J. Prudencio - Academia.edu (original) (raw)

Papers by J. Prudencio

Geophysical Research Letters

It is located in the Bransfield Strait, between −62.893 and −63.021° south and between −60.751 an... more It is located in the Bransfield Strait, between −62.893 and −63.021° south and between −60.751 and −60.495 west. This horseshoe-shaped caldera is located between the South Shetland Islands archipelago, at its north and the Antarctic Peninsula at its south (Figure 1, top right). It extends east-west and north-south for 12.85 and 14.41 km, respectively, thus covering an area of about 94.7 km 2 (Figure 1). The altitude of Deception Island varies from 160 m below sea level, in Port Foster, to its highest point, Mount Pond, at 539 m above sea level (Figure 1, bottom). The interest in deciphering the magmatic system of Deception island has steadily grown due to the increasing numbers of tourists during the summer season and the presence of Argentinian and Spanish research bases. Studies conducted in this volcano have extensively covered: geochemistry (

deep magma pulses: The 2011–2013 seismic series associated

This manuscript shows a new multidisciplinary interpretation approach of the internal structure o... more This manuscript shows a new multidisciplinary interpretation approach of the internal structure of Tenerife island. The cental core of this work is the determination of the three dimensional attenuation structure of the region using P-waves and the Coda Normalization (CN) method. This study has been performed using 45303 seismograms recorded in 85 seismic stations from an active experiment (air-gun shots) conducted in January of 2007. The interpretation of these new results is done combining the new images with previous studies performed in the area such as seismic velocity tomography, magnetic structure, magnetotelluric surveys or gravimetric models. Our new 3D images indicate the presence of seismic attenuation contrasts, with areas of high and low seismic attenuation patterns. High seismic attenuation zones are observed both in shallow and deeper areas. The shallowest area of Las Cañadas Caldera complex (1-3 km thick) is dominated by high attenuation behavior and it is interprete...

Journal of Geophysical Research: Solid Earth, 2021

We present a new three‐dimensional (3D) image of attenuation beneath Mt. Etna volcano based on th... more We present a new three‐dimensional (3D) image of attenuation beneath Mt. Etna volcano based on the coda normalization method. Mt. Etna is an ideal natural laboratory for the application of new or unconventional tomography techniques owing to high levels of seismicity spanning a wide range of epicentral distances and depths. We retrieved seismic waveforms from the database generated in the 2014 TOMO‐ETNA seismic experiment and performed a joint interpretation of tomographic and geophysical inversion models to better constrain interpretations of the volcanic structure. We compared the attenuation tomography results with seismic inversion models (two P wave seismic models and a 3D coda wave seismic attenuation model) and the literature to highlight and interpret structural elements and their impact on the volcano dynamics. We created a new image of the inner structure of Mt. Etna that will help to constrain present and future volcanic behavior. In particular, we focused on magma storage below the summit area and identified a large high‐attenuation volume that is characterized by physical properties compatible with the presence of magma and other fluids. The existence of such a large volume of magma in the shallow crust below Mt. Etna has implications for the eruptive potential of the volcano.

Computers & Geosciences, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Geophysical Research: Solid Earth, 2018

We image seismic intrinsic () and scattering () attenuations in Long Valley Caldera, California, ... more We image seismic intrinsic () and scattering () attenuations in Long Valley Caldera, California, by analyzing more than 1,700 vertical component waveforms from local earthquakes. Observed energy envelopes are fit to the diffusion model and seismic attenuation images are produced using twodimensional space weighting functions. Low intrinsic and low scattering attenuation anomalies in the center south of the caldera correspond to the location of an earthquake swarm in 2014. We identify high intrinsic and high scattering attenuation anomalies in the fluid-rich western and eastern areas of the caldera. From a comparison with other geophysical images (magnetotellurics and seismic tomography) we attribute these anomalies to a hydrothermal system (high attenuation). Average to high attenuation values are also observed at the adjacent Mammoth Mountain (southwest of the caldera) and may also have a hydrothermal origin. High intrinsic attenuation at low frequencies to the west of the Hartley Springs Fault may be produced by the magmatic system that produced the Inyo Craters. Seismic attenuation imaging provides insights into subsurface structures that are complementary to velocity and conductivity images.

