Methodology

Latest update : 11 April 2011.

Latest articles

Education, outreach and team

Monday 11 April 2011, by briandx // Methodology

Education and outreach
Another important expected contribution is the training of young scientists and specialists. The PI, Michel Campillo, has a long record of teaching and supervising responsibilities, with many of his former students and postdocs now working as researchers and leaders in the academic world and in industry. Both the leading (UJF, LGIT) and the partner (IPGP) organizations are among the best French educational institutions with very strong undergraduate and graduate (...) Read more »

Social and economical implications of the project

Monday 11 April 2011, by briandx // Methodology

Last but not least, we are concerned by the possible implications of our research. First of all, we expect that these new developments will have applications for the limitation of human and economic losses due to natural hazards. We must continue to investigate the changes of velocity associated with the preparation of volcanic eruptions to have a systematic and reliable precursory signal. The next step will be to investigate the behaviour of explosive volcanoes. Although with long (...) Read more »

Applications in controlled environments

Monday 11 April 2011, by briandx // Methodology

Monitoring geological objects in the perspective of natural hazard mitigation is not the only objective of this proposal. Faults for instance have a complex behavior and the number of unknown is very large when considering physical models. In absence of in situ control of the mechanical state at depth, it is necessary to validate our approach with controlled change at a scale somehow similar to the one of the geological objects like faults or volcanoes. There are several domains of (...) Read more »

Methodological developments

Monday 11 April 2011, by briandx // Methodology

While in ideal conditions the correlation of noise would converge to the exact Green function of the Earth, in practical application the accuracy of the reconstruction is limited. More specifically, spurious fluctuations remain in the correlations that sometime cover the useful signal. They are related to the finite duration of our signal, the uneven distribution of sources and their temporal correlations. Because our investigation of the changing Earth requires the highest level of (...) Read more »

Origin and structure of the seismic noise: understanding interaction between the Solid Earth, the Ocean, and the Atmosphere

Monday 11 April 2011, by briandx // Methodology

A significant improvement of the accuracy of the noise-based imaging and monitoring methods will be achieved with better taking into account the heterogeneous distribution of seismic noise sources and its evolution in time. Knowledge of the origin of the ambient noise will also help us to better understand certain meteorological phenomena. Most continuous seismic recordings are composed of signals excited by non-tectonic sources, related to the forcing from the atmosphere and the oceans. (...) Read more »

Developing noise based monitoring methods

Monday 11 April 2011, by briandx // Methodology

Our first results in the Piton de la Fournaise volcano and in the Parkfield area were obtained with the data of short period networks. As a consequence, we could only reconstruct relatively short period ( 5 s) surface waves reflecting transient changes in superficial layers of the crust. Using broadband networks, we will be able to extract surface waves in a broad period range. We will monitor deep zones that have not been probed before. In particular, it will give us access to the (...) Read more »

Fundamental developments

Monday 11 April 2011, by briandx // Methodology

Empirical Green function reconstruction from "imperfect" wavefields
The theory in the simple cases is relatively well understood now (Roux et al., 2005, Snieder, 2004, van Tiggelen, 2003, Wapenaar, 2005, Sanchez-Sesma and Campillo 2006, Colin de Verdière 2006 among others). Our efforts must concentrate now on the cases where an only imperfect reconstruction can be achieved. This is the case with the ambient noise for which there is no guarantee that it exhibits the random properties (...) Read more »

Introduction

Monday 11 April 2011, by briandx // Methodology

The main goal of this proposal is to build up on our first very promising results and to develop methods using the ambient seismic noise to monitor slight changes of properties inside the solid Earth. The implication is the detection of transient changes of strain at depth. A major field of application is the study of potentially dangerous natural objects like volcanoes or active fault zones and also the monitoring of changes induced by human activity in different contexts : environmental (...) Read more »