GPR, TDR, and geochemistry measurements above an active gas vent to study near-surface gas-migration pathways

The migration of deep gas to the atmosphere along faults and associated structures is important in many fields, from studying the natural contribution of atmospheric greenhouse gases leaking from geothermal areas to ensuring the safety of man-made natural gas and carbon dioxide (C O2 ) geologic-storage sites. Near-surface geophysical and geochemical techniques were applied to a naturally occurring gas vent located along a deep terrestrial fault to better understand the structure and geophysical response of this gas-migration pathway. A number of ground-penetrating radar (GPR) profiles were first conducted across the vent. Spot samples were then measured along one of these profiles for in situ apparent permittivity (using time-domain reflectometry — TDR), complex permittivity on dried samples (using a capacitivecell), soil-gas composition, and clay and bulk mineralogy. Results show how the migrating gas induces secondary effects that modify the signature of the vent as seen in the GPR profiles. In particul...

[1]  S. Lombardi,et al.  Carbon dioxide and radon gas hazard in the Alban Hills area (central Italy) , 2003 .

[2]  Hardy Pfanz,et al.  Root respiration response to high CO2 concentrations in plants from natural CO2 springs , 2005 .

[3]  David Lopes de Castro,et al.  4-D ground penetrating radar monitoring of a hydrocarbon leakage site in Fortaleza (Brazil) during its remediation process: a case history , 2003 .

[4]  Sookyun Wang,et al.  Dissolution of a mineral phase in potable aquifers due to CO2 releases from deep formations; effect of dissolution kinetics , 2004 .

[5]  F. Ludwig,et al.  Long-term effects of elevated atmospheric CO2 on species composition and productivity of a southern African C4 dominated grassland in the vicinity of a CO2 exhalation , 2005, Plant Ecology.

[6]  Alan G. Green,et al.  Results of 3-D georadar surveying and trenching the San Andreas fault near its northern landward limit , 2003 .

[7]  E. Pettinelli,et al.  GPR and EM31 investigations on an active CO/sub 2/ gas vent , 2004, Proceedings of the Tenth International Conference on Grounds Penetrating Radar, 2004. GPR 2004..

[8]  Grant S. Bromhal,et al.  Ground-penetrating radar survey and tracer observations at the West Pearl Queen carbon sequestration pilot site, New Mexico , 2005 .

[9]  U. Asprion,et al.  Visualization of tectonic structures in shallow‐depth high‐resolution ground‐penetrating radar (GPR) profiles , 1997 .

[10]  A. Green,et al.  Location and geometry of the Wellington Fault (New Zealand) defined by detailed three‐dimensional georadar data , 2004 .

[11]  Luigi Marini,et al.  Fluxes of deep CO2 in the volcanic areas of central-southern Italy , 2004 .

[12]  John A. Hole,et al.  Application of geomorphic analysis and ground-penetrating radar to characterization of paleoseismic sites in dynamic alluvial environments: an example from southern California , 2003 .

[13]  Alessandro Galli,et al.  Time domain reflectrometry: Calibration techniques for accurate measurement of the dielectric properties of various materials , 2002 .

[14]  A. D. Santis,et al.  Correlation between near-surface electromagnetic soil parameters and early-time GPR signals: An experimental study , 2007 .

[15]  A. R. Pisani,et al.  Laboratory investigations into the electromagnetic properties of magnetite/silica mixtures as Martian soil simulants , 2005 .

[16]  Pilar Villamor,et al.  Detailed shallow geometry and vertical displacement estimates of the Maleme Fault Zone, New Zealand, using 2D and 3D georadar , 2006 .

[17]  J. Hering,et al.  Comparative characterization of volcanic ash soils exposed to decade-long elevated carbon dioxide concentrations at Mammoth Mountain, California , 2002 .

[18]  V. V. Grechnev,et al.  Homologous large‐scale activity in solar eruptive events of 24–26 November 2000 , 2004 .

[19]  Salvatore Lombardi,et al.  NEAR-SURFACE GAS GEOCHEMISTRY TECHNIQUES TO ASSESS AND MONITOR CO2 GEOLOGICAL SEQUESTRATION SITES , 2006 .