Bulletin of Volcanology, 2018

We present a P-wave scattering image of the volcanic structures under Tenerife Island using the a... more 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 (−1) and scattering quality factor attenuation (−1) images to interpret the structures in terms of intrinsic and scattering attenuation variations on a 2D plane, corresponding to a depth of 2000 m, and check the robustness of the scattering imaging. The results show that scattering patterns are similar to total attenuation patterns in the South of the island. There are two main areas where patterns differ: at Cañadas-Teide-Pico Viejo Complex high total attenuation and average-to-low scattering values are observed. We interpret the difference as induced by intrinsic attenuation. In the Santiago Ridge Zone (SRZ) region, high scattering values correspond to average total attenuation. In our interpretation, the anomaly is induced by an extended scatterer, geometrically related to the surficial traces of Garachico and El Chinyero historical eruptions and the area of highest seismic activity during the 2004-2008 seismic crises.

Bulletin of Volcanology, 2017

We present intrinsic-and scattering-Q attenuation images for Usu volcano (Japan) by analyzing ove... more We present intrinsic-and scattering-Q attenuation images for Usu volcano (Japan) by analyzing over 1800 vertical seismograms. By fitting the observed envelopes to the diffusion model, we obtained intrinsic and scattering attenuation values at three different frequency bands. Using a back-projection method and assuming a Gaussiantype weighting function, we obtained the 2D images of intrinsic and scattering attenuation. Resolution tests confirm the robustness and reliability of the obtained images. We found that scattering attenuation is the dominant process of energy loss in the frequency range analyzed, which suggests strong spatial heterogeneity. The resultant scattering attenuation images show an increase of attenuation toward Editorial responsibility: T. Nishimura J.

Surveys in Geophysics, 2017

In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g.... more 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

Journal of Geophysical Research: Solid Earth, 2015

In this manuscript we present a new interpretation of the seismic series that accompanied eruptiv... more In this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of El Hierro, Canary Islands, during 2011-2013. We estimated temporal variations of the Gutenberg-Richter b value throughout the period of analysis, and performed high-precision relocations of the preeruptive and syneruptive seismicity using a realistic 3-D velocity model. Our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust. These magma pulses occurred within a small and well-defined volume resulting in the emplacement of fresh magma along the crust-mantle boundary underneath El Hierro. We analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust. Our results suggest that very high earthquake rates underneath El Hierro represent the response of a stable lower crust to stress perturbations with pulsatory character, linked to the injection of magma from the mantle. Magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms. The absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity, had diffusive character. We conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill. Our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the Moho. We suggest, within this framework, that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement.

Surveys in Geophysics, 2015

Geophysical Research Letters, 2015

In this work we present intrinsic and scattering seismic attenuation 2-D images of Stromboli Volc... more 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 Q i and Q s 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.

Surveys in Geophysics, 2015

The seismic and volcanological structure of Deception Island (Antarctica) is an intense focus top... more 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 4 km. The results, once compared with our current knowledge on the geological, geochemical, and geophysical structure of the region, depict Deception as apiecemeal caldera structure leant 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 3 km. The northern contour of the anomaly coincides with the calderic rim both at 1 and 2 km, while smaller anomalies connect it with deeper structures below 3 km, dipping towards the Bransfield Trough. In our interpretation, the large upper anomaly is caused by a high-temperature shallow (1 to 3 km deep) geothermal system, located beneath the sedimentfilled bay in the collapsed blocks and heated by smaller, deeper contributions of molten materials (magma) rising from southeast.

Geophysical Journal International, 2014

We present a 3-D model of P and S velocities beneath El Hierro Island, constructed using the trav... more We present a 3-D model of P and S velocities beneath El Hierro Island, constructed using the traveltime data of more than 13 000 local earthquakes recorded by the Instituto Geográfico Nacional (IGN, Spain) in the period from 2011 July to 2012 September. The velocity models were performed using the LOTOS code for iterative passive source tomography. The results of inversion were thoroughly verified using different resolution and robustness tests. The results reveal that the majority of the onshore area of El Hierro is associated with a high-velocity anomaly observed down to 10-12-km depth. This anomaly is interpreted as the accumulation of solid igneous rocks erupted during the last 1 Myr and intrusive magmatic bodies. Below this high-velocity pattern, we observe a low-velocity anomaly, interpreted as a batch of magma coming from the mantle located beneath El Hierro. The boundary between the low-and highvelocity anomalies is marked by a prominent seismicity cluster, thought to represent anomalous stresses due to the interaction of the batch of magma with crust material. The areas of recent eruptions, Orchilla and La Restinga, are associated with low-velocity anomalies surrounding the main high-velocity block. These eruptions took place around the island where the crust is much weaker than the onshore area and where the melted material cannot penetrate. These results put constraints on the geological model that could explain the origin of the volcanism in oceanic islands, such as in the Canaries, which is not yet clearly understood.

