@article{fdi:010087285,
  title = {{O}ptimal resolution tomography with error tracking and the structure of the crust and upper mantle beneath {I}reland and {B}ritain},
  author = {{B}onadio, {R}. and {L}ebedev, {S}. and {M}eier, {T}. and {A}rroucau, {P}. and {S}chaeffer, {A}. {J}. and {L}icciardi, {A}ndrea and {A}gius, {M}. {R}. and {H}oran, {C}. and {C}ollins, {L}. and {O}'{R}eilly, {B}. {M}. and {R}eadman, {P}. {W}. and {I}reland {A}rray {W}orking {G}roup},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he classical {B}ackus-{G}ilbert method seeks localized {E}arth-structure averages at the shortest length scales possible, given a data set, data errors, and a threshold for acceptable model errors. {T}he resolving length at a point is the width of the local averaging kernel, and the optimal averaging kernel is the narrowest one such that the model error is below a specified level. {T}his approach is well suited for seismic tomography, which maps 3-{D} {E}arth structure using large sets of seismic measurements. {T}he continual measurement-error decreases and data-redundancy increases have reduced the impact of random errors on tomographic models. {S}ystematic errors, however, are resistant to data redundancy and their effect on the model is difficult to predict. {H}ere, we develop a method for finding the optimal resolving length at every point, implementing it for surface-wave tomography. {A}s in the {B}ackus-{G}ilbert method, every solution at a point results from an entire-system inversion, and the model error is reduced by increasing the model-parameter averaging. {T}he key advantage of our method stems from its direct, empirical evaluation of the posterior model error at a point. {W}e first measure inter-station phase velocities at simultaneously recording station pairs and compute phase-velocity maps at densely, logarithmically spaced periods. {N}umerous versions of the maps with varying smoothness are then computed, ranging from very rough to very smooth. {P}hase-velocity curves extracted from the maps at every point can be inverted for shear-velocity ({VS}) profiles. {A}s we show, errors in these phase-velocity curves increase nearly monotonically with the map roughness. {W}e evaluate the error by isolating the roughness of the phase-velocity curve that cannot be explained by any {E}arth structure and determine the optimal resolving length at a point such that the error of the local phase-velocity curve is below a threshold. {A} 3-{D} {VS} model is then computed by the inversion of the composite phase-velocity maps with an optimal resolution at every point. {T}he estimated optimal resolution shows smooth lateral variations, confirming the robustness of the procedure. {I}mportantly, the optimal resolving length does not scale with the density of the data coverage: some of the best-sampled locations display relatively low lateral resolution, probably due to systematic errors in the data. {W}e apply the method to image the lithosphere and underlying mantle beneath {I}reland and {B}ritain. {O}ur very large data set was created using new data from {I}reland {A}rray, the {I}rish {N}ational {S}eismic {N}etwork, the {UK} {S}eismograph {N}etwork and other deployments. {A} total of 11?238 inter-station dispersion curves, spanning a very broad total period range (4-500 s), yield unprecedented data coverage of the area and provide fine regional resolution from the crust to the deep asthenosphere. {T}he lateral resolution of the 3-{D} model is computed explicitly and varies from 39 km in central {I}reland to over 800 km at the edges of the area, where the data coverage declines. {O}ur tomography reveals pronounced, previously unknown variations in the lithospheric thickness beneath {I}reland and {B}ritain, with implications for their {C}aledonian assembly and for the mechanisms of the {B}ritish {T}ertiary {I}gneous {P}rovince magmatism.},
  keywords = {{ROYAUME} {UNI} ; {IRLANDE}},
  booktitle = {},
  journal = {{G}eophysical {J}ournal {I}nternational},
  volume = {226},
  numero = {3},
  pages = {2158--2188},
  ISSN = {0956-540{X}},
  year = {2021},
  DOI = {10.1093/gji/ggab169},
  URL = {https://www.documentation.ird.fr/hor/fdi:010087285},
}