The energy released during an earthquake is mostly dissipated in the fault zone and subordinately as radiated seismic waves. on-fault budget partitioned into frictional heat, generation of new grain surface by microfracturing, crystal-lattice distortion associated with dislocation defects. relative contribution these components debated difficult to assess, but this partitioning strongly influences mechanics. We use high-resolution scanning-electron-microscopy techniques, especially analyze...

Availability of fluids and induced metamorphic reactions are primary factors controlling the rheological behaviour rocks. During subduction, enhance kinetics eclogitization reactions, playing a fundamental role in promoting strain localization shear zone nucleation. In particular, reaction-induced grain-size reduction has long been considered one most effective weakening mechanisms. To investigate relationship between fluid-rock interaction, metamorphism deformation, we focus on pre-Alpine...

Metamorphism causes major changes in the mineralogy and rheology of the lithosphere. However, without coupled deformation fluid flow, unaltered lithosphere remains long time stiff metastable, thus sustaining large differential stresses. This is relevant to subduction of oceanic lithosphere, where fluid presence vs absence affects seismicity eclogitization. The subduction-zone behavior hydrated slabs has been deeply studied recent...

The processes that rule coupling/decoupling and rupture mechanisms along the plate interface in deep portions of active subduction zones are largely inferred from geophysical observations. These observations highlight a wide range deformation mechanism may coexist, such as: aseismic slip, episodic non-volcanic tremor slip (ETS), regular earthquakes. Despite high amount data obtained through indirect approaches, our comprehension occurring is still limited. In particular, at great depth...

This paper discusses the results of field-based geological investigations exhumed rocks exposed in Musgrave Ranges (Central Australia) and Nusfjord (Lofoten, Norway) that preserve evidence for lower continental crustal earthquakes with focal depths approximately 25–40 km. These studies have established deformation dry crust is characterized by a cyclic interplay between viscous creep (mylonitization) brittle, seismic slip associated formation pseudotachylytes (a solidified melt produced...

Understanding fault behavior in carbonates is critical because they represent loci of earthquake nucleation. Models fault-slip mode generally assume: (1) seismic sliding and aseismic occur different patches, (2) creep restricted to lithology-controlled weak domains, (3) rate-weakening patches are interseismically locked. We studied three carbonate-hosted seismogenic normal faults central Italy by combining (micro)structural geochemical analyses rocks integrated with new coupling estimates....

In subduction zones, fluids released by dehydration reactions strongly influence rock rheology and seismicity. particular, the occurrence of deep Episodic Tremor Slow Slip events (deep ETS) along interface, at 25-60 km depth1, is likely fostered simultaneous presence fluctuating fluid pressure rheological heterogeneities, that allow for strain partitioning into low-strain domains radiating tremor, high-strain accommodating slow slip events. The Erro-Tobbio meta-peridotite (Ligurian Alps)...

The meta-granitoids of the Zillertal unit Tauern window (eastern Alps) record a sequence Alpine deformations, developed during exhumation, ranging from ductile (at amphibolite-upper greenschist facies metamorphic conditions) to brittle conditions close base seismogenic crust). In core unit, high grade deformation (stage1) is common and localized steeply-dipping strike-slip shear zones, mainly striking around E-W hierarchically organized in thick (up several metres), km-long mylonitic major...

Field studies established that seismicity in the lower crust is linked to brittle failure of dry, strong rocks. Failure these rocks implies build-up differential stresses gigapascal (GPa) levels, but this requirement contrasts with current models continental lithosphere deformation, which favour distributed flow weak viscous crust. Although several mechanisms have been proposed generate transiently high stresses, direct measurements are lacking. Recent advancements microanalytical techniques...

Exhumed pseudotachylytes (quenched coseismic frictional melts) and their wall-rocks represent a source of information to investigate earthquake mechanics at hypocentre depth. Pseudotachylytes produced eclogite-facies conditions in subducted oceanic rocks are particular interest as they open window into the elusive intermediate-depth earthquakes1. Here we present observations from hosted gabbros peridotites Moncuni (Lanzo Massif, W Alps). These record seismic faulting occurred ca. 70 km depth...

<p>The Woodroffe Thrust (WT) in the Musgrave Ranges (central Australia) is a shallowly south-dipping crustal-scale mylonitic zone extending E-W for over 600 km. The WT, developed during intracontinental Petermann Orogeny (630-520 Ma), placed hanging wall lower-crustal granulite to upper-amphibolite facies rocks of Fregon Subdomain (FS) footwall amphibolite-facies mid-crustal gneisses and granitoids Mulga Park (MPS). WT mylonites largely affect MPS minor extent FS. Towards hosts...

The seismogenic environments build up the highest differential stresses on Earth. Differential stress of as much hundreds MPa to few GPa is accumulated during interseismic loading stage and it abruptly released in a sequence fast, high-stress events (earthquake rupture tip propagation, frictional fault slip, thermomechanical interactions) determining large-magnitude, local changes near plane. A major challenge obtain quantification these represented by their heterogeneity space time....

The origin of intermediate-depth seismicity in subducting oceanic lithosphere is still debated. A key for interpretation provided by deep-seated pseudotachylytes (quenched frictional melts produced during seismic slip along a fault), exhumed counterparts the actual deep seismicity, that can record relevant information on processes at hypocenter depths. Pseudotachylytes crosscutting dry ophiolitic peridotite/gabbros Moncuni (Lanzo ultramafic Massif, W. Alps)[1] have been interpreted to formed...

<p>During exhumation, metamorphic rocks change their rheological behavior from dominantly ductile to brittle. Especially at the “brittle-ductile transition” bottom of brittle crust, which coincides roughly with domain where most “shallow” earthquakes nucleate, exhibit a close interplay between flow and fracturing.</p><p>In Neves area (Tauern window, Eastern Alps) exhumation across...

<p>Intermediate-depth subduction seismicity is still hiding most of its secrets. While plate unbending recognised as the main stress loading mechanism, processes responsible for earthquake nucleation are unclear and depend upon question whether failure occur in a wet dehydrating slab or completely dry lithosphere. The recent observation subduction-related pseudotachylytes (quenched frictional melts produced during seismic slip along fault) ophiolites Moncuni (Lanzo...