HR: 08:15h
AN: S11D-01 INVITED     [Abstracts]
TI: Precision Seismology --- Applications and Comments
AU: * Richards, P G
EM: richards@LDEO.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AB: Since {\em Quantitative Seismology --- Theory and Methods} by Aki and Richards appeared in 1980, its co-authors made major career changes that emphasized {\em applications} rather than theory. The senior author promoted integration of scientific information about earthquakes and its public transfer as the founding science director of the Southern California Earthquake Center. The junior author researched practical issues of nuclear explosion monitoring and subsequently addressed two issues using earthquake data, entailing orders of magnitude increase in precision from previous practice. Both issues have entailed the use of cross-correlation methods to find and analyze similar waveforms from extensive archives. Both are influenced by fine-scale heterogeneities in the deforming Earth. Both have involved contributions from many colleagues. The first issue, concerns observations that a systematic change in travel times has occurred for seismic waves traversing some paths through the Earth's inner core. Though claimed in 1996, and offered as evidence that the inner core has super-rotation, extraordinary claims demand extraordinary evidence. As reported in more detail by J. Zhang et al and Y. Li et al at this meeting, earthquake doublets in the South Sandwich Islands have recently been discovered to provide extraordinary evidence. The second issue, concerns the classic problem of earthquake location. It now appears that relative locations for a significant fraction of all earthquakes (in some regions, a majority) can be obtained with precision of a few hundred meters. Examples will be presented from China, the Charlevoix region of eastern Canada, the New Madrid region of the central U.S., and northern California. These two issues indicate that the successes of precision seismology largely depend upon easily searchable archives, of digital data from stations that have operated at the same site for decades.
DE: 7200 SEISMOLOGY
DE: 7207 Core and mantle
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting