Spectral evidence for source multiplicity in explosions: Application to regional discrimination of earthquakes and explosions

1988 ◽  
Vol 78 (5) ◽  
pp. 1773-1795
Author(s):  
Douglas R. Baumgardt ◽  
Kathleen A. Ziegler
Keyword(s):  
Simulation Studies ◽  
Nuclear Explosions ◽  
Western Norway ◽  
Cepstral Analysis ◽  
Delay Times ◽  
Individual Source ◽  
Multiple Shot ◽  
Mine Blasts ◽  
Regional Discrimination ◽  
Mine Explosions

Abstract Spectral and cepstral analysis were performed on regional-array NORESS recordings of mining explosions in Scandinavia and Russia in order to detect the effects of delayed explosions or “ripple firing” commonly used in mine-blasting practice. NORESS array-stacked spectra, corrected for instrument and noise, were computed in windows on Pn, Pg, Sn, and Lg waves from the mine blasts by averaging individual channel spectra, frequency by frequency, across the array. For comparison, spectra were also computed for six western Norway earthquakes located near the Blasjo and Titania Norwegian mines. Also, stack spectra of P coda, Sn, and Lg were computed using NORSAR seismograms for presumed peaceful nuclear explosions (PNEs) located at near-regional distances (Δ > 10°) in western Russia. The NORSAR spectra were determined in the same manner as the NORESS spectra, except that an individual source correction was applied to the spectra. Comparison of western Norway mine-blast spectra and nearby earthquakes shows that the earthquake Pn spectra are peaked in the 8- to 16-Hz band, with little energy below 6 Hz, whereas the explosion spectra have flatter spectra from 3 to 16 Hz. This difference in the Pn spectra may be caused by the earthquakes occurring at greater depths than the explosions, differences in the near-source media, or source mechanism effects in the earthquake spectra. The main difference between earthquake and explosion spectra is that the explosion spectra exhibit marked scalloping or modulation patterns not observed in the earthquake spectra. The modulation patterns are identical in spectra of all phases, indicating that they are caused by multiple-shot sequences or ripple firing. Simulated multiple-source spectra, determined using the NORESS seismograms for one of the western Norway earthquakes, resulted in spectra that resembled many of the explosion modulation patterns. Based on the simulation studies and cepstral analysis of the spectra, the mine explosions appear to be composed of two to three separate explosions delayed by between 80 to 150 msec. Moreover, the NORSAR spectra of PNEs indicate that these signals are also produced by multiple explosions, although they have larger delay times of between 0.9 to 1.5 sec. These results show that spectral modulations in seismogram spectra of economic explosions, including mine explosions and nuclear explosions fired for peaceful, economic purposes, can be used to distinguish them from earthquakes and nuclear-explosion weapons tests.

Spectral characteristics of regional phases recorded at Noress

1988 ◽  
Vol 78 (2) ◽  
pp. 708-725
Author(s):  
Anne Suteau-Henson ◽  
Thomas C. Bache
Keyword(s):  
Soviet Union ◽  
Nuclear Explosion ◽  
Spectral Characteristics ◽  
Low Frequency ◽  
Spectral Ratio ◽  
Spectral Ratios ◽  
Data Set ◽  
Nuclear Explosions ◽  
The Soviet Union ◽  
Mine Blasts

Abstract The spectral characteristics of Pn and Lg are studied for regional events recorded at the NORESS array in Norway. The emphasis is on the potential value of spectral ratios for identifying events as earthquake, chemical explosions, and nuclear explosions. The events studied include a suite of explosions from the Titania Mine in southwest Norway, a suite of events of unknown source type from a site offshore about 90 km from this mine, suites of explosions from several mines in the Soviet Union about 1000 km from NORESS, events from several locations along the 90° azimuth from NORESS, an apparent earthquake in the North Atlantic, and a nuclear explosion (PNE) at a range of 1560 km. The event identification issues addressed are as follows: (1) Can earthquakes and explosions be identified based on the ratio of high- and low-frequency energy in their signal spectra? (2) Do spectral ratios separate mine blasts from earthquakes for all source areas? (3) Will spectral ratio discriminants be effective for identifying decoupled underground nuclear explosions? We conclude that spectral ratios can sometimes separate events. An example is separation of the Titania mine blasts from the events at the nearby offshore locations, although we cannot be sure how much this is due to path differences. However, in general, spectral ratios vary as much within classes of events as they do among different classes. The PNE in our data set allows the simulation of spectra from a decoupled nuclear explosion by simply applying the frequency-dependent decoupling factor to the observed Pn spectrum for this event. After applying a distance correction, the spectrum for this simulated decoupled nuclear explosion is similar to those for the Soviet Union mine blasts in our data set.

