Jean Battaglia

Location of seismic events and eruptive fissures on the Piton de la Fournaise volcano using seismic amplitudes

[1] We present a method for locating the source of seismic events on Piton de la Fournaise. The method is based on seismic amplitudes corrected for station site effects using coda site amplification factors. Once corrected, the spatial distribution of amplitudes shows smooth and simple contours for many types of events, including rockfalls, long-period events and eruption tremor. On the basis of the simplicity of these distributions we develop inversion methods for locating their origins. To achieve this, the decrease of the amplitude as a function of the distance to the source is approximated by the decay either of surface or body waves in a homogeneous medium. The method is effective for locating rockfalls, long-period events, and eruption tremor sources. The sources of eruption tremor are usually found to be located at shallow depth and close to the eruptive fissures. Because of this, our method is a useful tool for locating fissures at the beginning of eruptions.

Dynamic dyke propagation deduced from tilt variations preceding the March 9, 1998, eruption of the Piton de la Fournaise volcano

During the hour preceding the March 9, 1998, eruption of the Piton de la Fournaise volcano, the deformation network of the Observatory recorded some large deformations in the summit area. A broadband seismic station of the GEOSCOPE global network, RER, is located about 8 km away from the summit of the volcano. Signals from that station may be interpreted as tilt changes. The combination of the above two kinds of signals allows, by using a tensile fault model, to constrain the geometry as well as some characteristics (volume, propagation velocity) of the dyke that intruded the summit area during the hour preceding the beginning of eruptive activity.

Tilt signals derived from a GEOSCOPE VBB station on the Piton de la Fournaise volcano

We report some very long period transients observed on a very broadband seismic station of the GEOSCOPE network, which is situated 8 km away from the summit of the Piton de la Fournaise volcano. We transform the ground velocity measured by the seismic station into tilt and test the result by comparing with data from Blum-type classical pendulum tiltmeters located in the same vault. The comparison validates the use of the horizontal seismometers for measuring tilt for periods shorter than 25 hours. The method is applied to the transients observed prior to several eruptions and magmatic intrusions since 1991. Because of the moderate distance between GEOSCOPE station and the summit of the volcano, the obtained tilt measurements provide information about eruptions and intrusions which complement the information on the geometry and location of the magmatic source provided by the summit tilt network.

Anatomy of a Strombolian eruption: Inferences from particle data recorded with thermal video

Over the past decade, a proliferation of new technologies has pushed forward our ability to measure the dynamics of volcanic emissions as they exit, and ascend above, the vent. Measuring parameters of all particles as they exit the vent during an explosive eruption is the best way to gather parameters such as size, shape, velocity, and mass for the solid (particulate) fraction of the plume, in our case this being the lapilli and bomb component. We compute particle velocities and size distributions using high spatial resolution (centimeter-sized pixel) thermal infrared imagery collected at 200 Hz for small explosive eruptions at Stromboli (Italy). Our study covers 13 eruptions from Strombolis southwest crater that occured in October 2012, plus 13 eruptions from the southwest crater, and 5 eruptions from the northeast crater in May 2014. We obtain a statistically robust database for size, mass, and velocity of 83,000 particles. Most particles have sizes of 5 to 15 cm so that the majority of individual particle masses are below 0.4 kg. However, 4950 (6%) of the particles are heavier than 5 kg and represent 59% of the total mass erupted. We also show that the smallest particles detected have the highest velocities with the maximum recorded vent-leaving velocity being 240 m/s. While the thermal data provide insights into particle emission and launch dynamics, correlation with seismic data sheds light on the source mechanism. Our results lead us to suggest that pyroclast-dominated explosions are a consequence of the presence of a viscous, degassed cap at the head of the magma column, whereas gas-dominated events are a consequence of slug bursting in a “cleaner” conduit, the cap having been lost by convective overturn.

Modern Multispectral Sensors Help Track Explosive Eruptions

Due to its massive air traffic impact, the 2010 eruption of Eyjafjallajokull was felt by millions of people and cost airlines more than U.S.

Seismic anisotropy and its precursory change before eruptions at Piton de la Fournaise volcano, La Réunion

1.7 billion. The event has, thus, become widely cited in renewed efforts to improve real-time tracking of volcanic plumes, as witnessed by special sections published last year in Journal of Geophysical Research, (117, issues D20 and B9).

