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Fluid ascent and magma storage beneath Gunung Merapi revealed by multi-scale seismic imaging
Luehr B.-G.a, Koulakov I., Rabbel W.c, Zschau J.a, Ratdomopurbo A.d, Brotopuspito K.S.e, Fauzi P.f, Sahara D.P.g
a Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Germany
b Inst. of Petroleum Geol. and Geophys, Russian Federation
c Institute of Geosciences, CAU, Germany
d EOS, Nanyang Techn. University, Singapore
e FMIPA, Universitas Gadjah Mada, Indonesia
f Meteorological and Geophys. Agency (BMG), Indonesia
g Dept. Geophys. and Meteorology, Inst. of Technology Bandung (ITB), Indonesia
[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]Magma is fed to a volcano through a complex “plumbing” system that involves not only shallow structures beneath the volcano edifice, but also deep structures and processes within the underlying crust and upper mantle. This paper summarizes seismic experiments carried out over many years at Gunung Merapi in Central Java. These have resolved the 3D seismic velocity structure of the Merapi edifice, and provided a 3D structural image of the lithosphere and subduction zone beneath Central Java. Earthquake locations reveal that with distance from the trench, the dip of the subducting slab steepens from nearly horizontal (0-150km), through 45° (150-250km), to 70° (>250km). The slab appears as a 30km thick double layer of seismicity in a depth range of 80km to 150km, and it can be identified seismically to a depth of more than 600km. The active volcanoes of Merapi, Sumbing, and Lawu are located at the edge of a large low velocity body that extends from the upper crust to the upper mantle beneath Central Java. Shear wave signals recorded above this anomaly are strongly attenuated compared to neighboring areas. The anomalous body has a detected volume of >50,000km3 and a decrease in P and S velocities relative to adjacent regions of up to 30%. The resulting Vp/Vs ratio of up to 1.9 is unusually high for lower crust. Additionally, the anomaly extends along a 45 degree-slope downward from beneath the volcanic arc and meets the slab at 100km depth. We interpret this sloping anomaly as a pathway for fluids and partial melts. Increased seismicity is observed at depths of ~100km, possibly as a result of dehydration of the subducting slab with related fluid releases causing partial melting of overlying mantle material. The large velocity reduction and high Vp/Vs ratio in the region are consistent with an increase in temperature, a reduction of shear strength, and the presence of fluids or melts of 13 to 25vol.%. The detected strong anomaly beneath Central Java is unique in size and amplitude compared to other subduction zones. The geophysical evidence suggests that this segment of the arc has a high magma flux and is thus capable of developing even larger shallow crustal reservoirs and more voluminous explosive eruptions in the future. © 2013 Elsevier B.V.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Author keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Crustal reservoirs,Earthquake location,Explosive eruption,Geophysical evidence,Merapi,Seismic tomography,Subduction volcanism,Volcano seismology[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Indexed keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Merapi,Seismic tomography,Subduction volcanism,Volcano-seismology[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Funding details” size=”size-sm” text_align=”text-left”][vc_column_text]This research project was funded by the German Federal Ministry of Education and Research (BMBF) within the special program GEOTECHNOLOGIEN, and the GeoForschungsZentrum Potsdam (GFZ) . Ivan Koulakov was supported by projects IP SB RAS #20 and ONZ-7.3 RAS . Essential support of the project was provided by the Center for Volcanology and Geologic Hazard Mitigation (CVGHM) Bandung , the Volcanological Technology Research Center (BPPTK) Yogyakarta , the Gadjah Mada University (UGM) Yogyakarta , Institut Teknologi Bandung (ITB) Bandung , and the Meteorological and Geophysical Agency (BMG) Jakarta . We would like to thank all Indonesian and German colleagues and students participating in the fieldwork. Instruments were provided by the Geophysical Instrument Pool Potsdam (GIPP), the Christian Albrecht University, Kiel, and the GEOMAR Helmholtz Center for Ocean Research, Kiel. Many thanks also to the reviewers for their critical, constructive and helpful comments. Our special thanks are going to John Pallister for his constructive support and hints, and to Eohan Hologhan for improving the structure of the manuscript and the English writing.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”DOI” size=”size-sm” text_align=”text-left”][vc_column_text]https://doi.org/10.1016/j.jvolgeores.2013.03.015[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]