Okmok volcano, one of the most active volcanoes in the Aleutian Islands, erupted between July 12 and August 19, 2008, and produced a new tephra cone (Ahmanilix) up to 253 m high. A co‐eruptive deposit thickness map and the post‐eruptive elevation change rate map are generated for this phreatomagmatic eruption using the new, high‐resolution (2 meter) digital elevation model (DEM) time‐series provided

Large earthquakes are difficult to model in real‐time with traditional inertial seismic measurements. Several algorithms that leverage high‐rate RT‐GNSS positions have been proposed and it has been shown that they can supplement the earthquake monitoring effort. However, analyses of the long‐term noise behavior of high‐rate RT‐GNSS positions, which are important to understand how the data can be used

Gas hydrate is an ice‐like form of water and low molecular weight gas stable at temperatures of roughly ‐10° C to 25° C and pressures of ~3 to 30 MPa in geologic systems. Natural gas hydrates sequester an estimated one‐sixth of Earth’s methane and are found primarily in deepwater marine sediments on continental margins, but also in permafrost areas and under continental ice sheets. When gas hydrate

Characteristics of atmosphere‐generated seismic noise below 0.05 Hz are investigated when surface pressure is large. In this paper, large pressure means pressure power spectral density exceeding 100 Pa 2 /Hz (at 0.01 Hz). We discuss three main points. The first point is existence of two frequency ranges that show high coherence between co‐located pressure and vertical seismic data. The lower frequency

Numerous late Paleoproterozoic to early Mesoproterozoic mafic magmatic rocks are exposed in the southwestern Yangtze Block, corresponding to early breakup of the Nuna supercontinent. Geochronological data reveal three episodes of mafic magmatism at ~1740 Ma, 1700 Ma and 1500 Ma. The two older generations have MORB‐like Nb/Ta ratios and superchondritic Nd‐Hf isotopes, indicating that they were likely

When low‐permeability and organic‐rich rocks such as shale experience sufficient heating, chemical reactions including shale dehydration and maturation of organic matter lead to internal fluid generation. This may cause substantial pore fluid overpressure and fracturing. In the vicinity of igneous intrusions emplaced in organic‐rich shales, temperatures of several hundred degrees accelerate these processes

Phase relations of carbonated basalts have been investigated at 13–20 GPa and 1200–1600 oC, to model the decarbonation process of stagnant slab in the mantle transition zone (MTZ). Two synthetic mixes with CO2 contents of 2.5 wt% (PC‐a) and 5.0 wt% (PC‐b) were used as the starting materials. The estimated solidus was ~1350 oC at the top of the MTZ (~13–15 GPa), which declined to ~1250 oC for pressures

The recently developed frequency‐Bessel transformation (F‐J) method is effective to extract multimode surface wave dispersion curves from ambient noise cross‐correlation functions (CCFs). However, this method is currently limited to the vertical‐vertical component CCFs, and only Rayleigh wave dispersion curves can be obtained. In this study, we first relate the F‐J spectrogram to the spatial autocorrelation

High‐temperature hydrothermal venting has been discovered on all modern mid‐ocean ridges at all spreading rates. Although significant strides have been made in understanding the underlying processes that shape such systems, several first order discrepancies between model predictions and observations remain. One key paradox is that numerical experiments consistently show entrainment of cold ambient

Trans‐lithospheric faults represent weak zones where some of the most intense interaction between the lithospheric mantle and melts occurs. We carried out detailed petrological observations and mineral chemical analyses of feldspar‐bearing wehrlites entrained in the Mesozoic basalts from Liaoyuan, northeastern North China Craton (NCC) to obtain new insights into the nature and consequences of wehrlitization

Detrital zircon U‐Pb data are routinely used to assess provenance in sedimentary systems. However, recent studies have suggested that zircon provenance interpretation may be biased by grain‐size dependent selective transport and deposition. In this study, we present zircon grain‐size and U‐Pb data from 11 sandstone and 11 mudstone samples from the late Paleozoic Eagle and Paradox basins to test whether

