Interseismic coupling, seismic potential, and earthquake recurrence on the southern front of the Eastern Alps (NE Italy)

We report the discovery of Aeronian (Middle Llandovery) graptolites, and corals of probable Devonian age, in boudins hosted by greenschists, within the Southalpine Metamorphic Basement. These discoveries provide key constraints to the depositional age range of the protoliths. This remarkable occurrence of almost undeformed graptolites and compound corals in boudins within a metamorphic shear zone indicates very marked local strain partitioning.

Download Full-text

Interseismic coupling and seismic potential along the Central Andes subduction zone

Journal of Geophysical Research Atmospheres ◽

10.1029/2010jb008166 ◽

2011 ◽

Vol 116 (B12) ◽

Cited By ~ 113

Author(s):

Mohamed Chlieh ◽

Hugo Perfettini ◽

Hernando Tavera ◽

Jean-Philippe Avouac ◽

Dominique Remy ◽

...

Keyword(s):

Subduction Zone ◽

Central Andes ◽

Seismic Potential ◽

Interseismic Coupling

Download Full-text

Magnitude and source area estimations of severe prehistoric earthquakes in the western Eastern Alps

10.5194/nhess-2021-281 ◽

2021 ◽

Author(s):

Patrick Oswald ◽

Michael Strasser ◽

Jens Skapski ◽

Jasper Moernaut

Keyword(s):

Source Area ◽

Eastern Alps ◽

Earthquake Activity ◽

Negative Evidence ◽

Earthquake Recurrence ◽

Recurrence Rates ◽

Earthquake Scenarios ◽

Recurrence Intervals ◽

Lake Site ◽

Prehistoric Earthquakes

Abstract. In slowly deforming intraplate tectonic regions such as the Alps only limited knowledge exists on the occurrence of severe earthquakes, their maximum possible magnitude and their potential source areas. This is mainly due to long earthquake recurrence rates exceeding the time span of instrumental earthquake records and historical documentation. Lacustrine paleoseismology aims at retrieving long-term continuous records of seismic shaking. A paleoseismic record from a single lake provides information on events for which seismic shaking exceeded the intensity threshold at the lake site. In addition, when positive and negative evidence for seismic shaking from multiple sites can be gathered for a certain time period, minimum magnitudes and source locations can be estimated for paleo-earthquakes by a reverse application of an empirical intensity prediction equation in a geospatial analysis. Here, we present potential magnitudes and source locations of four paleo-earthquakes in the western Eastern Alps based on the integration of available and updated lake paleoseismic data. The paleoseismic records at Plansee and Achensee covering the last ~10 kyrs were extended towards the age of lake initiation after deglaciation to obtain the longest possible paleoseismic catalogue at each lake site. Our results show that 25 severe earthquakes are recorded in the four lakes Plansee, Piburgersee, Achensee and potentially Starnbergersee over the last ~16 kyrs, from which four earthquakes are interpreted to left imprints in two or more lakes. Earthquake recurrence intervals range from ca. 1,000 to 2,000 years with a weakly periodic to aperiodic recurrence behavior for the individual records. We interpret that relatively shorter recurrence intervals in the more orogen-internal archives Piburgersee and Achensee are related to enhanced tectonic loading, whereas a longer recurrence rate in the more orogen-external archive Plansee might reflect a decreased stress transfer across the current-day enhanced seismicity zone. Plausible epicenters of paleo-earthquake scenarios coincide with the current enhanced seismicity regions. Prehistoric earthquakes with a minimum moment magnitude (MW) 5.8–6.1 might have occurred around the Inn valley, the Brenner region and the Fernpass-Loisach region, and might have reached up to MW 6.3 at Achensee. The paleo-earthquake catalogue might hint at a shift of severe earthquake activity near the Inn valley from east to west to east during Postglacial times. Shakemaps highlight that such severe earthquake scenarios not solely impact the enhanced seismicity region of Tyrol, but widely affect adjacent regions like southern Bavaria in Germany.

