|Fig. Fluid pressure diffusion along a strike-slip fault||
Six young scientists - F. Cappa (PI), L. De Barros, L. Stehly, A. Sladen, M.L. Doan, E. Larose - and international experts and collaborators - Y. Guglielmi (CEREGE), S. Garambois (ISTerre), J. Rutqvist (LBNL), C. Bean (UCD), R. Viesca (TUFTS), J.P. Avouac (CALTECH), J.P. Ampuero (CALTECH) - are involved in the project.
The main objective is to improve our understanding of the role of fluids on the rupture of earthquake faults.
To date, few data are available to study the couplings between fluids, fault slip and seismicity. In this project, we propose to develop a new in-situ approach based on the hydraulic stimulation of a small fault segment (10 m) under controlled experimental conditions. The fluid injections will produce small fault slip (few millimeters) and will be monitored with a dense network of sensors, including pressuremeters, strainmeters, seismometers and electrical imaging.
This original experiment will be conduct at 300 m-depth at the Low Noise Underground Laboratory of Rustrel in France.
Fluids in the Earth’s crust have long been recognized as playing an important role in the mechanics of faults and earthquakes, but the influence on seismic rupture has not been precisely determined yet mainly due to the lack of observations near the seismogenic zone and multiphysics modeling. In this project, we propose to explore jointly the mechanical and seismological response of faults to fluid pressures, using a combined in-situ experimental and modeling approach. The main goal is to provide new observations in a seismogenic area and the appropriate theoretical models for a better understanding of the hydromechanical and seismic/aseismic behavior of fault zones under the different fluid pressure conditions operating in the brittle crust. The main questions addressed in this project are: (1) how do faults with fluids slip?, (2) do the fluids participate only in the rupture triggering phase or in the entire rupture process?, (3) are the fluid pressures and seismic waves measured in the near-surface part of active faults a good marker of deformation and a precursor of rupture at depth?, and (4) what are the processes generating the seismic and mechanical observations on faults which can be used to improve the rupture forecasting?
• Task 1 (PI: F. Cappa) is devoted to the coordination and integration of the different parts of the project, including in-situ measurements, data analysis, theoretical modeling and methodological developments.
• Task 2 (PI: L. De Barros) is experimental and focuses on (1) the development of the in-situ experiments under controlled hydraulic and mechanical conditions and (2) the joint analysis of the recorded dataset.
• Task 3 (PI: F. Cappa) is numerical and focuses on the development of hydromechanical models of fault rupture under different fluid pressure regimes. The developed models will be used both to analyze the data collected during the in-situ experiment and for large-scale modeling of crustal faults.
• Task 4 (PI: L. Stehly) will integrate our data and upscale them, by performing numerical modeling and looking at large-scale faults and earthquakes data.
FUNDING from ANR
BEGINNING on March 2014
DURATION 48 months
Key Publications related to the project
- Guglielmi Y., Cappa F., Avouac J.-P., Henry P. et Elsworth D., Seismicity triggered by fluid injection–induced aseismic slip, Science, vol. 348, n°6240, pp. 1224-1226.
- Science Perspective, 12 June 2015.
- Nature News, 11 June 2015.
Video: Seismicity and aseismic slip induced by fluid injection directly in a fault
Videos: Fluid pressure diffusion and associated slip along two crustal faults