Geophysics

  • Article
    | Open Access

    In ultraslow-spreading ridges intermittent detachment faulting could contribute to discontinuous magmatic accretion supporting the development of massive sulfide deposits. Here the authors using a multi-scale magnetic survey of the Southwest Indian Ridge constrain that an episode of detachment faulting took place 0.7-1.48 Ma, with the present fault active since 0.33 Ma.

    • Tao Wu
    • , Maurice A. Tivey
    •  & Yunlong Liu
  • Article
    | Open Access

    Low-frequency earthquakes are a series of small earthquakes with lower dominant frequencies than ordinary earthquakes. By comparing the simulated earthquakes with the real data, we find that low-frequency earthquakes represent an earthquake rupture process that arrests spontaneously.

    • Xueting Wei
    • , Jiankuan Xu
    •  & Xiaofei Chen
  • Article
    | Open Access

    The 2013 Castor seismic sequence, offshore Spain, is a rare example of seismicity induced by gas storage operations. Here we show that early seismicity marked the progressive failure of a fault in response to pore pressure diffusion, while later larger earthquakes resulted by the failure of loaded asperities.

    • Simone Cesca
    • , Daniel Stich
    •  & William L. Ellsworth
  • Article
    | Open Access

    Seismic imaging of subducted plates offers a way to improve plate tectonic reconstructions. Here, Braszus et al. use new ocean-bottom seismometer data from the Lesser Antilles to locate subducted spreading centres and faults thus providing a new understanding of the evolution of the Caribbean plate.

    • Benedikt Braszus
    • , Saskia Goes
    •  & Marjorie Wilson
  • Article
    | Open Access

    The downhill motion of soils on hillslopes is not well understood. Here, the authors present laboratory experiments and show that hillslopes are made perpetually fragile by environmental perturbations that prevent them from stabilizing.

    • Nakul S. Deshpande
    • , David J. Furbish
    •  & Douglas J. Jerolmack
  • Article
    | Open Access

    The authors present a high-resolution palaeomagnetic record for a Late Cretaceous limestone in Italy. They claim that their record robustly shows a ~12° true polar wander oscillation between 86 and 78 Ma, with the greatest excursion at 84–82 Ma.

    • Ross N. Mitchell
    • , Christopher J. Thissen
    •  & Joseph L. Kirschvink
  • Article
    | Open Access

    Models of the viscosity evolution of mantle rocks are central to analyses of postseismic deformation but constraints on underlying physical processes are lacking. Here, the authors present measurements of microscale stress heterogeneity in olivine suggesting that long-range dislocation interactions contribute to viscosity evolution.

    • David Wallis
    • , Lars N. Hansen
    •  & Ricardo A. Lebensohn
  • Article
    | Open Access

    Monitoring the flux of gas from volcanoes is a fundamental component of volcano monitoring programs and is used as a basis for eruption forecasting. Here, the authors present a new method using video images of volcanic gas plumes to measure the speed of convective structures and to estimate volcanic fluxes.

    • Julia Woitischek
    • , Nicola Mingotti
    •  & Andrew W. Woods
  • Article
    | Open Access

    Based on diamond-anvil cell experiments and cutting-edge secondary ion mass spectrometry analyses, the authors here show that hydrogen may be an important constituent in the Earth’s core and also in the metallic cores of any terrestrial planet or moon having a mass in excess of 10% of the Earth.

    • Shoh Tagawa
    • , Naoya Sakamoto
    •  & Hisayoshi Yurimoto
  • Article
    | Open Access

    Laboratory experiments reproducing earthquake slip in non cohesive fault rocks under fluid pressurised conditions are challenging. Thanks to these experiments, the authors show that earthquake slip occurring in tsunamigenic subduction zone faults is controlled by dilatancy and pressurisation processes.

    • S. Aretusini
    • , F. Meneghini
    •  & G. Di Toro
  • Article
    | Open Access

    A novel model for submarine tephra dispersal by hydrothermal megaplumes is proposed. The energy flux inferred from our model aligns with megaplume observations, and suggests that the catastrophic release of hot crustal fluids, as opposed to lava heating, is responsible for megaplume generation.