ABSTRACT In the present work we are going to analyze the same data-set used to develop the 3D vel... more ABSTRACT In the present work we are going to analyze the same data-set used to develop the 3D velocity tomographies to realize 2D intrinsic and scattering attenuation tomography. For that we are going to apply the diffusion model which is an approximation of the general energy transport theory developed by Wegler et al. (2001) and Wegler (2003). So, this new models will be a complement to the better understanding of velocity anomalies and will allow remove some grades of uncertainty of the other studies. As a result of the inversion using the diffusion model we have obtained values of S-waves intrinsic attenuation coefficient (b) and diffusivity coefficient (d) in the frequency range of 6-12 Hz for Tenerife and 4-20 Hz for Deception Island. We have quantified the attenuation by the quality factor because is more representative. We also compare attenuation images with velocity tomographies. For the case of Tenerife we confirm that Tenerife Island is a very heterogeneous area. Moreover we corroborate that high velocity zones are coincident with low attenuation zones and low velocity zones are coincident with high attenuation zones. If we compare these results with those obtained by Zandomeneghi et al. (2009) we can observe the greater concordance between velocity tomography model and this model. If we observe the high attenuation anomaly of the center of the island and we combine with other studies is highly compatible with the presence of partially molten material.

ABSTRACT A three-dimensional S wave attenuation tomography of Tenerife island has been obtained w... more ABSTRACT A three-dimensional S wave attenuation tomography of Tenerife island has been obtained with measurements of coda-normalization method. We used about 75000 waveforms relative to the dataset from an active seismic experiments using offshore shots (air guns) recorded at over 100 onshore seismic stations. The rays were traced in a 3D velocity model. The spatial resolution in our tomography is the same as that obtained by velocity tomography: we resolve 600m cubic cells. Results have shown that there is likewise agreement with the velocity tomography, the low velocity external zones being consistent with regions featuring high attenuation effects and the high velocity zones in the center of the island with regions featuring low attenuation effects. Therefore, our observations agree with the volcanic characteristics of the medium.

Geophysical Research Letters

It is located in the Bransfield Strait, between −62.893 and −63.021° south and between −60.751 an... more It is located in the Bransfield Strait, between −62.893 and −63.021° south and between −60.751 and −60.495 west. This horseshoe-shaped caldera is located between the South Shetland Islands archipelago, at its north and the Antarctic Peninsula at its south (Figure 1, top right). It extends east-west and north-south for 12.85 and 14.41 km, respectively, thus covering an area of about 94.7 km 2 (Figure 1). The altitude of Deception Island varies from 160 m below sea level, in Port Foster, to its highest point, Mount Pond, at 539 m above sea level (Figure 1, bottom). The interest in deciphering the magmatic system of Deception island has steadily grown due to the increasing numbers of tourists during the summer season and the presence of Argentinian and Spanish research bases. Studies conducted in this volcano have extensively covered: geochemistry (

deep magma pulses: The 2011–2013 seismic series associated

This manuscript shows a new multidisciplinary interpretation approach of the internal structure o... more This manuscript shows a new multidisciplinary interpretation approach of the internal structure of Tenerife island. The cental core of this work is the determination of the three dimensional attenuation structure of the region using P-waves and the Coda Normalization (CN) method. This study has been performed using 45303 seismograms recorded in 85 seismic stations from an active experiment (air-gun shots) conducted in January of 2007. The interpretation of these new results is done combining the new images with previous studies performed in the area such as seismic velocity tomography, magnetic structure, magnetotelluric surveys or gravimetric models. Our new 3D images indicate the presence of seismic attenuation contrasts, with areas of high and low seismic attenuation patterns. High seismic attenuation zones are observed both in shallow and deeper areas. The shallowest area of Las Cañadas Caldera complex (1-3 km thick) is dominated by high attenuation behavior and it is interprete...

