Janire Prudencio

Two-dimensional seismic attenuation images of Stromboli Island using active data

In this work we present intrinsic and scattering seismic attenuation 2-D images of Stromboli Volcano. We used 21,953 waveforms from air gun shots fired by an oceanographic vessel and recorded at 33 inland and 10 ocean bottom seismometer seismic stations. Coda wave envelopes of the filtered seismic traces were fitted to the energy transport equation in the diffusion approximation, obtaining a couple of separate Qi and Qs in six frequency bands. Using numerically estimated sensitivity kernels for coda waves, separate images of each quality factor were produced. Results appear stable and robust. They show that scattering attenuation prevails over intrinsic attenuation. The scattering pattern shows a strong concordance with the tectonic lineaments in the area, while an area of high total attenuation coincides with the zone where most of the volcanic activity occurs. Our results provide evidence that the most important attenuation effects in volcanic areas are associated with the presence of geological heterogeneities.

The 3D Attenuation Structure of Deception Island (Antarctica)

The seismic and volcanological structure of Deception Island (Antarctica) is an intense focus topic in Volcano Geophysics. The interpretations given by scientists on the origin, nature, and location of the structures buried under the island strongly diverge. We present a high-resolution 3D P-wave attenuation tomography model obtained by using the coda normalization method on 20,293 high-quality waveforms produced by active sources. The checkerboard and synthetic anomaly tests guarantee the reproduction of the input anomalies under the island down to a depth of 4xa0km. The results, once compared with our current knowledge on the geological, geochemical, and geophysical structure of the region, depict Deception as a piecemeal caldera structure coming out of the Bransfield Trough. High-attenuation anomalies contouring the northeastern emerged caldera rim correlate with the locations of sediments. In our interpretation, the main attenuation contrast, which appears under the collapsed southeastern caldera rim, is related to the deeper feeding systems. A unique P-wave high-attenuation spherical-like anomaly in the inner bay extends between depths of 1 and 3xa0km. The northern contour of the anomaly coincides with the calderic rim both at 1 and 2xa0km, while smaller anomalies connect it with deeper structures below 3xa0km, dipping toward the Bransfield Trough. In our interpretation, the large upper anomaly is caused by a high-temperature shallow (1–3xa0km deep) geothermal system, located beneath the sediment-filled bay in the collapsed blocks and heated by smaller, deeper contributions of molten materials (magma) rising from southeast.

New Insights on Mt. Etna’s Crust and Relationship with the Regional Tectonic Framework from Joint Active and Passive P-Wave Seismic Tomography

In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g., those from Mt. Etna and the Aeolian Islands archipelago) testifies to the complexity of the tectonic and geodynamic setting. Despite the large number of studies that have focused on this area, the relationships among volcanism, tectonics, magma ascent, and geodynamic processes remain poorly understood. We present a tomographic inversion of P-wave velocity using active and passive sources. Seismic signals were recorded using both temporary on-land and ocean bottom seismometers and data from a permanent local seismic network consisting of 267 seismic stations. Active seismic signals were generated using air gun shots mounted on the Spanish Oceanographic Vessel ‘Sarmiento de Gamboa’. Passive seismic sources were obtained from 452 local earthquakes recorded over a 4-month period. In total, 184,797 active P-phase and 11,802 passive P-phase first arrivals were inverted to provide three different velocity models. Our results include the first crustal seismic active tomography for the northern Sicily area, including the Peloritan–southern Calabria region and both the Mt. Etna and Aeolian volcanic environments. The tomographic images provide a detailed and complete regional seismotectonic framework and highlight a spatially heterogeneous tectonic regime, which is consistent with and extends the findings of previous models. One of our most significant results was a tomographic map extending to 14xa0km depth showing a discontinuity striking roughly NW–SE, extending from the Gulf of Patti to the Ionian Sea, south-east of Capo Taormina, corresponding to the Aeolian–Tindari–Letojanni fault system, a regional deformation belt. Moreover, for the first time, we observed a high-velocity anomaly located in the south-eastern sector of the Mt. Etna region, offshore of the Timpe area, which is compatible with the plumbing system of an ancient shield volcano located offshore of Mt. Etna.

Database of multi-parametric geophysical data from the TOMO-DEC experiment on Deception Island, Antarctica

Deception Island volcano (Antarctica) is one of the most closely monitored and studied volcanoes on the region. In January 2005, a multi-parametric international experiment was conducted that encompassed both Deception Island and its surrounding waters. We performed this experiment from aboard the Spanish oceanographic vessel ‘Hespérides’, and from five land-based locations on Deception Island (the Spanish scientific Antarctic base ‘Gabriel de Castilla’ and four temporary camps). This experiment allowed us to record active seismic signals using a large network of seismic stations that were deployed both on land and on the seafloor. In addition, other geophysical data were acquired, including bathymetric high precision multi-beam data, and gravimetric and magnetic profiles. To date, the seismic and bathymetric data have been analysed but the magnetic and gravimetric data have not. We provide P-wave arrival-time picks and seismic tomography results in velocity and attenuation. In this manuscript, we describe the main characteristics of the experiment, the instruments, the data, and the repositories from which data and information can be obtained.

A 3D joint interpretation of magnetotelluric and seismic tomographic models: The case of the volcanic island of Tenerife

In this work we have done a 3D joint interpretation of magnetotelluric and seismic tomography models. Previously we have described different techniques to infer the inner structure of the Earth. We have focused on volcanic regions, specifically on Tenerife Island volcano (Canary Islands, Spain). In this area, magnetotelluric and seismic tomography studies have been done separately. The novelty of the present work is the combination of both techniques in Tenerife Island. For this aim we have applied Fuzzy Clusters Method at different depths obtaining several clusters or classes. From the results, a geothermal system has been inferred below Teide volcano, in the center of Tenerife Island. An edifice hydrothermally altered and full of fluids is situated below Teide, ending at 600m below sea level. From this depth the resistivity and VP values increase downwards. We also observe a clay cap structure, a typical feature in geothermal systems related with low resistivity and low VP values. We perform a 3D joint interpretation of magnetotelluric and seismic tomography models.We apply Fuzzy Clusters Method at different depths obtaining several clusters or classes.We infer a geothermal system, including a clay clap structure, below Teide volcano.

Scattering images from autocorrelation functions of P-wave seismic velocity images: the case of Tenerife Island (Canary Islands, Spain)

We present a P-wave scattering image of the volcanic structures under Tenerife Island using the autocorrelation functions of P-wave vertical velocity fluctuations. We have applied a cluster analysis to total quality factor attenuation (Qt−1

Seismic tomography model reveals mantle magma sources of recent volcanic activity at El Hierro Island (Canary Islands, Spain)

{Q}_t^{-1}

Advances on the automatic estimation of the P-wave onset time

) and scattering quality factor attenuation (QPSc−1