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Deep fluid circulation likely triggered the large extensional events of the 2016–2017 Central Italy seismic sequence. Nevertheless, the connection between fault mechanisms, main crustal‐scale thrusts, and the circulation and interaction of fluids with tectonic structures controlling the sequence is still debated. Here, we show that the 3D temporal and spatial mapping of peak delays, proxy of scattering attenuation, detects thrusts and sedimentary structures and their control on fluid overpressure and release. After the mainshocks, scattering attenuation drastically increases across the hanging wall of the Monti Sibillini and Acquasanta thrusts, revealing fracturing and fluid migration. Before the sequence, low‐scattering volumes within Triassic formations highlight regions of fluid overpressure, which enhances rock compaction. Our results highlight the control of thrusts and paleogeography on the sequence and hint at the monitoring potential of the technique for the seismic hazard assessment of the Central Apennines and other tectonic regions. Plain Language Summary There is widespread evidence that the Amatrice‐Visso‐Norcia seismic sequence (2016–2017, Central Italy) was triggered by fluid circulation across the Apennine Chain. However, how, and why fluids migrated across the fault network is still under debate. Seismic attenuation describes how seismic waves lose energy during their propagation. When used as an imaging attribute, it has demonstrated the potential to recover the spatial extension and mechanisms of fracturing and fluid movement across volcanoes and faults. Here, we map scattering attenuation through the peak delay measurements in 3D before (2013–2016) and during the 2016–2017 sequence. Scattering attenuation separated fractured zones from regions of compaction, controlled, before and during the sequence by thrusts and lithological differences. High scattering (strong fracturing) increases through time due to intense fracturing, while low scattering (higher compaction of the rocks) marks areas where earthquakes will occur. Our results highlight the importance of the main thrusts, as they separate compartments of the shallow crust characterized by different scattering attenuation anomalies, the Triassic deposits in fluid accumulation, and subsequent triggering of normal faults. Key Points Scattering attenuation detects the control of thrusts and lithology on post‐seismic fracturing and fluid migration during the AVN sequence Overpressurized fluids compact low‐scattering rocks at thrusts' roots before earthquakes Detecting fluid overpressure and fracturing suggests an unexploited monitoring potential of scattering attenuation

To date, eight meteoroid impacts have been identified in the seismic record of NASA's InSight mission on Mars, occurring either within 300 km or beyond 3,500 km. We report the association of a high‐frequency marsquake, S0794a, with a new 21.5‐m‐diameter impact crater discovered at an intermediate distance of 1,640 km in the tectonically active Cerberus‐Fossae graben system. This impact enables the direct comparison between surface and subsurface sources, as well as providing the first data point in the critical gap between previous impacts, both in distance and crater size. Additionally, the location of this event necessitates a reassessment of assumed seismic raypaths that were thought to propagate along a slow crustal waveguide. We find that the raypaths instead penetrate and travel through the faster mantle, implying numerous identified marsquake epicenters should be relocated up to two times farther from InSight, with implications for seismically derived impact rates and regional seismicity. Plain Language Summary We have used global and high‐resolution orbital imaging to discover a fresh crater that appeared at the same time as one of the quakes detected by NASA's InSight lander. This means the seismometer detected a meteoroid strike rather than geological activity within the planet. We know the location of this impact as well as the timing of seismic energy arriving by different types of vibrations which traveled through Mars at different speeds. With this information, we can work out that these waves penetrated below the crust and into the mantle rather than being confined to the crust as previously thought. This new path of propagation leads us to question how far away other marsquakes were from the InSight lander. This has implications for both how often marsquakes occur as well as how frequently meteoroids hit Mars. Key Points We associate a new 21.5‐m Mars impact crater in the tectonically active Cerberus Fossae region with InSight's seismic event, S0794a The location derived seismically and via orbital imaging implies the impact's energy traveled significant distances through the mantle This challenges previous assumptions of a crustal waveguide, resulting in more distant locations for many high‐frequency marsquakes