Download Full-text

HT–LP crustal syntectonic anatexis as a source of the Permian magmatism in the Eastern Southern Alps: evidence from xenoliths in the Euganean trachytes (NE Italy)

Journal of the Geological Society ◽

10.1144/jgs2020-031 ◽

2020 ◽

Vol 177 (6) ◽

pp. 1211-1230

Author(s):

Raffaele Sassi ◽

Claudio Mazzoli ◽

Renaud Merle ◽

Valentina Brombin ◽

Massimo Chiaradia ◽

...

Keyword(s):

Eastern Alps ◽

Isotopic Signature ◽

Southern Alps ◽

Crustal Component ◽

Content Type ◽

Crustal Rocks ◽

Ne Italy ◽

Crustal Thinning ◽

Supplementary Material ◽

Migmatitic Gneiss

Oligocene trachytes from the Euganean Hills include various regionally metamorphosed gneissic and granulitic xenoliths. These xenoliths provide the unique opportunity to investigate South Alpine intermediate to deep crustal levels that are not at present exposed in the Eastern Alps. The estimated P–T conditions are in the range of 780–850°C and 0.45–0.55 GPa for a migmatitic gneiss xenolith. Sensitive high-resolution ion microprobe (SHRIMP II) U–Pb analyses on zircon from this xenolith provide concordant ages around 259.7 ± 3.5 Ma, consistent with a proton-induced X-ray emission (PIXE) U–Th–Pb age on monazite of 262 ± 12 Ma. The Sr–Nd–Pb isotopic compositions, and major and trace element data show distinct origins for the different types of xenoliths. Mafic granulite xenoliths have an isotopic signature close to mantle-derived rocks and to Permian gabbroic rocks from the Western Southern Alps. Metapelite xenoliths have high Sr and low Nd initial ratios like those of acid crustal rocks and could possibly represent the source of the crustal component that is dominant in the acid Permian supervolcanoes. The migmatitic xenolith provides the first documented evidence for a Permian thermal event associated with crustal thinning in the Eastern Southern Alps. Here the South Alpine basement escaped most of the Alpine crustal shortening and still preserves most of the original Permian extension under thick Mesozoic cover.Supplementary material: Microprobe analyses of mineralogical phases and Ti-in-biotite geothermometric calculations are available at https://doi.org/10.6084/m9.figshare.c.5032337

Download Full-text

Fossil submarine hydrothermalism in metabasalts from the Gudon (Bressanone) amphibolite (Southalpine basement, Eastern Alps, NE Italy)

European Journal of Mineralogy ◽

10.1127/ejm/2018/0030-2720 ◽

2018 ◽

Vol 30 (2) ◽

pp. 355-366 ◽

Cited By ~ 1

Author(s):

Dario Visonà ◽

Christine M. Meyzen ◽

Paolo Nimis ◽

Fabrizio Nestola

Keyword(s):

Eastern Alps ◽

Ne Italy ◽

Southalpine Basement

Download Full-text

Is it possible to study palaeoenvironmental changes in Alpine spring habitats? A few examples from the south-eastern Alps (NE Italy)

Journal of Limnology ◽

10.4081/jlimnol.2011.s1.155 ◽

2011 ◽

Vol 70 (1s) ◽

pp. 155 ◽

Cited By ~ 1

Author(s):

Maria Letizia FILIPPI ◽

Gayane PILIPOSIAN ◽

Laura MARZIALI ◽

Nicola ANGELI ◽

Valeria LENCIONI ◽

...

