scholarly journals An evaluation of generalized likelihood Ratio Outlier Detection to identification of seismic events in Western China

1996 ◽  
Author(s):  
S.R. Taylor ◽  
H.E. Hartse
Keyword(s):  
Outlier Detection ◽  
Likelihood Ratio ◽  
Western China ◽  
Seismic Events ◽  
Generalized Likelihood Ratio

scholarly journals An evaluation of generalized likelihood ratio outlier detection to identification of seismic events in western China

1997 ◽  
Vol 87 (4) ◽  
pp. 824-831
Author(s):  
Steven R. Taylor ◽  
Hans E. Hartse
Keyword(s):  
Outlier Detection ◽  
Likelihood Ratio ◽  
High Frequency ◽  
Low Frequency ◽  
Test Site ◽  
Detection Technique ◽  
Western China ◽  
Generalized Likelihood Ratio ◽  
Event Identification ◽  
Nuclear Explosions

Abstract The generalized likelihood ratio outlier detection technique for seismic event identification is evaluated using synthetic test data and frequency-dependent Pg/Lg measurements from western China. For most seismic stations that are to be part of the proposed International Monitoring System (IMS) for the Comprehensive Test Ban Treaty (CTBT), there will be few or no nuclear explosions in the magnitude range of interest (e.g., mb < 4) on which to base an event-identification system using traditional classification techniques. Outlier detection is a reasonable alternative approach to the seismic discrimination problem when no calibration explosions are available. Distance-corrected Pg/Lg data in seven different frequency bands ranging from 0.5 to 8 Hz from the Chinese Digital Seismic Station WMQ are used to evaluate the technique. The data are collected from 157 known earthquakes, 215 unknown events (presumed earthquakes and possibly some industrial explosions), and 18 known nuclear explosions (1 from the Chinese Lop Nor test site and 17 from the East Kazakh test site). A feature selection technique is used to find the best combination of discriminants to use for outlier detection. Good discrimination performance is found by combining a low-frequency (0.5 to 1 Hz) Pg/Lg ratio with high-frequency ratios (e.g., 2 to 4 and 4 to 8 Hz). Although the low-frequency ratio does not discriminate between earthquakes and nuclear explosions well by itself, it can be effectively combined with the high-frequency discriminants. Based on the tests with real and synthetic data, the outlier detection technique appears to be an effective approach to seismic monitoring in uncalibrated regions.

Fault Detection in Linear Discrete Dynamic Systems by a Pattern Recognition of a Generalized-Likelihood-Ratio

1990 ◽  
Vol 112 (2) ◽  
pp. 276-282 ◽  
Author(s):  
S. Tanaka ◽  
P. C. Mu¨ller
Keyword(s):  
Pattern Recognition ◽  
Likelihood Ratio ◽  
Dynamic Systems ◽  
Abrupt Change ◽  
Detection Method ◽  
Discrete Dynamical System ◽  
Generalized Likelihood Ratio ◽  
Robust Detection ◽  
Chi Squared ◽  
Discrete Dynamic Systems

The detection of an abrupt change in the parameters of a linear discrete dynamical system is considered in the framework of the easily implemented generalized-likelihood-ratio (GLR) method. This paper proposes a robust detection method based on a pattern recognition of the maximum GLR provided by the conventional step-hypothesized GLR method. A numerical example demonstrates that the proposed method is highly superior to the conventional step-hypothesized GLR method and to the Chi-squared test in both detection rate and detection speed.

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