- © 2012
Online material: P-wave tomography model for the United States; scripts for plotting cross-sections.
In 2011, the Transportable Array of USArray (http://www.iris.edu/USArray/), the seismological component of EarthScope (http://www.earthscope.org/), continued to extend east of the Rocky Mountains and the Great Plains and into the Midwest and Gulf Coast regions where not many routinely processed data were available for previous regional- or global-scale traveltime inversions. In previous papers (Burdick et al. 2008, 2009, 2010) we presented 3-D tomographic models of mantle P-wavespeed from global and USArrayTA traveltime data through November 2007, December 2008, and January 2010, respectively. Here we present a model update using USArrayTA data through March 2011. The new model, MITP_USA_2011MAR, is available as an electronic supplement. Interpretation of the 3-D tomographic images is beyond the scope of this brief research note.
The method for traveltime tomography used here is described in previous papers (Li et al. 2008; Burdick et al. 2008), but for the sake of completeness we include a brief summary. We perform global (linearized) inversions of P-wave traveltime residuals using an adaptable grid with a minimum grid spacing of 0.3° × 0.3° × 45 km. The spacing of the adaptable grid is adjusted based on raypath coverage in each mantle volume. The data included in the inversion consist of ∼10 million P-wave residuals from the International Seismological Centre and the National Earthquake Information Center processed using the algorithms developed by Engdahl et al. (1998)—henceforth referred as the EHB catalog—and the database …