    • Samuel S. Pegler
    •  & David J. Ferguson
  • Article
    | Open Access

    The authors here study the origin of seismic Love waves induced by ocean waves. The study finds Love waves to originate along steep bathymetry and underlying geological interfaces, particularly sedimentary basins, yielding spatio-temporal information about ocean-land coupling in deep water.

    • Florian Le Pape
    • , David Craig
    •  & Christopher J. Bean
  • Article
    | Open Access

    Here, the authors compile a global geochemical database of Neogene-Quaternary intraplate volcanism. By comparing the distribution and composition of these rocks with tomographic models they show that intraplate volcanism can be used to constrain upper-mantle structure at the time of eruption.

    • P. W. Ball
    • , N. J. White
    •  & S. N. Stephenson
  • Article
    | Open Access

    Meltwater Pulse 1A was the most rapid global sea-level rise event during the last deglaciation, but the source of the freshwater causing this rise is debated. Here, the authors use a data-driven inversion approach to show that the North American and Eurasian Ice Sheets were the dominant contributors.

    • Yucheng Lin
    • , Fiona D. Hibbert
    •  & Sarah L. Bradley
  • Article
    | Open Access

    Here, the authors follow a new approach using analytic solutions for Poiseuille-Couette channel flow to compute asthenospheric viscosities under the Caribbean. Active asthenospheric flow observed under the Caribbean contradicts the traditional view that the asthenosphere is only a passive lubricating layer for Earth’s tectonic plates.

    • Yi-Wei Chen
    • , Lorenzo Colli
    •  & Hejun Zhu
  • Article
    | Open Access

    Recently triggered seismic events such as the Pohang earthquake have exceeded predictions of average energy releases by a factor of 1000. A new framework is proposed to define maximum event magnitudes as a function of pre-existing critical stresses and fluid injection volume.

    • Ziyan Li
    • , Derek Elsworth
    •  & M. W. McClure
  • Article
    | Open Access

    Along the cold subduction geotherm, glaucophane remains stable down to pressure and temperature (P–T) conditions of ca. 240 km depth, whereas under the warm subduction geotherm, it dehydrates and breaks down into pyroxenes and silica between ca. 50 and 100 km depths.

    • Yoonah Bang
    • , Huijeong Hwang
    •  & Yongjae Lee
  • Article
    | Open Access

    The authors here present a deep learning method to determine the source focal mechanism of earthquakes in realtime. They trained their network with approximately 800k synthetic samples and managed to successfully estimate the focal mechanism of four 2019 Ridgecrest earthquakes with magnitudes larger than Mw 5.4.

    • Wenhuan Kuang
    • , Congcong Yuan
    •  & Jie Zhang
  • Article
    | Open Access

    The authors here present geodetic and seismic data for a complete eruptive cycle (2005-2018) for Sierra Negra volcano, Galapagos Island. The data shows the largest pre-eruptive inflation (6.5 m) and rates of seismicity ever observed before a basaltic eruption and provides a rare illustration of caldera resurgence mechanisms.

    • Andrew F. Bell
    • , Peter C. La Femina
    •  & Michael J. Stock
  • Article
    | Open Access

    Here, the authors identify that magnetotelluric conductive anomalies commonly observed on the trenchward-side of volcanic arcs in subduction zones can be explained by subducted sediments. High-pressure experiments show that these sediment melts will react with the overlying mantle wedge to produce electrically conductive phlogopite pyroxenites.

    • M. W. Förster
    •  & K. Selway
  • Article
    | Open Access

    Albite is one of the major constituents in the Earth’s crust. Here, the authors report that under hydrous cold subduction conditions, albite undergoes breakdown into hydrated smectite and other phases, which release alkaline fluids into the mantle wedge.

    • Gil Chan Hwang
    • , Huijeong Hwang
    •  & Yongjae Lee
  • Article
    | Open Access

    Crustal doubling in Tibet and the Himalayas by underthrusting of the Indian plate is thought to require the presence of a mafic layer above the Moho. Here, the authors present seismic data which shows that the middle Lhasa Terrane has very low velocity (Vp < 6.7 km/s) throughout the 80 km thick crust, which they suggest is predominantly felsic in composition.

