scholarly journals Basement sliding and the formation of fault systems on Mt Etna volcano

2021 ◽  
Author(s):  
John Murray
Keyword(s):  
Convincing Evidence ◽  
Fault System ◽  
Fault Systems ◽  
Landslide Hazards ◽  
Mt Etna ◽  
Order Of Magnitude ◽  
Additional Process ◽  
Fracture Opening ◽  
Gravitational Spreading ◽  
Laboratory Analogue

The influence of faulting on the eruptive mechanisms of Mt Etna has been intensively studied, especially regarding the importance of regional tectonics, magma pressure, gravitational spreading and east flank instability. Here we examine the influence of an additional process: the wholesale sliding of the Etna massif along its sloping basement. Using laboratory analogue experiments, we create a series of model volcanoes on sloping basements, with obstructions to represent the mountains and hills surrounding Etna, and an unconstrained downslope edge to represent the unbuttressed seaward slopes. We find that analogues of all the Etna fault systems can be produced in the same model. Furthermore, we find that the relative velocities of transcurrent faulting and extension of each model flank fault system match those of Mt Etna in every case. We also find convincing evidence that gravitational spreading of the summit cone, combined with downslope sliding, controls the position of future eruptive vents around the summit, by creating faults and fractures that form paths of least resistance for magma intrusions. The intruding magma in turn augments fracture opening by an order of magnitude, in a feedback process that dominates within the summit graben. We conclude that gravitational spreading and sliding are the dominant processes in creating faults at Etna, and that these two processes, augmented by magma pressure, are responsible for the rapid seaward movement of the eastern slopes, tectonically cut off from the stable western flanks. The influence of regional tectonism is up to two orders of magnitude lower. The conceptual model derived here could make an important contribution to the investigation and monitoring of eruptive, seismic and landslide hazards, by providing a unified mechanical system that can be used to understand deformation.

scholarly journals The Role of Faults in Groundwater Circulation before and after Seismic Events: Insights from Tracers, Water Isotopes and Geochemistry

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1499
Author(s):  
Davide Fronzi ◽  
Francesco Mirabella ◽  
Carlo Cardellini ◽  
Stefano Caliro ◽  
Stefano Palpacelli ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Central Italy ◽  
Tracer Tests ◽  
Integrated Approach ◽  
Fault System ◽  
Tectonic Structures ◽  
Fault Systems ◽  
Isotopic Analyses ◽  
Before And After

The interaction between fluids and tectonic structures such as fault systems is a much-discussed issue. Many scientific works are aimed at understanding what the role of fault systems in the displacement of deep fluids is, by investigating the interaction between the upper mantle, the lower crustal portion and the upraising of gasses carried by liquids. Many other scientific works try to explore the interaction between the recharge processes, i.e., precipitation, and the fault zones, aiming to recognize the function of the abovementioned structures and their capability to direct groundwater flow towards preferential drainage areas. Understanding the role of faults in the recharge processes of punctual and linear springs, meant as gaining streams, is a key point in hydrogeology, as it is known that faults can act either as flow barriers or as preferential flow paths. In this work an investigation of a fault system located in the Nera River catchment (Italy), based on geo-structural investigations, tracer tests, geochemical and isotopic recharge modelling, allows to identify the role of the normal fault system before and after the 2016–2017 central Italy seismic sequence (Mmax = 6.5). The outcome was achieved by an integrated approach consisting of a structural geology field work, combined with GIS-based analysis, and of a hydrogeological investigation based on artificial tracer tests and geochemical and isotopic analyses.

scholarly journals Seismic characteristics of polygonal fault systems in the Great South Basin, New Zealand

2020 ◽  
Vol 12 (1) ◽  
pp. 851-865
Author(s):  
Sukonmeth Jitmahantakul ◽  
Piyaphong Chenrai ◽  
Pitsanupong Kanjanapayont ◽  
Waruntorn Kanitpanyacharoen
Keyword(s):  
Three Dimensional ◽  
Late Eocene ◽  
Seismic Survey ◽  
Fault System ◽  
Normal Faults ◽  
Tier 2 ◽  
South Basin ◽  
Fault Systems ◽  
Tier 1 ◽  
Polygonal Fault