MeMoVolc consensual document: a review of cross-disciplinary approaches to characterizing small explosive magmatic eruptions

The Piton de la Fournaise volcano exhibits frequent eruptions preceded by seismic swarms and is a good target to test hypotheses about magmatically induced variations in seismic wave properties. We use a permanent station network and a portable broadband network to compare seismic anisotropy measured via shear wave splitting with geodetic displacements, ratios of compressional to shear velocity (Vp/Vs), earthquake focal mechanisms, and ambient noise correlation analysis of surface wave velocities and to examine velocity and stress changes from 2000 through 2012. Fast directions align radially to the central cone and parallel to surface cracks and fissures, suggesting stress-controlled cracks. High Vp/Vs ratios under the summit compared with low ratios under the flank suggest spatial variations in the proportion of fluid-filled versus gas-filled cracks. Secular variations of fast directions (ϕ) and delay times (dt) between split shear waves are interpreted to sense changing crack densities and pressure. Delay times tend to increase while surface wave velocity decreases before eruptions. Rotations of ϕ may be caused by changes in either stress direction or fluid pressure. These changes usually correlate with GPS baseline changes. Changes in shear wave splitting measurements made on multiplets yield several populations with characteristic delay times, measured incoming polarizations, and fast directions, which change their proportion as a function of time. An eruption sequence on 14 October 2010 yielded over 2000 shear wave splitting measurements in a 14 h period, allowing high time resolution measurements to characterize the sequence. Stress directions from a propagating dike model qualitatively fit the temporal change in splitting.

Short term precursors of Strombolian explosions at Yasur volcano (Vanuatu)

A workshop entitled “Tracking and understanding volcanic emissions through cross-disciplinary integration: a textural working group” was held at the Université Blaise Pascal (Clermont-Ferrand, France) on the 6–7 November 2012. This workshop was supported by the European Science Foundation (ESF). The main objective of the workshop was to establish an initial advisory group to begin to define measurements, methods, formats and standards to be applied in the integration of geophysical, physical and textural data collected during volcanic eruptions. This would homogenize procedures to be applied and integrated during both past and ongoing events. The workshop comprised a total of 35 scientists from six countries (France, Italy, Great Britain, Germany, Switzerland and Iceland). The four main aims were to discuss and define: standards, precision and measurement protocols for textural analysis; identification of textural, field deposit, chemistry and geophysical parameters that can best be measured and combined; the best delivery formats so that data can be shared between and easily used by different groups; and multi-disciplinary sampling and measurement routines currently used and measurement standards applied, by each community. The group agreed that community-wide, cross-disciplinary integration, centred on defining those measurements and formats that can be best combined, is an attainable and key global focus. Consequently, we prepared this paper to present our initial conclusions and recommendations, along with a review of the current state of the art in this field that supported our discussions.

Thermal characterization of diamond films through modulated photothermal radiometry.

The seismic wavefield associated with Strombolian activity is usually dominated by explosion quakes (EQs), tremor, and various signals generated by surface phenomena. Looking at the seismicity recorded at Yasur volcano in 2008, we found that beside the transient events which occur simultaneously with surface explosions, the seismicity includes events related to a deeper process. These long period (LP) events form a family of similar events located below the southeastern part of the crater rim at a depth of about 700–1200 m below the summit. They are commonly followed by EQs with a variable delay. The examination of about 20,000 LP-EQ sequences at several stations near the summit shows that interevent delays follow distributions peaked around 11–12 s. This short delay compared to the relatively great source depth of the LPs favors a causal relationship linked to pressure transfer rather than gas slug propagation after nucleation at the LP source.

Seismic Monitoring at Piton de la Fournaise

Diamond (Dia) films are promising heat-dissipative materials for electronic packages because they combine high thermal conductivity with high electrical resistivity. However, precise knowledge of the thermal properties of the diamond films is crucial to their potential application as passive thermal management substrates in electronics. In this study, modulated photothermal radiometry in a front-face configuration was employed to thermally characterize polycrystalline diamond films deposited onto silicon (Si) substrates through laser-assisted combustion synthesis. The intrinsic thermal conductivity of diamond films and the thermal boundary resistance at the interface between the diamond film and the Si substrate were investigated. The results enlighten the correlation between the deposition process, film purity, film transverse thermal conductivity, and interface thermal resistance.