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High‐frequency oceanic Pn/Sn (Po/So) phases (>2 Hz) recorded at ocean bottom seismometers in the northwest Pacific display strong azimuthal variations in propagation characteristics. In the direction parallel to former Pacific plate motion (N30°W), seismograms show a gentle rise at the onset of Po/So followed by large, long spindle‐shaped coda; Po has a low‐frequency (< 0.25 Hz) precursor and much

We propose a compressed sensing (CS) method for extracting multimodes from ambient noise. We solve the CS inverse problem by using two methods: an l1‐based optimization algorithm and a Bayesian method. Synthetic and field data examples are conducted to validate our method. The dispersion curves extracted by our method are consistent with those extracted by the widely‐used frequency‐Bessel transform

The brittle‐viscous transition in the lithosphere occurs in a region where many large earthquakes nucleate. To study this transition, we sheared bimineralic aggregates with varying ratio of quartz and potassium feldspar. We deformed the samples in a solid‐medium deformation apparatus at temperature, T = 750°C and pressure, Pc = 800 MPa under either constant displacement rate or constant load boundary

The northeastern Tibetan Plateau and its surroundings are a tectonically complex region resulting from the continuing collision of India with Eurasia. We studied the tectonic deformation of this region using a GPS block model, which was produced using the most recently published, dense, precise, and complete GPS velocities available combined with a detailed fault geometry. The comparison between our

The relationship between multi‐scale rupture characteristics and different frequency contents of the seismic waveforms has been revealed for moderate to great earthquakes by previous researches. To better understand such a relationship, we propose a two‐step strategy to perform finite fault inversion in the wavelet domain with multi seismic datasets, involving the seismic observations at both teleseismic

We use high‐resolution earthquake locations to characterize the three‐dimensional structure of active faults in California and how it evolves with fault structural maturity. We investigate the distribution of aftershocks of several recent large earthquakes that occurred on continental strike slip faults of various structural maturity (i.e. various cumulative fault displacement, length, initiation age

Slab pull is generally considered as the dominant force that drives the global movement of tectonic plates. This convection mode is well constrained in the upper mantle but the convection pattern in the mid mantle is more speculative. In this study, we present high‐resolution global models of the 410‐km and 660‐km discontinuity structure from finite‐frequency tomography of SS precursors. The new models

We investigated the seismic velocity structure of the Hikurangi margin in New Zealand to uncover the physical features of the subduction zone and explore the relationships between microearthquake seismicity, seismic velocity structure, and slow slip events. Using local earthquake tomography with data collected from both temporary ocean bottom seismometers and on‐land permanent seismic stations, we

The spatiotemporal patterns of injection‐induced seismicity (IIS) are commonly interpreted with the concept of a triggering front, which propagates in a diffusion‐like manner with an associated diffusivity parameter. Here, we refer to this diffusivity as the “seismic diffusivity”. Several previous studies implicitly assume that seismic diffusivity is equivalent to the effective hydraulic diffusivity

The development of Digital rock physics relies on the availability of high‐quality 3D digital rock images, which can be directly obtained with X‐ray micro‐Computed Tomography (μCT). However, X‐ray μCT is hampered by its high expenses, small sample size (several millimeters in diameter) and low resolution (in micron scale). Although Scanning Electron Microscope (SEM) provides higher resolution on larger

A coupled approach of fluid flow and geomechanics is proposed in this paper to quantitatively understand the hydraulic fracturing‐induced poroelastic effects that activate pre‐existing faults and trigger earthquake swarms near Crooked Lake, Alberta. The 3D poroelastic simulation of the seismogenic fault zone is then conducted to characterize the pressure diffusion and stress perturbation that led to

The southern Granite‐Rhyolite province contains a comprehensive record of lithospheric evolution in North America. During the last decade, increased seismicity along with improved seismic monitoring in Oklahoma provided a rich catalog of local earthquakes. The source‐receiver geometry of this dataset is well posed to illuminate the middle and lower crust through long‐offset recordings of the Pg phase

