@article{fdi:010079044,
  title = {{M}igration of seismic activity associated with phreatic eruption at {M}erapi volcano, {I}ndonesia},
  author = {{M}{\'e}taxian, {J}ean-{P}hilippe and {S}antoso, {A}. {B}. and {C}audron, {C}orentin and {C}holik, {N}. and {L}abonne, {C}. and {P}oiata, {N}. and {B}eauducel, {F}ran{\c{c}}ois and {M}onteiller, {V}. and {F}ahmi, {A}. {A}. and {R}izal, {M}. {H}. and {N}andaka, {I}gma},
  editor = {},
  language = {{ENG}},
  abstract = {{P}hreatic activity of {M}erapi started after nearly 2 years of quiescence following the {O}ctober-{N}ovember 2010 eruption which was the largest in more than 100 years. {A} dozen eruptions identified by visual andior seismic observations took place between {A}ugust 2012 and {A}pril 2014. {W}e present in this work the results of a detailed analysis of the {A}pril 20, 2014 phreatic eruption. {W}e attempted to reconstruct the eruptive process, which lasted for over 30 min. {T}o this end, we determined the wavefield composition by polarization analysis, located high-frequency earthquakes occurring in the initial part of the eruption process and then determined the seismic source migration of low-frequency part of the tremor-like signal [0.3-3 {H}z] over time. {S}ource depth of low-frequency signal was obtained by comparing the slowness vector calculated using 3 stations of the seismic antenna with a slowness vector model obtained by ray tracing in the structure, taking into account the topography and a 1{D} velocity model obtained by spatial auto-correlation analysis. {T}he results allow to distinguish 3 different phases: 1) {H}igh-frequency transients interpreted as the result of a sudden decompression caused by the transition of the volcanic fluid to a gaseous phase that occurred approximately 1.5 km deep. {T}his decompression process in the hydrothermal system generated a migration of the low-frequency seismic source from 900 m to 1800 m above sea level: 2) {A} second decompression process revealed by high-frequency micro-seismicity and associated to the migration of the low-frequency tremor source which is marked first by a descent phase, followed by a sharp ascent until reaching the surface. {T}he evolution of the back-azimuth during the migration process indicates a slight inclination of the conduit, presumably in the orientation of the dome fracture, in the {NW}-{SE} direction. {T}his direction is consistent with the alignment of regional tectonic structures and with the directivity of eruption deposits. 3) {T}he seismic source then remains positioned at the altitude of the dome for over 10 min. {T}his phase probably corresponds to the ash emission process. {T}he average migration speed of the low-frequency seismic source from the starting eruptive process to ash emission is about 5 m/s.},
  keywords = {{S}eismology ; {V}olcano ; {M}erapi ; {A}rray ; {S}lowness ; {R}ay tracing ; {P}hreatic ; {INDONESIE} ; {MERAPI} {VOLCAN}},
  booktitle = {},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {396},
  numero = {},
  pages = {art. 106795 [17 p.]},
  ISSN = {0377-0273},
  year = {2020},
  DOI = {10.1016/j.jvolgeores.2020.106795},
  URL = {https://www.documentation.ird.fr/hor/fdi:010079044},
}