Statistical analysis and interpretation of surface-wave anelastic attenuation data for the stable interior of North America

1975 ◽  
Vol 65 (5) ◽  
pp. 1115-1128 ◽  
Author(s):  
Robert B. Herrmann ◽  
Brian J. Mitchell
Keyword(s):  
North America ◽  
Hudson Bay ◽  
Seismic Region ◽  
Period Range ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Confidence Levels ◽  
Anelastic Attenuation ◽  
Rapid Transition ◽  
Attenuation Values

Abstract As a byproduct of determining the source characteristics of some earthquakes and underground nuclear explosions, a body of fundamental-mode Rayleigh- and Love-wave anelastic attenuation values is available for propagation paths in the stable interior of North America in the 5- to 50-sec-period range. The anelastic attenuation values were obtained from four earthquakes occurring in the New Madrid seismic region, one earthquake in the northern Hudson Bay region, and three underground nuclear explosions in the western United States. In obtaining the anelastic attenuation data, a simple statistical test was applied to test the reliability of the observations. The anelastic attenuation coefficients are presented together with their 95 per cent confidence levels. A stochastic form of the Backus-Gilbert inverse formalism was applied to a subset of these data to yield a Qβ model for the stable interior of North America. The model is characterized by relatively low Qβ values for the upper crust and a rapid transition to much higher values for the lower crust.

S waves generated by small seismic sources

1966 ◽  
Vol 290 (1422) ◽  
pp. 448-460
Keyword(s):  
Wave Motion ◽  
Wave Generation ◽  
Good Resolution ◽  
University Of Michigan ◽  
Period Range ◽  
S Waves ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Wide Range ◽  
The University

Observations of S waves from small earthquakes recorded at near distances indicate that the relative S wave generation extends over a wide range. Similar measurements from underground nuclear explosions indicate a ratio of S to P wave generation to be below the observed values for 70 % of the earthquakes studied. The observation of S waves from small events at teleseismic distances is made difficult by interference of microseisms in the period range where S waves may be expected. The observation is also made difficult by the physical requirement that two horizontal component seismographs are required to obtain good resolution of S wave motion. Some measurements have been made at the University of Michigan by means of three-component seismometers in arrays to obtain better resolution of S wave motion. The results of these measurements suggest that improvements in S wave signal/noise ratios similar to those obtained for P waves are possible. The use of S waves from small events at teleseismic distances should not be considered of value as a method of detection. It does, however, offer promise as an added method of identification for small seismic events.

Seismic-source energies of underground nuclear explosions

1972 ◽  
Vol 62 (3) ◽  
pp. 763-774 ◽  
Author(s):  
William R. Perret
Keyword(s):  
Free Field ◽  
Seismic Source ◽  
Elastic Response ◽  
Seismic Sources ◽  
Porous Rocks ◽  
Seismic Region ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Order Of Magnitude ◽  
Total Energies

Abstract Records of particle velocity in the free-field geological environment near underground nuclear explosions may be interpreted to yield the energy flux at a measuring station near or within the region of elastic response of the rock. Such data from 21 events in several types of rock have yielded energy fluxes. Total energies associated with the motion propagated into the seismic region have been derived from all but seven of these. The total energies are a measure of the seismic-source strength, and the ratios of these energies to those released by the explosion are measures of the energy coupled into the Earth as seismic motion. Explosions in granite, dolomite, or wet tuff produce seismic sources of the order of 2 per cent of the explosively released energy. Similar explosions in porous rocks such as dry tuff and desert alluvium provide seismic sources an order of magnitude weaker than those in hard or wet rock.

Regional attenuation models in Central and Eastern North America using the NGA-East database

2021 ◽  
pp. 875529302110187
Author(s):  
Jeff Bayless
Keyword(s):  
North America ◽  
Frequency Dependence ◽  
Gulf Coast ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Amplitude Spectrum ◽  
Active Regions ◽  
Atlantic Coastal Plain ◽  
Eastern North America ◽  
Anelastic Attenuation

The anelastic attenuation term found in ground motion prediction equations (GMPEs) represents the distance dependence of the effect of intrinsic and scattering attenuation on the wavefield as it propagates through the crust and contains the frequency-dependent quality factor, [Formula: see text], which is an inverse measure of the effective anelastic attenuation. In this work, regional estimates of [Formula: see text] in Central and Eastern North America (CENA) are developed using the NGA-East regionalization. The technique employed uses smoothed Fourier amplitude spectrum (FAS) data from well-recorded events in CENA as collected and processed by NGA-East. Regional [Formula: see text] is estimated using an assumption of average geometrical spreading applicable to the distance ranges considered. Corrections for the radiation pattern effect and for site response based on [Formula: see text] result in a small but statistically significant improvement to the residual analysis. Apparent [Formula: see text] estimates from multiple events are combined within each region to develop the regional models. Models are provided for three NGA-East regions: the Gulf Coast, Central North America, and the Appalachian Province. Consideration of the model uncertainties suggests that the latter two regions could be combined. There were not sufficient data to adequately constrain the model in the Atlantic Coastal Plain region. Tectonically stable regions are usually described by higher [Formula: see text] and weaker frequency dependence ([Formula: see text]), while active regions are typically characterized by lower [Formula: see text] and stronger frequency dependence, and the results are consistent with these expectations. Significantly different regional [Formula: see text] is found for events with data recorded in multiple regions, which supports the NGA-East regionalization. An inspection of two well-recorded events with data both in the Mississippi embayment and in southern Texas indicates that the Gulf Coast regionalization by Cramer in 2017 may be an improvement to that of NGA-East for anelastic attenuation. The [Formula: see text] models developed serve as epistemic uncertainty alternatives in CENA based on a literature review and a comparison with previously published models.