Seismic radiation patterns of mine blasts

2021 ◽  
Author(s):  
Florian Bleibinhaus ◽  
Bernd Trabi
Keyword(s):  
Iron Ore ◽  
Reduction Potential ◽  
Homogeneous Model ◽  
Elastic Model ◽  
Radiation Patterns ◽  
Iron Ore Mine ◽  
Delay Times ◽  
Seismic Vibrations ◽  
Sensitive Structure ◽  
Mine Blasts

<p>Seismic vibrations induced by mine blasting are often a nuisance to residents and may even threaten the integrity of sensitive structure in the vicinity of mines. In this study we investigate the potential to reduce such vibrations through the interference with a second blast sequence. Assuming perfectly repeatable source wavelets and an acoustic, homogeneous model, we predict the radiation patterns of blast sequences with the Fourier shift theorem as a function of azimuth and incidence, and we benchmark those predictions with observations from a seismic array deployed at the iron ore mine Mt Erzberg, Austria. We then use our model to optimize the delay times of blast sequences with an inverse algorithm geared towards minimizing the predicted vibrations in certain target zones. Due to its symmetry, a single row of blasts has no azimuthal reduction potential. A second, quasi-simultaneous mine blast can, however, reduce blast-induced vibrations by up to 20% according to our model. In this study, we discuss the principles and the potential of this approach to vibration reduction. In a second study, we will present applied results obtained with a fully elastic model.</p>

Crust and upper mantle structure in the northwest Basin and Range province

1982 ◽  
Vol 72 (3) ◽  
pp. 911-923
Author(s):  
Keith F. Priestley ◽  
Alan S. Ryall ◽  
Glenn S. Fezie
Keyword(s):  
Great Basin ◽  
Seismic Waves ◽  
Mono Lake ◽  
Low Velocity ◽  
Basin And Range Province ◽  
Crust And Upper Mantle ◽  
Nuclear Explosions ◽  
Upper Mantle Structure ◽  
Delay Times ◽  
Broad Region

abstract Seismic waves from nuclear explosions and from well-located local earthquakes have been recorded along several profiles through western Nevada, southeast Oregon, and eastern California. Pn delay times from these data and from additional travel times of NTS explosions recorded across the western Nevada seismic network have been interpreted in terms of varying crustal thickness of the western Great Basin. Our interpretation of these data implies that the crust thins from greater than 32 km thick in the vicinity of Mono Lake to 20 to 22 km thick over a broad region in northwest Nevada. The Pn headwave propagates to a distance of about 550 km with a velocity of 7.8 km/sec. At distances greater than 600 km a low velocity (7.44 km/sec), larger amplitude phase is observed. This phase may result from long-period energy diffracting into a shadow zone. A prominent, high-velocity second arrival following Pn by 1 to 2 sec in the distance range 340 to 475 km, is interpreted as a reflection from the base of the lithosphere at 60 to 70-km depth.

Ultraviolet Absorption of Refractory Elements by a Dual Laser Plasma Method

1988 ◽  
Vol 102 ◽  
pp. 243-246
Author(s):  
J.T. Costello ◽  
W.G. Lynam ◽  
P.K. Carroll
Keyword(s):  
Absorption Spectra ◽  
Laser Plasma ◽  
Optical Pulse ◽  
Ionic Species ◽  
Neutral Species ◽  
Plasma Method ◽  
Plasma Technique ◽  
Refractory Elements ◽  
Delay Times ◽  
Dual Laser

AbstractThe dual laser-produced plasma technique for the study of ionic absorption spectra has been developed by the use of two Q-switched ruby lasers to enable independent generation of the absorbing and back-lighting plasmas. Optical pulse handling is used in the coupling cicuits to enable reproducible pulse delays from 250 nsec. to 10 msec, to be achieved. At delay times > 700 nsec. spectra of essentially pure neutral species are observed. The technique is valuable, not only for obtaining the neutral spectra of highly refractory and/or corrosive materials but also for studying behaviour of ionic species as a function of time. Typical spectra are shown in Fig. 1.

Delayed Auditory Feedback with Different Delay Times at Each Ear

1964 ◽  
Vol 7 (4) ◽  
pp. 369-371
Author(s):  
Samuel Fillenbaum
Keyword(s):  
Delay Interval ◽  
Auditory Feedback ◽  
Normal Subjects ◽  
Delayed Auditory Feedback ◽  
Delay Times

Binaurally asynchronous delayed auditory feedback (DAF) was compared with synchronous DAF in 80 normal subjects. Asynchronous DAF (0.10 sec difference) did not yield results different from those obtained under synchronous DAF with a 0.20 sec delay interval, an interval characteristically resulting in maximum disruptions in speech.

Benefits from Computerized Adaptive Testing as Seen in Simulation Studies

1999 ◽  
Vol 15 (2) ◽  
pp. 91-98 ◽  
Author(s):  
Lutz F. Hornke
Keyword(s):  
Measurement Error ◽  
Computerized Adaptive Testing ◽  
Test Procedure ◽  
Adaptive Testing ◽  
Parameter Estimates ◽  
Simulation Studies ◽  
Computerized Adaptive Test ◽  
Item Banks ◽  
Item Parameters ◽  
General Reliability

Summary: Item parameters for several hundreds of items were estimated based on empirical data from several thousands of subjects. The logistic one-parameter (1PL) and two-parameter (2PL) model estimates were evaluated. However, model fit showed that only a subset of items complied sufficiently, so that the remaining ones were assembled in well-fitting item banks. In several simulation studies 5000 simulated responses were generated in accordance with a computerized adaptive test procedure along with person parameters. A general reliability of .80 or a standard error of measurement of .44 was used as a stopping rule to end CAT testing. We also recorded how often each item was used by all simulees. Person-parameter estimates based on CAT correlated higher than .90 with true values simulated. For all 1PL fitting item banks most simulees used more than 20 items but less than 30 items to reach the pre-set level of measurement error. However, testing based on item banks that complied to the 2PL revealed that, on average, only 10 items were sufficient to end testing at the same measurement error level. Both clearly demonstrate the precision and economy of computerized adaptive testing. Empirical evaluations from everyday uses will show whether these trends will hold up in practice. If so, CAT will become possible and reasonable with some 150 well-calibrated 2PL items.

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