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The value of auxiliary stations and the need for network calibration

Description: To address the question of the value of auxiliary stations placed before the GSE by the Ad Hoc Committee on Nuclear Test Ban, we examined the published location error estimates given by both the NEIS and the IDC. The results of our analysis demonstrate the well-known principle that the uncertainty in the location for a given event decreases as the number of defining phases (or stations) increases and as the azimuthal coverage increases. More importantly, however, the results also show that the location uncertainty dramatically decreases as the distance to the nearest station decreases. We also show that the empirically observed rate of overlap of corresponding IDC and NEIS error ellipses is inconsistent with expectation as determined by statistically modeling the performance of each. To overcome this shortcoming the IMS must be calibrated.
Date: February 1, 1996
Creator: Denny, M.
Partner: UNT Libraries Government Documents Department

Seismic results from DOE`s non-proliferation experiment: A comparison of chemical and nuclear explosions

Description: The basic results from the US Department of Energy`s (DOE`s) NonProliferation Experiment (NPE) for seismic signal generation are that the source function for a chemical explosion is equivalent to that of a nuclear explosion of about twice the yield and that the seismic moment measurements are consistent between freefield, local, and regional measurements. In addition, evidence was found that Pn in the Basin and Range province of the western United States is a turning ray and is simply proportional to the source function while the transfer functions for Pg and Lg are low-pass in nature.
Date: January 1, 1995
Creator: Denny, M.; Goldstein, P.; Mayeda, K. & Walter, W.
Partner: UNT Libraries Government Documents Department

The source depth of burial experiment at Shagan River, Kazakstan

Description: The seismic field experimentation team at Los Alamos National Laboratory collaborated with Lawrence Livermore, the Defense Special Weapons Agency (DSWA) and the National Nuclear Center of the Republic of Kazakstan to record the Source Depth of Burial Experiment during the summer of 1997. A series of three 25 ton explosions at depths of 50, 300 and 550 meters along with associated 50 to 100 kg Green`s function explosions and a 5 ton proof of concept explosion were instrumented at near source (0.1 to 20 km) and regional distances (100 to 1,100 km) using portable seismic data acquisition equipment. The near source data represent the first US recordings of seismic data at the former Soviet Union`s Semipalatinsk nuclear test site. The main objective of the Depth of Burial Experiment was to test whether source depth can help identify underground nuclear explosions from observations at distance ranges of 100--1,000 km. A secondary objective was to help calibrate the Kazakstan seismic network, especially the primary IMS station at Makanchi and the auxiliary IMS stations at Kurchatov and Aktyubinsk. Near-source records show the 50 m deep explosion generated much higher amplitude surface (R{sub g}) waves than did either of the deeper explosions. Impulse P-wave arrivals dominated the traces from the 300 and 550 meter deep explosions. P-wave amplitudes, 10--20 Hz, appeared to be a stronger function of source than of path or site. Apparent P velocity was highly path dependent, with higher velocities parallel to the local, NW-SE fabric of the geologic structure. Empirical Green`s function results for the 25 ton shots show increasing corner frequency with depth, consistent with predictions of the Mueller-Murphy source model.
Date: December 31, 1998
Creator: Pearson, D.C.; Phillips, W.S.; Glenn, L.A. & Denny, M.D.
Partner: UNT Libraries Government Documents Department

Recent applications of bandpass filtering

Description: Bandpass filtering has been applied recently in two widely different seismic applications: S.R. Taylor and A.A. Velasco in their source-path amplitude-correction (SPAC) algorithm and N.K. Yacoub in his maximum spectral energy algorithm for picking teleseismic P-wave arrival times. Though the displacement spectrum is the intermediate product in both cases, the filters and scaling corrections used to estimate it are entirely different. They tested both and found that the scaling used by Taylor and Velasco worked in all cases tested whereas Yacoub's did not. They also found that bandpass filtering as implemented by Taylor and Velasco does not work satisfactorily; however, the Gaussian filter used by Yacoub does work. The bandpass filter of Taylor and Velasco works satisfactorily when the results are centered in the band; however, a comb filter with the same number of poles and zeros as the bandpass used by Taylor and Velasco works better than the bandpass filter.
Date: March 15, 1999
Creator: Denny, M D
Partner: UNT Libraries Government Documents Department

Seismic-source corner frequencies from the depth of burial experiment

Description: The results from the depth of burial experiment (DOB) are consistent with cube-root scaling and with previous observations that the source corner frequency for underground explosions increases with depth. The corner frequencies, however, were overpredicted by Mueller and Murphy (1971) and underpredicted by Denny and Johnson (1991).
Date: November 23, 1998
Creator: Denny, M.D.
Partner: UNT Libraries Government Documents Department

A Mining/Contained Explosion Source Phenomenology Experiment to Improve Nuclear Test Monitoring

Description: We propose an experiment to investigate the similarities and differences in source phenomenology and regional seismic discriminant behavior between normal production mining explosions and fully contained nuclear tests. The experiment would consist of a minimum of two large, nearly co-located explosions, which would be recorded at regional distances: (1) a normal delay fired production mining explosion, and (2) a single chemical explosion contained and buried at underground nuclear test depth.
Date: January 13, 2000
Creator: Walter, W.R.; Denny, M.; Pearson, C. & Myers, S.
Partner: UNT Libraries Government Documents Department