The 3D Attenuation Structure of Deception Island (Antarctica)

Abstract

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 a piecemeal caldera structure coming out of the Bransfield Trough. Highattenuation 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 toward the Bransfield Trough. In our interpretation, the large upper anomaly is caused by a high-temperature shallow (1-3 km 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.

Three‐dimensional attenuation model of Sierra Negra Volcano, Galápagos Archipelago

“…Attenuation is more sensitive to temperature gradients and melt than velocity; thus, it is better able to define these high‐melt pockets. Other studies have shown similar discrepancies in size of high‐ and low‐ V p anomalies [e.g., Prudencio et al , ].…”

Investigating the Apparent Seismic Diffusivity of Near-Receiver Geology at Mount St. Helens Volcano, USA

“…Within the frequency range 3-18 Hz, a value of 250 m is obtained for on-volcano stations and 430 m for off volcano. 250 m is comparable with typical values of between 100 m and 1000 m found at other volcanic sites [8,9,[38][39][40][41][42] where scattering effects have been observed to dominate over intrinsic attenuation. However, away from the strongly scattering regime close to a volcano, typical crustal values are in the range of 100 km and so 430 m for off-volcano stations is several orders of magnitude lower than it should be.…”

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

“…A way to solve these difficulties is to jointly interpret tomography images based on the measurement of different physical quantities that greatly help in the recognition of zones with different geological characteristics. There are new examples in which velocity (traveltime) tomography is associated with seismic wave attenuation imaging [e.g., Martinez‐Arevalo et al , ; De Siena et al , ; Prudencio et al , ]. This association is essential in volcanoes, where the correct interpretation of the spatial distribution of the physical properties in terms of partial melt materials is necessary.…”