Fault slip is often localized in phyllosilicate‐rich fault gouges in a manner consistent with the relatively low friction coefficients measured for dry and especially wet phyllosilicates in laboratory experiments. However, the microphysics controlling these low friction coefficients remains unclear. Here, we propose a microphysical model, inspired by microstructural observations, for the prediction

This paper presents a fast sweeping method (FSM) to calculate the first‐arrival traveltimes of the qP, qSV, and qSH waves in two‐dimensional (2D) transversely isotropic media, whose symmetry axis may have an arbitrary orientation (tilted transverse isotropy, TTI). The method discretizes the anisotropic eikonal equation with finite difference approximations on a rectangular mesh, and solves the discretized

A combined paleomagnetic and geochronological study was conducted on the red beds of the Zhesi Formation (ZSF) in the Xilinhot–Songliao Block (XSB) and the andesites and sandstones of the Qingfengshan Formation (QFF) in the North China Block (NCB). The ZSF tuffs and the QFF andesites were dated to 265.3 ± 1.8 Ma and 254.8–257.1 Ma, respectively, using the zircon U–Pb LA–ICP–MS method. A total of 246

Shallow earthquakes in the depth range 0 – 30 km make up more than 60% of all world's earthquakes. However, resolving their seismic source parameters such as the depth and moment tensor components presents a challenge. Here, we investigate the effect of frequencies higher than 0.025 Hz on centroid‐moment‐tensor inversion for the earthquakes occurring in the top 10 km of the Earth's crust. For a synthetic

In an effort to achieve higher‐resolution imaging as well as detailed lithology descriptions, it is important to consider attenuation as an aid in compensating for seismic wave amplitude and phase distortions due to the viscoelastic properties of natural rocks. We have evaluated elastic‐wave attenuation on a variety of Gulf of Mexico (GoM) rock salt samples (>95% halite by weight) in the laboratory

We report a reanalysis of active‐source wide‐angle seismic data collected along the Greenland‐Iceland Ridge during the 1996 Seismic Investigation of the Greenland Margin (SIGMA) experiment. Interpreting the crustal structure of volcanic rifted margins has suffered from nonuniqueness because thick crust at the continent‐ocean transition may not be totally of igneous origin. In this regard, the Greenland‐Iceland

The northeastern Lau Basin is one of the fastest opening and magmatically most active back‐arc regions on Earth. Although the current pattern of plate boundaries and motions in this complex mosaic of microplates is reasonably understood, the internal structure and evolution of the back‐arc crust are not. We present new geophysical data from a 290 km long east‐west oriented transect crossing the Niuafo’ou

P ‐to‐S converted waves observed in controlled‐source, multicomponent ocean bottom seismometer (OBS) records were used to derive the Vp/Vs structure of Cascadia Basin sediments. We used P ‐to‐S waves converted at the basement to derive an empirical function describing the average Vp/Vs of Cascadia sediments as a function of sediment thickness. We derived one‐dimensional interval Vp/Vs functions from

Laboratory‐scale experiments on intact rocks are critical to the development of physics‐based fundamental understanding of various geophysical phenomenon. In this work, the capability of ultrasonic wave transmission (T‐mode) and reflection (R‐mode) to monitor damage progression in uniaxially loaded prismatic intact rock specimens has been analyzed, as it is imperative to study the observations and

Here we determined the P‐wave velocity of liquid Fe84Si16 up to 56 GPa based on inelastic X‐ray scattering measurements in a laser‐heated diamond‐anvil cell. We found that silicon significantly increases the P‐wave velocity of liquid iron under high pressure. The equation of state (EoS) of liquid Fe‐Si is obtained from the present sound velocity measurements. When extrapolating the present data to

In the southwest Japan subduction zone, short‐term slow slip events (SSEs) accompanying nonvolcanic tremor (ETS: episodic tremor and slip) occur repeatedly with recurrence intervals of several months. It is important to know the detailed slip areas of the SSEs because short‐term SSEs occur at the downdip extension of a megathrust earthquake rupture zone, and hence the SSEs play a key role in the stress

