How do the distribution and characteristics of subsurface fluids change over time? Far from an esoteric question, this fundamental
issue dominates the energy industry (not just petroleum and natural gas, but also geothermal), resource management (particularly with
regard to water), and natural hazards (especially volcanoes). Despite its critical importance, there are only few and limited means of addressing the problem.
NEWTON-g targets a technological breakthrough and proposes a change of paradigm to address this need, by developing new tools for gravity measurement that are based on innovative
new technologies. Our broad goal is to propose a new concept for gravimetry through the development of new instrumentation that can be widely adopted by researchers
and monitoring agencies in charge of studying subsurface fluid characteristics.
The main objectives of NEWTON-g are:
To overcome the current limits of terrain gravimetry, that are imposed by the high cost
and by the characteristics of currently available gravimeters
Spring-based relative gravimeters, first introduced in the 1930s, are the most widely used for geophysical applications. They measure the change in the equilibrium position of
a proof mass suspended from a spring, resulting from a change in the gravity field. Superconducting gravimeters (SGs; first introduced in the 1970s) offer an alternative to spring-based instruments,
although still provide relative measurements only. Instead of a mechanical spring, SGs exploit the magnetic levitation of a superconducting sphere in a field of superconducting persistent coils. They have
high power requirements and occupy a large physical footprint; therefore, they are not well suited for field deployments. State of the art absolute gravimeters exploit the free-fall of macroscopic test masses.
Transportable free-fall absolute gravimeters (FFAGs ) were developed starting in in the late 1960s. They employ a laser interferometer to precisely monitor the free-fall trajectory of the test mass. FFAGs are
not well-suited for field use in harsh conditions because of large size and high power requirement. Furthermore, they cannot record gravity data continuously for extended intervals. All of the above gravimeters
come at very high costs and no new methods for measuring gravity have been introduced for nearly five decades, so all existing gravimeters are based on older technologies and principles. Given the current state
of the art, it is clear that the development of new instruments represents a fundamental step that can move gravimetry from a niche field into a cornerstone resource for geophysical monitoring and research.
To design and produce a new "gravity imager", including an absolute quantum gravimeter and an array of low-cost gravimeters based on MEMS technology
Through the MEMS gravimeters that will be produced as part of NEWTON-g, most barriers that have limited the development of continuous
gravimetry for geophysical applications will be broken down. Indeed, thanks to small size and low power consumption, MEMS devices are especially well suited for use under rugged environmental conditions.
Furthermore, thanks to the low cost, it will be possible to install extended arrays of gravity sensors, thus detecting underground mass changes with high spatial and temporal resolution, including in
hazardous areas (like the summit region of an active volcano) where gravimeters are rarely installed owing to the high risk of losing expensive instrumentation to eruptive activity.
The quantum gravimeter
that will be developed under NEWTON-g will be the ideal complement to the MEMS devices. Compared to standard FFAGs, we expect that the new quantum gravimeter will be (i) easier to install, with the ability
to complete a high-quality absolute measurement within 1–1.5 hours of arrival at the installation site; (ii) less affected by ground vibrations thanks to an innovative technology involving active compensation
of ground vibration noise; (iii) able to measure continuously for extended periods of time and (iv) cheaper, if not in terms of production costs, then in terms of maintenance costs.
approach of NEWTON-g, based on the joint use of MEMS and quantum gravimeters, represents a paradigm shift in the use of gravimetry for geophysical applications. The deployment will involve an array of
MEMS devices anchored to the quantum gravimeter; the latter will provide a high-resolution reference to calibrate the signals from the MEMS devices.
To field-test the newly-developed "gravity imager" at Mt. Etna volcano, where a 30-year history of gravity measurements will provide context for NEWTON-g deployments
Our specific target for testing the new gravity measurement technologies developed under NEWTON-g will be Mount Etna (Italy), a
persistently active volcano that has been a UNESCO world heritage since 2013. Owing to its persistent activity, with a wide spectrum of eruptive styles, large volcano-related gravity changes often
develop at Mt. Etna, over different time scales. The volcano has also been well studied and is the site of a comprehensive existing monitoring infrastructure, including some continuous gravity stations.
Furthermore, the active crater zone of Etna can be reached by car by authorized personnel. This combination of factors provides a unique and attractive scenario for testing and benchmarking the new gravity instruments.
To deploy strategies for incorporating the data produced by the new measurement system into early warning systems, hazard reporting and crisis management plans
eruptions threaten several countries across Europe, including Greece, Italy,
Iceland, Russia and overseas territories of EU countries. Historical records
show that some of these volcanoes have the potential to produce destructive
eruptions. A recent example of volcanic eruption impact on civil society is
the 2010 eruption of the Eyjafjallajökull volcano (Iceland), that forced
most countries in northern Europe to close their airspace for some days to
weeks, due to volcanic ash. Volcanic hazards with the potential of affecting
urbanized areas and economic sectors in the near and far field, imply a
demand for the associated risk to be mitigated and, in turn, imply that
emergency response agencies must have easy access to critical information
for early warning and volcanic hazard assessment. Given the unique insights
into subsurface fluids provided by gravity, the technique has exceptional
utility for characterizing the hazard potential at a given volcano.
objectives of NEWTON-g include the design and development of a new prototype gravity measurement system and its field application at Mount Etna volcano, including incorporation of the data produced
by the new system into early warning systems, hazard reporting and crisis management plans for the detection and assessment of short-term (days-months) volcanic hazard. Such an effort may serve as a model for how
volcano observatories around the world might use the tools and methods developed by NEWTON-g for their own monitoring programs.
To shift the center of production of gravimeters from North America to Europe
There is currently no capability in Europe for the manufacture of gravity monitoring equipment, despite the widespread application of
gravity in a variety of fields. Indeed, all the gravimeters available on the market are produced in the USA and Canada. With the realization of the gravity imaging system, jointly exploiting MEMS and
quantum devices, proposed by NEWTON-g, the center of production for both absolute gravity technology, as well as less expensive relative instrumentation, would move from North America to Europe.