Location of tremor sources and estimation of lava output using tremor source amplitude on the Piton de la Fournaise volcano: 1. Location of tremor sources

We present a study of the tremor that accompanied several eruptions of the Piton de la Fournaise volcano. We locate tremor sources in several frequency bands with a method based on the use of seismic amplitudes corrected for the recording site effect. The location of the sources is obtained by approximating the decay of the amplitude as a function of the hypocentral distance using the body wave amplitude decay. For frequencies above 1.5 Hz, sources are generally found at hallow depth and close to the location of the eruptive vents or fissures. The best correlation between the position of the vents and tremor sources is obtained for the 5-10 Hz frequency band suggesting the tremor in that band is directly generated at the eruption sites. Lower frequencies seem to be related to deeper processes than the eruption process observed at the surface. As sources are found at shallow depth, locating the tremor origin does not appear to be efficient for mapping the underground plumbing system of the volcano. On the other hand, during some eruptions, it appears as an efficient tool for monitoring the evolution of the eruption such as the opening of new eruptive fissures.