[vc_empty_space][vc_empty_space]
3D electrical conductivity tomography of volcanoes
Soueid Ahmed A., Revil A., Byrdina S., Coperey A., Gailler L., Grobbe N., Viveiros F., Silva C., Jougnot D., Ghorbani A., Hogg C., Kiyan D., Rath V., Heap M.J., Grandis H., Humaida H.
[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]© 2018 Elsevier B.V.Electrical conductivity tomography is a well-established galvanometric method for imaging the subsurface electrical conductivity distribution. We characterize the conductivity distribution of a set of volcanic structures that are different in terms of activity and morphology. For that purpose, we developed a large-scale inversion code named ECT-3D aimed at handling complex topographical effects like those encountered in volcanic areas. In addition, ECT-3D offers the possibility of using as input data the two components of the electrical field recorded at independent stations. Without prior information, a Gauss-Newton method with roughness constraints is used to solve the inverse problem. The roughening operator used to impose constraints is computed on unstructured tetrahedral elements to map complex geometries. We first benchmark ECT-3D on two synthetic tests. A first test using the topography of Mt. St Helens volcano (Washington, USA) demonstrates that we can successfully reconstruct the electrical conductivity field of an edifice marked by a strong topography and strong variations in the resistivity distribution. A second case study is used to demonstrate the versatility of the code in using the two components of the electrical field recorded on independent stations along the ground surface. Then, we apply our code to real data sets recorded at (i) a thermally active area of Yellowstone caldera (Wyoming, USA), (ii) a monogenetic dome on Furnas volcano (the Azores, Portugal), and (iii) the upper portion of the caldera of Kīlauea (Hawai’i, USA). The tomographies reveal some of the major structures of these volcanoes as well as identifying alteration associated with high surface conductivities. We also review the petrophysics underlying the interpretation of the electrical conductivity of fresh and altered volcanic rocks and molten rocks to show that electrical conductivity tomography cannot be used as a stand-alone technique due to the non-uniqueness in interpreting electrical conductivity tomograms. That said, new experimental data provide evidence regarding the strong role of alteration in the vicinity of preferential fluid flow paths including magmatic conduits and hydrothermal vents.[/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]Conductivity distributions,Electrical conductivity,Electrical conductivity distribution,Gauss-Newton methods,Resistivity distributions,Surface conductivity,Tetrahedral elements,Topographical effects[/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][/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][{‘$’: “We acknowledge the support of the University of Melbourne through a project funded by the Commonwealth of Australia (contract CR-2016-UNIV.MELBOURNE-147672-UMR5275 ). The electrical conductivity data and field samples at Yellowstone were collected under the research permit YELL-2016-SCI-7006. S. Haas, S. Gunther, and park rangers at Yellowstone National Park are thanked for assistance with permitting and logistics. The drill-hole cores from Yellowstone were provided to us by the Core Research Center (CRC). We thank the staff of the CRC and P. Dobson for providing us help and information about the cores. Lidar data over Yellowstone study area are available at https://doi.org/10.5069/G99P2ZKK . These data were acquired and processed by the National Center for Airborne Laser Mapping (NCALM – http://www.ncalm.org ), funded by National Science Foundataion (NSF)’s Division of Earth Sciences, Instrumentation and Facilities Program (EAR- 1043051 ) and were provided to us by the OpenTopography Facility also funded by NSF (Awards 1226353 & 1225810 ). This research was also funded by Labex grant OSUG@2020 (ANR10 LABX56), the CNRS-INSU program SYSTER , and a CNRS-INSU project . The Kīlauea study was funded by a CNRS INSU project. We are grateful to T. Neal, J. Sutton, S. Swanson, S. Brantley and the HVO’s staff in Hawai’i for their support. We also thank the HVO Park for its support and access authorization. We also acknowledge all the volunteers for their participation to the field data acquisition. We thank D. Thomas, J. Kauahikaua, J.F. Lénat, S. Hurwitz, and J. Vandemeulebrouck, and C. Bouligand for fruitful discussions, and S. Roques for her help with the petrophysical measurements. The Volcanological Survey of Indonesia, more particularly A. B. Santoso and G. Suantika, are thanked for their help with the collection of some core samples in Indonesia. M.J. Heap thanks the Buttle Family, Pee Jay tours, GNS Science, and all those that helped in the collection of the samples from Whakaari/White Island. We also thank B. Ritzinger for his help in the preparation of the cores from Yellowstone. Finally, we thank the Editor and the two referees for their work and very constructive comments”}, {‘$’: “We acknowledge the support of the University of Melbourne through a project funded by the Commonwealth of Australia (contract CR-2016-UNIV.MELBOURNE-147672-UMR5275). The electrical conductivity data and field samples at Yellowstone were collected under the research permit YELL-2016-SCI-7006. S. Haas, S. Gunther, and park rangers at Yellowstone National Park are thanked for assistance with permitting and logistics. The drill-hole cores from Yellowstone were provided to us by the Core Research Center (CRC). We thank the staff of the CRC and P. Dobson for providing us help and information about the cores. Lidar data over Yellowstone study area are available at https://doi.org/10.5069/G99P2ZKK. These data were acquired and processed by the National Center for Airborne Laser Mapping (NCALM – http://www.ncalm.org), funded by National Science Foundataion (NSF)’s Division of Earth Sciences, Instrumentation and Facilities Program (EAR-1043051) and were provided to us by the OpenTopography Facility also funded by NSF (Awards 1226353 & 1225810). This research was also funded by Labex grant OSUG@2020 (ANR10 LABX56), the CNRS-INSU program SYSTER, and a CNRS-INSU project. The Kīlauea study was funded by a CNRS INSU project. We are grateful to T. Neal, J. Sutton, S. Swanson, S. Brantley and the HVO’s staff in Hawai’i for their support. We also thank the HVO Park for its support and access authorization. We also acknowledge all the volunteers for their participation to the field data acquisition. We thank D. Thomas, J. Kauahikaua, J.F. Lénat, S. Hurwitz, and J. Vandemeulebrouck, and C. Bouligand for fruitful discussions, and S. Roques for her help with the petrophysical measurements. The Volcanological Survey of Indonesia, more particularly A. B. Santoso and G. Suantika, are thanked for their help with the collection of some core samples in Indonesia. M.J. Heap thanks the Buttle Family, Pee Jay tours, GNS Science, and all those that helped in the collection of the samples from Whakaari/White Island. We also thank B. Ritzinger for his help in the preparation of the cores from Yellowstone. Finally, we thank the Editor and the two referees for their work and very constructive comments”}][/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.2018.03.017[/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]