268 Geophysics in Geothermal Exploration Figure 9.13 Surface density grid, with the outline of Petite Terre in black and the trace of the faults in red. A negative anomaly is observed between the two faults, which may indicate a collapse zone. 9.4 Final model Geophysical data allowed for the placement of a reservoir, a heat source, the base of the volcanic substratum, as well as a number of areas with higher vertical permeability (chimneys) connecting the reservoir to surface material ejection zones. These areas likely correspond to relatively fractured environments, with the two major craters, Lac Dziani and La Vigie, being aligned along the main deformation direction of N150°E. The electrical profile also helped differentiate the volcanic rocks, distinguishing denser basalt-like rocks from the resistive trachytic ashes found around the maars. The combination of all the data was used to position, with varying degrees of confidence, two N150°E-oriented faults, with the southernmost one being relatively certain, while uncertainties remain regarding the northern one. Following these
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