Under upper crustal conditions, deformations are primarily brittle (i.e., localized) and accommodated by frictional mechanisms. At greater depth, deformations are ductile (i.e., distributed) and accommodated by crystal plasticity, diffusion mass transfer or cataclastic flow. The transition from the brittle to the ductile domain is not associated with a critical depth, but rather varies in time and

The continuous convergence between the Indian and Eurasian plates caused massive lithospheric deformation in the Tibetan Plateau and led to excessive crustal material escaping through its southeastern margin. However, the mechanisms that accommodate the escaping materials and whether they intrude into the Indochina Peninsula are continually under debate. Seismic Lg waves mostly propagate within the

This study presents a 3D model of the crustal and uppermost mantle shear wave velocity and radial anisotropy beneath the Iran Plateau constructed by Rayleigh and Love waves from ambient noise. We correlate three years of continuous seismic ambient noise data recorded in ninety‐eight stations to obtain cross correlation functions. Then, we measure Rayleigh (8‐60 s) and Love (8‐50 s) wave dispersion

Laboratory studies suggest that seismogenic rupture on faults in carbonate terrains can be explained by a transition from high friction, at low sliding velocities (V), to low friction due to rapid dynamic weakening as seismic slip velocities are approached. However, consensus on the controlling physical processes is lacking. We previously proposed a microphysically‐based model (the ‘Chen‐Niemeijer‐Spiers’

The Atotsugawa fault is one of the most active faults in Japan and the strain accumulation at the fault is considered to be caused by an aseismic shear zone in the fluid‐rich lower crust. To identify the shear zone and investigate the origin of the aqueous fluid in the lower crust, we deployed a Network‐MT survey in addition to a conventional wideband‐MT survey around the fault and performed an inversion

Geological observations show that fault zone composition varies and often accommodates a mixture of brittle and ductile deformation. There is growing evidence that the nature of this mixture may play an important role in determining whether the fault creeps steadily or slides in slow slip events (SSEs) and/or fast earthquakes. Using numerical experiments of slip events in a fault zone of finite thickness

It has been standard practice for about two decades to compute GPS‐based station velocity uncertainties using the apparent noise statistics of the non‐linear position residuals rather than assume white noise (WN) behavior. The latter choice would yield unrealistic velocity uncertainties. The most common noise types used are power‐law, usually close to flicker noise (FN), over most frequencies mixed

Structural fault complexity at depth affects seismic hazard, earthquake physics and regional tectonic behavior, but constraining such complexity is challenging. We present earthquake source models of the 21 February 2008, Mw 6.0 Wells event that occurred in the Basin and Range in the western USA suggesting the rupture of both the shallow and deep parts of a listric fault. We use a large data set including

There is recent experimental evidence that the effective pressure coefficient for pore volume exceeds unity in limestones with dual porosity structure. Within the realm of linear poroelastcity, this means that the unjacketed pore modulus is negative. This would be a rather unusual rock behavior since it implies that the pore volume increases for a positive pressure increment during hydrostatic compression

Submarine landslides can be several orders of magnitude larger than their terrestrial counterparts and can pose significant hazards across entire ocean basins. The landslide failure mechanism strongly controls the associated tsunami hazard. The Tampen Slide offshore Norway is one of the largest landslides on Earth but remains poorly understood due to its subsequent burial beneath up to 450 m of sediments

To discern spatial and explore possible existence of temporal variations of upper crustal anisotropy in an ∼15 km section of the San Jacinto Fault Zone (SJFZ) that is composed of the Buck Ridge and Clark faults in southern California, we conduct a systematic shear wave splitting investigation using local S‐wave data recorded by three broadband seismic stations located near the surface expression of

Rheologic variations in the Earth’s crust (like elastic plate thickness or crustal rigidity) modulate the rate at which seismic moment accumulates for potentially hazardous faults of the San Andreas Fault System (SAFS). To quantify rates of seismic moment accumulation, GNSS and InSAR data were used to constrain surface deformation rates of a 4D viscoelastic deformation model that incorporates rheological

