Preprints
Filtering by Subject: Tectonics and Structure
Field evidence for the lateral emplacement of igneous dykes: Implications for 3D mechanical models and the plumbing beneath fissure eruptions.
Published: 2018-06-06
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Seismological and geodetic data from modern volcanic systems strongly suggest that magma is transported significant distance (tens of kilometres) in the subsurface away from central volcanic vents. Geological evidence for lateral emplacement preserved within exposed dykes includes aligned fabrics of vesicles and phenocrysts, striations on wall rocks and the anisotropy of magnetic susceptibility. [...]
Off-fault Focal Mechanisms not Representative of Interseismic Fault Loading Suggest Deep Creep on the Northern San Jacinto Fault
Published: 2018-06-01
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Within the San Bernardino basin, some focal mechanisms show normal slip that is inconsistent with the expected interseismic strike-slip loading of the region. The discrepancy may owe to deep (> 10 km depth), creep along the nearby northern San Jacinto fault. The enigmatic normal slip microseismicity occurs to the northeast of the fault and primarily below 10 km depth, consistent with off-fault [...]
Coulomb pre-stress and fault bends: ignored yet vital factors for earthquake triggering
Published: 2018-06-01
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Tectonics and Structure
Successive locations of individual large earthquakes (Mw>5.5) over years to centuries can be difficult to explain with simple Coulomb stress transfer (CST), because seismicity can miss out nearest-neighbour along-strike faults where coseismic CST increases are greatest. We show that “Coulomb pre-stress” may explain this, because magnitudes are >±50 bars if interseismic loading and local [...]
Origin and time evolution of subduction polarity reversal from plate kinematics of Southeast Asia
Published: 2018-05-28
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
We present a regional model of plate geometry and kinematics of southeast Asia since the Late Cretaceous, embedded in a global plate model. The model involves subduction polarity reversals and sheds new light on the origin of the subduction polarity reversal presently observed in Taiwan. We show that this subduction zone reversal is inherited from subduction of the Proto South China Sea plate and [...]
The Mesozoic and Palaeozoic granitoids of north-western New Guinea
Published: 2018-05-09
Subjects: Earth Sciences, Geochemistry, Geology, Other Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
A large portion of the Birds Head Peninsula of NW New Guinea is an inlier that reveals the pre-Cenozoic geological history of the northern margin of eastern Gondwana. The peninsula is dominated by a regional basement high exposing Gondwanan (Australian) Palaeozoic metasediments intruded by Palaeozoic and Mesozoic granitoids. Here, we present the first comprehensive study of these granitoids, [...]
Pre-existing basement thrusts influence rifting in the Taranaki Basin, New Zealand
Published: 2018-05-04
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
Discrete structures (e.g. faults) or pervasive fabrics (e.g. foliation), which may occur in pre-rift sedimentary and/or crystalline basement rock, can control the growth and geometry of rift-related normal fault arrays. Previous studies examining how such structures/fabrics affect rift geometry typically rely only on plan-view correlations between the strike and dip of observed or, in some cases, [...]
Structural Evolution of Salt-Influenced Fold-and-Thrust belts: A Synthesis and New Insights From Basins Containing Isolated Salt Diapirs
Published: 2018-04-30
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
Lateral shortening is expressed in unique ways in salt basins, especially if pre-shortening diapirs are present. We present an overview and new 3-D conceptual models capturing the evolution of shortening structures formed in salt provinces dominated by precursor isolated diapirs (termed isolated-diapir provinces). In such provinces, isolated diapirs form only a minor volumetric component of a [...]
Rivers, reefs, and deltas; Geomorphological evolution of the Jurassic of the Farsund Basin, offshore southern Norway
Published: 2018-04-26
Subjects: Earth Sciences, Geology, Geomorphology, Physical Sciences and Mathematics, Tectonics and Structure
In many petroleum-bearing, data-poor ‘frontier’ basins, source, reservoir, and seal distribution is poorly constrained, making it difficult to identify petroleum systems and play models. However, 3D seismic reflection data provide an opportunity to directly map the three-dimensional distribution of key petroleum system elements, thereby supplementing typically sparse, one-dimensional sedimentary [...]
