@article{fdi:010086464,
  title = {{W}hat causes the persistent seismicity below the eastern flank of {P}iton de la {F}ournaise (la {R}{\'e}union {I}sland) ? {E}lasto-plastic models of magma inflation},
  author = {{G}erbault, {M}uriel and {F}ontaine, {F}. {J}. and {P}eltier, {A}. and {G}ot, {J}. {L}. and {H}assani, {R}. and {F}errazzini, {V}. and {G}ailler, {L}. and {D}uputel, {Z}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}dentifying the causes of flank destabilization of active volcanic edifices is key to prevent catastrophic events. {T}he persistent seismicity recorded below the eastern flank of {P}iton de la {F}ournaise shield volcano (la {R}e ' union {I}sland), both in between and during eruptive events, may give indications on the mechanical stability of this edifice. {W}hether this asymmetric "cup" shaped seismicity is linked to magma injections and whether it sparks a gravitational flank slide motivates this study. {H}ere we model the elasto-plastic behavior of this volcanic edifice at crustal scale, with the 3{D} finite-element code {A}deli. {F}irst, we test the influence of tensile failure, recently implemented in combination to a {D}rucker-{P}rager shear failure criterion; a pressurized cavity below a flat top surface triggers shear failure in general, with tensile failure restricted to the surface and cavity tip. {T}hen we include the topography of {P}iton de la {F}ournaise in the gravity field. {C}onsidering first only elasticity, deviatoric stresses attain about 35 {MP}a below the volcanic edifice and displacements are maximum in the horizontal east-west direction, reaching 30 m near sea-level. {I}ntroducing plastic behavior produces a rather symmetric cup shape plastic domain around the volcano's summit, that extends at depth with reducing bedrock effective friction (which acts is a proxy for reduced standard friction due to pore fluid pressurization). {A}n asymmetric listric shear zone develops down to -3 km (bsl) only if the tensile strength, cohesion and friction angle are set as low as 1.5 {MP}a, 3 {MP}a and 3 degrees, respectively; these values hence provide a lower bound for the edifice's effective strength. {T}he second part of this study explores the influence of an internal overpressure, which is either applied as a vertical inflation source located about 500 m below the surface of the eastern flank, simulating a distal dike, or from a deeper ellipsoid simulating the magma reservoir located at depth ca. 0 km (near sea level) below the summit. {T}he resulting strain pattern forms a cup-shaped shear zone dipping down below the eastern flanks of the edifice, reaching depth -2 km (bsl) if effective friction angle is <= 5 degrees. {W}hereas the deep base of the dike and the eastern edge of the magma reservoir coincide geometrically in the models, the inflating dike produces a shear zone 1 km shallower than does the inflating magma reservoir, the latter coinciding better with the shape of the observed seismic cup. {H}ence, we propose that this structure is a mechanical consequence of continuous magma supply in the reservoir, coherent with previous interpretations. {T}his means that at least originally it did not need to form as a pre-existing weak zone or a magma-filled structure. {H}owever, this shear zone delimits an underlying domain in dilatation relative to a constricted hanging-wall; it may thus promote magma sills. {I}t also branches to the surface with planar radial shear zones comparable to some observed eruptive fissures. {T}he 3{D} kinematics of this shear zone does not rule out the possibility of a giant flank slide, although it does not appear today as imminent.},
  keywords = {{V}olcano flankslides ; {E}lasto-plastic behavior ; {M}agma inflation ; {S}eismicity ; {REUNION}},
  booktitle = {},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {431},
  numero = {},
  pages = {107628 [25 ]},
  ISSN = {0377-0273},
  year = {2022},
  DOI = {10.1016/j.jvolgeores.2022.107628},
  URL = {https://www.documentation.ird.fr/hor/fdi:010086464},
}