Journal: Journal of Geophysical Research: Solid Earth

Abbreviation

J. Geophys. Res. Solid Earth

Publisher

Wiley

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ISSN

2169-9313
0148-0227
2169-9356

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Publications1 - 10 of 56
  • Challenges in Submarine Fiber-Optic Earthquake Monitoring
    Item type: Journal Article
    Igel, Jonas K.H.; Klaasen, Sara; Noe, Sebastian; et al. (2024)
    Journal of Geophysical Research: Solid Earth
    Utilizing existing telecommunication cables for Distributed Acoustic Sensing (DAS) experiments has eased the collection of seismological data in previously difficult-to-access areas such as the ocean bottom. To assess the potential of submarine DAS for monitoring seismic activity, we conducted an experiment from mid-October to mid-December 2021 using a 45 km long dark fiber extending from the Greek island of Santorini along the ocean bottom to the neighboring island of Ios. This region is of great geophysical and public interest because of its historical and recent seismic and volcanic activity, especially along the Kolumbo volcanic chain. Besides recording anthropogenic noise and around 1,000 seismic events, we observe the primary and secondary microseisms in the submarine section, the latter inducing Scholte waves in a sediment layer where the cable is well-coupled. By using the spectral element wave propagation solver Salvus, we compute synthetic strains for earthquakes with varying degrees of model complexity. Despite including topography, a water layer, and a heterogeneous velocity model, we are unable to reproduce the lack of coherence in our observed earthquake waveforms. Backpropagation simulations for four observed earthquakes indicate that clear convergence of the wavefield, and thus the ability to constrain a source region, is only possible when all model complexities are considered. We conclude that, despite the promising emergence of DAS, monitoring capabilities are limited by often unfavorable cable geometries, cable coupling, and the complexity of the medium. Interrogating multiple cables simultaneously or jointly analyzing DAS and seismometer data could help improve future monitoring experiments.
  • Serpentinization, Carbonation, and Metasomatism of Ultramafic Sequences in the Northern Apennine Ophiolite (NW Italy)
    Item type: Journal Article
    Schwarzenbach, Esther M.; Vogel, Monica; Früh-Green, Gretchen L.; et al. (2021)
    Journal of Geophysical Research: Solid Earth
    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 on the ocean floor and triggering hydrothermal alteration. Seawater circulation is documented by (Jurassic) seawater-like 87Sr/86Sr values and δ13C values of 1.1–3.0‰ in carbonate veins of the ophicalcites. Bulk rock ophicalcites have low 87Sr/86Sr values of 0.70489–0.70599, elevated SiO2 contents, and talc druses filling calcite veins that record Si-metasomatism. In contrast, underlying serpentinites have 87Sr/86Sr values above Jurassic seawater values. Bulk rock δD and δ18O values of ophicalcites and serpentinites suggest interaction with an evolved seawater-derived and/or magmatic fluid. These chemical signatures result from a complex history of serpentinization, carbonation, and metasomatism. Multiphase water-rock interaction includes infiltration of basement-derived fluids during initial mantle upwelling within an opening ocean basin, followed by localized high-temperature fluid infiltration, extensive seawater circulation resulting in carbonation, and oxidation near the seawater-exposed surface, and finally, fluid-rock interaction with overlying mafic lithologies leading to Si-metasomatism. The studied sequence represents an excellent example of the evolution from serpentinite to ophicalcite during continuous uplift and exposure of ultramafic rocks on the seafloor and documents the complex hydrothermal evolution of ultramafic rocks associated with this process. The extensive chemical transformation of mantle peridotites likely has an impact on geochemical cycles and subduction zone processes.
  • Cohesion-Induced Stabilization in Stick-Slip Dynamics of Weakly Wet, Sheared Granular Fault Gouge
    Item type: Journal Article
    Dorostkar, Omid; Guyer, Robert A.; Johnson, Paul A.; et al. (2018)
    Journal of Geophysical Research: Solid Earth
  • A Physical Model for Three-Phase Compaction in Silicic Magma Reservoirs
    Item type: Journal Article
    Huber, Christian; Parmigiani, Andrea (2018)
    Journal of Geophysical Research: Solid Earth
  • Grain Friction Controls Characteristics of Seismic Cycle in Faults With Granular Gouge
    Item type: Journal Article
    Dorostkar, Omid; Carmeliet, Jan (2019)
    Journal of Geophysical Research: Solid Earth
    Mature faults at their core contain granular gouge, created due to communition of host rocks, which its frictional behavior controls earthquake nucleation and rupture patterns. In this work, we consider a fault system with granular gouge to study the effect of grain friction on the characteristics of seismic cycles. Our results show that particle friction controls the evolution of fault frictional strength as well as accumulation and release of elastic strain energy. Our discrete element simulations show that the stick-slip frictional strength and dilation of the fault, as well as their variations, nonlinearly increase with the particle friction, but at high particle friction saturate. By statistical analyses on a large number of slip events, we find that the average recurrence time and its variations decrease with particle friction. A fault with higher grain friction shows more small slip events and also contains a limited number of extreme events. High particle friction introduces a more complex nucleation phase with higher stored energy and many recurrent small failures. We analyze the pseudo acoustic emission, which is based on monitoring the velocity signal of particles, and find higher temporal and more spatially distributed pseudo acoustic emissions for fault with higher grain friction. Our findings in this study show that, in faults with granular gouge, where the fault zone walls are totally engaged to the gouge layer, the friction at grain-scale controls the characteristics of stick-slip cycles including timing and amount of energy release.
