Accession Number : ADP204507

Title :   Regional Small-Event Identification Using Seismic Networks and Arrays,

Corporate Author : SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA INST OF GEOPHYSICS AND PLANET ARY PHYSICS

Personal Author(s) : Hedlin, Michael A. ; Vernon, Frank L. ; Minster, J. B. ; Orcutt, John A.

PDF Url : ADP204507

Report Date : 14 AUG 1995

Pagination or Media Count : 11

Abstract : In view of the importance of small seismic events to a monitored CTBT we have begun a survey of globally distributed regional seismic recordings of eatthquakes, quarry blasts and explosions with m sub b is approximately 2.5. The first goal of this project is to test the effectiveness of our automated time-frequency discriminant (ATFD) at distinguishing quarry blasts from single explosions and earthquakes using regional array and network recordings. We intend to use these data to develop and test enhancements of the technique and develop complementary discriminants for use when the ATFD proves to be ineffective. As part of this program we intend to determine if a low frequency spectral signature (perhaps caused by source finiteness) might be used for discrimination at far-regional distances. We will analyze these waveforms using the standard multi-taper estimation technique and a new wavelet based technique that will allow us to process 3-component data and analyze the evolution of spectral amplitude and polarization with time and frequency. The ATFD uses a binary sonogram which is derived from the original, spectral, sonogram by the application of filters which replace local spectral information with a binary code which simply reflects local spectral highs and lows. The ATFD calculates a two-dimensional Fourier transform of the binary sonogram which reveals the dependence of the binary pattern on frequency and time. In view of its resemblance to the cepstrum (which identifies periodicities in single spectra), and the fact that it is derived from onset and coda phases we refer to it as the coda cepstrum. We are currently working on an adaptive coda cepstrum which iteratively solves for filters that are optimal for extracting any time-independent pattern that exists in the sonogram of an individual event.

Descriptors :   *SEISMIC DETECTION, *SEISMIC WAVES, *ARMS CONTROL, *NUCLEAR EXPLOSION DETECTION, *SEISMIC DISCRIMINATION, FOURIER TRANSFORMATION, SOFTWARE ENGINEERING, SYMPOSIA, AUTOMATION, VERIFICATION, MONITORING, UNDERGROUND EXPLOSIONS, RECORDING SYSTEMS, EARTHQUAKES, CROSS CORRELATION, SEISMOLOGICAL STATIONS, SPECTRUM SIGNATURES, CEPSTRUM TECHNIQUE.

Subject Categories : Government and Political Science
      Seismology
      Seismic Detection and Detectors
      Nuclear Weapons

Distribution Statement : APPROVED FOR PUBLIC RELEASE