation, compaction of the Hemic peat, and ponding. On still better drained, often very steep, positions of the toposequence, soils consist of Hemic peat to a depth of nearly 1 m. Some amount of littledecomposed Fibric peat or highly decomposed Sapric peat may be included, depending on local drainage. These soils are only slightly acid and, because of greater organic decomposition, contain about one-half as much organic matter as the wetter peats. The density of these soils increases and the field moisture