  • Extensional Polarity Change in Continental Rifts: Inferences From 3-D Numerical Modeling and Observations
    Item type: Journal Article
    Balázs, Attila; Matenco, Liviu; Vogt, Katharina; et al. (2018)
    Journal of Geophysical Research: Solid Earth
  • The Plumbing System Feeding the Lusi Eruption Revealed by Ambient Noise Tomography
    Item type: Journal Article
    Fallahi, Mohammad Javad; Obermann, Anne; Lupi, Matteo; et al. (2017)
    Journal of Geophysical Research: Solid Earth
  • Distribution and Sources of Carbon in Serpentinized Mantle Peridotites at the Atlantis Massif (IODP Expedition 357)
    Item type: Journal Article
    Ternieten, Lotta; Früh-Green, Gretchen L.; Bernasconi, Stefano M. (2021)
    Journal of Geophysical Research: Solid Earth
    The carbon geochemistry of serpentinized peridotites and gabbroic rocks recovered during IODP Expedition 357 on the Atlantis Massif (AM) was examined to characterize carbon sources and the fate of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in seawater during long-lived hydrothermal circulation and serpentinization. Carbon isotopes reveal three stages of carbonate formation, starting at least 38,000 yr ago: (a) Early dispersed carbonate precipitation, with low water/rock ratios and high temperatures (50°C–190°C); (b) carbonate vein formation related to high and focused fluid fluxes still at high temperatures (30°C–200°C); and (c) seawater circulation leading to cold carbonate precipitation controlled by late, brittle fractures during uplift, and unroofing of the oceanic core complex. Our study reveals three main DIC sources in the system: (a) DIC from abiotic hydrothermal degradation of dissolved organic matter (OM); (b) DIC from seawater; and (c) DIC from mantle-derived volatiles. Basement rocks containing dispersed carbonates are characterized by high concentrations (∼800 ppm) of total non-carbonate carbon (NCC) and 13C-depleted carbonates. We propose that high seawater fluxes in the southern part of the AM likely favor the transport and incorporation of marine DOC in serpentinites and that carbonates record isotopic signals of OM decay. Our study indicates that organic carbon accounts for a significant proportion of the total carbon stored in the AM and suggests that serpentinites may be an important sink of DOC from seawater.
  • Global Frictional Equilibrium via Stochastic, Local Coulomb Frictional Slips
    Item type: Journal Article
    Zhang, Shihuai; Ma, Xiaodong (2021)
    Journal of Geophysical Research: Solid Earth
    Based on the assumption that fault slip dominates in the stress relaxation in the brittle crust, Coulomb theory allows for the crustal stress estimation with an empirical frictional coefficient. However, natural variability of fault friction and slip uncertainty exist in the Earth's crust. To address the extent to which heterogeneous frictional slips influence crustal stress and its evolution, we establish a quasi-static, 2D model to represent the fractured crustal rock mass. The model consists of randomly oriented fractures with heterogeneous distribution of frictional coefficients. The global mechanical response is quantitatively related to the cascades of local frictional slips under specific boundary conditions. The temporal evolution of stress is explicitly modeled by an iterative process where a simple slip law is assumed for critical fractures. We particularly illustrate the stress evolution in a normal faulting stress regime, considering different distributions of frictional coefficients. All cases indicate that the decrease in differential stress manifests as a self-organized process, eventually leading to the frictional equilibrium of the fractured rock mass. The final stress state upon equilibrium jointly depends on the orientation and frictional coefficient of all fractures therein. The model informs that the global stress state of a stochastic system can depart substantially from a deterministic estimation via an empirical frictional coefficient. This model quantitatively corroborates and extends the notion of frictional equilibrium, and reveals far more profound influence of system heterogeneity on the local and global stress evolution.
  • From Orogeny to Rifting: The Role of Inherited Structures During the Formation of the South China Sea
    Item type: Journal Article
    Li, Kai; Brune, Sascha; Erdős, Zoltán; et al. (2024)
    Journal of Geophysical Research: Solid Earth
    Many of the world's rifts and rifted margins have developed within former orogens. The South China Sea (SCS) formed during Cenozoic rifting by utilizing pre-existing orogenic structures, like thrust faults, thickened crust, and corresponding thermal weaknesses. The mechanisms explaining how inherited structures influence the spatiotemporal evolution of a rift remain a topic of on-going research. Here, we explore the impact of orogenic inheritance on rift evolution through a numerical forward model that reproduces geodynamic and landscape evolution processes. By imposing time-dependent phases of shortening and extension, we model rifted margin formation that is consistent with the available geological and geophysical observations of the SCS. Our numerical models allow us to identify thrust faults that are reactivated as normal faults during extensional phases. Not all pre-existing thrust faults, however, undergo full reactivation, as their behavior is influenced by variations in lithospheric strength and the pre-existing structural discontinuities. We further show that inherited orogenic structures compete with each other during extensional reactivation and ultimately govern the location of continental breakup. Our results provide valuable insights into the broader implications of inherited orogenic structures and how they affect subsequent rift system evolution.
Publications1 - 10 of 56