Controls on early‐rift geometry: new perspectives from the Bilila‐Mtakataka fault, Malawi
Published: 2018-04-23
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
This study investigates the controls to fault and rift geometry for a young rift system. Our case study is a large fault in southern Malawi. The geometry of the fault at the surface, the scarp, and structures within the rocks the fault cuts through, are measured. We also calculate the scarp height. The orientation and height of the fault scarp implies that local stresses influence its geometry, [...]
Bimodal or quadrimodal? Statistical tests for the shape of fault patterns
Published: 2018-04-23
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
Natural fault patterns, formed in response to a single tectonic event, often display significant variation in their orientation distribution. The cause of this variation is the subject of some debate: it could be ‘noise’ on underlying conjugate (or bimodal) fault patterns or it could be intrinsic ‘signal’ from an underlying polymodal (e.g. quadrimodal) pattern. In this contribution, we present [...]
Pre-Alpine contrasting tectono-metamorphic evolutions within the Southern Steep Belt, Central Alps
Published: 2018-04-16
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure
In the Southern Steep Belt, Italian Central Alps, relicts of the pre-Alpine continental crust are preserved. Between Valtellina and Val Camonica, a poly-metamorphic rock association occurs, which belongs to the Austroalpine units and includes two classically subdivided units: the Languard-Campo nappe (LCN) and the Tonale Series (TS). The outcropping rocks are low to medium grade muscovite, [...]
The seismic history of the Pisia fault (eastern Corinth rift, Greece) from fault plane weathering features and cosmogenic 36Cl dating
Published: 2018-04-14
Subjects: Earth Sciences, Geomorphology, Physical Sciences and Mathematics, Tectonics and Structure
The deformation of the eastern Corinth rift (Greece) is distributed along several E-W trending active normal faults. Here, the 25-km-long Pisia fault experienced up to 150 cm of coseismic displacement during the 1981 Alkyonides earthquake sequence (M = 6.7, 6.4, 6.3). Using terrestrial laser scanning, coupled with analyses of color changes, lichen colonization and karstic features, we identify [...]
Crustal strain in the Marmara pull-apart region associated with the propagation process of the North Anatolian Fault
Published: 2018-04-11
Subjects: Earth Sciences, Geology, Physical Sciences and Mathematics, Stratigraphy, Tectonics and Structure
Propagation processes of plate-scale faults through continental lithosphere are poorly documented. The North Anatolian fault (NAF) is a continental right-lateral transform with striking evidence for propagation processes in the Marmara Sea pull-apart region. Earlier work [Armijo et al., 1999] suggests that in the Dardanelles, where the principal, northern branch of that fault (NNAF) enters into [...]
Coulomb stress transfer and fault interaction over millennia on non-planar active normal faults: the Mw 6.5-5.0 seismic sequence of 2016-2017, central Italy.
Published: 2018-03-27
Subjects: Earth Sciences, Physical Sciences and Mathematics, Tectonics and Structure
In order to investigate the importance of including strike-variable geometry and the knowledge of historical and palaeoseismic earthquakes when modelling static Coulomb stress transfer and rupture propagation, we have examined the August–October 2016 A.D. and January 2017 A.D. central Apennines seismic sequence (Mw 6.0, 5.9, 6.5 in 2016 A.D. (INGV) and Mw 5.1, 5.5, 5.4, 5.0 in 2017 A.D. [...]
Ambient noise image Campi Flegrei 2011-2013
Published: 2018-03-26
Subjects: Earth Sciences, Environmental Monitoring, Environmental Sciences, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology
Earthquakes at Campi Flegrei have been low-magnitude and sparse for more than thirty years, denying onshore monitoring observations of their usual source for structural constraint: seismic tomography. Here, we used ambient seismic noise recorded between 2011 and 2013 to reconstruct period-dependent Rayleigh-wave velocity maps of caldera-wide structures and volcanic reservoirs. The lowest [...]