We estimate depth‐dependent azimuthal anisotropy and shear wave velocity structure beneath the Alaska subduction zone by the inversion of a new Rayleigh wave dispersion dataset from 8 to 85 s period. We present a layered azimuthal anisotropy model from the forearc region offshore to the subduction zone onshore. In the forearc crust, we find a trench‐parallel pattern in the Semidi and Kodiak segments, while a trench‐oblique pattern is observed in the Shumagins segment. These fast directions agree well with the orientations of local faults. Within the subducted slab, a dichotomous pattern of anisotropy fast axes is observed along the trench, which is consistent with the orientation of fossil anisotropy generated at the mid‐ocean ridges of the Pacific‐Vancouver and Kula‐Pacific plates that is preserved during subduction. Beneath the subducted slab, a trench‐parallel pattern is observed near the trench, which may indicate the direction of mantle flow. Plain Language Summary The azimuthal anisotropy of seismic waves refers to the directional dependence of the seismic wave propagation speed. We present a comprehensive azimuthal anisotropy model of the Alaska subduction zone to a depth of 200 km, revealing anisotropy caused by local faults and fractures, fossil anisotropy inherited from the oceanic plate within the subducted slab, and sub‐slab mantle flow. The along‐strike variation of crustal anisotropy indicates variations in the stress regime in the forearc region. The along‐strike variation of anisotropy within the subducted slab identifies different origins of the subducted slab. Our model contributes to the understanding of the anisotropic structure and the sources of anisotropy in subduction zones. Key Points A new model of depth‐dependent azimuthal anisotropy of the Alaska subduction zone is built based on a new surface wave dataset The along‐strike variation in the azimuthal anisotropy of the forearc crust is caused by faults and fractures Azimuthal anisotropy within the subducted slab is controlled by fossil anisotropy produced at different mid‐ocean ridges

Mantle plumes were conceived as thin, vertical conduits in which buoyant, hot rock from the lowermost mantle rises to Earth’s surface, manifesting as hotspot-type volcanism far from plate boundaries. Spatially correlated with hotspots are two vast provinces of slow seismic wave propagation in the lowermost mantle, probably representing the heat reservoirs that feed plumes. Imaging plume conduits has proved difficult because most are located beneath the non-instrumented oceans, and they may be thin. Here we combine new seismological datasets to resolve mantle upwelling across all depths and length scales, centred on Africa and the Indian and Southern oceans. Using seismic waves that sample the deepest mantle extensively, we show that mantle upwellings are arranged in a tree-like structure. From a central, compact trunk below ~1,500 km depth, three branches tilt outwards and up towards various Indo-Austral hotspots. We propose that each tilting branch represents an alignment of vertically rising blobs or proto-plumes, which detached in a linear staggered sequence from their underlying low-velocity corridor at the core–mantle boundary. Once a blob reaches the viscosity discontinuity between lower and upper mantle, it spawns a ‘classical’ plume-head/plume-tail sequence. Indo-African mantle upwellings are arranged in a tree-like structure, which might reflect linear staggered detachment of proto-plumes from the lowermost mantle, according to seismic tomographic imaging.

Despite the high detection level of the Italian seismic network and the risk associated with its fault networks, Central‐Southern Italy has no unique geophysical model of the crust able to illuminate its complex tectonics. Here, we obtain seismic attenuation and scattering tomography models of this area; both reveal high attenuation and scattering anomalies characterizing the entire Apenninic Chain and related to its East‐ and West‐dipping extensional Quaternary tectonic alignments. Fault‐associated fractured zones become preferential ways for circulating and degassing high‐attenuation CO2‐bearing fluids. A previously undetected fluid source area is a high‐attenuation volume below the Matese complex, while a similar smaller anomaly supports a fluid source near L'Aquila. The most prominent low attenuation and scattering volumes reveal a locked aseismic zone corresponding to the Fucino‐Morrone‐Porrara fault systems, representing a zone of significant seismic hazard. Plain Language Summary Geophysical methods are the most used tools for imaging the subsurface. Still, their resolution and reliability depend on the amount of good‐quality data and the sensitivity of the technique used for the target structures. Improvements in the seismic detection infrastructures of the last decade allow imaging zones characterized by sparse seismicity, like Central‐Southern Italy. Once combined with these data, new imaging techniques targeting attributes with higher sensitivity to stress and fluid saturation provide unprecedented resolution on tectonic interactions and fluid sources in this area. Here, we measured and mapped in 3D the energy lost by seismic waves during their propagation. Our results show a high‐attenuation volume elongated in the direction of the Apenninic Chain and particularly intense in Southern Italy, mapping fluid‐filled fracturing and a fluid source likely coinciding with the Matese area. The principal normal and reverse faults in the area control high‐attenuation zones. The most prominent low attenuation and scattering volume marked locked areas with low seismic energy release, suggesting them as the zones of stress accumulation. Key Points Scattering and attenuation tomography image the tectonics of the Apennine Mountain Belt Chain High‐attenuation anomalies mark crustal sources of CO2 following major structural alignments A high‐attenuation/high‐scattering volume reveals an extended fluid source beneath the Matese Mountains

