Relevant publications

Gravity measurements below 10-9 g with a transportable absolute quantum gravimeter

Vincent Ménoret, Pierre Vermeulen, Nicolas Le Moigne, Sylvain Bonvalot, Philippe Bouyer, Arnaud Landragin & Bruno Desruelle

Scientific Reports, volume 8, Article number: 12300 (2018)

Abstract

Gravimetry is a well-established technique for the determination of sub-surface mass distribution needed in several fields of geoscience, and various types of gravimeters have been developed over the last 50 years. Among them, quantum gravimeters based on atom interferometry have shown toplevel performance in terms of sensitivity, long-term stability and accuracy. Nevertheless, they have remained confined to laboratories due to their complex operation and high sensitivity to the external environment. Here we report on a novel, transportable, quantum gravimeter that can be operated under real world conditions by non-specialists, and measure the absolute gravitational acceleration continuously with a long-term stability below 10 nm.s^−2 (1 μGal). It features several technological innovations that allow for high-precision gravity measurements, while keeping the instrument light and small enough for field measurements. The instrument was characterized in detail and its stability was evaluated during a month-long measurement campaign.

 

The added value of time-variable microgravimetry to the understanding of how volcanoes work

Daniele Carbone, Michael P. Poland, Michel Diament & Filippo Greco

Earth-Science Reviews, volume 169 (2017)
ZENODO version

Abstract

During the past few decades, time-variable volcano gravimetry has shown great potential for imaging subsurface processes at active volcanoes (including some processes that might otherwise remain “hidden”), especially when combined with other methods (e.g., ground deformation, seismicity, and gas emissions). By supplying information on changes in the distribution of bulk mass over time, gravimetry can provide information regarding processes such as magma accumulation in void space, gas segregation at shallow depths, and mechanisms driving volcanic uplift and subsidence.
Despite its potential, time-variable volcano gravimetry is an underexploited method, not widely adopted by volcano researchers or observatories. The cost of instrumentation and the difficulty in using it under harsh environmental conditions is a significant impediment to the exploitation of gravimetry at many volcanoes. In addition, retrieving useful information from gravity changes in noisy volcanic environments is a major challenge. While these difficulties are not trivial, neither are they insurmountable; indeed, creative efforts in a variety of volcanic settings highlight the value of time-variable gravimetry for understanding hazards as well as revealing fundamental insights into how volcanoes work.
Building on previous work, we provide a comprehensive review of time-variable volcano gravimetry, including discussions of instrumentation, modeling and analysis techniques, and case studies that emphasize what can be learned from campaign, continuous, and hybrid gravity observations. We are hopeful that this exploration of time-variable volcano gravimetry will excite more scientists about the potential of the method, spurring further application, development, and innovation.

 

Measurement of the Earth tides with a MEMS gravimeter

Richard P. Middlemiss, Antonio Samarelli, Douglas J. Paul, James Hough, Sheila Rowan & Giles D. Hammond

Nature, volume 531, pages 614–617 (2016)
CORE version

Abstract

The ability to measure tiny variations in the local gravitational acceleration allows, besides other applications, the detection of hidden hydrocarbon reserves, magma build-up before volcanic eruptions, and subterranean tunnels. Several technologies are available that achieve the sensitivities required for such applications (tens of microgal per hertz^1/2): free-fall gravimeters, springbased gravimeters, superconducting gravimeters, and atom interferometers. All of these devices can observe the Earth tides: the elastic deformation of the Earth’s crust as a result of tidal forces. This is a universally predictable gravitational signal that requires both high sensitivity and high stability over timescales of several days to measure. All present gravimeters, however, have limitations of high cost (more than 100,000 US dollars) and high mass (more than 8 kilograms). Here we present a microelectromechanical system (MEMS) device with a sensitivity of 40 microgal per hertz^1/2 only a few cubic centimetres in size. We use it to measure the Earth tides, revealing the long-term stability of our instrument compared to any other MEMS device. MEMS accelerometers—found in most smart phones—can be mass-produced remarkably cheaply, but none are stable enough to be called a gravimeter. Our device has thus made the transition from accelerometer to gravimeter. The small size and low cost of this MEMS gravimeter suggests many applications in gravity mapping. For example, it could be mounted on a drone instead of low-flying aircraft for distributed land surveying and exploration, deployed to monitor volcanoes, or built into multi-pixel density-contrast imaging arrays.

 
Public project deliverables

Deliverable 4.1 - Parameters definition for devices design
Mehdi Nikkhoo, Eleonora Rivalta, Daniele Carbone & NEWTON-g consortium
submission date: 05 October 2018
Work Package: WP4 - Data analysis
Lead Beneficiary: Helmholtz-Zentrum Potsdam. Deutsches GeoForschungsZentrum (GFZ)

ZENODO - https://doi.org/10.5281/zenodo.1492735

 

Deliverable 2.1 - Gravity imager design review
Laura Antoni-Micollier, Jean Lautier-Gaud & NEWTON-g consortium
submission date: 30 November 2018
Work Package: WP2 – Development of the gravity imager
Lead Beneficiary: MUQUANS

ZENODO - https://doi.org/10.5281/zenodo.2542583