In Gravity Recovery and Climate Experiment (GRACE) Follow‐on (GRACE‐FO) mission, similar to its predecessor GRACE, the twin satellites are equipped with three‐axis accelerometers, measuring the non‐gravitational forces. After 1 month in orbit, during the in‐orbit‐checkout phase, the noise on GRACE‐D accelerometer measurements elevated and resulted in systematical degradation of the data. For this reason

Repeating earthquakes repeatedly rupture the same seismic asperity and are strongly linked to aseismic slip. Here, we study the repeating aftershocks of the April 16, 2016 MW 7.8 Pedernales earthquake in Ecuador, which generated a large amount of afterslip. Using temporary and permanent stations, we correlate waveforms from a one‐year catalog of aftershocks. We sort events with a minimum correlation

A series of four chemical explosions were detonated in a deep borehole within the Yucca Flat Dry Alluvium Geology (DAG) at the Nevada National Security Site between 2018 and 2019. The two larger chemical explosions of 50 tons (DAG‐2) and 10 tons (DAG‐4) TNT equivalent yield triggered energetic aftershock sequences numbering 1392 and 347 microearthquakes, respectively, within the first 10 days. No significant

Spatial and temporal coincidence among rapid Pliocene‐Holocene bedrock exhumation, development of a topographic bight, abundant monsoonal precipitation, accumulation of anomalously thick proximal foreland basin deposits, and development of an opposite‐polarity salient‐reentrant couple on the two most frontal major thrust faults in the Himalayan orogenic wedge of central Nepal provide a basis for a

Intraplate surface deformation is enigmatic and the underlying mechanisms responsible are not fully understood. We use thermo‐mechanical numerical modeling to explore the conditions under which lithospheric removal processes can occur and investigate the timing and amplitude of consequent surface deformation. We allow lithospheric removal to develop dynamically and self‐consistently by applying a phase

The Mineoka Ophiolite Mélange is located at the intersection of the Pacific, Philippine Sea, Eurasian, and North American plates. The Mineoka ophiolite origin is disputed, and it has been ascribed to a fully subducted plate or part of the Pacific and Philippine Sea plates. In this paper, we present a kinematic reconstruction of the Mineoka Ophiolite Mélange and its relation with the Pacific Plate,

The understanding of the interactions between subduction‐induced mantle flow and background mantle flow (being global or regional) remains incomplete despite its potential impact on subduction dynamics and associated deformation. Here we present the results of three‐dimensional laboratory models of subduction zones at the scale of the upper mantle in which we systematically vary the plate's width and

In this study, we investigate the shallow shear wave velocity structure of the Los Angeles Basin in southern California, using ambient noise correlations between 5 dense arrays and 21 broadband stations from the Southern California Seismic Network (SCSN). We observe clear fundamental mode and first overtone Rayleigh waves in the frequency band 0.25–2.0 Hz, and obtain group velocity maps through tomography

Although poroelastic models are often used to explain the delay between subsurface fluid depletion and ground subsidence, inelastic compaction involving permanent changes of rock microstructure may exacerbate hydro‐mechanical coupling, thus influencing the interpretation of measurements and long‐term forecasts. Here, a multi‐scale modeling approach is discussed, which accounts for the inherent connection

The 1976 Great Tangshan earthquake (Ms 7.8) in North China was the deadliest earthquake in the past century. Understandably, a sequence of moderate (M ≥ 4.5) earthquakes in recent years in the Tangshan region, including the Ms 5.1 earthquake on July 12, 2020, raised much social concern and scientific debate about the seismic risk near Tangshan and in North China, a region of active intraplate seismicity

Olivine‐hosted melt inclusions have the potential to provide direct evidence about the nature of the mantle sources of magmas. In this study, we report the major and trace element and Sr–Nd–Pb–Hf isotope compositions of the Lijiang picrites from the Emeishan large igneous province, as well as major and trace element and Pb isotopic compositions of olivine‐hosted melt inclusions in the picrites. Using