AbstractA well-developed multi-tier polygonal fault system is located in the Great South Basin offshore New Zealand’s South Island. The system has been characterised using a high-quality three-dimensional seismic survey tied to available exploration boreholes using regional two-dimensional seismic data. In this study area, two polygonal fault intervals are identified and analysed, Tier 1 and Tier 2. Tier 1 coincides with the Tucker Cove Formation (Late Eocene) with small polygonal faults. Tier 2 is restricted to the Paleocene-to-Late Eocene interval with a great number of large faults. In map view, polygonal fault cells are outlined by a series of conjugate pairs of normal faults. The polygonal faults are demonstrated to be controlled by depositional facies, specifically offshore bathyal deposits characterised by fine-grained clays, marls and muds. Fault throw analysis is used to understand the propagation history of the polygonal faults in this area. Tier 1 and Tier 2 initiate at about Late Eocene and Early Eocene, respectively, based on their maximum fault throws. A set of three-dimensional fault throw images within Tier 2 shows that maximum fault throws of the inner polygonal fault cell occurs at the same age, while the outer polygonal fault cell exhibits maximum fault throws at shallower levels of different ages. The polygonal fault systems are believed to be related to the dewatering of sedimentary formation during the diagenesis process. Interpretation of the polygonal fault in this area is useful in assessing the migration pathway and seal ability of the Eocene mudstone sequence in the Great South Basin.

scholarly journals Application of the Wiener filter to magnetic profiling in the volcanic environment of Mt. Etna (Italy)

1996 ◽  
Vol 39 (1) ◽  
Author(s):  
C. Del Negro
Keyword(s):  
Synthetic Data ◽  
Wiener Filter ◽  
Magnetic Anomalies ◽  
Fault System ◽  
Volcanic Area ◽  
Wiener Filters ◽  
Mt Etna ◽  
Band Pass ◽  
Magnetic Profile ◽  
Mean Square Error Criterion

The frequency-domain Wiener filtering was applied to magnetic anomalies in the volcanic area of Mt. Etna. This filter, under suitable conditions (additive noise, linear processing and mean-square error criterion), can furnish an effective tool for discriminating the geologic feature of interest (the signal) from the noise. The filter was first tested with synthetic data. Afterwards it was applied to a magnetic profile carried out across the principal fault system of the Mt. Etna volcano, that hosted the dykes feeding both the 1989 and the 1991-93 eruptions. The magnetic anomalies linked to the volcanic section and those linked to the contact between the clay basement and the lava coverage show significant spectral overlap. Thus by estimating the power spectrum of the signal, obtained resolving the forward problem, a least-squares Wiener filter has been designed. In such context, it was possible to verify the effectiveness of Wiener filters, whereas traditional band-pass filtering proved inadequate. In fact, analysis of the noise showed that all the meaningful components of the observed magnetic field were resolved. The results put further constraints on location and geometry of the shallow plumbing system of Mt. Etna.

Mapping the regional tectonic asset of the Discovery quadrangle of Mercury

2021 ◽  
Author(s):  
Valentina Galluzzi ◽  
Luigi Ferranti ◽  
Lorenza Giacomini ◽  
Pasquale Palumbo
Keyword(s):  
Imaging System ◽  
Space Environment ◽  
Fault System ◽  
Geophysical Research ◽  
Fault Systems ◽  
Space Agency ◽  
Regional Tectonic ◽  
Italian Space Agency ◽  
Dual Imaging ◽  
Map Series

