Abstract

An integrated approach that combines geophysical surveys and numerical simulations is proposed to study the processes that govern the fluid flow along active fault zones. It is based on the reconstruction of the architecture of the investigated fault system, as well as the identification of possible paths for fluid migration, according to the distribution of geophysical parameters retrieved by multi-methodological geophysical prospecting. The aim is to establish, thanks to constraints deriving from different types of data (e.g., geological, geochemical and/or hydrogeological data), an accurate 3D petrophysical model of the survey area to be used for simulating, by numerical modelling, the physical processes likely taking place in the imaged system and its temporal evolution. The effectiveness of the proposed approach is tested in an active fault zone in the Matese Mts (southern Italy), where recent, accurate geochemical measurements have registered very high anomalous values of non-volcanic natural emissions of CO₂. In particular, a multi-methodological geophysical survey, consisting of electrical resistivity tomography, self-potential and passive seismic measurements, integrated with geological data, was chosen to define the 3D petrophysical model of the investigated system and to identify possible source geometries. Three different scenarios were assumed corresponding to three different CO₂ source models. The one that hypothesizes a source located along the fault plane at the depth of the carbonate basement was found to be the best candidate to represent the test site. Indeed, the performed numerical simulations provide CO₂ flow estimates comparable with the values observed in the investigated area. These findings are promising for gas hazards, as they suggest that numerical simulations of different CO₂ degassing scenarios could forecast possible critical variations in the amount of CO₂ emitted near the fault.

中文翻译：

---

基于地球物理调查的活动断裂带非火山 CO2 脱气的 3D 数值模拟

摘要

提出了一种结合地球物理调查和数值模拟的综合方法来研究控制沿活动断层带的流体流动的过程。它基于多方法地球物理勘探反演的地球物理参数分布，重建被调查断层系统的结构，以及识别流体运移的可能路径。由于来自不同类型数据（例如地质、地球化学和/或水文地质数据）的限制，其目的是建立一个准确的勘测区 3D 岩石物理模型，用于通过数值建模模拟物理过程可能发生在成像系统及其时间演变中。₂ . 特别是，选择了一种多方法地球物理调查，包括电阻率层析成像、自电位和被动地震测量，并与地质数据相结合，用于定义所研究系统的 3D 岩石物理模型并确定可能的源几何形状。对应于三种不同的 CO ₂源模型，假设了三种不同的情景。假设源位于碳酸盐基底深度沿断层平面的那个被发现是代表测试地点的最佳候选者。事实上，所进行的数值模拟提供了 CO ₂流量估计值与在调查区域观察到的值相当。这些发现对气体危害很有希望，因为它们表明不同 CO ₂脱气场景的数值模拟可以预测断层附近排放的 CO ₂量可能发生的关键变化。