Data Services Products: EMC-Alaska_CVM_AKAN2020 3D P- and S-wave velocity models of Alaska from the joint inversion of regional earthquake locations, body-wave data, and surface-wave data

Summary

3D compressional- and shear-wave velocity models of Alaska, covering nearly the entire state, from the joint tomographic inversion of regional earthquake locations, body-wave data, and surface-wave data, the latter from ambient noise; an estimate of Vp/Vs is also provided.

Description

Name Alaska_CVM_AKAN2020
Title 3D P- and S-wave velocity models of Alaska from the joint inversion of regional earthquake locations, body-wave data, and surface-wave data.
Type 3-D Tomography Earth Model
Sub Type Compressional and shear-wave velocity (km/s)
Year 2020
Data Revision r.1.0 (revision history)
 
Short Description   The model incorporates seismic data from seismic stations throughout most of Alaska and adjacent Canada, including data from the IRIS Transportable Array and the onshore Alaska Amphibious Community Seismic Experiment, to image the compressional- and shear-wave velocity structure of the Alaska region from the joint inversion of regional earthquake locations, body-wave arrival times, and surface-wave phase velocity dispersion from ambient noise cross-correlations.
Authors:  
Avinash Nayak
Department of Geoscience (Now at Berkeley National Laboratory)
University of Wisconsin-Madison
1215 W. Dayton St., Madison, WI 53706, USA
 
Clifford Thurber
Department of Geoscience
University of Wisconsin-Madison
1215 W. Dayton St., Madison, WI 53706, USA
 
Previous Model None
Reference Model None
Model Download Alaska-CVM-AKAN2020-1.0.nc (see metadata ), is the netCDF file for the model as a function of depth
Model Homepage
Depth Coverage -1 to 300 km (below earth surface)
Area Alaska and adjacent Canada (approx. 50.9°/72.1° latitude and -173.2°/-126.8° longitude)
 
Data Set Description The dataset includes absolute P- and S-wave velocity models across most of Alaska and adjacent Canada from the joint inversion of regional earthquake locations, body-wave data, and surface-wave data.

Figure 1
P-wave velocity results at different depths (b.s.l.).

Figure 2
S-wave velocity results at different depths (b.s.l.).

Citations and DOIs

To cite the original work behind this Earth model:

  • Nayak, A., D. Eberhart-Phillips, N. Ruppert, H. Fang, M. Moore, C. Tape, D. Christensen, G. Abers & C.H Thurber (2020). Three-dimensional seismic velocity models for Alaska from joint tomographic inversion of body-wave and surface-wave data, Seism. Res. Lett. Focus Section – Earthscope Alaska and Canada, https://doi.org/10.1785/0220200214.

To cite IRIS DMC Data Products effort:

  • Trabant, C., A. R. Hutko, M. Bahavar, R. Karstens, T. Ahern, and R. Aster (2012), Data Products at the IRIS DMC: Stepping Stones for Research and Other Applications, Seismological Research Letters, 83(5), 846–854, https://doi.org/10.1785/0220120032.

DOI for this EMC webpage: https://doi.org/10.17611/dp/emc.202.akcvmakan1

References

  • Thurber, C. H., Initial Development of Alaska Community Seismic Velocity Models, USGS Final Technical Report, Award G19AP00019 (submitted).
  • Thurber, C., D. Eberhart-Phillips, A. Nayak, N. Ruppert, M. Driskell, and H. Fang, Toward a Community Seismic Velocity Model for Alaska, SSA Annual Meeting, Seattle, WA, May 2019.

Credits

V0.0 Model provided by Clifford Thurber
V1.0 Model provided by Avinash Nayak

Revision History


revision 0.0: Thurber, C.H., 2020, Initial Development of Alaska Community Seismic Velocity Models, USGS Final Technical Report, Award G19AP00019) uploaded in April 2020.

revision 1.0: Statewide velocity model of Alaska AKAN2020 uploaded in September 2020 is a minor revision of the previous model The following are the major updates in the inversion methodology:

  1. The maximum Vp/Vs in the initial model is restricted to 2.2 in the new inversions compared to 2.6 in the previous inversions.
  2. The surface wave data is more finely sampled in the period range. We invert for phase velocities sampled at 32 and 29 discrete periods for Rayleigh waves and Love waves, respectively, in the new inversions compared to 17 and 15 discrete periods, respectively, in the previous inversions. The period range is the same.
  3. We apply signal-to-noise (SNR) ratio dependent quality weights to the surface-wave phase travel times in the new inversions. SNR in the range ~2-8 is scaled to quality weights in the range ~0.5-1. The earlier inversions did not include any quality weights for surface-wave data.
  4. The relative weight between body-wave data and surface-wave data is now automatically recalculated based on the misfits at each iteration.
  5. The value of Vp/Vs ratio damping parameter at each node is made proportional to the square of the difference between its current value and a reference value of ~1.75.
  6. We now provide values of Derivative Weighted Sum (DWS) at each node for Vp and Vs. The model is assumed to be reliable at nodes with DWS > 150.
  7. The damping and smoothing parameters are slightly smaller in the new inversions. The model variance is slightly greater in the new model.

Timeline

2020-04-02
Data Revision 0.0
2020-09-28
Data Revision 1.0

Categories

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