The September 2018, \\[M_w\\] 7.5 Sulawesi earthquake occurring on the Palu-Koro strike-slip fault system was followed by an unexpected localized tsunami. We show that direct earthquake-induced uplift and subsidence could have sourced the observed tsunami within Palu Bay. To this end, we use a physics-based, coupled earthquake–tsunami modeling framework tightly constrained by observations. The model combines rupture dynamics, seismic wave propagation, tsunami propagation and inundation. The earthquake scenario, featuring sustained supershear rupture propagation, matches key observed earthquake characteristics, including the moment magnitude, rupture duration, fault plane solution, teleseismic waveforms and inferred horizontal ground displacements. The remote stress regime reflecting regional transtension applied in the model produces a combination of up to 6 m left-lateral slip and up to 2 m normal slip on the straight fault segment dipping \\[65^{\\circ }\\] East beneath Palu Bay. The time-dependent, 3D seafloor displacements are translated into bathymetry perturbations with a mean vertical offset of 1.5 m across the submarine fault segment. This sources a tsunami with wave amplitudes and periods that match those measured at the Pantoloan wave gauge and inundation that reproduces observations from field surveys. We conclude that a source related to earthquake displacements is probable and that landsliding may not have been the primary source of the tsunami. These results have important implications for submarine strike-slip fault systems worldwide. Physics-based modeling offers rapid response specifically in tectonic settings that are currently underrepresented in operational tsunami hazard assessment.

Seismic surveys along subduction zones have identified anomalously high ratio of P‐ to S‐wave velocity (VP/VS) in the subducting oceanic crust that are possibly due to the presence of pore water. Such interpretations postulate that the pore structure is homogeneous at the scale of the seismic wavelength. Here we present the first statistical evidence of a heterogeneous pore structure in oceanic crust at scales larger than laboratory samples. The spatial correlation of measured bulk density profiles of the crustal section of the Samail ophiolite suggests that the pore structure is heterogeneous at scales smaller than ∼1 m. Wave‐induced fluid flow cannot follow the loading during the seismic wave propagation at this estimated heterogeneity, which implies that fluid‐filled microscopic pores and cracks have a limited impact on the observed high VP/VS anomalies in the subducting oceanic crust. Large‐scale cracks may therefore play an important role in shaping these anomalies. Plain Language Summary Seismic studies along subduction zones have identified unusually high ratios of P‐ to S‐wave velocity (VP/VS) in the subducting oceanic crust, which indicates the presence of water‐filled cracks and pores. The close link between pore water and local seismic activity highlights the importance of quantitatively interpreting these seismic anomalies in terms of pore characteristics. Previous interpretations have assumed that the microscopic pore structure is quite homogeneous, even at macroscopic scales as large as the seismic wavelength. However, our analysis of a bulk density profile of the crustal section of the Samail ophiolite, Oman, which is a fossilized oceanic plate preserved on land, indicates that the pore structure is more heterogeneous than previously assumed. This means that the fluid flow within the unit volume that represents the macroscopic physical properties of the rock cannot follow the wave‐induced loading during seismic wave propagations. This results in a relatively small impact of water on the seismic velocity, as inferred from theoretical models that predict the effective elastic properties of rock containing fluid‐filled cracks. Therefore, microscopic cracks may not have a large impact on the high VP/VS values of subducting oceanic crust, whereas large‐scale cracks may play a more significant role. Key Points The bulk density of the crustal section of the Samail ophiolite is more spatially heterogeneous than previously assumed The effect of fluid‐saturated microcracks on low‐frequency seismic velocities is modeled as an unrelaxed condition for this heterogeneity The high VP/VS anomaly in the subducting oceanic crust can be explained by both microcracks and large‐scale cracks

