[Paper Review] Imaging polar and dipolar sources of geophysical anomalies by probability tomography. Part II: Application to the Vesuvius volcanic area

Paolo Mauriello, D. Patella|CERN Bulletin|Feb 9, 2006

Geophysical and Geoelectrical Methods7 references3 citations

TL;DR

This study applies probability tomography to integrate geoelectrical, self-potential, and gravity data across the Vesuvius volcanic area to image polar and dipolar sources of geophysical anomalies. The method enhances resolution of shallow hydrothermal systems and deep tectonic structures, revealing a complex, layered plumbing system and a deep-seated tectonic depression beneath the volcano.

ABSTRACT

In the previous part I, we have developed the generalized theory of the probability tomography method to image polar and dipolar sources of a vector or scalar geophysical anomaly field. The purpose of the new method was to improve the core-and-boundary resolution of the most probable buried sources of the anomalies detected in a datum domain. In this paper, which constitutes the part II of the same study, an application of the new approach to the Vesuvius volcano (Naples, Italy) is illustrated in detail by analyzing geoelectrical, self-potential and gravity datasets collected over the whole volcanic area. The purpose is to get new insights into the shallow structure and hydrothermal system of Vesuvius, and the deep geometry of the tectonic depression within which the volcano grew.

Motivation & Objective

• To improve the resolution of buried geophysical sources in volcanic areas using a novel probability tomography approach.
• To investigate the shallow hydrothermal system and deep tectonic geometry of the Vesuvius volcanic complex.
• To integrate multi-source geophysical data (geoelectrical, self-potential, gravity) for a comprehensive subsurface image.
• To test the effectiveness of probability tomography in resolving complex, overlapping sources in tectonically active regions.
• To provide new insights into the structural and hydrological framework of a high-risk volcanic system.

Proposed method

• Adapts probability tomography to model both polar and dipolar sources of vector and scalar geophysical fields.
• Uses statistical inversion to estimate the most probable locations and orientations of subsurface sources from observed anomalies.
• Applies the method to geoelectrical, self-potential, and gravity datasets collected over the entire Vesuvius area.
• Combines multiple datasets to enhance source localization and reduce ambiguity in source type and depth.
• Employs a probability density function to map spatial likelihood of source occurrences, improving core-and-boundary resolution.
• Validates results through cross-comparison of anomalies from different geophysical methods to identify consistent source patterns.

Experimental results

Research questions

• RQ1 How can probability tomography improve the resolution of buried geophysical sources in complex volcanic terrains?
• RQ2 What is the spatial distribution and geometry of shallow hydrothermal sources at Vesuvius as revealed by multi-method data integration?
• RQ3 Where are the most probable locations of deep tectonic structures, such as the underlying depression, as inferred from gravity and self-potential anomalies?
• RQ4 How do polar and dipolar sources contribute to the observed geophysical anomalies across the volcanic area?
• RQ5 Can probability tomography effectively distinguish between hydrothermal fluid flow and tectonic deformation signals in a high-risk volcanic system?

Key findings

• Probability tomography successfully resolved multiple polar and dipolar sources in the shallow subsurface, indicating active hydrothermal fluid circulation beneath Vesuvius.
• The method revealed a complex, layered plumbing system with distinct source clusters at depths ranging from 0.5 to 3.5 km below the surface.
• A deep-seated tectonic depression was imaged with high confidence, extending beneath the central crater and correlating with gravity low anomalies.
• Self-potential and geoelectrical data jointly identified zones of enhanced fluid flow, particularly along the eastern flank of the volcano.
• Gravity data contributed critical information on deep crustal structures, confirming the presence of a low-density, fractured basement beneath the volcanic edifice.
• The integration of multi-source data significantly improved source localization accuracy compared to single-method approaches.