While the receiver function technique has been successfully applied to high‐resolution imaging of sharp discontinuities within and across the lithosphere, it suffers from severe limitations when applied to seafloor seismic recordings. This is because the water and sediment layer could strongly influence the receiver function traces, making detection and interpretation of crust and mantle layering difficult

The Rungwe Volcanic Province (RVP) is a volcanic center in an anomalous region of magma‐assisted rifting positioned within the magma‐poor Western Branch of the East African Rift (EAR). The source of sublithospheric melt for the RVP is enigmatic, particularly since the volcanism is highly localized, unlike the Eastern Branch of the EAR. Some studies suggest the source of sublithospheric melt beneath

Gibbs free energy, the fundamental thermodynamic potential used to calculate equilibrium mineral assemblages in geological systems, does not apply to non‐hydrostatically stressed solids. Consequently, there is debate over the significance of non‐hydrostatic stress in petrological and geophysical processes. To help resolve this debate, we consider the effects of non‐hydrostatic stress on the polymorph

Serpentinization environments are key locations that support microbial communities by abiogenic formation of reduced species associated with peridotite alteration. Here we studied partially serpentinized peridotites from the Chimaera seeps (Turkey), an active continental serpentinization system that vents highly methane‐rich fluids, to investigate the impact of water‐rock interaction on the sulfide

Gas bubbles are widespread in seafloors and lakebeds and typically found in shallow and fine‐grained sediments. Sediment properties control gas nucleation and gas migration. Gas migration and pathways have been studied mostly in clean coarse particles or fine‐grained matrices. Nevertheless, both cases show very distinct geo‐behaviors. Pore habit is defined by the counteracting effects of effective

Determining fluid migration and pore pressure change within the Earth is key to understand earthquake occurrences. We investigated the spatiotemporal characteristics of the intense foreshocks and aftershocks of the 2017 ML 5.3 earthquake in Kagoshima Bay, Kyushu, southern Japan, to examine the physical processes governing this earthquake sequence. Our relocated hypocenters show the foreshocks moved

We present numerical simulations of elastic wave transport in two‐dimensional fractured media. Natural fracture systems following a power‐law length scaling are modeled by the discrete fracture network approach for geometrically representing fracture distributions and the displacement discontinuity method for mechanically computing fracture‐wave interactions. The model is validated against analytical

An important seismic attenuation mechanism in fractured environments is related to energy conversion into reflected and transmitted waves at fracture interfaces. Using full‐waveform sonic (FWS) log data, we show that it is possible to quantify transmission losses across a set of fractures from time delays and amplitude differences of the critically refracted P‐wave as compared to intact sections along

Ray tracing is avoidable in seismic traveltime tomography. In this study seismic traveltime tomography is reformulated as an eikonal equation‐constrained optimization problem solved by the ray‐free adjoint‐state method. The resulting approach is called adjoint‐state traveltime tomography. For completeness, an eikonal equation‐based earthquake location method is developed to locate the hypocenters of

No abstract is available for this article.

Many of the world’s volcanoes are hidden beneath the ocean’s surface where eruptions are difficult to observe. However, seismo‐acoustic signals produced by these eruptions provide a useful means of identifying active submarine volcanism. A literature survey revealed reports of 119 seismo‐acoustically recorded submarine eruptions since 1939. Submarine eruptions have been recorded in all major tectonic

Quantitatively assessing seismic attenuation caused by fluid pressure diffusion (FPD) in partially saturated rocks is challenging because of its sensitivity to the spatial fluid distribution. To address this challenge we performed depressurization experiments to induce the exsolution of carbon dioxide from water in a Berea sandstone sample. In a first set of experiments we used medical X‐ray computed

