Download Volume II Accomplisments (28 Mb pdf). - IRIS
Download Volume II Accomplisments (28 Mb pdf). - IRIS
Download Volume II Accomplisments (28 Mb pdf). - IRIS
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
The Plume-slab Interaction beneath Yellowstone Revealed by<br />
Multiple-frequency Tomography<br />
Yue Tian (Princeton University (now at Chevron), USA), Ying Zhou (Virginia Tech, USA), Karin Sigloch (Ludwig-<br />
Maximilians-Universität, Germany), Guust Nolet (Université de Nice/Antipolis, France), Gabi Laske (University of<br />
California, San Diego, USA)<br />
S-velocity structure under the Yellowstone region is obtained from multiple-frequency tomography of a mixed data set of<br />
shear waves and Love waves. In this study, we used a total of 211440 data measurements measured from 36344 seismic waveforms,<br />
and over 95% of the waveforms are from <strong>IRIS</strong>. A strong slow anomaly (Y0) with large velocity gradient is observed under<br />
the Yellowstone Caldera (Figures 1-2), reaching ~200 km depth. Y0 connects to a slow anomaly (Y1) in the transition zone,<br />
which is centered at ~1° north of Y0 (Figure 2AA’). To the southwest, Y0 abuts a belt of strong slow anomalies (SR0) under the<br />
eastern Snake River Plain. Down in the lower mantle, a plume-shaped conduit (Y2) is observed with its top directly under Y1.<br />
The plume comes from south, tilting ~40° from vertical, reaches as deep as 1500 km, but spreads out at 700–1100 km depth.<br />
The spreading of SR2 can be explained either if the 660-km discontinuity acts as a barrier, or if the slab fragment S1 [Sigloch et<br />
al., 2008; Tian et al., 2009] acts as a barrier for the uprising Y2 (Figure 1b). Y2 might have distorted in two ways in response to<br />
the barrier. Part of Y2 might have navigated its path around S1 and found its way up through the slab gap, and the other part of<br />
Y2 might have smeared southwestward along the base of S1 and formed SR2. Though much of this explanation is speculative,<br />
it is clear that we witness a complex interaction between upwellings and downwellings in this part of the mantle. The very high<br />
resolution we obtained under the Yellowstone region would not be possible without the USArray, one of the densest networks<br />
in the world. The eastward movement of the USArray will make it possible to image detailed structure under the central and<br />
eastern US with similar resolution.<br />
References<br />
Sigloch, K., N. McQuarrie, and G. Nolet (2008), Two-stage subduction history under North America inferred from finite-frequency tomography,<br />
Nature Geoscience, 1, 458–462.<br />
Tian, Y., K. Sigloch, and G. Nolet (2009), Multiple-frequency SH-wave tomography of the western U.S. upper mantle, Geophys. J. Int., 178,<br />
1384–1402.<br />
Acknowledgements: NSF grants EAR-0309298, EAR-0105387, and EAR-0809464.<br />
Figure 1. Three-dimensional view of the plume-slab interaction system under<br />
the Yellowstone and the eastern Snake River Plain, looking from the southwest.<br />
The green triangle represents the location of the Yellowstone Caldera. a: Slow<br />
anomalies only. b: Superimposing the fast anomalies on top of the slow anomalies.<br />
Labels S1, N1, S2, N2, SG identify the same subduction structure as in<br />
Sigloch et al. [2008] and Tian et al. [2009].<br />
Figure 2. Great-circle cross sections of the velocity structure under the<br />
Yellowstone Caldera (YC) and the eastern Snake River Plain (SRP). The black dot<br />
and 0° represent the location of the Yellowstone Caldera and the mid-point of<br />
the great circle arc. In the cross-section views, each grid along the arc represents<br />
1°. Labels S1, S2, N2, SG identify the same subduction structure as in Sigloch et<br />
al. [2008] and Tian et al. [2009].<br />
2010 <strong>IRIS</strong> Core Programs Proposal | <strong>Volume</strong> <strong>II</strong> | Upper Mantle Structure and Dynamics | <strong>II</strong>-215