Journal of Geophysical Research: Solid Earth, 2021

We present a new three‐dimensional (3D) image of attenuation beneath Mt. Etna volcano based on th... more We present a new three‐dimensional (3D) image of attenuation beneath Mt. Etna volcano based on the coda normalization method. Mt. Etna is an ideal natural laboratory for the application of new or unconventional tomography techniques owing to high levels of seismicity spanning a wide range of epicentral distances and depths. We retrieved seismic waveforms from the database generated in the 2014 TOMO‐ETNA seismic experiment and performed a joint interpretation of tomographic and geophysical inversion models to better constrain interpretations of the volcanic structure. We compared the attenuation tomography results with seismic inversion models (two P wave seismic models and a 3D coda wave seismic attenuation model) and the literature to highlight and interpret structural elements and their impact on the volcano dynamics. We created a new image of the inner structure of Mt. Etna that will help to constrain present and future volcanic behavior. In particular, we focused on magma storage below the summit area and identified a large high‐attenuation volume that is characterized by physical properties compatible with the presence of magma and other fluids. The existence of such a large volume of magma in the shallow crust below Mt. Etna has implications for the eruptive potential of the volcano.

Computers & Geosciences, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Geophysical Research: Solid Earth, 2018

We image seismic intrinsic () and scattering () attenuations in Long Valley Caldera, California, ... more We image seismic intrinsic () and scattering () attenuations in Long Valley Caldera, California, by analyzing more than 1,700 vertical component waveforms from local earthquakes. Observed energy envelopes are fit to the diffusion model and seismic attenuation images are produced using twodimensional space weighting functions. Low intrinsic and low scattering attenuation anomalies in the center south of the caldera correspond to the location of an earthquake swarm in 2014. We identify high intrinsic and high scattering attenuation anomalies in the fluid-rich western and eastern areas of the caldera. From a comparison with other geophysical images (magnetotellurics and seismic tomography) we attribute these anomalies to a hydrothermal system (high attenuation). Average to high attenuation values are also observed at the adjacent Mammoth Mountain (southwest of the caldera) and may also have a hydrothermal origin. High intrinsic attenuation at low frequencies to the west of the Hartley Springs Fault may be produced by the magmatic system that produced the Inyo Craters. Seismic attenuation imaging provides insights into subsurface structures that are complementary to velocity and conductivity images.

Bulletin of Volcanology, 2018

We present a P-wave scattering image of the volcanic structures under Tenerife Island using the a... more 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 (−1) and scattering quality factor attenuation (−1) images to interpret the structures in terms of intrinsic and scattering attenuation variations on a 2D plane, corresponding to a depth of 2000 m, and check the robustness of the scattering imaging. The results show that scattering patterns are similar to total attenuation patterns in the South of the island. There are two main areas where patterns differ: at Cañadas-Teide-Pico Viejo Complex high total attenuation and average-to-low scattering values are observed. We interpret the difference as induced by intrinsic attenuation. In the Santiago Ridge Zone (SRZ) region, high scattering values correspond to average total attenuation. In our interpretation, the anomaly is induced by an extended scatterer, geometrically related to the surficial traces of Garachico and El Chinyero historical eruptions and the area of highest seismic activity during the 2004-2008 seismic crises.

Bulletin of Volcanology, 2017

We present intrinsic-and scattering-Q attenuation images for Usu volcano (Japan) by analyzing ove... more We present intrinsic-and scattering-Q attenuation images for Usu volcano (Japan) by analyzing over 1800 vertical seismograms. By fitting the observed envelopes to the diffusion model, we obtained intrinsic and scattering attenuation values at three different frequency bands. Using a back-projection method and assuming a Gaussiantype weighting function, we obtained the 2D images of intrinsic and scattering attenuation. Resolution tests confirm the robustness and reliability of the obtained images. We found that scattering attenuation is the dominant process of energy loss in the frequency range analyzed, which suggests strong spatial heterogeneity. The resultant scattering attenuation images show an increase of attenuation toward Editorial responsibility: T. Nishimura J.

Surveys in Geophysics, 2017

In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g.... more 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

Journal of Geophysical Research: Solid Earth, 2015

In this manuscript we present a new interpretation of the seismic series that accompanied eruptiv... more In this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of El Hierro, Canary Islands, during 2011-2013. We estimated temporal variations of the Gutenberg-Richter b value throughout the period of analysis, and performed high-precision relocations of the preeruptive and syneruptive seismicity using a realistic 3-D velocity model. Our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust. These magma pulses occurred within a small and well-defined volume resulting in the emplacement of fresh magma along the crust-mantle boundary underneath El Hierro. We analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust. Our results suggest that very high earthquake rates underneath El Hierro represent the response of a stable lower crust to stress perturbations with pulsatory character, linked to the injection of magma from the mantle. Magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms. The absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity, had diffusive character. We conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill. Our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the Moho. We suggest, within this framework, that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement.