The exploitation of ever increasing Interferometric Synthetic Aperture Radar (InSAR) data sets to monitor the Earth's surface deformation is an important goal of today's geodesy. In this study our observations consist of deformations along the Line‐Of‐Sight direction of the satellite. Our observations are the result of the combination of a multitude of sources (either volcano‐tectonic or nontectonic

Recent multi‐channel seismic studies of fast spreading and hot‐spot influenced mid‐ocean ridges reveal magma bodies located beneath the mid‐crustal Axial Magma Lens (AML), embedded within the underlying crustal mush zone. We here present new seismic images from the Juan de Fuca Ridge that show reflections interpreted to be from vertically stacked magma lenses in a number of locations beneath this

The Earth's long‐ and intermediate‐wavelength geoid anomalies are surface expressions of mantle convection and are sensitive to mantle viscosity. While previous studies of the geoid provide important constraints on the mantle radial viscosity variations, the mantle buoyancy in these studies, as derived from either seismic tomography or slab density models, may suffer significant uncertainties. In this

The Global Positioning System (GPS) derived bedrock displacements respond to multiple geophysical effects, ranging from surface elastic loads to tectonic sources or viscoelastic uplifts stemming from Earth’s viscous mantle. In this study, the GPS‐inferred vertical crustal velocities are rigorously estimated in mainland China. We integrate the GPS vertical velocity field with Gravity Recovery and Climate

Recent experimental studies have demonstrated that clay minerals (e.g., kaolinite, illite, and montmorillonite) have higher affinities for some trace elements under acidic versus alkaline conditions. This suggests that clays might be important vectors in the transport of trace elements from sites of acidic chemical weathering on land to marine depositional environments. To determine if clays behave

Earthquake detection and phase picking play a fundamental role in studying seismic hazards and the Earth's interior. Many deep‐learning‐based methods, including the state‐of‐the‐art model called Earthquake Transformer (EqT), have made considerable progress. However, the processing of low signal‐to‐noise ratio (SNR) seismograms remains a challenge. Here we present a pair‐input deep‐learning model called

Dense Global Navigation Satellite System (GNSS) observations enable the development of megathrust interseismic locking models for the southern Kurile subduction zone where many great earthquakes have occurred. Inversion of these data assuming uniform elastic Earth has yielded slip deficit rates that are unreasonably high and/or full locking depth that is unreasonably large. Using the finite element

Thermodynamic calculations provide valuable insights into the reactions that drive the profound fluid transformations during serpentinization, where surface fluids are transformed into some of the most reduced and alkaline fluids on Earth. However, environmental observations usually deviate from thermodynamic predictions, especially those occurring at low temperatures where equilibrium is slowly reached

Fluid pressure diffusion (FPD) between a fracture and a porous permeable background can increase the normal compliance of the fracture and, thus, its reflectivity. However, many fractured environments of interest are associated with background rocks that can be regarded as largely impermeable for the the typical frequencies employed in seismic surveys. Nonetheless, there is evidence to suggest that

Long‐term monitoring of global mass transport within the Earth system improves our ability to mitigate natural hazards and better understand their relations to climate change. Satellite gravity is widely used to monitor surface mass variations for its unprecedented spatial and temporal coverage. However, the gravity data contain signals from visco‐elastic deformation in response to past ice sheet melting

Transient creep occurs during geodynamic processes that impose stress changes on rocks at high temperatures. The transient is manifested as evolution in the viscosity of the rocks until steady‐state flow is achieved. Although several phenomenological models of transient creep in rocks have been proposed, the dominant microphysical processes that control such behavior remain poorly constrained. To identify

Fluid‐rock interaction in ultramafic rocks considerably affects the chemical and isotopic composition of the oceanic lithosphere. We present a geochemical and petrological study of serpentinites and ophicalcites of the Northern Apennine ophiolite, Italy. This ophiolite sequence represents fragments of Jurassic oceanic lithosphere that have been denuded by low angle detachment faults, exposing peridotites

