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P- and S-velocity models for the western US

Model highlights: In these first models of the DNA series, the shallow depth extent of the Juan de Fuca subduction system is imaged with a low velocity "slab window" to the south of the Mendocino Triple Junction. Beneath Yellowstone, a low velocity conduit dips to the northeast. The model uses Earthscope data up to October 2007 and the coverage therefore extends from the Pacific coast to the mid-Rocky Mountains (~110 deg W).


Model specifications:

  • Parameters: DNA07-P and DNA07-S are P- and S-velocity models
  • Coverage: Stations available cover the region from the Pacific coast to the Rocky Mountains (110 deg W), from the Mexican boarder (31 deg N) to the Canadian boarder (49 deg N).
  • Data source: More than 600 stations were used from the USArray transportable array, regional seismic networks, and temporary seismic deployments.
  • Data type: Relative traveltimes of teleseismic body waves (P, S and SKS) are used to constrain the model.
  • Inversion: The matrix is constructed using ray-theory and inverted using LSQR with appropriate damping and smoothing.
  • Resolution: The model can resolve mantle structure to a depth of ~750km and with a lateral and vertical resolution of ~200km.

Xue, M., R.M. Allen. Mantle Structure Beneath the Western US and its Implications for Convection Processes. J. Geophys. Res. in press.

We present tomographic images of the mantle structure beneath the western USA. Our Dynamic North America Models of P- and S-velocity structure (DNA07-P and DNA07-S) use teleseismic body-waves recorded at ~600 seismic stations provided by the Earthscope Transportable Array and regional networks. DNA07-P and -S benefit from the unprecedented aperture of the network while maintaining a dense station distribution providing high-resolution body-wave imaging of features through the transition zone and into the lower mantle. The main features imaged include (1) the Juan de Fuca subduction system that bottoms at ~400 km beneath Oregon, implying interaction with the Yellowstone anomaly; (2) a low velocity conduit beneath Yellowstone National Park that bottoms at ~500 km and dips towards the northwest; (3) shallow low velocity anomalies (upper 200 km) beneath the eastern Snake River Plain (ESRP) and the High Lava Plains, and a deep low velocity anomaly (>600km) beneath the ESRP but not Newberry; (4) a low velocity "slab gap" to ~400 km depth immediately south of the Mendocino Triple Junction and south of the Gorda slab; and (5) high velocity "drips" beneath the Transverse Ranges, the southern Central Valley/Sierra Nevada, and central Nevada. These observations reveal extremely heterogeneous mantle structure for the western USA and suggest we are only just beginning to image the complex interactions between geologic objects. The transportable array allows for analysis of the relationships between these anomalies in an internally consistent single tomographic model. The DNA07 velocity models are available for download and slicing at http://dna.berkeley.edu .


The following have contributed to the development of the DNA models: Richard Allen (UC Berkeley) Shu-Huei Hung (National Taiwan University) Mathias Obrebski (UC Berkeley) Robert Porritt (UC Berkeley) Fred Pollitz (USGS) Mei Xue (formerly UC Berkeley, now Tongji University)

Support for this project is provided by the Earthscope program of the National Science Foundation, and the University of California, Berkeley. The 3D visualization has been facilitated by the Keck Caves of the University of California, Davis.

This page is maintained by Richard Allen