@article{fdi:010066018,
  title = {{G}radients from {GOCE} reveal gravity changes before {P}isagua {M}w=8.2 and {I}quique {M}w=7.7 large megathrust earthquakes},
  author = {{A}lvarez, {O}. and {N}acif, {S}. and {S}pagnotto, {S}. and {F}olguera, {A}. and {G}imenez, {M}. and {C}hlieh, {M}ohamed and {B}raitenberg, {C}.},
  editor = {},
  language = {{ENG}},
  abstract = {{C}onsiderable improvements in the measurement of the {E}arth gravity field from {GOCE} satellite mission have provided global gravity field models with homogeneous coverage, high precision and good spatial resolution. {I}n particular, the vertical gravity gradient ({T}zz), in comparison to the classic {B}ouguer anomaly, defines more accurately superficial mass heterogeneities. {M}oreover, the correction of these satellite-derived data from the effect of {E}arth topographic masses by means of new techniques taking into account the {E}arth curvature, improves results in regional analyses. {I}n a recent work we found a correlation between {T}zz and slip distribution for the 2010 {M}aule {M}w = 8.8 earthquake. {I}n the present work, we derive the vertical gravity gradient from the last {GOCE} only model, corrected by the topographic effect and also by the sediments on depocenters of the offshore region at the {P}eru {C}hile margin, in order to study a spatial relationship between different lobes of the gravity derived signal and the seismic sources of large megathrust earthquakes. {I}n particular, we analyze this relation for the slip models of the 1996 {M}w = 7.7 {N}azca, 2001 {M}w = 8.4 {A}requipa, 2007 {M}w = 8.0 {P}isco events and for the slip models of the 2014 {M}w = 8.2 {P}isagua and {M}w = 7.7 {I}quique earthquakes from {S}churr et al. (2014), including the previously analyzed 2010 {M}w = 8.8 {M}aule event. {T}hen we find a good correlation between vertical gravity gradients and main rupture zones, correlation that becomes even stronger as the event magnitude increases. {B}esides this, a gravity fall in the gravity gradient was noticed over the area of the main slip patches at least for the two years before 2014 {M}w = 8.2 {P}isagua and {M}w = 7.7 {I}quique earthquakes. {A}dditionally, we found temporal variations of the gravity field after 2010 {M}w = 8.8 {M}aule event, related to the main patches of the slip distribution, and coseismic deformation. {T}herefore, we analyzed vertical gravity gradient field variations as an indirect measure of the variable seismic coupling finding a potential relationship between {T}zz and the seismic b-value. {T}hese relationships exemplify the strong potential of the satellite only derived models as a predictive tool to determine potential seismic energy released in a subduction segment, determining the potential size of a potential rupture zone, and in particular internal slip distribution that allows inferring coseismic displacement field at surface.},
  keywords = {{V}ertical gravity gradient ; {M}egathrust earthquakes ; {E}arthquake interaction ; {F}orecasting, and prediction ; {S}ubduction ; {C}ontinental margins ; {S}outh {A}ndes ; {ANDES} ; {PEROU} ; {CHILI}},
  booktitle = {{T}ectonics of the {A}rgentine and {C}hilean {A}ndes},
  journal = {{J}ournal of {S}outh {A}merican {E}arth {S}ciences},
  volume = {64, part 2},
  numero = {{N}o special},
  pages = {273--287},
  ISSN = {0895-9811},
  year = {2015},
  DOI = {10.1016/j.jsames.2015.09.014},
  URL = {https://www.documentation.ird.fr/hor/fdi:010066018},
}