Faults

Understanding the dynamics of crustal faults is a new target for GéoSciences Réunion.

The originality of our approach is to combine the analysis of (1) large crustal faults with long seismic cycles, e.g. the Nojima fault and the Median Tectonic Line in Japan and (2) ring faults of basaltic calderas characterized by a succession of several tens of seismic cycles in a few days during the caldera collapse.

 

CO2 DEGASSING IN ACTIVE FAULTS

 

Fourier Transform Infrared microscopy (FTIR) allows to map water and carbon concentrations in natural glasses at the micro-scale. FTIR mapping of two generations of pseudotachylytes (i.e. friction melts) from the Nojima fault (Japan) reveals that 90 wt% of the CO2 is exsolved during fault slip, due to the low solubility of carbon in melts. Earthquakes are therefore a significant source of CO2.

Famin et al., (2008); Sulem and Famin (2009) 

               

 

Deformation of Piton de la Fournaise related to the April 2007 caldera collapse. Tiltmeter data reveal successive seismic cycles starting first by a period of stress relaxation then followed by a phase of linear stress increase. The first step of each cycle is similar to that observed after the 2004 Parkfield earthquake (after Brenguier et al., 2008).

Staff involved: Vincent Famin, Laurent Michon.