@article{fdi:010086328, title = {{C}urrent motion and deformation of the {N}azca {P}late : new constraints from {GPS} measurements}, author = {{J}arrin, {P}. and {N}ocquet, {J}ean-{M}athieu and {R}olandone, {F}. and {M}ora-{P}aez, {H}. and {M}othes, {P}. and {C}isneros, {D}.}, editor = {}, language = {{ENG}}, abstract = {{W}e use new {GPS} data to determine an updated {E}uler pole describing the present-day motion of the oceanic {N}azca {P}late. {O}ur solution includes continuous {GPS} (c{GPS}) measurements at {M}alpelo {I}sland offshore {C}olombia, two sites in the {G}alapagos archipelago, {E}aster {I}sland and {S}alas y {G}omez {I}sland in the western part of the plate and {R}obinson {C}rusoe {I}sland offshore {C}hile. {A} careful analysis of geodetic time-series reveals that (1) previous estimates using former c{GPS} site {EISL} are biased by several millimetres per year eastward due to station malfunctioning (2) north velocity component of c{GPS} site {GLPS} at {S}anta {C}ruz {I}sland in the {G}alapagos is impacted by volcanic deformation at the 1-2 mm yr(-1) level, probably caused by the recurrent volcanic activity of the {S}ierra {N}egra volcano. {I}n addition, we find shortening at similar to 1 mm yr(-1) between {E}aster {I}sland (c{GPS} {ISPA}) and {S}alas y {G}omez {I}sland (c{GPS} {ILSG}), consistent with the elastic deformation induced by rapid opening at the {E}ast {P}acific rise. c{GPS} site at {R}obinson {C}rusoe {I}sland shows similar to 4-5 mm yr(-1) abnormally fast {E}ast velocity induced by the visco-elastic relaxation following the {M}aule {M}-w 8.8 2010 earthquake. {U}sing this information, we determine a new {E}uler pole (longitude: -90.93 degrees {E}, latitude 56.19 degrees {N}, 0.588 deg {M}yr(-1)) describing the present-day {N}azca-{S}outh {A}merica {P}late motion, using five sites ({M}alpelo {I}sland, two sites in the {G}alapagos archipelago, {E}aster {I}sland and {S}alas y {G}omez {I}sland). {T}he proposed {E}uler pole provides a weighted root mean square (wrms) of residual velocities of 0.6 mm yr(-1), slightly higher than usually observed for other major tectonic plates and accounting for the uncertainty of potential volcanic-tectonic deformation. {O}ur model predicts a maximum convergence rate at 65.5 +/- 0.8 mm yr(-1) at latitude similar to 30 degrees {S} along the {C}hile trench, decreasing to 50.8 +/- 0.7 mm yr(-1) in northern {C}olombia and 64.5 +/- 0.9 mm yr(-1) in southern {C}hile (1 sigma confidence level). {C}omparison with the geological models {NUVEL}1{A} and {MORVEL} indicates constant decrease since 3.16 {M}a of opening rate along the {N}azca-{A}ntarctic {P}late boundary spreading centres at similar to 1 cm yr(-1) per {M}yr. {C}ombined with the {ITRF}2014 pole for the {P}acific and {A}ntarctic plates, our derived {E}uler pole predicts closure at the similar to 1 mm yr(-1) level for {P}acific-{A}ntarctic-{N}azca {P}late circuit. {H}owever, combining our results with {MORVEL} estimates for the {C}ocos {P}late, the non-closure of the {P}acific-{C}ocos-{N}azca {P}late circuit is 9.7 +/- 1.6 mm yr(-1), 30 per cent lower than the 14 +/- 5 mm yr(-1) reported in {MORVEL} model, but still significant. {A} small (similar to 1.5 mm yr(-1)) velocity residual at {M}alpelo {I}sland neither supports the hypothesis of an independent {M}alpelo microplate offshore {C}olombia nor large scale internal deformation induced by thermal contraction. {O}ur solution rather suggests that non-closure of the {P}acific-{C}ocos-{N}azca {P}late circuit arises from the determination of the {C}ocos {P}late motion in {MORVEL}, an hypothesis further supported by the large discrepancy between {MORVEL}'s prediction and the observed {GPS} velocity observed at {C}ocos {I}slands (c{GPS} {ISCO}).}, keywords = {{P}late motions ; {S}atellite geodesy ; {P}acific {O}cean ; {S}outh {A}merica ; {PACIFIQUE} ; {AMERIQUE} {DU} {SUD} ; {NAZCA} {PLAQUE}}, booktitle = {}, journal = {{G}eophysical {J}ournal {I}nternational}, volume = {232}, numero = {2}, pages = {842--863}, ISSN = {0956-540{X}}, year = {2022}, DOI = {10.1093/gji/ggac353}, URL = {https://www.documentation.ird.fr/hor/fdi:010086328}, }