Muography for volcanoes, Europe
Dr Cristina Cârloganu, Laboratoire de Physique de Clermont (CNRS/IN2P3), France
The atmospheric muon flux transmittance through volcanoes can be measured with muon telescopes deployed at various distances from the target (up to few kilometres). From this measurement a radiographic (2D) image of the edifice density structure is inferred provided that high energy, ballistic muons can be efficiently selected among all the charged particles measured by the telescopes [Ambrosino et al, 2015]. The muography is potentially high resolution imaging (better than 10 mrad x10 mrad) though the angular resolution is artificially degraded in order to preserve the resolution of the density measurement. This contribution presents the first muographic imaging of Puy de Dôme obtained with data taken from several locations between 2013 and 2018. The methodological approach used to reconstruct the densities from muon counts was validated using data sets obtained with telescopes operated in different modes and deployed both in surface and underground sites. The simulation and analysis chain can be reliably used to infer the potential of muographic measurements on any volcano of interest. The muography data taken on Puy de Dôme are not sufficient to attempt a tomographic reconstruction of the volcano, though they were already used to test in a robust way geological models. However, combined with high density gravimetry data [Portal et al, 2016] they offer a first 3D map of the Puy de Dôme density, rather stable against different choices for the regularisation of the inversion.
New applications of muon absorption radiography to the fields of archaeology and civil engineering
Professor Giulio Saracino, Università di Napoli Federico II and INFN, Sezione di Napoli, Italy
In recent years, cosmic muons have been used successfully to obtain information on the internal structure of volcanic cones. A new generation of detectors has been specially developed to operate in outdoor environments, with low power consumption, reliable, remotely controllable and easily transportable and installable. This technique promises to be useful also for applications in archeology and civil engineering. It can be used together with other geological prospecting methods or alternatively to them when the usual methods can not be used profitably. In particular, the muon radiography is able to identify cavities and anomalies of the density present in the ground, exploring large volumes of soil above the detector. In order to understand the potential of the method in this field, some measurements were carried out at the natural laboratory of Mt. Echia, in the city of Naples, Italy. In the past centuries, many cavities have been created by digging in the yellow tuff of Monte Echia, the site of the ancient Greek city of Partenope, the first settlement of the current city of Naples (VIII century BC). A muon tracker was installed in two different positions, under a tuff thickness of about 40m, obtaining muographic images of the cavities visible from the detector. The known cavities have been carefully modeled and their muographic images have been reproduced. The agreement between measured data and expected results is excellent. Signals of the presence of unknown cavities are observed. Furthermore, the method also provided a map of average absolute density of the hill. The excellent results obtained have demonstrated the ability of the muographical method to operate even in a very urbanized environment, where many of the ordinary geological prospecting systems often fail to operate in a useful way.
Muography for volcanoes, Japan
Professor Hiroyuki Tanaka, University of Tokyo, Japan
Humans have viewed volcanoes as both as a threat, due to their potential to cause major disasters, as well as appreciating their mysterious beauty. The 20th century developments of geophysics, geochemistry, petrology, and mineralogy have enriched people’s knowledge of Earth, and recently, predicting when the eruption starts has become possible by observing its precursors. However, prediction of “how the eruption follows the sequence, and when it will end” are developing and ongoing efforts. Volcano research has long been dominated by classical mechanics, largely disregarding the potential of particle physics to augment existing techniques. The purpose of this talk is to present a potential of a new imaging technique called muography to apply to studying geodynamics of volcanoes. High-energy muons that are produced via the reaction between primary cosmic rays and the Earth’s atmosphere can be used as a probe to explore the density distribution in gigantic objects including shallow parts of the Earth's crust. Muography has the potential to serve as a useful paradigm to transform our understanding of underground structures as the X-ray transformed our understanding of medicine and the body. Existing results for various volcanoes will be discussed here, and an outlook regarding anticipated future observations will be briefly discussed.
Passive, continuous monitoring of carbon dioxide geostorage using muon tomography
Professor Jon Gluyas, Durham University, UK
Carbon capture and storage is a transition technology from a past and present fueled by coal, oil and gas and a, hoped for, future dominated by renewable energy sources. The technology involves the capture of carbon dioxide emissions from fossil fuel power stations and other point sources, compression of the CO2 into a fluid, transporting it and then injecting it deep beneath the Earth’s surface into depleted petroleum reservoirs and other porous formations. Once injected, the CO2 must be monitored to ensure none leaks back to surface. A variety of methods have been deployed to monitor the CO2 storage site and many such methods have been adapted from oilfield practice. However, such methods are commonly indirect, episodic, require active signal generation and remain expensive throughout the monitoring period that may last for hundreds of years. Models were built to simulate CO2 storage conditions and the potential for using variations in cosmic-ray muon attenuation as a function of CO2 abundance tested. From this we developed a passive, continuous monitoring method for CO2 storage sites using muon tomography, the tools for which can be deployed during the active drilling phase (development) of the storage site. To do this it was necessary to develop a muon detector that could be used in the hostile environment (saline, high temperature) of the well bore. A prototype detector has been built and tested at the 1.1km deep Boulby potash mine on the NE coast of England.
Borehole muography of subsurface reservoirs
Dr Alain Bonneville Pacific Northwest National Laboratory, USA
Imaging subsurface rock formations or geological objects like oil and gas reservoirs, mineral deposits, cavities or even magmatic plumbing systems under active volcanoes has been for many years a major quest of geophysicists and geologists. Since these objects cannot be observed directly, different indirect methods have been developed. They are all based on variations of certain physical properties of the subsurface materials that can be detected from the ground surface or from boreholes. To determine the density distribution, a new imaging technique using cosmic ray muon detectors deployed in a borehole has been developed and a first prototype of borehole muon detector successfully tested. In addition to providing a static image of the subsurface density in three dimensions (or 3D tomography), borehole muography can also inform on the variations of density with time which became recently of major importance. The injection of large volumes of fluids, mainly water and CO2, in subsurface reservoirs is indeed increasingly performed in various applications (e.g., aquifer storage and recovery, waste water disposal, enhanced oil recovery, carbon sequestration). This raises several concerns about the mechanical integrity of the reservoirs themselves and their surroundings. Determining the field scale induced displacement of fluids and the temporal and spatial deformations of the ground surface is thus a priority. Finally, to improve imaging of 3D subsurface structures, a combination of seismic data, gravity data, and muons can be used and this promises to be a powerful way to improve spatial resolution and reduce uncertainty.
Muon geotomography for underground resource exploration and imaging
Dr Doug Schouten, CRM GeoTomography Technologies, Inc, Canada
Professor Raffaello D’Alessandro, Università degli Studi di Firenze and INFN Sezione di Firenze, Italy