Seismic discrimination between earthquakes and explosions in the Middle East and North Africa

Conference · Tue Jul 01 04:00:00 EDT 1997

OSTI ID:610742

Walter, W R; Harris, D B; Myers, S C

The recently signed Comprehensive Test Ban Treaty provides for an international network of primary and auxiliary seismic monitoring stations (IMS) to verify its compliance. Calibration is required to confidently use these stations to identify and discriminate between earthquakes, mine-related events and clandestine nuclear explosions, particularly for small to moderate seismic events recorded regionally at only a few stations. Given the lack of regional recordings of underground nuclear tests in most of the world, we are making use of mining and industrial explosions to test discriminants. For example we use the Multimax compiled dataset of small earthquakes and quarry explosions in Israel to test regional discriminants at local distances with mixed results. Further complicating calibration is the fact that many INK sites have not yet been installed and others have very short operating histories. When IMS data is available, there is often a lack of independent information (ground truth ) on the seismic sources. Here we describe a procedure for calibrating stations with limited data and apply it to the IMS auxiliary station MDT in Morocco. Data was initially available for three months in 1990 when MDT was operated as part of MEDNET. An event detector was run over the continuous data and regional events identified and roughly located using S-P time and back azimuth. The procedure uses spatial and temporal clustering to identify ''known'' mine blasts. The spatial clustering is done using the waveform correlation technique of Harris (1991) to find events with similar sources and locations. Temporal clustering looks at the time of day and repetition in time of events with the mine blasts occurring during working hours and days repeatedly over a period of time. A set of ''known'' earthquakes is also determined using location, time of day, distribution in time and size criteria. With these independent libraries of identified seismic events, we evaluate promising regional discriminants such as high frequency P/Lg. We also examine distance and path effects on the discriminants. Preliminary results indicate high frequency P/Lg provides some separation between mine blasts and earthquakes at MDT.

• Research Organization: Lawrence Livermore National Lab., CA (US)
• Sponsoring Organization: USDOE, Washington, DC (US)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 610742
• Report Number(s): UCRL-JC--127898; CONF-970967--; ON: DE98051132
• Country of Publication: United States
• Language: English

Related Subjects

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
58 GEOSCIENCES
AFRICA
CALIBRATION
COMPLIANCE
DISTRIBUTION
EARTHQUAKES
EXPLOSIONS
MIDDLE EAST
MINING
MONITORING
NUCLEAR EXPLOSION DETECTION
NUCLEAR EXPLOSIONS
SEISMIC DETECTION
SEISMIC EVENTS
SEISMIC SOURCES
WAVE FORMS