<p>The Discovery quadrangle of Mercury (H-11) located in the area between 22.5°S–65°S and 270°E–360°E encompasses structures of paramount importance for understanding Mercury’s tectonics. The quadrangle is named after Discovery Rupes, a NE-SW trending lobate scarp, which is one of the longest and highest on Mercury (600 km in length and 2 km high). By examining the existing maps of this area (Trask and Dzurisin, 1984; Byrne et al., 2014), several other oblique trending structures are visible. More mapping detail could be achieved by using the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) imagery.</p> <p>We aim at mapping the structures of H-11 at high-resolution by using MESSENGER/MDIS basemaps, in order to understand its regional tectonic history by following the work done in the Victoria quadrangle (H-2) (Galluzzi et al., 2019). Differently from H-2, located in the same longitudinal range but at opposite latitudes, this area lacks in N-S trending scarps, such as the Victoria-Endeavour-Antoniadi fault system, which dominates the northern hemisphere structural framework. The existing tectonic theories predict either an isotropic pattern of faults (global contraction) or an ordered distribution and orientation of faults (tidal despinning) for Mercury. If we expect that the existing tectonic patterns were governed by only one of the two processes or both together, it is difficult to understand how such different trends formed within these two complementary areas. The structural study done for H-2 reveals that the geochemical discontinuities present in Mercury’s crust may have guided and influenced the trend and kinematics of faults in that area (Galluzzi et al., 2019). In particular, the high-magnesium region seems to be associated with fault systems that either follow its boundary or are located within it. These fault systems show distinct kinematics and trends. The south-eastern border of the HMR is located within H-11. Hence, with this study, we aim at complementing the previous one to better describe the tectonics linked to the presence of the HMR. Furthermore, this geostructural map will complement the future geomorphological map of the area and will be part of the 1:3M quadrangle geological map series which are being prepared in view of the BepiColombo mission (Galluzzi, 2019). <em>Acknowledgments: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0.</em></p> <p>Byrne et al. (2014). Nature Geoscience, 7(4), 301-307.<br />Galluzzi, V. (2019). In: Planetary Cartography and GIS, Springer, Cham, 207-218.<br />Galluzzi et al. (2019). Journal of Geophysical Research: Planets, 124(10), 2543-2562.<br />Trask and Dzurisin (1984). USGS, IMAP 1658.</p>

Fault slip envelope: A new parametric investigation tool for fault system strength and slip

2020 ◽  
Author(s):  
Roger Soliva ◽  
Frantz Maerten ◽  
Laurent Maerten ◽  
Jussi Mattila
Keyword(s):  
Mechanical Properties ◽  
Fault Slip ◽  
Fault System ◽  
Nuclear Waste Repository ◽  
Computation Method ◽  
Strength Anisotropy ◽  
Stress Regime ◽  
Fault Systems ◽  
Geological Conditions ◽  
Wide Range

<p>The fact that inherited fault systems show strong variability in their 3D shape provides good reasons to consider the strength of the Earth’s brittle crust as variably anisotropic. In this work we quantify this strength anisotropy as a function of fault system complexity by combining 3D boundary element model, frictional slip theory and fast iterative computation method. This method allows to analyze together a very large number of scenarios of stress and fault mechanical properties variations through space and time. Using both synthetic and real fault system geometries we analyze a very large number of numerical simulations (125,000) to define for the first time macroscopic rupture envelopes for fault systems, referred to as “fault slip envelopes”. Fault slip envelopes are defined using variable friction, cohesion and stress state, and their shape is directly related to the fault system 3D geometry and the friction coefficient on fault surfaces. The obtained fault slip envelopes shows that very complex fault geometry implies low and isotropic strength of the fault system compared to geometry having limited fault orientations relative to the remote stresses, providing strong strength anisotropy. This technique is applied to the realistic geological conditions of the Olkiluoto high-level nuclear waste repository (Finland). The model results suggests that Olkiluoto fault system has a better probability to slip under the present day Andersonian thrust stress regime, than for the strike-slip and normal stress regimes expected in the future due to the probable presence of an ice sheet. This new tool allows to quantify the anisotropy of strength and probability of slip of 3D real fault networks as a function of a wide range of possible geological conditions an mechanical properties. This significantly helps to define the most conservative fault slip hazard case or to account for potential uncertainties in the input data for slip. This technique therefore applies to earthquakes hazard studies, geological storage, geothermal resources along faults and fault leaks/seals in geological reservoirs.</p>

scholarly journals Rheological control on the dynamics of explosive activity in the 2000 summit eruption of Mt. Etna