Knowledge of the internal state of rock is key to anticipate its rheological response and susceptibility to external factors. Time‐dependent failure in rock is controlled by internal state changes, like damage accumulation or strength degradation. But assessing internal states and changes thereof, non‐destructively and independent of external forcing is not straight forward. Residual strains, measured

The Earth’s lowermost mantle is characterized by two large‐low shear velocity provinces (LLSVPs). The regions outside the LLSVPs have been suggested to be strongly influenced by subducted slabs and therefore, much colder than the LLSVPs. However, localized low‐velocity seismic anomalies have been detected in the subduction‐influenced regions, whose origin remains unclear. Here, three‐dimensional geodynamic

Near‐fault motion is often dominated by long‐period, pulse‐like particle velocities with fault‐normal polarization that, when enhanced by directivity, may strongly excite mid‐ to high‐rise structures. We assess the extent to which plastic yielding may affect amplitude, frequency content, and distance scaling of near‐fault directivity pulses. Dynamic simulations of 3D strike‐slip ruptures reveal significant

No abstract is available for this article.

We demonstrate the feasibility of finite frequency ambient noise tomography (ANT) in mapping broadband surface wave phase velocities in the western US using data from the USArray. We obtain cross‐correlation functions (CCFs) of ambient noise data between pairs of stations, and then construct a 2‐D phase sensitivity kernel for each CCF between a pair of stations by treating one station as a ‘virtual’

Stripe‐like patterns of surface wave arrival‐angle deviations have been observed by several seismological studies around the world, but this phenomenon has not been explained so far. Here we test the hypothesis that systematic arrival‐angle deviations observed at the AlpArray broadband seismic network in Europe are interference patterns caused by diffraction of surface waves at single small‐scaled

Understanding and modeling variability of ground motion is essential for building accurate and precise ground motion prediction equations, which can net site‐specific characterization and reduced hazard levels. Here, we explore the spatial variability in peak ground velocity (PGV) at Sage Brush Flats along the San Jacinto Fault in southern California. We use data from a dense array (0.6 x 0.6 km2,

Experimental results demonstrate that amorphous materials can be generated by frictional sliding at a wide range of conditions, and that once formed the frictional strength of the fault is reduced. Nevertheless, amorphous materials have not been described in many natural faults, and their importance in natural systems is not well understood. We have identified amorphous materials within a 3‐mm‐thick

Long‐period (LP) ground motions with periods of ~2–10 s caused by large earthquakes are strongly amplified in sedimentary basins, posing serious threats to modern cities to cause resonance and damage to skyscrapers, oil storage tanks, long‐span bridges, and other structures with long natural periods. Since the LP ground motions are comprised of surface waves traveling for longer distances with much

Infrasound measurements at open‐vent volcanoes are crucial parameter for monitoring and exploring the explosive source dynamics. Volcano infrasound depicts the pressure variation within the volcanic conduit generated by the sudden expansion of volcanic gases during the fragmentation process and it can provide important constraints on the explosive source parameters (i.e. volumetric flux, exit velocity)

Locating change regions of seismic velocities and seismic scattering properties associated with volcanic activities and earthquakes is important for structural monitoring. To increase such applications, we propose to use sparse modeling to estimate spatial distributions of seismic scattering property changes. The sparse modeling is an inversion technique that enables us to estimate model parameters

To complement velocity distributions, seismic attenuation provides additional important information on fluid properties of hydrocarbon reservoirs in exploration seismology, as well as temperature distributions, partial melting and water content within the crust and mantle in earthquake seismology. Full waveform inversion (FWI), as one of the state‐of‐the‐art seismic imaging techniques, can produce

Estimation of paleomagnetic directions plays a crucial role in magnetostratigaphy, paleogeographic reconstruction, and constraining past geomagnetic field behavior. While analysis and aggregation of paleomagnetic directional data are performed in a hierarchical fashion, the standard statistical framework employed by paleomagnetists does not consider uncertainty propagation through each level of the