Clusters of Cenozoic volcanoes are found in Korea and Northeast China away from plate boundaries, but the mechanisms responsible for their formation is still unknown. To resolve this issue, we derive an S‐wave velocity model of the upper mantle structure beneath East Asia using 131,947 S‐wave relative traveltimes from 974 earthquakes recorded at 1,948 seismic stations in China, Korea, Taiwan, and Japan

The fractal texture (or fabric) of porous media, which supports fluid flow at different scales, is the main cause of wave anelasticity (dispersion and attenuation) on a wide range of frequencies. To model this phenomenon, we develop a theory of wave propagation in a fluid saturated infinituple‐porosity media containing inclusions at multiple scales, based on the differential effective medium (DEM)

Repeated earthquake cycles produce topography, fault damage zones, and other geologic structures along faults. These geomorphic and structural features indicate the presence of co‐seismic permanent (inelastic) surface deformation, yet a long‐standing question in earthquake research is how much of the co‐seismic deformation field is elastic versus inelastic. These questions arise in part because it

High burial temperature and a lack of material for traditional thermal proxies significantly impede the understanding of the thermal history of carbonate stratigraphic sequences in deep time. Carbonate clumped isotope thermometry interpreted through models of solid‐state isotopic reordering and in‐situ U‐Pb dating provides a new methodology for reconstructing thermal histories of such successions.

The world‐class magmatic sulfide deposits in the Norilsk region exhibit a remarkable spatial and temporal association with the Siberian large igneous province (LIP). However, the details of the causal connection between the Siberian LIP and the ore deposits have remained contentious. Here we address the problem by modeling of assimilation, crystallization and flow behavior of magmas based on aggregated

The spatial‐temporal variations of b‐value in the Gutenberg‐Richter’s relation are understood as stress meter and premonitory indicator of strong events. The characterization of the Gutenberg‐Richter’s relation is complicated by the difficulty of identifying the completeness magnitude Mc, since its inaccurate estimate may lead to biased conclusions on b‐value. Therefore, many methods have been proposed

The 2019 Ridgecrest earthquake sequence initiated on July 4th with a series of foreshocks, including a Mw 6.4 event, that culminated a day later with the Mw 7.1 mainshock and resulted in rupture of a set of cross‐faults. Here we use sub‐pixel correlation of optical satellite imagery to measure the displacement, finite strain and rotation of the near‐field coseismic deformation to understand the kinematics

The well‐established variation in the depth of earthquakes along both branches of the East African Rift System offers an opportunity to probe the controls on the depth‐extent of seismogenesis, and the length‐scales over which this may vary. We present an updated compilation of well‐determined earthquake depths from teleseismic and regional seismic data for the East African Rift System, combined with

Most fracture data analysis techniques for attributes such as dip and aperture, treat the attributes independently of their respective spatial locations. A power‐law cumulative frequency for fracture apertures, for example, tells us nothing about their spatial distribution. Lacunarity is a technique for analyzing multi‐scale binary and non‐binary data and is ideally suited for analysis that relates

To examine the upper limit of the analyzable wavelength ranges (upper limit wavelength, ULW) of the spatial autocorrelation (SPAC) method in microtremor surveys, we have derived a formula evaluating stochastic errors of a phase velocity estimate obtained by the SPAC method. We then followed our previous paper to evaluate biases generated in a phase velocity estimate that come from the presence of the

Deep‐learning has achieved good performance and demonstrated great potential for solving forward and inverse problems. In this work, two categories of innovative deep‐learning‐based inverse modeling methods are proposed and compared. The first category is deep‐learning surrogate‐based inversion methods, in which the Theory‐guided Neural Network (TgNN) is constructed as a deep‐learning surrogate for

Akutan Island hosts a volcano considered as one of most active in the Aleutian Arc. We build a new tomography model including the 3D distributions of the Vp, Vs and Vp/Vs ratio based on arrival time data from more than 4000 local earthquakes recorded by 13 seismic stations. In this model, we reveal a columnar anomaly of high Vp, low Vs and high Vp/Vs ratio with a top boundary at a depth of ∼6 km below