The firn layer covers 98% of Antarctica's ice sheets, protecting underlying glacial ice from the external environment. Accurate measurement of firn properties is essential for assessing cryosphere mass balance and climate change impacts. Characterizing firn structure through core sampling is expensive and logistically challenging. Seismic surveys, which translate seismic velocities into firn densities, offer an efficient alternative. This study employs Distributed Acoustic Sensing technology to transform an existing fiber‐optic cable near the South Pole into a multichannel, low‐maintenance, continuously interrogated seismic array. The data resolve 16 seismic wave propagation modes at frequencies up to 100 Hz that constrain P and S wave velocities as functions of depth. Using co‐located geophones for ambient noise interferometry, we resolve very weak radial anisotropy. Leveraging nearby SPICEcore firn density data, we find prior empirical density‐velocity relationships underestimate firn air content by over 15%. We present a new empirical relationship for the South Pole region. Plain Language Summary Firn, the layer of compacted snow merging into glacial ice covering Antarctica, acts as an insulating blanket that mitigates environmental perturbations to the polar ice sheet. Understanding the density and seismic characteristics of the firn layer helps scientists better infer its properties and variation, including factors relevant to glacial stability and sea level change. Firn density is the major uncertainty source for measuring ice sheet mass changes via satellite and airborne sensing. Traditional methods of assessing firn density involve drilling or snow pit analyses and are expensive and time‐consuming. We utilize the rapidly developing technology of Distributed Acoustic Sensing to transform a data communication cable near the South Pole into a dense array of seismic sensors, allowing us to noninvasively estimate firn properties by studying seismic waves propagating in the firn to assess its physical properties. Our findings suggest that previous parameterizations overestimate firn density by over 5% and underestimate its air content by over 15% and highlight the value of seismology for advancing glaciological and polar region's climate research. Key Points Distributed Acoustic Sensing repurposes an 8 km fiber‐optic cable at the South Pole into a dense seismic array Gathered data resolve 16 dispersion modes at frequencies up to 100 Hz that constrain P‐ and S‐wave velocities in the firn layer Previous density‐velocity empirical relations overestimate the dry firn density at South Pole

\"Mechanics of Rubber Bearings for Seismic and Vibration Isolation collates in a compact form all of the information on the mechanics of the increasingly important technology of multi-layer rubber bearings. It explores a unique & comprehensive combination of relevant topics, covering all prerequisite fundamental theory and providing a number of closed form solutions to various boundary value problems as well as a comprehensive historical overview on the use of this technique.The authors progress logically through increasingly complex analyses; many of the results presented are new and are needed for a proper understanding of these bearings and for the design and analysis of vibration isolation or seismic isolation systems. The advantages afforded by adopting these natural rubber systems\"otheir cost effectiveness, simplicity, and reliability\"is clearly explained to designers and users of this emerging technology, bringing into focus the design and specification of bearings for buildings, bridges and industrial structures\"-- \"Mechanics of Rubber Bearings collates in a compact form all of the information on the mechanics of the increasingly important technology of multi-layer rubber bearings\"--

The amplitude‐dependent seismic attenuation in the crust and uppermost mantle was investigated using spectral analysis of crustal and intraslab earthquakes that occurred in two areas in northeastern Japan. P‐wave attenuation (Q−1${Q}^{-1}$ ) was found to be weakly proportional to amplitude (A$A$ ) in both areas, following the relationship, Q−1∝An${Q}^{-1}\\mathit{\\propto }{A}^{n}$ . Quantitative analysis reveals that amplitude‐dependent attenuation is more pronounced in the uppermost mantle (n ∼ 0.16) than in the crust (n ∼ 0.05). This depth‐dependent behavior of attenuation may be attributed to increasing temperature and pressure, which enhance dislocation density and mobility. Our findings challenge the common assumption of amplitude‐independent attenuation. Although we infer dislocation mechanisms as the primary cause of the amplitude‐dependent energy dissipation, further experimental studies under high temperature and pressure conditions are necessary for better understanding of the complex nature of seismic attenuation and the underlying processes. Plain Language Summary Seismic attenuation, the energy loss per one cycle as seismic waves propagate through the Earth, has traditionally been considered amplitude independent. Our research challenges this assumption, revealing a weak amplitude dependence of attenuation. We found this effect is more pronounced in the uppermost mantle than in the crust. This depth‐dependent behavior likely results from increasing temperature and pressure affecting the microstructure of rocks. These findings will improve the accuracy of seismic wave propagation models and enhance our understanding of Earth's internal structure, contributing to advancements in seismology. Key Points We revealed amplitude‐dependent attenuation in both the crust and the uppermost mantle using a spectral analysis Amplitude‐dependent attenuation is more dominant in the uppermost mantle than in the crust We quantified amplitude‐dependent attenuation with an exponent of about 0.05 for the crust and 0.16 for the uppermost mantle