scholarly journals Discriminating underground nuclear explosions leading to late-time radionuclide gas seeps

2020 ◽  
Author(s):  
Dylan Robert Harp ◽  
Suzanne Michelle Bourret ◽  
Philip H. Stauffer ◽  
Ed Michael Kwicklis
Keyword(s):  
Late Time ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Gas Seeps

Morphological and isozyme variation in Salicornia europaea (s.l.) (Chenopodiaceae) in northeastern North America

1987 ◽  
Vol 65 (7) ◽  
pp. 1410-1419 ◽  
Author(s):  
S. L. Wolff ◽  
R. L. Jefferies
Keyword(s):  
North America ◽  
Atlantic Coast ◽  
Hudson Bay ◽  
Salicornia Europaea ◽  
Electrophoretic Variation ◽  
James Bay ◽  
Northeastern North America ◽  
Electrophoretic Patterns ◽  
Anther Length ◽  
Vegetative Characters

Morphological and electrophoretic variation has been documented within and among populations of Salicornia europaea L. (s.l.) in northeastern North America. Univariate and multivariate analyses (discriminant analyses) of measurements of floral and vegetative characters delimited three morphologically distinct groups of populations: Atlantic coast tetraploids (2n = 36), Hudson Bay diploids, and Atlantic coast and James Bay diploids (2n = 18). The two diploid groups were morphologically distinct from the midwestern diploid, S. rubra Nels., based on anther length, width of the scarious border of the fertile segment, and the overall width of the fertile segment. Electrophoretic evidence supported the delimitation of the three distinct morphological groups of populations of S. europaea with the exception of the population from James Bay, which had electrophoretic patterns identical with those of plants from Hudson Bay but resembled the Atlantic coast diploids morphologically. Most enzyme systems assayed were monomorphic. Only homozygous banding patterns were detected in diploid plants and electrophoretic variation was not observed within populations of S. europaea or S. rubra but was detected between groups of populations. Four multilocus phenotypes were evident; these corresponded to the major groups recognized on the basis of ploidy level and morphology. Reasons that may account for the paucity of isozymic variation are discussed.

Distribution of the middorsal stripe dimorphism in the wood frog, Rana sylvatica, in eastern North America

1980 ◽  
Vol 58 (9) ◽  
pp. 1643-1651 ◽  
Author(s):  
Frederick W. Schueler ◽  
Francis R. Cook
Keyword(s):  
United States ◽  
North America ◽  
Rana Sylvatica ◽  
Wood Frog ◽  
Eastern North America ◽  
Hudson Bay ◽  
Northeastern United States ◽  
Southern Ontario ◽  
Maritime Canada ◽  
Eurasian Species

The frequency of the middorsally striped morph of Rana sylvatica in Ontario and Manitoba varies from absence in southern Ontario to 80% on the coast of Hudson Bay, with a general value of 20–30% in the boreal forest, a rise to 50% on the forest–grassland ecotone in southern Manitoba, and a decline westward to 20% on the edge of the prairies. This morph is rare in the northeastern United States and Maritime Canada. The suggested relationship between its frequency and the "grassiness" of the background on which predators view it is reexamined, and it is suggested that a linkage with earlier transformation as demonstrated in Eurasian species may explain certain anomalies.

Study of low-magnitude seismic events near the Novaya Zemlya nuclear test site

1997 ◽  
Vol 87 (6) ◽  
pp. 1563-1575
Author(s):  
Frode Ringdal
Keyword(s):  
Monitoring Network ◽  
Test Site ◽  
Nuclear Test ◽  
P Wave ◽  
Scaling Effects ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Novaya Zemlya ◽  
Source Scaling ◽  
Low Magnitude

Abstract A study of available seismic data shows that all but one of the 42 known underground nuclear explosions at Novaya Zemlya have been detected and located by stations in the global seismic network. During the past 30 years, only one seismic event in this area has been unambiguously classified as an earthquake (1 August 1986, mb = 4.3). Several other small events, most of which are thought to be either chemical explosions or aftereffects of nuclear explosions, have also been detected. Since 1990, a network of sensitive regional arrays has been installed in northern Europe in preparation for the global seismic monitoring network under a comprehensive nuclear test ban treaty (CTBT). This regional network has provided a detection capability for Novaya Zemlya that is shown to be close to mb = 2.5. Three low-magnitude events have been detected and located during this period, as discussed in this article: 31 December 1992 (mb = 2.7), 13 June 1995 (mb = 3.5), and 13 January 1996 (mb = 2.4). To classify the source types of these events has proved very difficult. Thus, even for the mb = 3.5 event in 1995, we have been unable to provide a confident classification of the source as either an earthquake or explosion using the available discriminants. A study of mb magnitude in different frequency bands shows, as expected, that the calculation of mb at regional distances needs to take into account source-scaling effects at high frequencies. Thus, when comparing a 4 to 8 or 8 to 16 Hz filter band to a “teleseismic” 2 to 4 Hz band, the smaller events have, relatively speaking, significantly more high-frequency energy (up to 0.5 mb units) than the larger events. This suggests that a P-wave spectral magnitude scale might be appropriate. The problem of accurately locating small events using a sparse array network is addressed using the 13 January 1996 event, which was detected by only two arrays, as an illustrative example. Our analysis demonstrates the importance of using accurately calibrated regional travel-time curves and, at the same time, illustrates how array processing can be used to identify an interfering phase from a local disturbance, thereby avoiding location errors due to erroneous phase readings.

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