The Grenada Basin separates the active Lesser Antilles Arc from the Aves Ridge, described as a Cretaceous‐Paleocene remnant of the “Great Arc of the Caribbean.” Although various tectonic models have been proposed for the opening of the Grenada Basin, the data on which they rely are insufficient to reach definitive conclusions. This study presents, a large set of deep‐penetrating multichannel seismic

The earthquake magnitude‐frequency distribution is characterized by the b‐value, which describes the relative frequency of large versus small earthquakes. It has been suggested that changes in b‐value after an earthquake can be used to discriminate whether that earthquake is part of a foreshock sequence or a more typical mainshock‐aftershock sequence, with a decrease in b‐value heralding a larger earthquake

The Grenada back‐arc basin is located between the Aves Ridge, which hosted the remnant Early Paleogene “Great Caribbean Arc,” and the Eocene to Present Lesser Antilles Arc. Several earlier studies have proposed different modes of back‐arc opening for this basin, including N‐S and E‐W directions. The main aim of this study is to constrain the circumstances leading to the opening of the basin. Three

The intradecadal fluctuations in the length‐of‐day variation (∆LOD) are considered likely to play an important role in core motions. Two intradecadal oscillations, with ∼5.9 and ∼8.5 years periods (referred to as SYO and EYO, respectively), have been detected in previous studies. However, whether the SYO and the EYO have exhibited stable damping trends since 1962 and whether geomagnetic jerks are possible

The literature often reports space–time relations between the abnormal variations of different kinds of nonseismological (i.e., geophysical, geochemical, and atmospheric) parameters and the occurrence of earthquakes. The integration of such observations with seismological ones could improve the quality of the seismic hazard assessment in the medium‐short term (months to days). Each considered parameter

Sixteen rhyolitic and dacitic Cretaceous and Paleocene‐Eocene lavas from the Lesser Caucasus have been subjected to paleomagnetic and multimethod paleointensity experiments to analyze the variations of the Earth's magnetic field. Paleointensity experiments were performed with two methods. Thellier‐type experiments with the IZZI method on 65 specimens (nine flows) yielded 15 successful determinations

The Lesser Antilles subduction zone is a challenging region when it comes to unraveling its seismogenic behavior. Over the last century, the subduction megathrust has been seismically quiet, with no large thrust event recorded, which raises the question whether this subduction zone is able to produce large interplate earthquakes or not. However, two historical earthquakes in the 19th century, a M 7–8

We model the depth and Vs structure of the Hales discontinuity (H‐D) beneath Eastern Dharwar Craton (EDC) and Southern Granulite Terrain (SGT) using P wave receiver function (P‐RF) analysis and joint inversion with Rayleigh wave phase velocity dispersion. We calculate P‐RFs at higher frequency (fmax = 0.46 Hz), compared to previous studies, to show that the H‐D P‐to‐S converted phase (Phs) is distinct

In explosive submarine eruptions, volcanic jets transport fragmented tephra and exsolved gases from the conduit into the water column. Upon eruption the volcanic jet mixes with seawater and rapidly cools. This mixing and associated heat transfer ultimately determines whether steam present in the jet will completely condense or rise to breach the sea surface and become a subaerial hazard. We develop

The segmentation of mid‐ocean ridges is a defining characteristic of seafloor spreading, yet some tectonic processes operating at segment boundaries remain poorly understood. Here, we analyze new satellite‐derived vertical gravity gradient (VGG) data, which reveal an abundance of off‐axis seafloor features that are oblique to ridges and transform faults and thus reflect the occurrence of ridge propagation

Quartz c‐axis fabrics in natural mylonites can vary to such an extent that they apparently give opposite senses of shear in a single thin section. Many hypotheses have been invoked to explain this. Here, we couple our self‐consistent multiscale approach for flow partitioning with the viscoplastic self‐consistent model for c‐axis fabric simulation to investigate quartz c‐axis fabric development. Quartz

We have developed a scaled analog model of a subduction zone simulating seismic cycle deformation phases. Its rheology is based on multilayered visco‐elasto‐plastic materials to account for the mechanical behavior of a continental lithospheric plate overriding a subducting oceanic plate. The seismogenic zone displays unstable slip behavior, extending at depth into a weak interface with stable slip