We investigate effects of realistic Earth's lithospheric structures on measurements of SKS seismic waves birefringence, which could be perturbed by different factors. We present SKS measurements recorded in four different tectonic settings. For each case, a realistic lithospheric structure is assumed and synthetic SKS splitting measurements are compared with the field observations. Our results show

Liquid immiscibility is a critical mechanism to diversify magma compositions. The physical separation of exsolved melt droplets is an essential process in generating new magmas. However, little attention has been paid to this physical process. In this study, we present a new model for segregation of immiscible melt droplets in which exsolution, settling, and coalescence are all considered. The separation

Fracture stiffness and flow properties have been measured in the laboratory using naturally fractured fault rock samples from the Little Grand Wash fault, Utah, USA. We compare fracture closure and related flow change during isotropic loading of two fractures which have been subject to various amounts of paleo‐reactive flow. The two tested fractures are described as (i) a small‐aperture fracture (0

Situated in a transition zone between the western and eastern North China Craton (NCC), the central North China Craton exhibits complex dynamics features. Significant lithosphere thinning is observed beneath the eastern NCC and the northern segment of the central NCC. To study how the crust responses to the distinct lateral variations of the lithospheric mantle, we develop a method for joint inversion

Fluid pressure changes affect fault stability and can promote the initiation of earthquakes and aseismic slip. However, the relationship between seismic and aseismic fault slip during fluid injection remains poorly understood. Here, we investigate, through 3D hydromechanical modeling, the spatiotemporal evolution of seismicity and aseismic slip on a permeable, slip‐weakening fault subjected to a local

The Himalayan orogen, which formed due to collision of the Indian and Asian continents during the Early Tertiary, is a prime example of a large, hot collisional orogen. Despite decades of study, the duration of partial melting of migmatitic rocks exposed in the Himalayan orogenic core remain highly controversial. As such, we have performed detailed petrological and geochronological analyses of garnet

We performed measurements of velocity variations for variable coda waves time lapse using empirical Green’s functions reconstructed by autocorrelation of seismic noise recorded during a period of 17 years in the region of l’Aquila, Italy. The time lapse approach permitted us to evaluate the spatial (depth) dependence of velocity variation (dv/v). By quantitatively comparing the 17 years of dv/v time

The Hispar Glacier is a useful site for studying surge mechanisms. Prior to this study only two‐dimensional (2D) flow velocities having low temporal resolution were available for this glacier, providing inadequate information about its surge evolution. In this study, 139 Sentinel‐1A images were used to obtain 3D flow velocity time series for the Hispar Glacier during the recent surge (2014‐2016). The

Temporal changes in the subsurface seismic velocity structure reflect the physical processes that modulate the properties of the media through which seismic waves propagate. These processes, such as healing of the surface damage zone and deep crustal deformation, are described by similar functional forms and operate on similar timescales, making it difficult to determine which process drives the observed

Mining activities are well known for being able to induce local seismicity but have not yet been shown to cause earthquakes over large distances. We analyze a particular group of seismic events recorded from 2014 to 2016 in north‐central British Columbia (BC) that appear to be triggered by the activities at the Mount Milligan mine. The spatial distribution of the studied events follows a NW‐SE linear

The Late Pennsylvanian glacial rhythmites of the Mafra Formation (Itararé Group) from the Paraná Basin of Southern Brazil, have a complex rock‐magnetic signature. Rock magnetic tests imply that both hematite and magnetite in varying grainsizes are responsible for the magnetic remanence. Thermal and alternating field (AF) demagnetization of the natural remanence reveal different behaviors that are attributed

In this response, we address the comments by D. Bilardello on the paper doi: 10.1029/2018JB016968 by Brandt et al. (2019). His main point is that the Mafra rhythmites are remagnetized as are supposed to be all Paleozoic sediments in the Paraná Basin in the context of a widespread Jurassic‐Cretaceous remagnetization in South America. In this way, the obtained results are not suitable for investigations

Chalcophile elements and lithium (Li) isotopes were measured on lavas from a 220‐km transect across the Kamchatka arc in order to investigate the fluid variations below arc volcanoes and to trace the geochemical behaviour of Li in convergent plate margins. From the Eastern Volcanic Front (EVF), through the Central Kamchatka Depression (CKD), into the Sredinny Range (SR) volcanic zones, chalcophile

