Distributed-Temperature-Sensing Using Optical Methods: A First Application in the Offshore Area of Campi Flegrei Caldera (Southern Italy) for Volcano Monitoring

Stefano Carlino,Aldo Minardo,Claudia Troise,Maurizio Mirabile,Mauro Caccavale,Luigi Zeni,Giuseppe De Natale,Marco Sacchi,Virág Darányi

doi:10.3390/rs8080674

Abstract

A temperature profile 2400 m along the off-shore active caldera of Campi Flegrei (Gulf of Pozzuoli) was obtained by the installation of a permanent fiber-optic monitoring system within the framework of the Innovative Monitoring for Coastal and Marine Environment (MON.I.C.A) project. The system consists of a submerged, reinforced, multi-fiber cable containing six single-mode telecom grade optical fibers that, exploiting the stimulated Brillouin scattering, provide distributed temperature sensing (DTS) with 1 m of spatial resolution. The obtained data show that the offshore caldera, at least along the monitored profile, has many points of heat discharge associated with fluid emission. A loose association between the temperature profile and the main structural features of the offshore caldera was also evidenced by comparing DTS data with a high-resolution reflection seismic survey. This represents an important advancement in the monitoring of this high-risk volcanic area, since temperature variations are among the precursors of magma migration towards the surface and are also crucial data in the study of caldera dynamics. The adopted system can also be applied to many other calderas which are often partially or largely submerged and hence difficult to monitor.

Highlights

The measurement of surface temperature and its temporal variation in active volcanic areas provides critical information to improve the understanding of physical processes occurring at depth.Quiescent and active volcanism is almost always accompanied by heat and fluid output [1], and thermal data are essential to assess the amount of energy being released and the mass transport within the shallow crust [2,3]
The temperature profiles acquired along the 2.4 km long fiber-optic cable and deployed on the 14 °C according to that reported in literature for the Gulf of Naples [38]
Our data highlight that the that the geothermal system into the off-shore section (Figure of the 10a–d) in geothermal system extends intoextends the off-shore section of the caldera accordance with accordance with the possible location of the magmatic source, as inferred from inversion geodetic the possible location of the magmatic source, as inferred from inversion geodetic and fluid-dynamic and fluid-dynamic modeling related to recent unrests (1970–1972, 1982–1984, 2005 to present time) modeling related to recent unrests

Summary

Introduction

The measurement of surface temperature and its temporal variation in active volcanic areas provides critical information to improve the understanding of physical processes occurring at depth. Quiescent and active volcanism is almost always accompanied by heat and fluid output [1], and thermal data are essential to assess the amount of energy being released and the mass transport within the shallow crust [2,3]. The thermal state of volcanoes and the temperature records are important in correlating the areas of higher heat discharge with the main tectonics and structural features of volcanic edifices. Among the different volcanic edifices, calderas are associated with the highest heat discharges at the surface as well as geothermal gradients [5].

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Results

Discussion

Conclusion