Generalized Radon Transform Imaging of the Lowermost Mantle Beneath East Asia With ScS and SKKS Waveform Data
Abstract
In earlier studies we developed generalized Radon transforms of ScS and SKKS data (separately) to image the lowermost mantle beneath Central America (Wang et al., JGR, 2006; Van der Hilst et al., Science, 2007; Wang et al., GJI, 2008). These GRTs map broad-band seismogram windows -- comprising the main arrivals and their coda and precursors -- into images that reveal multiple, piece-wise continuous (and statistically significant) interfaces in the lowermost mantle. Since the quality of the GRT imaging operator depends on the range of scatter angles sampled by the data, joint inversion of top-side (ScS) and under- side (SKKS) data would vastly increase the resolution of scatter interfaces. Therefore, as a logical follow- up of our earlier work, we developed a joint generalized Radon transform (GRT) of ScS and SKKS data for high resolution D" imaging in CMB regions well sampled by both ScS and SKKS. Once such region is Central America, but we have also started exploration of the core-mantle boundary region beneath East Asia. Global S and P wave (travel time) tomography (e.g. Li et al, GGG, 2008) reveals a large (seismically) faster-than-average structure in the lowermost mantle beneath East Asia. This structure, which is probably related to ancient episodes of subduction of oceanic lithosphere beneath mainland Asia, the western Pacific island arcs, and Indochina, is densely sampled both by ScS and SKKS waves. Based on data coverage and the tomographically inferred structures, we selected data associated with CMB reflection points in the region from 20°-60°N and 60°-130°E. We process ~380,000 ScS and ~260,000 SKKS data from ~9,000 earthquakes (mb > 5.0) recorded at one or more of a total of ~4,500 receivers. We will discuss the joint inversion and present preliminary 2D (and perhaps 3D) images of the D" region beneath Asia, which reveal very strong D" heterogeneity.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMDI31C1815S
- Keywords:
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- 0540 Image processing;
- 0545 Modeling (4255);
- 7203 Body waves;
- 7207 Core (1212;
- 1213;
- 8124);
- 7208 Mantle (1212;
- 1213;
- 8124)