Southeast Asia lies within one of the most complex tectonic settings on Earth and exhibits a range of features, including strongly curved subduction zones, arc‐continent collision, and slab break‐off, which are not well understood. To help gain insight into mantle structure and processes beneath this region, we perform an inversion for variations in Vp, Vs, and structure using arrival time information

The rupture process of the 2018 Mw 7.9 offshore Kodiak (Alaska) earthquake is still in hot dispute because of a lack of offshore observations, thus causing difficulties for understanding seismogenic tectonics and tsunami hazards. In this study, teleseismic body waves, high‐rate GPS, seismic waves preceding tsunami waves, static GPS, and tsunami data are jointly used to resolve the faulting geometry

We study the crustal structure of Sri Lanka by analyzing data from a temporary seismic network deployed in 2016–2017 to shed light on the amalgamation process from a geophysical perspective. Rayleigh wave phase dispersion curves from ambient noise cross correlation and receiver functions were jointly inverted using a transdimensional Bayesian approach. The Moho depths in Sri Lanka range between 30

The interest on low‐temperature geothermal resources is progressively increasing since their renewability and widespread availability. Despite their frequency, these resources and their development have been only partially investigated. This paper unravels the major physical processes driving a low‐temperature geothermal resource in NE Italy (Euganean Geothermal System) through conceptual and numerical

We present a three‐dimensional electrical resistivity model of the crust and upper mantle beneath the easternmost Kunlun fault (EKLf), obtained by three‐dimensional inversion of magnetotelluric (MT) data. The crust of the Songpan‐Ganzi block is characterized by high resistivity from the surface to a depth of around 20 km, and by low resistivity in the mid‐lower crust in the depth range 20–40 km. The

The tectonic uplift of the Tibetan Plateau is a focus in the geosciences. Middle‐lower crustal flow is a popular model to interpret the geodynamic mechanism on the margin of the Tibetan Plateau. The model predicts different surface and Moho topographies across the plateau boundary due to the different strengths of the surrounding blocks, that is, sharp boundaries on the eastern plateau boundary and

Landslide is one of the most dangerous geological hazards in mountainous regions, which causes large casualties. Fast and accurate location of a landslide is critical to disaster mitigation and early warning of secondary hazards. The landslide location is a difficult problem in a remote region with sparse seismic network due to low resolution of the velocity structure model. Green's functions from

Oceanic transform faults (OTFs) represent an attractive tectonic environment to investigate how slip is accommodated within the crust. However, as most of these fault systems grow in the deep ocean, where few local seismic observations are available, characterizing their earthquake behavior is complicated and remains a formidable challenge. Here we present a novel approach for retrieving precise centroid

Nazca subduction beneath South America is one of our best modern examples of long‐lived ocean‐continent subduction on the planet, serving as a foundation for our understanding of subduction processes. Within that framework, persistent heterogeneities at a range of scales in both the South America and Nazca plates is difficult to reconcile without detailed knowledge of the subducted Nazca slab structure

Brady Hot Springs geothermal field has exhibited subsidence, as measured by interferometric synthetic aperture radar (InSAR). Previous studies have examined both the temporal evolution of the deformation from 2004 through 2016 and the spatial extent of the deformation, directly relating the observed subsidence to volumetric changes below the surface. We extend the modeling at Brady to analyze a data

The temporal evolution of effusion rate is the main controlling factor of lava spreading and emplacement conditions. Therefore, it represents the most relevant parameter for characterizing the dynamics of effusive eruptions and thus for assessing the volcanic hazard associated with this type of volcanism. Since the effusion rate curves can provide important insights into the properties of the magma

Sedimentation and burial rate can vary considerably at continental slopes, due to constantly changing tectonic processes on the geological timescale. This variation may affect the transport of methane in sediment, as manifested in the change of pore water flux, methanogenesis, methane diffusion and hydrate removal from hydrate stability zone (HSZ) and further affect the accumulation of hydrate in submarine