Preprints
Filtering by Subject: Tectonics and Structure
Dynamic recrystallisation can produce porosity in shear zones
Published: 2020-03-18
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Creep cavities are increasingly recognised as an important syn-kinematic feature of shear zones but much about this porosity needs investigation. Largely, observations of creep cavities are restricted to very fine grained mature ultramylonites and it is unclear when they developed during deformation. Specifically, a question that needs testing is; should grain-size reduction during deformation [...]
On the formation of oceanic detachment faults and their influence on intra-oceanic subduction initiation: 3D thermomechanical modeling
Published: 2020-03-04
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
Extensional detachment faults, which have been widely documented in slow-spreading and ultraslow-spreading ridges on Earth, can effectively localize deformation due to their weakness. After the onset of oceanic closure, these weak oceanic detachments may directly control the nucleation of a subduction zone parallel to the former mid-ocean ridge, as is suggested for the Neotethys in Middle [...]
Slip on wavy frictional faults: is the 3rd dimension a sticking point?
Published: 2020-03-03
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
The formulation for the 3D triangular displacement discontinuity boundary element method with frictional constraints is described in detail. Its accuracy in comparison to analytical solutions is then quantified. We show how this can be used to approximate stress intensity factors at the crack tips. Using this method, we go on to quantify how slip is reduced on fault surfaces with topography, [...]
Analytical prediction of seismicity rate due to tides and other oscillating stresses
Published: 2020-03-03
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Planetary Geophysics and Seismology, Planetary Sciences, Tectonics and Structure
Oscillatory stresses are ubiquitous on earth and other solid-surface bodies. Tides and seasonal signals perpetually stress faults in the crust. Relating seismicity to these stresses offers fundamental insight into earthquake triggering. We present a simple model that describes seismicity rate due to perpetual oscillatory stresses. The model applies to large amplitude, non-harmonic, and [...]
Pre-inversion normal fault geometry controls inversion style and magnitude, Farsund Basin, offshore southern Norway
Published: 2020-02-29
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Inversion may localise along pre-existing structures within the lithosphere, far from the plate boundaries along which the causal stress is greatest. Inversion style and magnitude is expressed in different ways, depending on the geometric and mechanical properties of the pre-existing structure. A three-dimensional approach is thus required to understand how inversion may be partitioned and [...]
Mapping surface displacement using a pair of interferograms: comparative study
Published: 2020-02-26
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Interferometric analysis of Synthetic Aperture Radar satellite images (InSAR) measures only one component of ground deformation, in the satellite line-of-sight direction. In order to fully resolve the three dimensional (3D) ground displacement field, InSAR images acquired with different imaging geometries are required. Despite the increase in the number of SAR missions, an area is most frequently [...]
Structural inheritance and border fault reactivation during active early-stage rifting along the Thyolo fault, Malawi
Published: 2020-02-26
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Tectonics and Structure
We present new insights on the geometry, initiation and growth of the Thyolo fault, an 85 km long active border fault in the southern Malawi Rift, from high-resolution topography, field and microstructural observations. The Thyolo fault is located towards the edge of the Proterozoic Unango Terrane, and is the border fault of the Lower Shire Graben, which has experienced four phases of extension [...]
Geodetic Evidence for a Buoyant Mantle Plume Beneath the Eifel Volcanic Area, NW Europe
Published: 2020-02-25
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
The volcanism of the Eifel volcanic field (EVF), in west-central Germany, is often considered an example of hotspot volcanism given its geochemical signature and the putative mantle plume imaged underneath. EVF’s setting in a stable continental area provides a rare natural laboratory to image surface deformation and test the hypothesis of there being a thermally buoyant plume. Here we use Global [...]
P wave anisotropy caused by partial eclogitization of descending crust demonstrated by modelling effective petrophysical properties
Published: 2020-02-21
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
Seismological studies of large-scale processes at convergent plate boundaries typically probe lower crustal structures with wavelengths of several kilometers, whereas field-based studies typically sample the resulting structures at a much smaller scale. To bridge this gap between scales, we derive effective petrophysical properties on the 20-m, 100-m, and kilometer scales based on numerical [...]
Inchworm-like source evolution through a geometrically complex fault fueled persistent supershear rupture during the 2018 Palu Indonesia earthquake
Published: 2020-02-21
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
How does fault slip follow an earthquake rupture front propagating faster than the local shear-wave velocity (i.e., at supershear speed)? How does a supershear rupture front pass through a geometrically complex fault system? Resolving the evolution of such complex earthquake ruptures is fundamental to our understanding of earthquake-source physics, but these events have not been well captured by [...]
A new model for fault growth during syn-kinematic deposition
Published: 2020-02-04
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Constraining the mechanisms of fault growth is essential for understanding extensional tectonics. In these dynamic systems the propagation of existing faults through recent syn-kinematic depositions is a poorly understood yet critical process. To understand how underlying structures influence faulting, we examine fault growth in a 10 kyr magmatically-resurfaced region of the Krafla fissure swarm, [...]
Fault rupture during the December 26, 2018, Mw 4.9 Fleri earthquake (Mt. Etna): surface faulting in a volcano-tectonic environment
Published: 2020-02-04
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
On December 26, 2018, the largest instrumental earthquake ever recorded in Mt. Etna (Sicily, southern Italy) shook the eastern flank of the volcano, with epicenter near the Fleri village along the right-lateral Fiandaca Fault (focal depth less than 1 km, Mw 4.9). The mainshock was accompanied by widespread surface faulting. We surveyed and mapped the coseismic ground ruptures and collected [...]
High-resolution surface velocities and strain for Anatolia from Sentinel-1 InSAR and GNSS data
Published: 2020-02-04
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
Measurements of present-day surface deformation are essential for the assessment of long-term seismic hazard. The European Space Agencys Sentinel-1 satellites enable global, high-resolution observation of crustal motion from Interferometric Synthetic Aperture Radar (InSAR). We have developed new automated InSAR processing systems that exploit the first ~5 years of Sentinel-1 data to measure [...]
Avalonia, get bent! Paleomagnetism from SW Iberia confirms the Greater Cantabrian Orocline
Published: 2020-01-29
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
The amalgamation of Pangea formed the contorted Variscan-Alleghanian orogen, suturing Gondwana and Laurussia during the Carboniferous. From all swirls of this orogen, a double curve stands out in Iberia, the coupled Cantabrian Orocline and Central Iberian Curve. The Cantabrian Orocline formed subsequent to Variscan orogeny (ca. 315-295 Ma). The mechanisms of formation for this orocline are [...]
The mixology of precursory strain partitioning approaching brittle failure in rocks
Published: 2020-01-08
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
We examine the strain accumulation and localization process throughout twelve triaxial compression experiments on six rock types deformed in an X-ray transparent apparatus. In each experiment, we acquire 50-100 tomograms of rock samples at differential stress steps during loading, revealing the evolving 3D distribution of X-ray absorption contrasts, indicative of density. Using digital volume [...]