Fluids on faults facilitate triggering of earthquakes and affect seismic energy release. Their detection in the focal zone is, however, difficult. Here, we present mapping of stress changes and fluid flow based on determining seismic moment tensors (MTs), which describe focal mechanisms and shear/tensile/compressive fracturing modes of earthquake sources. We calculate highly accurate MTs of 4,500 microearthquakes

Changes in continental water storage generate vertical surface deformation, induce crustal stress perturbations, and modulate seismicity rates. However, the degree to which regional changes in terrestrial water content influence crustal stresses and the occurrence of earthquakes remains an open problem. We show how changes in groundwater storage, computed for a ∼1,000 km2 basin, focus deformation in

The effect of pressure on grain‐growth kinetics of olivine was investigated up to 10 GPa at 1773 K under relatively water‐poor conditions. The results are interpreted using a relation to obtain the activation volume = 5.0 ± 1.1 cm3/mol for n = 2 or = 5.2 ± 1.1 cm3/mol for n = 3. The small activation volume means that grain‐growth kinetics in pure olivine aggregates is fast even in the dry deep upper

Surface deformation and seismicity provide critical information to understand the dynamics of volcanic unrest. During 2006–2007, >80 mm/yr uplift was observed by interferometric synthetic aperture radar (InSAR) at the central Atka volcanic center, Alaska, coinciding with an increasing seismicity rate. On November 25, 2006, a phreatic eruption occurred at the Korovin volcanic vent, 5‐km north of the

It is essential to evaluate global tomography models, which provide important information for understanding Earth’s structure and dynamics. Long period surface waves propagating between antipodal stations are good candidates for this purpose since they depend on global‐scale velocity variations in the upper mantle. In this study, we extract minor‐ and major‐arc Rayleigh waves from ambient noise cross‐correlations

Diamond‐hosted majoritic garnet inclusions provide unique insights into the Earth's deep, and otherwise inaccessible, mantle. Compared with other types of mineral inclusions found in sub‐lithospheric diamonds, majoritic garnets can provide the most accurate estimates of diamond formation pressures because laboratory experiments have shown that garnet chemistry varies strongly as a function of pressure

As one of only two subduction zones to consume slow‐spreading Atlantic oceanic crust, and with one of the slowest convergence rates of any subduction system globally, the Lesser Antilles arc is an important endmember on the subduction spectrum. Back‐arc spreading is observed at many subduction zones. Yet, despite fulfilling many of the geodynamic requirements for spreading, the tectonic processes which

Mapping lava flows frequently during effusive eruptions provides crucial parameters to better understand their dynamics, in turn improving our ability to model lava flow behavior. New photogrammetric methods have recently been developed, shifting the paradigm of photogrammetry from pure method to a multidisciplinary approach able to reduce the cost of volcanic monitoring and widen the potential spectrum

We image seismic attenuation near the Hikurangi trench offshore New Zealand, using ocean bottom and land‐based seismometers, revealing high attenuation above a recurring shallow slow‐slip event and within the subducting Hikurangi Plateau. The Hikurangi subduction margin east of the North Island, New Zealand is the site of frequent shallow slow slip events. Overpressured fluids are hypothesized to lead

We present the first high‐resolution seismic images of the crust beneath the Arunachal Himalaya, using 22,525 high quality teleseismic Receiver Functions(RFs). Data from 32 broadband seismic stations deployed in the Arunachal Himalaya during 2010‐2016 is used for this purpose. In addition, data from the HIMNT, SIKKIM, Hi‐CLIMB and GANSSER networks are used to investigate along strike variations in

The slip budget at a subduction zone megathrust is met by a spectrum of slip behaviors including coseismic slip from great earthquakes, afterslip, episodic tremor and slip (ETS), long‐term slow slip events (SSEs), and quasisteady interseismic creep. Long‐term geodetic monitoring at the Nankai subduction zone in southwest Japan has recorded deformation observations spanning nearly a complete earthquake

Water‐saturated, hydrothermally altered rocks reduce the strength of volcanic edifices and increase the potential for sector collapses and far‐traveled mass flows of unconsolidated debris. Iliamna Volcano is an andesitic stratovolcano located on the western side of the Cook Inlet, ∼225 km southwest of Anchorage and is a source of repeated avalanches. The widespread snow and ice cover on Iliamna Volcano

