Evaluation of Seismic-Acoustic Analysis Methods for a Real-time UXO Monitoring System

Abstract

The Department of Defense (DoD) uses over two million rounds of high-explosive (HE) munitions per year ( Defense Science Board Task Force, 2003 ). A small percentage does not explode, thus generating unexploded ordnance (UXO) in current range areas at a substantial rate. As these ranges are closed, the DoD becomes responsible for the environmental restoration of the affected properties. Current methods of UXO remediation are costly because of high false alarm rates. Our current research is to develop a complementary technology that will alleviate false alarm rate by detecting, classifying, and locating UXO in near real time (less than 1 minute) as a munition impacts the range. This technology will utilize an array of buried seismic sensors in a calibrated range area, along with a set of algorithms based on theoretical and applied seismology and statistical analysis. Initial field tests at three sites focused on developing concepts of the seismic and acoustic location of ordnance impacts. Our research program developed from these initial field tests has four primary objectives: 1) fully implement a wired seismic-acoustic ordnance impact location system for live fire ranges; 2) develop a system capability to discriminate high-order (HE), low-order (partially exploded), and zero-order (UXO) events; 3) reduce location error to a stringent program metric of 1–2 m; and 4) investigate the feasibility of developing a wireless implementation of the technology. This paper describes the procedures and results from follow-on tests that were conducted in two locations at the U.S. Army Aberdeen Proving Ground (APG), Maryland. These tests were used to evaluate potential seismic-acoustic methods and system configurations for a Seismic-Acoustic Impact Monitoring Assessment (SAIMA) system for mitigating UXO hazards. Significant results from this work include: 1) seismic impulses from low-order impacts were detected at distances up to 1,000 meters; 2) classification features based on measurements of the amplitude of acoustic and seismic phases produce clear discrimination between HE and UXO impacts; 3) calculated location solutions for HE and UXO impacts yield an average location error of 10–20 meters; and 4) empirical observation and waveform modeling demonstrated that surface waves dominate the signal at all distances and therefore should be the primary phase used for all components of analysis. Furthermore, these tests demonstrated the current system design, allowing further enhancements, is capable of meeting the initial research objectives (1) and (2). Future research will focus on improving system performance with refinement of the sensor-layout geometry and the detection and location algorithms through system error analyses and follow-on field testing.