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10-14 Dec. 2007:
Next AGU Fall meeting will be held at San Francisco, CA, USA

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Current research topics:
  • Finite frequency tomography

  • Tomographic images of the crust and the upper mantle beneath the southeastern Tibet are obtained from the inversion of P and S-wave traveltimes according the 3-D finite-frequency kernel formulation. P and S-wave velocity models show the presence of a low-velocity anomaly in the crust and upper mantle to ~ 300 km depth beneath a north-south trending rift zone in southeast Tibet. This low-velocity anomaly is situated above a tabular, high-dipping-angle, high-velocity anomaly that extends into the upper mantle transition zone. The Vp/Vs ratio of this high-velocity anomaly suggests that temperature variations are not the only cause and a highly melt-depleted mantle is required. These observations provide clear evidence for the delamination of a thickened Eurasian mantle lithosphere and its causal relationship to the formation of the north-south trending rift in the southeastern Tibet.

  • Ambient noise tomography

  • Coming soon.....................................................................
Former research topics:
  • Ray theory based seismic tomography

  • Tomographic images provide us with snapshots of solid-state flow in Earth's mantle and can help determine if and how slabs of subducted lithospheric plates sink into Earth's lower mantle. Seismic tomography and plate motion history are combined to investigate slabs of subducted lithosphere in the lower mantle beneath the Americas. The geometry of the subducted plates is inferred through tomographic inversion of a large number of P and S-wave traveltimes, measured from broadband seismograms using waveform cross-correlation. The plate reconstructions are used to help identify the slab fragments in the tomographic model thus obtained.

  • Sp receiver function techniques

  • The receiver function method is a well-know method for investigating the structure of the Earth's crust and upper mantle. If the receiver function Ps has become a standard tool of seismological studies over many decades and provided important results on the crust and mantle structures for most previous regional studies, it remains however an undesirable disadvantage. The main problem with this method is that possible arrivals of converted phases Ps can be masked by reverbation of crustal origin which has a slowness close to that of the Ps phases from the uppermost mantle. A solution to this problem can be avoided by using the recently developed method of Sp receiver function, which considers the converted phases Sp in stead of Ps and has the advantage of being free of multiple reflections. Here Sp receiver function technique is used to investigate characteristics of the upper mantle discontinuities beneath the Western United States.