Surveys in Geophysics, 2015

Geophysical Research Letters, 2015

In this work we present intrinsic and scattering seismic attenuation 2-D images of Stromboli Volc... more 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 Q i and Q s 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.

Surveys in Geophysics, 2015

The seismic and volcanological structure of Deception Island (Antarctica) is an intense focus top... more 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 4 km. The results, once compared with our current knowledge on the geological, geochemical, and geophysical structure of the region, depict Deception as apiecemeal caldera structure leant 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 3 km. The northern contour of the anomaly coincides with the calderic rim both at 1 and 2 km, while smaller anomalies connect it with deeper structures below 3 km, dipping towards the Bransfield Trough. In our interpretation, the large upper anomaly is caused by a high-temperature shallow (1 to 3 km deep) geothermal system, located beneath the sedimentfilled bay in the collapsed blocks and heated by smaller, deeper contributions of molten materials (magma) rising from southeast.

Geophysical Journal International, 2014

We present a 3-D model of P and S velocities beneath El Hierro Island, constructed using the trav... more We present a 3-D model of P and S velocities beneath El Hierro Island, constructed using the traveltime data of more than 13 000 local earthquakes recorded by the Instituto Geográfico Nacional (IGN, Spain) in the period from 2011 July to 2012 September. The velocity models were performed using the LOTOS code for iterative passive source tomography. The results of inversion were thoroughly verified using different resolution and robustness tests. The results reveal that the majority of the onshore area of El Hierro is associated with a high-velocity anomaly observed down to 10-12-km depth. This anomaly is interpreted as the accumulation of solid igneous rocks erupted during the last 1 Myr and intrusive magmatic bodies. Below this high-velocity pattern, we observe a low-velocity anomaly, interpreted as a batch of magma coming from the mantle located beneath El Hierro. The boundary between the low-and highvelocity anomalies is marked by a prominent seismicity cluster, thought to represent anomalous stresses due to the interaction of the batch of magma with crust material. The areas of recent eruptions, Orchilla and La Restinga, are associated with low-velocity anomalies surrounding the main high-velocity block. These eruptions took place around the island where the crust is much weaker than the onshore area and where the melted material cannot penetrate. These results put constraints on the geological model that could explain the origin of the volcanism in oceanic islands, such as in the Canaries, which is not yet clearly understood.

ABSTRACT In the present work we are going to analyze the same data-set used to develop the 3D vel... more ABSTRACT In the present work we are going to analyze the same data-set used to develop the 3D velocity tomographies to realize 2D intrinsic and scattering attenuation tomography. For that we are going to apply the diffusion model which is an approximation of the general energy transport theory developed by Wegler et al. (2001) and Wegler (2003). So, this new models will be a complement to the better understanding of velocity anomalies and will allow remove some grades of uncertainty of the other studies. As a result of the inversion using the diffusion model we have obtained values of S-waves intrinsic attenuation coefficient (b) and diffusivity coefficient (d) in the frequency range of 6-12 Hz for Tenerife and 4-20 Hz for Deception Island. We have quantified the attenuation by the quality factor because is more representative. We also compare attenuation images with velocity tomographies. For the case of Tenerife we confirm that Tenerife Island is a very heterogeneous area. Moreover we corroborate that high velocity zones are coincident with low attenuation zones and low velocity zones are coincident with high attenuation zones. If we compare these results with those obtained by Zandomeneghi et al. (2009) we can observe the greater concordance between velocity tomography model and this model. If we observe the high attenuation anomaly of the center of the island and we combine with other studies is highly compatible with the presence of partially molten material.

ABSTRACT A three-dimensional S wave attenuation tomography of Tenerife island has been obtained w... more ABSTRACT A three-dimensional S wave attenuation tomography of Tenerife island has been obtained with measurements of coda-normalization method. We used about 75000 waveforms relative to the dataset from an active seismic experiments using offshore shots (air guns) recorded at over 100 onshore seismic stations. The rays were traced in a 3D velocity model. The spatial resolution in our tomography is the same as that obtained by velocity tomography: we resolve 600m cubic cells. Results have shown that there is likewise agreement with the velocity tomography, the low velocity external zones being consistent with regions featuring high attenuation effects and the high velocity zones in the center of the island with regions featuring low attenuation effects. Therefore, our observations agree with the volcanic characteristics of the medium.