Carbonation of oceanic lithosphere occurs widely during seawater alteration, and subducted carbonated oceanic lithosphere may play a key role in carbon recycling in subduction zones. Here we investigate the Ca isotopic composition of arc lavas from the Tonga rear arc and Mariana arc, western Pacific, to explore the effect of fluid‐mediated carbonate transfer in subduction zones. Fresh basalts (0.84

Determining whether seismicity near volcanoes is due primarily to tectonic or magmatic processes is a challenging but critical endeavor for volcanic eruption forecasting and detection, especially at poorly monitored volcanoes. Global statistics on the occurrence and timing of earthquakes near volcanoes both within and outside of eruptive periods reveal patterns in eruptive seismicity that may improve

The presence of light elements in the metallic cores of the Earth, the Moon, and other rocky planetary bodies has been widely proposed. Carbon is among the top candidates in light of its high cosmic abundance, siderophile nature, and ubiquity in iron meteorites. It is, however, still controversial whether carbon‐rich core compositional models can account for the seismic velocity observations within

The central Sunda plate, which forms the core of Southeast Asia, has been extensively studied based on analyses of data mainly from surface geological observations. In contrast, largely due to the limited coverage by seismic stations in the area, a number of key issues associated with mantle structure and dynamics remain enigmatic. These can possibly be constrained by investigating seismic azimuthal

Although sea‐level is the primary control over sedimentary architectures on continental shelves, deciphering such changes is still challenging, except for the easily recognized transgression‐regression cycles. This problem becomes more prominent in sedimentary units with relatively homogenous and fine‐grained lithologies that have been deposited over short periods. Here, we focus on a dominantly clayey

The mass dislocations caused by large coseismic slips in megathrust earthquakes are large enough to produce elastogravity waves. Despite, successful identification of elastogravity‐wave development during megathrust earthquakes, the nature of ground motions and hazard potentials in regional and teleseismic distances remains unknown. The dynamic ground motions from the March 11, 2011 MW9.0 Tohoku‐Oki

A Probabilistic Tsunami Hazard Assessment (PTHA) study on the Chinese Mainland and the Taiwan Island was conducted. Characterized by broad and shallow continental shelves, the offshore region along Chinese Mainland's east coast yields a significant nonlinear effect and bottom friction to the propagating long waves. To address these shallow‐water effects, a fully nonlinear Boussinesq model was used

It is well documented that the interplay between crustal thickening and surface processes determines growth of continent‐continent collision orogens from small and cold to large and hot. Additionally, studies have demonstrated that the structural style of a mountain belt is strongly influenced by inherited (extensional) structures, the pattern of erosion and deposition, as well as the distribution

The 2019 Ridgecrest, California, earthquake sequence represents a complex pattern of seismicity that is characterized by the occurrence of a well‐defined foreshock sequence followed by a mainshock and subsequent aftershocks. In this study, a detailed statistical analysis of the sequence is performed. Particularly, the parametric modeling of the frequency‐magnitude statistics and the earthquake occurrence

Large earthquakes and slow slip events typically nucleate along plate boundaries near the depth limit of the seismogenic zone, which is also recognized as the brittle‐plastic transition zone (BPT). High Vp/Vs ratios are commonly observed at the BPT in subduction zones, indicating the presence of aqueous fluid in pore spaces. We conducted experiments to investigate the rheology of quartz with different

Observations of ∼7 years of postseismic deformation following the 2012 M w 7.8 Haida Gwaii and 2013 M w 7.5 Craig earthquakes in western British Columbia and southeastern Alaska provides insight into the regional rheologic structure and seismological hazards. A stress‐driven afterslip‐only model cannot alone explain rates or spatial patterns of the far field and later stage postseismic deformation

The largest slip in great megathrust earthquakes often occurs in the 10–30 km depth range, yet seismic imaging of the material properties in this region has proven difficult. We utilize a dense onshore‐offshore passive seismic dataset from the southernmost Cascadia subduction zone where seismicity in the mantle of the subducted Gorda Plate produces S‐to‐P and P‐to‐S conversions generated within a few