Data Services Products: EMC-AF2019 3-D shear-wave model for Africa from waveform inversion with a massive dataset

Summary

AF2019 is an azimuthally anisotropic S-wave tomographic model of Africa computed using waveform tomography. It is computed from a database of over 1.2 million vertical component waveform fits. It samples the crust and upper mantle including the mantle transition zone.

Description

Name AF2019
Title 3-D shear-wave model for Africa from waveform inversion with a massive dataset
Type Tomographic Earth model
Sub Type Shear-wave velocity model
Year 2020
Data Revision r0.0 (revision history)
 
Short Description   AF2019 is an azimuthally anisotropic S-wave tomographic model of Africa computed using waveform tomography. It is computed from a database of over 1.2 million vertical component waveform fits. It samples the crust and upper mantle including the mantle transition zone.
 
Authors: Nicolas Luca Celli – Dublin Institute for Advanced Studies, Dublin, Ireland

Sergei Lebedev – Dublin Institute for Advanced Studies, Dublin, Ireland

Andrew J. Schaeffer – Geological Survey of Canada, Pacific Division, Sidney Subdivision, Natural Resources Canada, Sydney, BC, Canada

Carmen Gaina – Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Oslo, Norway


 
Previous model None
 
Reference Model Our 3D reference model comprises CRUST2 for the crust, with added topography and bathymetry, and our own 1D average for the upper mantle. The model distribution netCDF is truncated to depths >56 km because of the irregular gridding of the crustal depths. To plot cross-sections at the crustal depths, please use the dedicated tool in the distributed model bundle (see the readme in it for instructions).
 
Model Download AF2019.r0.0.nc (see metadata) is a pre-gridded model in netCDF 3 Classic format that includes the reference model.
AF2019_distribution.zip is the distribution model bundle (see the Reference Model section above
 
Depth Coverage The model samples depths from the crust to the bottom of the mantle transition zone (660). The best resolution is achieved at 56-410 km depth. While it samples the full transition zone, the model is underdamped in the lower transition zone (585-660 km depth), and there it should be used with extra care.
 
Area The model spans between longitude -25°/63°, latitude -40°/40° and depth down to 660 km
 
Data Set Description Our model is constrained by over 1.2 million seismograms. The global waveform dataset is from recordings at 6360 seismic stations, using 27550 earthquakes in total.
 
Model resolution Our model is focussed on the Africa region, with the data coverage in this region maximized (all freely available broadband data were included) and the regularisation tuned to optimize the resolution in Africa. The global data complements the regional dataset and ensures dense sampling of entire Africa and its surroundings. Every model-grid node of the model is sampled by at least 7767 paths. The model is parametrized using a triangular grid with an average 327 km inter-knot spacing and with a depth parametrization over 18 and 10 triangular basis functions for S- and P-wave velocities, respectively (S- wave velocities: 7, 20, 36, 56, 80, 110, 150, 200, 260, 330, 410−, 410+, 485, 585, 660−, 660+, 809 and 1007 km; P-wave velocities: 7, 20, 36, 60, 90, 150, 240, 350, 485 and 585 km).
 
 

S-wave velocity anomalies at four depths
Figure 1: S-wave velocity anomalies at four depths in the shallow upper mantle: a) 56 km; b) 80 km; c) 110 km; d) 150 km. The depth is indicated above each panel on the left, with the reference velocity on the right. Topography is superimposed as shading.

S-wave velocity anomalies at four depths
Figure 2: S-wave velocity anomalies at four depths in the deep upper mantle and transition zone: a) 200 km; b) 260 km; c) 330 km; d) 485 km. The depth is indicated above each panel on the left, with the reference velocity on the right. Topography is superimposed as shading.

Citations and DOIs

To cite the original work behind this Earth model:

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.2022.af2019.1


References

  • Bassin, C., Laske, G. & Masters, G. The Current Limits of Resolution for Surface Wave Tomography in North America. EOS Trans AGU 81, F897 (2000).
  • Lebedev, S. & van der Hilst, R. D. Global upper-mantle tomography with the automated multimode inversion of surface and S-wave forms. Geophys. J. Int. 173, 505–518 (2008).

Credits

  • r0.0 model provided by Nicolas Luca Celli

Revision History

revision r0.0: uploaded October 20, 2022.

Timeline

2022-10-21
online

Categories

02:19:35 v.b07c51d3