Feasibility of monitoring continuous-wave sources with seismic arrays

Abstract

s r!This paper identifies and explores the technical requirements and issues associated with remotely monitoring continuous wave (CW) sources with seismic arrays. Potential approaches to this monitoring problem will be suggested and partially evaluated to expose the monitoring challenges which arise when realistic local geologies and cultural noise sources are considered. The selective directionality and the adaptive noise cancellation properties of arrays are required to observe weak signals while suppressing a colored background punctuated with an unknown distribution of point and sometimes distributive sources. The array is also required to characterize the emitters and propagation environment so as to properly focus on the CW sources of interest while suppressing the remaining emitters. The proper application of arrays requires an appreciation of the complexity of propagation in a non-homogeneous earth. The heterogeneity often limits the available spatial coherence and therefore the size of the army. This adversely impacts the array gain and the array's ability to carefully resolve various emitters. Arrays must also contend with multipath induced by the source and the heterogeneous earth. If the array is to focus on an emitter and realize an enhancement in the signal to noise ratio, methods must be sought to coherently add the desired signal components while suppressing interference which may be correlated with the desired signal. The ihpact of these and other issues on army design and processing are described and discussed.

<title>Seismic and acoustic signal identification algorithms</title>

“…Downloaded From: http://proceedings.spiedigitallibrary.org/ on 10/05/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx 5. Figure 5 Flow diagram for state change (non-stationary process) detection and persistence test.…”

“…There has been considerable interest in using seismic and acoustic sensors to detect and identify continuous wave (CW) sources [1]{2] [3][4] [5]. This paper addresses the challenge of monitoring such sources within a seismic environment having limited interfering sources and under the constraint that the algorithm runs in real-time in an unattended ground sensor system and extends the techniques discussed in [4].…”

<title>Using array processing to isolate seismic signals from noise and interferers of cultural origin</title>

“…In pursuit of the above objectives, we mounted geophones on the interior walls of an underground concrete vault. The vault facilitated the use of three-dimensional anays [1]. Figure 1 depicts the major features of that vault.…”

“…This section discusses these benefits in more detail. 1 . IncoherentNoise Attenuation Consider the summation of the output of N sensors when the sensors record a single coherent signal in the presence of spatially incoherent Gaussian noise.…”