Solid Earth ◽  
2010 ◽  
Vol 1 (1) ◽  
pp. 61-69 ◽  
Author(s):  
D. Giordano ◽  
M. Polacci ◽  
P. Papale ◽  
L. Caricchi
Keyword(s):  
Solid Particles ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Summit Eruption ◽  
Intermediate Phases ◽  
Strombolian Eruption ◽  
Mt Etna ◽  
Order Of Magnitude ◽  
Crystal Content ◽  
Fire Fountain

Abstract. In the period from January to June 2000 Mt. Etna exhibited an exceptional explosive activity characterized by a succession of 64 Strombolian and fire-fountaining episodes from the summit South-East Crater. Textural analysis of the eruptive products reveals that the magma associated with the Strombolian phases had a much larger crystal content (>55 vol%) with respect to the magma discharged during the fire-fountain phases (~35 vol%). Rheological modelling shows that the crystal-rich magma falls in a region beyond a critical crystal content where small addition of solid particles causes an exponential increase of the effective magma viscosity. When implemented into the modeling of steady magma ascent dynamics (as assumed for the fire-fountain activity), a large crystal content as the one found for products of Strombolian eruption phases results in a one order of magnitude decrease of mass flow-rate, and in the onset of conditions where small heterogeneities in the solid fraction carried by the magma translate into highly unsteady eruption dynamics. We argue that crystallization on top of the magmatic column during the intermediate phases when magma was not discharged favoured conditions corresponding to Strombolian activity, with fire-fountain activity resuming after removal of the highly crystalline top. The numerical simulations also provide a consistent interpretation of the association between fire-fountain activity and emergence of lava flows from the crater flanks.

scholarly journals Fault interactions in a complex fault system: insight from the 1936–1997 NE Lut earthquake sequence

2020 ◽  
Vol 224 (2) ◽  
pp. 1157-1173
Author(s):  
M Marchandon ◽  
M Vergnolle ◽  
O Cavalié
Keyword(s):  
Fault System ◽  
Coulomb Stress ◽  
Coulomb Stress Changes ◽  
Fault Systems ◽  
Complex Fault ◽  
Stress Changes ◽  
Fault Interactions ◽  
Seismic Deformation ◽  
Earthquake Sequences ◽  
Conjugate Fault

SUMMARY Calculations of Coulomb stress changes have shown that moderate to large earthquakes may increase stress at the location of future earthquakes. Coulomb stress transfers have thus been widely accepted to explain earthquake sequences, especially for sequences occurring within parallel or collinear fault systems. Relating, under this framework, successive earthquakes occurring within more complex fault systems (i.e. conjugate fault system) is more challenging. In this study, we assess which ingredients of the Coulomb stress change theory are decisive for explaining the succession of three large (Mw 7+) earthquakes that occurred on a conjugate fault system in the NE Lut, East Iran, during a 30-yr period. These earthquakes belong to a larger seismic sequence made up of 11 earthquakes (Mw 5.9+) from 1936 to 1997. To reach our goal, we calculate, at each earthquake date, the stress changes generated by the static deformation of the preceding earthquakes, the following post-seismic deformation due to the viscoelastic relaxation of the lithosphere, and the interseismic deformation since 1936. We first show that accurately modelling the source and receiver fault geometry is crucial to precisely estimating Coulomb stress changes. Then we show that 7 out of 10 earthquakes of the NE Lut sequence, considering the uncertainties, are favoured by the previous earthquakes. Furthermore, the last two M7+ earthquakes of the sequence (1979 and 1997) have mainly been favoured by the moderate Mw ∼ 6 earthquakes. Finally, we investigate the link between the Coulomb stress changes due to previous earthquakes and the rupture extension of the next earthquake and show that a correlation does exist for some earthquakes but is not systematic.

