Alaska 2020 update for USGS G19AP00019: Initial Development of Alaska Community Seismic Velocity Models

Seismic velocity model AKEP2020 uses earthquake travel-time and ambient noise group velocity data to update Eberhart-Phillips et al. (2006: AKEP2006)

The model is provided in a table: vlAKEP2020xyzltlnSFDRE.tbl.txt

and in the simul output from velocity inversion: vlAKEP2020.out.txt

Map plots of Vp and Vp/Vs are also provided, with lines denoting limits of adequate data.

Velocity Inversion Procedure Notes for AKEP2020 model

The 2006 AK model and the 2020 updated model both use Transverse Mercator coordinate transformation with central meridian= -150 and counterclockwise rotation of 162.1.  Earth-flattening transformation is used for velocity during ray-tracing. The depths are relative to sea-level and station elevations are used. For the group-velocity data, the surface is taken as the 30-km median filtered topography.

Velocity with the 3D gridded model is defined by linearly interpolating between nodes.

A gradational inversion approach was used with earthquake and shot travel-time data, and group velocity observations for periods 6-15 s. The table provides, from the computed resolution matrix, the diagonal resolution element (DRE), and the spread function (SF), for each Vp and Vp/Vs node.

This material is based upon work supported by the U.S. Geological Survey under Grant No. G19AP00019.  Note that an earlier model, AKEP2018, from the first year of this funded project was reported in Eberhart-Phillips et al. (2019).

The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the U.S. Geological Survey. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Geological Survey