    • Gaochun Wang
    • , Hans Thybo
    •  & Irina M. Artemieva
  • Article
    | Open Access

    Chattering dust, or chemically reactive grains of sucrose containing pockets of pressurized carbon dioxide, are used in this experimental approach to study rock fractures. The chattering dust emits acoustic shocks that can be monitored and illuminates fracture geometry.

    • Laura J. Pyrak-Nolte
    • , William Braverman
    •  & David D. Nolte
  • Article
    | Open Access

    The authors show that seismogenic faults can be activated by stress perturbations by all possible modes of slip independently of the frictional properties. They demonstrate, that the nature of seismicity is mostly governed by the initial stress level along the faults.

    • François X. Passelègue
    • , Michelle Almakari
    •  & Marie Violay
  • Article
    | Open Access

    Transport properties of melts in the deep Earth have dictated the evolution of the early Earth’s magma oceans and also govern many modern dynamic processes, such as plate tectonics. Here, the authors find there is a reversal in the trends of transport properties of basaltic melts at pressures near 50 GPa, with implications for the timescales of early Earth’s magma oceans.

    • Arnab Majumdar
    • , Min Wu
    •  & John S. Tse
  • Article
    | Open Access

    The transition from wide continental rift to continental break-up remains enigmatic. Here, the authors show that northern margin of the South China Sea records the transition between wide continental rift to a highly extended continental margin, with strikingly similar structures and metamorphic core complexes to those described from the North American Cordillera and the Aegean.

    • Hongdan Deng
    • , Jianye Ren
    •  & Pan Luo
  • Article
    | Open Access

    Here, the authors combine bathymetry and sediment echosound data to present a submarine, volcanic map of the Tristan de la Cunha region. They find that the youngest volcanic expression of the Tristan de la Cunha mantle plume is currently located to the (south-) west of the island.

    • Wolfram H. Geissler
    • , Paul Wintersteller
    •  & Wilfried Jokat
  • Article
    | Open Access

    Although the surface deformation of tectonic plate boundaries is well determined by geological and geodetic measurements, the pattern of flow below the lithosphere remains poorly constrained. Here, the author finds that major earthquakes in California have occurred above the regions of current plastic strain accumulation in the mantle.

    • Sylvain Barbot
  • Article
    | Open Access

    The heat and electrical conductivity of Earth’s core matter represent key input quantities for geophysical models of the Earth’s core evolution and geodynamo. Here, the authors show how the scattering due to interactions between electrons has a relatively weak impact on the electrical and thermal conductivities of iron at core conditions.

    • L. V. Pourovskii
    • , J. Mravlje
    •  & D. Alfè
  • Article
    | Open Access

    Regions of the subducting oceanic crust are often considered to be overpressured, owing to fluid trapped beneath an impermeable seal along the overlying inter-plate boundary. Here, the authors show that slow slip earthquakes at the Cascadia subduction zone occur immediately below a 6-10 km-thick shear zone, in which slab-derived fluids are likely trapped at near-lithostatic pore pressures.

    • Andrew J. Calvert
    • , Michael G. Bostock
    •  & Martyn J. Unsworth
  • Article
    | Open Access

    The Central Atlantic Magmatic Province is the most aerially extensive magmatic event in Earth’s history, yet few constraints exist on the volumes of intrusions at depth. Here, the authors find limited intrusive volumes beneath the South Georgia Rift, consistent with modest potential mantle temperatures (<1500 °C) related to syn-rift decompression melting.

    • R. E. Marzen
    • , D. J. Shillington
    •  & S. H. Harder
  • Article
    | Open Access

    Earth surface continues to slip after large earthquakes at a slow velocity for a period of a year or more. In this study, the authors show how such slow slip before and after large earthquakes relates to the interaction of the brittle zone of the fault with the ductile zone at greater depth.

    • Giuseppe Petrillo
    • , Eugenio Lippiello
    •  & Alberto Rosso
  • Article
    | Open Access

    One of the largest continental microplates on Earth is situated in the center of the East African Rift System, and oddly, the Victoria microplate rotates counterclockwise with respect to the neighboring African tectonic plate. Here, the authors' modelling results suggest that Victoria microplate rotation is caused by edge-driven lithospheric processes related to the specific geometry of rheologically weak and strong regions.

    • Anne Glerum
    • , Sascha Brune
    •  & Manfred R. Strecker