Improved Characterization of Far-Regional and Near-Teleseismic Phases Observed in Central Asia
Final rept. 2 Nov 2005-30 Apr 2010
WESTON GEOPHYSICAL CORP LEXINGTON MA
Pagination or Media Count:
The early body-wave coda of far-regional events 14 - 29 degrees contains triplicated arrivals from upper-mantle discontinuities that could potentially improve seismic monitoring capabilities. However, far-regional seismograms are typically under-utilized in location and magnitude estimation because path-specific heterogeneity and multiple phase interactions make the arrival suite difficult to interpret accurately. In this report we present a set of techniques that were developed to improve phase characterization and identification at these distances. We have applied our techniques to data from two arrays in Kazakhstan MKAR Makanchi and KKAR Karatau, both of which record far-regional events throughout south-central Asia. Our techniques include improved array processing methods e.g., phase-coherence semblance stacking to characterize arrival time, back-azimuth and slowness of individual phases within the P-coda arrival suite, and methods to more accurately identify the measured arrivals e.g., -p transformation and clustering analysis to determine wavefield templates.