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Published May 1, 2020 | Version v1
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New Zealand Wide model 2.2 seismic velocity and Qs and Qp models for New Zealand

  • 1. GNS Science, UCalif. Davis
  • 2. GNS Science

Description

21-May-2022  There are updated Vp and Vp/Vs models 2.3, which incorporate the results from the Southern South Island region, at zenodo.org/record/6568301

13-July-2021  There are updated Qp and Qs models 2.3, which incorporate the results from the Kaikoura region, at zenodo.org/record/5098356

 

New Zealand Wide model 2.2 has a seismic velocity model for New Zealand developed from local-earthquake tomography studies. It is updated, from nzwide2.1 (zenodo.org/record/1043558), to incorporate results from the western North Island (Eberhart-Phillips and Fry, 2017) and the southern Hikurangi Cook Strait region (Henrys, et al., 2020). The Cook Strait results were interpolated and merged into the NZwide model and then additional inversion including some Kaikoura aftershocks was carried out to assure the model is appropriate for regional use.

 

The Qp model 2.2 is updated from Qpnzw1 (Eberhart-Phillips et al., 2015), to incorporate results from the eastern North Island (Eberhart-Phillips et al., 2017) and southern South Island (Eberhart-Phillips et al., 2018).

 

There has not been New Zealand wide Qs coverage until this year, and the NZwide 2.2 Qs model is the first complete Qs model. We are using the version name nzw2.2 to denote all the seismic property models since many applications require all the parameters. The Qs model 2.2 incorporates results from the eastern North Island (Eberhart-Phillips et al., 2017), western North Island and mantle wedge (Eberhart-Phillips et al., 2020), northern South Island (Eberhart-Phillips et al., 2014), and southern South Island (Eberhart-Phillips et al., 2018).

 

The models are provided in tables, where the Spread Function (SF) shows the resolution, such that where SF<4, there is little information.

vlnzw2p2dnxyzltln.tbl.txt

Qpnzw2p2xyzltln.tbl.txt

Qsnzw2p2xyzltln.tbl.txt

 

There are also simul format velocity and Q files.

vlnzw2p2.mod.txt

Qpnzw2p2.mod.txt

Qsnzw2p2.mod.txt

 

And map plots with white lines denoting limits of adequate data.

mapvpvpvsnzw2p2.pdf

mapQpnzw2p2.pdf

mapQsnzw2p2.pdf

 

Velocity and Q at any point within the 3D gridded models are defined by linearly interpolating between nodes.

The models use Transverse Mercator coordinate transformation with a central meridian= 173, and counterclockwise rotation of 140.  Earth-flattening transformation is used for velocity during ray-tracing. The depths are relative to sea-level. Density has been included in the velocity table, by using an empirical relationship (Gardner et al., 1974; Hill, 1978).

Files

mapQpnzw2p2.pdf

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Additional details

References

  • Eberhart-Phillips, D., S. Bannister, and M. Reyners (2017), Deciphering the 3-D distribution of fluid along the shallow Hikurangi subduction zone using P- and S-wave attenuation, Geophys. J . Int., 211, 1032–1045, doi:doi.org/10.1093/gji/ggx348.
  • Eberhart-Phillips, D., S. Bannister, and M. Reyners (2020), Attenuation in the mantle wedge beneath super-volcanoes of the Taupo Volcanic Zone, New Zealand, Geophys. J. Int., 220, 703-723, doi: 10.1093/gji/ggz455.
  • Eberhart-Phillips, D., and B. Fry (2017), A new scheme for joint surface wave and earthquake travel-time inversion and resulting 3-D velocity model for the western North Island, New Zealand, Phys. Earth and Plan. Int., 269, 98–111, doi:10.1016/j.pepi.2017.05.014.
  • Eberhart-Phillips, D., M. Reyners, and S. Bannister (2015), A 3-D Qp attenuation model for all of New Zealand, Seis. Res. Lett., 86, 1655-1663, doi:10.1785/0220150124.
  • Eberhart-Phillips, D., M. Reyners, P. Upton, and D. Gubbins (2018), Insights into the crustal structure and tectonic history of the southern South Island, New Zealand, from the 3-D distribution of P- and S-wave attenuation, Geophys. J . Int., 214, 1481-1505, doi:10.1093/gji/ggy194.
  • Eberhart-Phillips, D., S. Bannister, and S. Ellis (2014), Imaging P and S attenuation in the termination region of the Hikurangi subduction zone, New Zealand, Geophys. J . Int., 198, 516-536, doi: 510.1093/gji/ggu1151.
  • Gardner, G. H. F., L. W. Gardner, and A. R. Gregory (1974), Formation velocity and density - the diagnostic basics for stratigraphic traps, Geophysics, 39, 770-780.
  • Henrys, S., D. Eberhart‐Phillips, Bassett, D., Sutherland, R., Okaya, D., Savage, M., et al. (2020), Upper plate heterogeneity along the southern Hikurangi Margin, New Zealand, Geophys. Res. Let., 47, e2019GL085511., doi:10.1029/2019GL085511.
  • Hill, D. P. (1978), Seismic evidence for the structure and Cenozoic tectonics of the Pacific Coast States, in Cenozoic Tectonics and Regional Geophysics of the Western Cordillera, edited by R. B. Smith and G. P. Eaton, pp. 145-174.