Linking dynamic earthquake rupture to tsunami modeling for the Húsavík-Flatey transform fault system in North Iceland

2021 ◽  
Author(s):  
Fabian Kutschera ◽  
Sara Aniko Wirp ◽  
Bo Li ◽  
Alice-Agnes Gabriel ◽  
Benedikt Halldórsson ◽  
...  
Keyword(s):  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault System ◽  
Deformation Pattern ◽  
Tsunami Modeling ◽  
Earthquake Rupture ◽  
Worst Case ◽  
Fault Systems ◽  
Complex Fault ◽  
The Impact

<p>Earthquake generated tsunamis are generally associated with large submarine events on dip-slip faults, in particular on subduction zone megathrusts (Bilek and Lay, 2018). Submerged ruptures across strike-slip fault systems mostly produce minor vertical offset and hence no significant disturbance of the water column. For the 2018 Mw 7.5 Sulawesi earthquake in Indonesia, linked dynamic earthquake rupture and tsunami modeling implies that coseismic, mixed strike-slip and normal faulting induced seafloor displacements were a critical component generating an unexpected and devastating local tsunami in Palu Bay (Ulrich et al., 2019), with important implications for tsunami hazard assessment of submarine strike-slip fault systems in transtensional tectonic settings worldwide. </p><p>We reassess the tsunami potential of the ~100 km Húsavík Flatey Fault (HFF) in North Iceland using physics-based, linked earthquake-tsunami modelling. The HFF consists of multiple fault segments that localise both strike-slip and normal movements, agreeing with a transtensional deformation pattern (Garcia and Dhont, 2005). The HFF hosted several historical earthquakes with M>6. It crosses from off-shore to on-shore in immediate proximity to the town of Húsavík. We analyse simple and complex fault geometries and varying hypocenter locations accounting for newly inferred fault geometries (Einarsson et al., 2019), 3-D subsurface structure (Abril et al., 2020), bathymetry and topography of the area, primary stress orientations and the stress shape ratio constrained by the inversion of earthquake focal mechanisms (Ziegler et al., 2016).</p><p>Dynamic rupture models are simulated with SeisSol (https://github.com/SeisSol/SeisSol), a scientific open-source software for 3D dynamic earthquake rupture simulation (www.seissol.org, Pelties et al., 2014). SeisSol, a flagship code of the ChEESE project (https://cheese-coe.eu), enables us to explore simple and complex fault and subsurface geometries by using unstructured tetrahedral meshes. The dynamically adaptive, parallel software sam(oa)²-flash (https://gitlab.lrz.de/samoa/samoa) is used for tsunami propagation and inundation simulations and solves the hydrostatic shallow water equations (Meister, 2016). We consider the contribution of the horizontal ground deformation of realistic bathymetry to the vertical displacement following Tanioka and Satake, 1996. The tsunami simulations use time-dependent seafloor displacements to initialise bathymetry perturbations. </p><p>We show that up to 2 m of vertical coseismic offset can be generated during dynamic earthquake rupture scenarios across the HFF, which resemble historic magnitudes and are controlled by spontaneous fault interaction in terms of dynamic and static stress transfer and rupture jumping across the complex fault network. Our models reveal rake deviations from pure right-lateral strike-slip motion, indicating the presence of dip-slip components, in combination with large shallow fault slip (~8 m for a hypocenter in the East), which can cause a sizable tsunami affecting North Iceland. Sea surface height (ssh), which is defined as the deviation from the mean sea level, and inundation synthetics give an estimate about the impact of the tsunami along the coastline. We further investigate a physically plausible worst-case scenario of a tsunamigenic HFF event, accounting for tsunami sourcing mechanisms similar to the one causing the Sulawesi Tsunami in 2018.</p>

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