Keyword(s):

Eastern Alps ◽

The South ◽

South Eastern ◽

Ne Italy ◽

Palaeoenvironmental Changes

Download Full-text

The Altotiberina Low-Angle Normal Fault (Italy) Can Fail in Moderate-Magnitude Earthquakes as a Result of Stress Transfer from Stable Creeping Fault Area

Geosciences ◽

10.3390/geosciences10040144 ◽

2020 ◽

Vol 10 (4) ◽

pp. 144

Author(s):

Luigi Vadacca

Keyword(s):

Stress Transfer ◽

Normal Fault ◽

Normal Faults ◽

Seismic Potential ◽

Interseismic Coupling ◽

Rate And State Friction ◽

Seismic Cycles ◽

Dip Angle ◽

Locked Fault ◽

Moderate Magnitude

Geological and geophysical evidence suggests that the Altotiberina low-angle (dip angle of 15–20 ° ) normal fault is active in the Umbria–Marche sector of the Northern Apennine thrust belt (Italy). The fault plane is 70 km long and 40 km wide, larger and hence potentially more destructive than the faults that generated the last major earthquakes in Italy. However, the seismic potential associated with the Altotiberina fault is strongly debated. In fact, the mechanical behavior of this fault is complex, characterized by locked fault patches with a potentially seismic behavior surrounded by aseismic creeping areas. No historical moderate (5 ≤ Mw ≤ 5.9) nor strong (6 ≤ Mw ≤ 6.9)-magnitude earthquakes are unambiguously associated with the Altotiberina fault; however, microseismicity is scattered below 5 km within the fault zone. Here we provide mechanical evidence for the potential activation of the Altotiberina fault in moderate-magnitude earthquakes due to stress transfer from creeping fault areas to locked fault patches. The tectonic extension in the Umbria–Marche crustal sector of the Northern Apennines is simulated by a geomechanical numerical model that includes slip events along the Altotiberina and its main seismic antithetic fault, the Gubbio fault. The seismic cycles on the fault planes are simulated by assuming rate-and-state friction. The spatial variation of the frictional parameters is obtained by combining the interseismic coupling degree of the Altotiberina fault with friction laboratory measurements on samples from the Zuccale low- angle normal fault located in the Elba island (Italy), considered an older exhumed analogue of Altotiberina fault. This work contributes a better estimate of the seismic potential associated with the Altotiberina fault and, more generally, to low-angle normal faults with mixed-mode slip behavior.

Download Full-text

Genesis of the Eastern Adamello Plutons (Northern Italy): Inferences for the Alpine Geodynamics

Geosciences ◽

10.3390/geosciences12010013 ◽

2021 ◽

Vol 12 (1) ◽

pp. 13

Author(s):

Alessio Relvini ◽

Silvana Martin ◽

Bruna B. Carvalho ◽

Giacomo Prosser ◽

Luca Toffolo ◽

...

Keyword(s):

Fractional Crystallization ◽

Eastern Alps ◽

Thermodynamic Modelling ◽

Magmatic Complex ◽

Minor Elements ◽

Ne Italy ◽

Isotopic Analyses ◽

Eastern Border ◽

Geochemical Analyses ◽

Best Fit

The Corno Alto–Monte Ospedale magmatic complex crops out at the eastern border of the Adamello batholith, west of the South Giudicarie Fault (NE Italy). This complex includes tonalites, trondhjemites, granodiorites, granites and diorites exhibiting an unfoliated structure suggesting passive intrusion under extensional-to-transtensional conditions. Major, minor elements, REE and isotopic analyses and geochemical and thermodynamic modelling have been performed to reconstruct the genesis of this complex. Geochemical analyses unravel a marked heterogeneity with a lack of intermediate terms. Samples from different crust sections were considered as possible contaminants of a parental melt, with the European crust of the Serre basement delivering the best fit. The results of the thermodynamic modelling show that crustal melts were produced in the lower crust. Results of the geochemical modelling display how Corno Alto felsic rocks are not reproduced by fractional crystallization nor by partial melting alone: their compositions are intermediate between anatectic melts and melts produced by fractional crystallization. The tectonic scenario which favored the intrusion of this complex was characterized by extensional faults, active in the Southalpine domain during Eocene. This extensional scenario is related to the subduction of the Alpine Tethys in the Eastern Alps starting at Late Cretaceous time.

Download Full-text