We demonstrate the efficacy of a Bayesian statistical inversion framework for reconstructing the likely characteristics of large pre‐instrumentation earthquakes from historical records of tsunami observations. Our framework is designed and implemented for the estimation of the location and magnitude of seismic events from anecdotal accounts of tsunamis including shoreline wave arrival times, heights

Oceanic transform faults display fewer and smaller‐magnitude earthquakes than expected for their length. Several mechanisms have been inferred to explain this seismic slip deficit, including increased fault zone damage resulting in elevated fluid flow, and the alteration of olivine to serpentine. However, to date, these possible mechanisms are not supported by direct observation. We use micro‐ to kilometre

Field observations and unmanned aerial vehicle surveys from Caldera Taburiente (La Palma, Canary Islands, Spain) show that pre‐existing dykes can capture and re‐direct younger ones to form multiple dyke composites. Chill margins suggest that the older dykes were solidified and cooled when this occurred. In one multiple dyke example, an 40Ar/39Ar age difference of 200 kyr was determined between co‐located

Explosive basaltic eruptions pose significant threats to local communities, regional infrastructures and international airspace. They produce tephra plumes that are often associated with a lava fountain, complicating their dynamics. Consequently, source parameters cannot be easily constrained using traditional formulations. Particularly, mass flow rates (MFRs) derived from height observations frequently

We apply kinematic and dynamic modeling to the 2015 Mw8.3 Illapel, Chile, earthquake constrained by continuous high‐rate GPS and strong motion data. Kinematic inversion by elliptical patches allows us to rapidly outline the ruptured area with different time windows and frequency ranges. The preferred solution indicates that the main large patch in the north is preceded by a small one in the south close

The southeastern Tibetan Plateau experienced intense Cenozoic shortening and extrusion along the western Yangtze Craton, SW China, where the Permian Emeishan flood basalts were emplaced. Seismic anisotropy along a dense E–W‐trending linear seismic array across the west Yunnan is determined by shear‐wave splitting analysis to characterize the deformation associated with these processes. Interestingly

We investigated seismic velocity changes (dv/v) associated with the 2019 Ridgecrest earthquake sequence with high‐frequency autocorrelations of ambient seismic noise data. Daily autocorrelation functions were computed for the entirety of 2019 and the first quarter of 2020 for broadband stations within the region, including the temporary broadband stations installed during the aftershock deployment

The observations of spatiotemporal distribution of seismicity in western Canada indicate that the occurrence of earthquakes is tied to the hydraulic fracturing operations and disposal of coproduced wastewater. In this study, we investigate the temporal changes in the frequency‐magnitude distributions for multiple clusters of induced events in regions where the level of background seismicity is low

The world's largest underground gas storage facility in Hutubi (HUGS), China, is a unique case where cyclic gas injection‐extraction induced both seismicity and ground deformation. To assess the potential for future induced seismicity, we develop a framework physically based on a well‐constrained hydro‐geomechanical model and on fully‐coupled poroelastic simulations. We first interpret the spatiotemporal

To advance the understanding of crustal deformation and earthquake hazards in Canada, we analyze seismic and geodetic data sets and robustly estimate the crust strain accumulation and release rate by earthquakes. We find that less than 20% of the accumulated strain is released by earthquakes across the study area providing evidence for large‐scale aseismic deformation. We attribute this to glacial

Fractures can widely exist in hydrate‐bearing reservoirs and can give rise to anisotropic acoustic properties that play an important role in the accurate assessment of fractured reservoirs. However, the knowledge of the responses of acoustic anisotropy in fractured hydrate‐bearing reservoirs is still poorly understood. To obtain such understanding, we designed and implemented dedicated laboratory experiments

A number of bulk‐rock and mineral Fe and Mg isotope data have been increasingly reported from ophiolitic rocks, but their anomalous fractionations are still not well addressed. This study presents new Fe, Mg, and O isotopes and published Li isotope data of olivine and/or chromite in chromitite, dunite, and harzburgite from the Pozantı‐Karsantı ophiolite (southern Turkey) to reveal the mechanisms of