Surface-wave calibration studies for improved monitoring of a CTBT

Conference · Thu Dec 31 04:00:00 EST 1998

OSTI ID:314144

Patton, H J; Jones, L E

Seismic calibration of the International Monitoring System (IMS) and other key monitoring stations is critical for effective verification of a Comprehensive Test Ban Treaty (CTBT). Detection, location, and identification all depend upon calibration of source and path effects to ensure maximum efficiency of the IMS to monitor at small magnitudes. This project gathers information about the effects of source and propagation on surface waves for key monitoring areas in central Asia with initial focus on western China. Source calibration focuses on surface-wave determinations of focal depth and seismic moment, M{sub o}, for key earthquakes, which serve as calibration sources in location studies and for developing regional magnitude scales. The authors present a calibration procedure for Lg attenuation, which exploits an empirical relationship between M{sub o} and 1-Hz Lg amplitude for stable and tectonic continental regions. The procedure uses this relationship and estimates of M{sub o} to predict Lg amplitudes at a reference distance of 10 km from each calibrated source. Path-specific estimates of Q{sub o} in the power-law formula of Q (Q = Q{sub o}f{sup {zeta}}) are made using measurements of 1-Hz Lg amplitudes observed at the station and amplitudes predicted for the reference distance. Nuttli`s formula for m{sub b}(Lg) is thus calibrated for the source region of interest, and for paths to key monitoring stations. Path calibration focuses on measurement of surface-wave group velocity dispersion curves in the period range of 5 to 50 s. Concentrating on the Lop Nor source region initially, they employ broadband data recorded at CDSN stations, regional event (M > 4.0), and source-receiver path lengths from 200 to 2000 km. Their approach emphasizes path-specific calibration of key stations and source regions and will result in a family of regionally appropriate phase-match filters, designed to extract fundamental mode surface-wave arrivals for each region of interest. They characterize and quantify regional variability in surface wave dispersion measurements by creating slowness residual maps for a given period and set of paths, and by performing variogram analysis by wave type (Love and Rayleigh Waves), wave period, and station. Results from the slowness residual maps yield point measurements which form the raw input for kriged correction surfaces appropriate to specific source regions. The variogram analysis yields correlation lengths used for smoothing in the kriging process.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 314144
• Report Number(s): LA-UR--98-3077; CONF-980920--; ON: DE99001832
• Country of Publication: United States
• Language: English

Related Subjects

35 ARMS CONTROL
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
CALIBRATION
NUCLEAR EXPLOSION DETECTION
NUCLEAR WEAPONS
SEISMIC DETECTION
SEISMIC SOURCES
SEISMIC SURFACE WAVES
TESTING
TREATIES
WAVE PROPAGATION