Crustal Effects on Regional Seismic Phases in Aseismic Regions of Northern Eurasia: Constraints From PNE Recordings
WYOMING UNIV LARAMIE DEPT OF GEOLOGY AND GEOPHYSICS
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The University of Wyoming database of seismic recordings of Peaceful Nuclear Explosions PNEs has been recently extended to 19 PNEs recorded along 7 long-range refractionreflection profiles QUARTZ, CRATON, KIMBERLITE, RIFT, METEORITE, and RUBY 2 lines. These profiles form a grid traversing the East European Platform, the Ural Mountains, the West Siberian Basin, the Baikal Rift, and the Siberian craton in two directions,., and include dense and reversed linear as well as fan PNE recordings RUBY. Dense, 3-component recordings along subparallel and crossing profiles provide us with unique opportunities to study large-scale propagation effects of regional seismic phases, allow detailed examination of the regional seismic phases, correlation between the individual PNE records and with geologic and tectonic features. In this report, we extend traditional, travel-time analysis of PNE arrivals to amplitude and waveform inversion and show how short-period PNE recordings are used to constrain the effects of crustal structure on seismic arrivals within 1000 - 3000 km ranges. These new constraints include 1 characterization of crustal attenuation through coda measurements and 2 imaging of the crustal structure using receiver function techniques. Both of these factors are of primary importance for modeling of crustal-guided phases, such as the Pg and Lg, Energy-balance considerations in three dimensions show that an extensive coda is inherent to all P-wave phases. This coda can be explained by crustal scattering and is a result of effectively areal excitation of short-period scattered waves Pg, Sg, Lg, Rg within the crust by the waves incident from the mantle, or, conversely, by generation of mantle phases from crustal-guided waves within a distributed source region. The resulting estimates of coda Q range between Q380 near 2 Hz and Q430 around 5 Hz and can be associated with crustal attenuation.
- Computer Programming and Software
- Seismic Detection and Detectors