scholarly journals Discrimination of Small Earthquakes and Buried Single-Fired Chemical Explosions at Local Distances (<150  km) in the Western United States from Comparison of Local Magnitude (ML) and Coda Duration Magnitude (MC)

2020 ◽  
Author(s):  
Keith D. Koper ◽  
Monique M. Holt ◽  
Jonathan R. Voyles ◽  
Relu Burlacu ◽  
Moira L. Pyle ◽  
...  
Keyword(s):  
United States ◽  
High Frequency ◽  
Characteristic Curve ◽  
Moment Tensor ◽  
Western United States ◽  
Local Magnitude ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Duration Magnitude ◽  
Chemical Explosions

ABSTRACT Seismologists distinguish underground nuclear explosions from more commonly occurring earthquakes using moment tensor inversion, high-frequency P/S amplitude ratios, mb:Ms comparisons, and P-pP differential travel times. These methods are generally successful for large seismic events (M&gt;3–4) well recorded at regional-to-teleseismic distances (&gt;150  km); however, it is unclear whether they can be modified to work for small events (M&lt;3) well recorded only at local distances (&lt;150  km). Here, we evaluate a recently proposed, local-distance seismic source discriminant—the difference between local magnitude (ML) and coda duration magnitude (MC)—using seismograms of earthquakes and buried, single-fired chemical explosions recorded in three regions of the western United States. The quantity ML–MC was previously found to be sensitive to source depth, effectively discriminating mine blasts, induced earthquakes, and very shallow tectonic earthquakes from deeper crustal earthquakes. In this study, we report the first evaluation of ML–MC as a depth discriminant using data from buried, single-fired explosions that, unlike the seismic sources studied earlier, are good analogs for underground nuclear explosions. We find that even when using generic, uncalibrated methods of assigning magnitudes, ML–MC separates single-fired explosions and earthquakes. The area under the receiver operating characteristic curve is 0.92 for 19 explosions and 14 earthquakes in Washington, 0.90 for 22 explosions and 90 earthquakes in Wyoming, and 0.99 for three explosions and 149 earthquakes in Nevada. ML:MC comparisons have the potential to enhance discrimination based on high-frequency P/S amplitudes ratios—which perform less well at local than regional distances—because the two metrics have complementary sensitivities.

Seismic effects of the MILROW and CANNIKIN nuclear explosions

1972 ◽  
Vol 62 (6) ◽  
pp. 1411-1423 ◽  
Author(s):  
E. R. Engdahl
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Test Site ◽  
High Gain ◽  
High Yield ◽  
Upper Crust ◽  
Seismic Effects ◽  
Underground Nuclear Explosions ◽  
Low Level ◽  
Nuclear Explosions

abstract Seismic effects of the underground nuclear explosions MILROW (October 1969, about 1 megaton) and CANNIKIN (November 1971, under 5 megatons) were monitored by a network of continuously recording, high-frequency, high-gain seismographs located on Amchitka and nearby islands. Each explosion was immediately followed by hundreds of small, discrete events (mB &lt; 4), of similar focal mechanism and with a characteristic low-frequency signature, which were apparently related to the deterioration of the explosion cavity. This activity intensified, then terminated within minutes of a large, complex multiple event and concurrent formation of a surface subsided area that signaled complete collapse of the explosion cavity (MILROW, 37 hr; CANNIKIN, 38 hr). A number of small explosion-stimulated tectonic events, apparently unrelated to the collapse phenomenon, occurred intermittently for several weeks following each explosion—near the explosion cavity and up to 13 km southeast of CANNIKIN ground zero along the Island. These events were confined to the upper crust of the Island, had characteristic high-frequency signatures, and, near the Rifle Range Fault, had focal mechanisms which could be correlated with pre-existing faulting. The evidence points to a short-term interaction of the explosions with local ambient tectonic stresses. Because these stresses are of relatively low level on Amchitka, the observed seismic effects were significantly less extensive and smaller than similar effects reported from high-yield explosions at the Nevada Test Site. Continuous monitoring of the natural seismicity of the Amchitka region since 1969 has not revealed other evidence for an interaction between either MILROW or CANNIKIN and natural tectonic processes. The structural stability and apparent low level of stress in the upper crust of Amchitka suggest that the Island effectively is seismically decoupled from the active subduction zone below.

scholarly journals Rapid clay precipitation in explosion-induced fractures

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1176-1180 ◽  
Author(s):  
Erika Swanson ◽  
Aviva Sussman ◽  
Jennifer Wilson
Keyword(s):  
Fold Increase ◽  
Data Sets ◽  
Nuclear Waste Storage ◽  
Near Surface ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Waste Storage ◽  
Fracture Opening ◽  
Chemical Explosions ◽  
Induced Fractures

Abstract Fractures within the earth control rock strength and fluid flow, but their dynamic nature is not well understood. As part of a series of underground chemical explosions in granite in Nevada, we collected and analyzed microfracture density data sets prior to, and following, individual explosions. Our work shows an ∼4-fold increase in both open and filled microfractures following the explosions. Based on the timing of core retrieval, filling of some new fractures occurs in as little as 6 wk after fracture opening under shallow (<100 m) crustal conditions. These results suggest that near-surface fractures may fill quite rapidly, potentially changing permeability on time scales relevant to oil, gas, and geothermal energy production; carbon sequestration; seismic cycles; and radionuclide migration from nuclear waste storage and underground nuclear explosions.

Full Moment Tensor Solutions of U.S. Underground Nuclear Tests for Event Screening and Yield Estimation

2021 ◽  
Author(s):  
Michael E. Pasyanos ◽  
Andrea Chiang
Keyword(s):  
Moment Tensor ◽  
Test Site ◽  
Event Identification ◽  
Nuclear Explosions ◽  
Explosion Monitoring ◽  
Yield Determination ◽  
Nuclear Tests ◽  
Chemical Explosions ◽  
Material Conditions ◽  
Full Moment Tensor

ABSTRACT Moment tensor (MT) solutions are proving increasingly valuable in explosion monitoring, especially now that they are more routinely calculated for the unconstrained, full (six component) MT. In this study, we have calculated MTs for U.S. underground nuclear tests conducted at the Nevada National Security Site using seismic recordings primarily from the Livermore Nevada Network. We are able to determine them for 130 nuclear explosions from 1970 to 1996 for a range of yields and under a variety of material conditions, which we have supplemented with 10 additional chemical explosions at the test site. The result is an extensive database of MTs that can be used to assess the performance of important monitoring tasks such as event identification and yield determination. We test the explosion event screening on the fundamental lune of the MT eigensphere and find MT screening to be a robust discriminant between earthquakes and explosions. We then explore the estimation of moment-derived yield, in which we find that material properties are the largest contributor to differences in the estimated moment-to-yield ratio. Further research conducted on this dataset can be used to develop, test, and improve various explosion monitoring methodologies.

scholarly journals HISTORICAL SEISMIC STATIONS IN USSR AND REGISTRATION UNDERGROUND NUCLEAR EXPLOSIONS

2021 ◽  
pp. 47-52
Author(s):  
K. S. Nepeina ◽  
V. A. An
Keyword(s):  
United States ◽  
Soviet Union ◽  
Test Site ◽  
The United States ◽  
Time Service ◽  
Seismic Stations ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Russian Academy Of Sciences ◽  
Academy Of Sciences

During the Cold War of the 20th century and the classification of information between the largest nuclear states the Soviet Union (USSR) and the United States of America (USA), data on the registration of nuclear explosions were not published in the reports of the Unitied Seismic Observation Service. However, underground nuclear explosions were recorded. For example, underground nuclear explosions, produced by the United States on Amchitka island, were recorded by more than 30 stations of the USSR at epicentral distances Δ ~ 8–160°. Tests at the Nevada Test Site were found especially well throughout the USSR seismic stations. As a result of processing the bulletins of registered events, checking the values with the time service, the registration parameters for the Soviet stations were destroyed. However, thanks to an employee of the laboratory 5-s of the Institute of Physics of the Earth named after O.Yu. Schmidt of the USSR Academy of Sciences Kh.D. Rubinstein is kept at the Institute for the Dynamics of Geospheres of the Russian Academy of Sciences named after Academician M.A. Sadovsky. Only after 1985 messages from some seismic stations of the former USSR began to be published in the operational reports of the Geophysical Service of the Russian Academy of Sciences. This material is intended to publish that layer of invaluable information on the registration of underground nuclear explosions, made by the United States, which has been so carefully created for decades, and has not been published anywhere at the moment.

Magnitude determination at regional and near-regional distances in the United States

1967 ◽  
Vol 57 (4) ◽  
pp. 591-639
Author(s):  
J. F. Evernden
Keyword(s):  
United States ◽  
Velocity Structure ◽  
The United States ◽  
Western United States ◽  
Eastern United States ◽  
Origin Time ◽  
Distance Data ◽  
Chemical Explosions ◽  
Low Amplitude ◽  
Magnitude Determination

abstract This report deals with the problems of variation of Pn amplitudes in the regional and near-regional distance ranges (200-2100 kilometers). The data used were recorded by Long Range Seismic Measurement vans of the VELA Seismological Center as a result of earthquakes throughout the United States and numberous nuclear and chemical explosions in the same region. It is shown that the patterns of Pn amplitudes versus Δ in Western United States and Eastern United States are markedly different and that these differences are related to different velocity structures in the two regions. These differences extend to at least 150 kilometers depth. Neither the Western United States nor Eastern United States amplitude patterns conform even approximately to that predicted or suggested by Gutenberg and Richter in the 1000-2000 kilometer range. The predicted zone of low-amplitude signals in that distance range does not exist and overestimation of magnitude by as much as 1.5 magnitude units is frequently done because of failure to properly understand the patterns of radiation. By proper calibration of the Western United States by use of numerous events, it is now possible to make consistent estimates of magnitude at all distance ranges for most explosions and earthquakes. Obtaining consistent estimates of amplitude as a function of distance for a particular event requires a knowledge of the energy distribution between the several refracted phases used between 200 and 2500 kilometers distance. Data on hand show that the energy partition function is reasonably uniform throughout the regions investigated but that locally it may vary radically, resulting in a ten-fold change in relative excitation of two refracted phases. Patterns of energy radiation and decay are probably approximately determinable from knowledge of velocity structure and vice versa. Both are best determinable from explosion data where origin time and focus are accurately known.

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