Strike-slip fault reactivation in the Western Alps due to Glacial Isostatic Adjustment

2020 ◽  
Author(s):  
Juliette Grosset ◽  
Stéphane Mazzotti ◽  
Philippe Vernant ◽  
Jean Chéry ◽  
Kevin Manchuel
Keyword(s):  
Slip Rate ◽  
Western Alps ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault Reactivation ◽  
Maximum Effect ◽  
Glacial Isostatic Adjustment ◽  
Fault Systems ◽  
Isostatic Adjustment ◽  
The Impact

<p>The Western Alps represent the zone of highest seismicity density in metropolitan France. The seismicity is mainly located along two NE-SW strike-slip fault systems: the right-lateral Belledonne Fault and the left-lateral Durance Fault. Glacial Isostatic Adjustment (GIA) is one of the most common processes given to explain intraplate seismicity (e.g., Scandinavia, North America) and is also proposed as a cause of present-day deformation in the Alps. In order to test the impact of deglaciation from the Last Glacial Maximum on pre-existing vertical strike-slip faults in the Western Alps (Belledonne and Durance Faults), we use a finite-element approach to model fault reactivation throughout the deglaciation period, from ca. 18 kyr up to today. The models are tuned to fit present-day deformation rates observed by geodesy (uplift rate up to 2 mm/yr and horizontal radial extension). Simplified models (homogeneous icecap and Earth rheology) show that, under optimum conditions, GIA stress perturbations can activate a NE-SW right-lateral strike-slip fault such as the Belledonne Fault, requiring the fault to have been pre-stressed up to near-failure equilibrium before the onset of deglaciation. The maximum effect of GIA is 1.7 meters of right-lateral slip over 20 kyr, with a peak of displacement between 20 and 10 ka. These models indicate that GIA can result in a maximum slip rate of 0.08 mm/yr averaged over the Holocene, in association with earthquakes up to Mw = 7 (if all displacement is taken in one event). These results are consistent with local paleoseismicity and geomorphology evidence on the Durance fault. However, the impact of GIA on the left-lateral Belledonne Fault is poorly constrained by these simple models. Additional models based on realistic Alpine icecap reconstructions and regional rheology structures will also be presented, that allow us to test the specific effects of GIA on Holocene deformation along both the Belledone and Durance Fault systems.</p>

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>

Assessment of thermal circulations in strike-slip fault systems: the Terme di Valdieri case (Italian western Alps)

2008 ◽  
Vol 299 (1) ◽  
pp. 317-339 ◽  
Author(s):  
A. Baietto ◽  
P. Cadoppi ◽  
G. Martinotti ◽  
P. Perello ◽  
P. Perrochet ◽  
...  
Keyword(s):  
Western Alps ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault Systems

scholarly journals Slip‐rate on the Main Köpetdag (Kopeh Dagh) Strike‐slip fault, Turkmenistan, and the active tectonics of the South Caspian

Tectonics ◽  
2021 ◽  
Author(s):  
Richard Thomas Walker ◽  
Y. Bezmenov ◽  
G. Begenjev ◽  
S. Carolin ◽  
N. Dodds ◽  
...  
Keyword(s):  
Active Tectonics ◽  
Slip Rate ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
The South

scholarly journals The structure and late Quaternary slip rate of the Rafsanjan strike-slip fault, SE Iran

Geosphere ◽  
2011 ◽  
Vol 7 (5) ◽  
pp. 1159-1174 ◽  
Author(s):  
M. Fattahi ◽  
R.T. Walker ◽  
M. Talebian ◽  
R.A. Sloan ◽  
A. Rasheedi
Keyword(s):  
Late Quaternary ◽  
Slip Rate ◽  
Strike Slip ◽  
Strike Slip Fault

Influence of erosion and sedimentation on strike-slip fault systems: insights from analogue models

2006 ◽  
Vol 28 (3) ◽  
pp. 421-430 ◽  
Author(s):  
Erwan Le Guerroué ◽  
Peter Robert Cobbold
Keyword(s):  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault Systems ◽  
Analogue Models
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