Encore Ubaye: Earthquake Swarms, Foreshocks, and Aftershocks in the Southern French Alps

Thouvenot, François; Jenatton, Liliane; Scafidi, Davide; Turino, Chiara; Potin, Bertrand; Ferretti, Gabriele

doi:10.1785/0120150249

Cited by 15 publications

(54 citation statements)

References 24 publications

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“…Leclère et al (2013) provided an estimation of fluid pressure along the fault planes based on the Mohr-Coulomb failure criteria. They show that the Thouvenot et al (2016). c Cross section A-B showing the relationships between the crystalline basement, the autochthonous sedimentary cover and the Embrunais-Ubayenappes, after Leclère et al (2013) Vol.…”

Section: The 2003-2004 Earthquake Swarm In the Ubaye Valleymentioning

confidence: 99%

“…The active area lies several kilometres NW from the focal zone of the 2003-2004 earthquake swarm. In total 13.000 earthquakes were recorded and 3.000 earthquakes were relocated using the double-difference method (Thouvenot et al 2016). The seismicity aligned along a 11-km-long zone with a NNW-SSE strike at depth between 4 and 11 km.…”

Section: The 2012-2015 Earthquake Swarm In the Ubaye Valleymentioning

confidence: 99%

“…Focal mechanisms of 13 earthquakes with ML C 3 confirm the complexity of the swarm geometry, although the fault planes for the two ''mainshocks'' are very consistent (strikes of 156°and 160°, dips of 52°and 55°, respectively), with a clear normal faulting and a slight dextral strike-slip component. Thouvenot et al (2016) calculated striking and dipping of the swarm focal zone. The resultant strike and dip are 165°and 80°, respectively.…”

Section: The 2012-2015 Earthquake Swarm In the Ubaye Valleymentioning

confidence: 99%

“…Earthquake swarms have been observed in volcanic regions (Hensch et al 2008;Vidale et al 2006), in geothermal areas with quaternary volcanism (Fischer and Horálek, 2003;Fischer et al 2014) and in non-volcanic areas with fluid-driven seismicity (Got et al 2011) where fluid overpressure or fluid migration can be a trigger mechanism of seismic activity. Earthquake swarms are characterized as sequences with no clear mainshock (Hill 1977;Scholz 2002); however, they can display a great variety and complex behaviour depending on tectonic environment (Shelly et al 2013;Vavryčuk et al 2013;Thouvenot et al 2016;Yoshida et al 2016;Vavryčuk and Hrubcová 2017).…”

Section: Introductionmentioning

confidence: 99%

“…The second earthquake swarm occurred in the period of 2012-2015 being located a few kilometres to the northwest from the previous one. It was initiated by a shock with ML = 4.3 and reactivated after 2 years by another ML = 4.8 shock with an identical epicentre but of a deeper focus (Thouvenot et al 2016). Earthquakes in the area are monitored since 1994 by the SISMALP seismic network, which consists of 44 short-period one-or three-component seismic stations.…”

Section: Introductionmentioning

confidence: 99%

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Tectonic stress regime in the 2003–2004 and 2012–2015 earthquake swarms in the Ubaye Valley, French Alps

Fojtíková

Vavryčuk

2018

Pure Appl. Geophys.

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We study two earthquake swarms that occurred in the Ubaye Valley, French Alps within the past decade: the 2003-2004 earthquake swarm with the strongest shock of magnitude ML = 2.7, and the 2012-2015 earthquake swarm with the strongest shock of magnitude ML = 4.8. The 2003-2004 seismic activity clustered along a 9-km-long rupture zone at depth between 3 and 8 km. The 2012-2015 activity occurred a few kilometres to the northwest from the previous one. We applied the iterative joint inversion for stress and fault orientations developed by Vavryčuk (2014) to focal mechanisms of 74 events of the 2003-2004 swarm and of 13 strongest events of the 2012-2015 swarm. The retrieved stress regime is consistent for both seismic activities. The r 3 principal axis is nearly horizontal with azimuth of * 103°. The r 1 and r 2 principal axes are inclined and their stress magnitudes are similar. The active faults are optimally oriented for shear faulting with respect to tectonic stress and differ from major fault systems known from geological mapping in the region. The estimated low value of friction coefficient at the faults 0.2-0.3 supports an idea of seismic activity triggered or strongly affected by presence of fluids.

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Section: The 2003-2004 Earthquake Swarm In the Ubaye Valleymentioning

confidence: 99%

Section: The 2012-2015 Earthquake Swarm In the Ubaye Valleymentioning

confidence: 99%

Section: The 2012-2015 Earthquake Swarm In the Ubaye Valleymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Tectonic stress regime in the 2003–2004 and 2012–2015 earthquake swarms in the Ubaye Valley, French Alps

Fojtíková

Vavryčuk

2018

Pure Appl. Geophys.

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How Alpine seismicity relates to lithospheric strength

Spooner

Scheck‐Wenderoth

Cacace

et al. 2022

Int J Earth Sci (Geol Rundsch)

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Despite the amount of research focussed on the Alpine orogen, different hypotheses still exist regarding varying spatial seismicity distribution patterns throughout the region. Previous measurement-constrained regional 3D models of lithospheric density distribution and thermal field facilitate the generation of a data-based rheological model of the region. In this study, we compute the long-term lithospheric strength and compare its spatial variation to observed seismicity patterns. We demonstrate how strength maxima within the crust (~ 1 GPa) and upper mantle (> 2 GPa) occur at temperatures characteristic of the onset of crystal plasticity in those rocks (crust: 200–400 °C; mantle: ~ 600 °C), with almost all seismicity occurring in these regions. Correlation in the northern and southern forelands between crustal and lithospheric strengths and seismicity show different patterns of event distribution, reflecting their different tectonic settings. Seismicity in the plate boundary setting of the southern foreland corresponds to the integrated lithospheric strength, occurring mainly in the weaker domains surrounding the strong Adriatic plate. In the intraplate setting of the northern foreland, seismicity correlates to modelled crustal strength, and it mainly occurs in the weaker and warmer crust beneath the Upper Rhine Graben. We, therefore, suggest that seismicity in the upper crust is linked to weak crustal domains, which are more prone to localise deformation promoting failure and, depending on the local properties of the fault, earthquakes at relatively lower levels of accumulated stress than their neighbouring stronger counterparts. Upper mantle seismicity at depths greater than modelled brittle conditions, can be either explained by embrittlement of the mantle due to grain-size sensitive deformation within domains of active or recent slab cooling, or by dissipative weakening mechanisms, such as thermal runaway from shear heating and/or dehydration reactions within an overly ductile mantle. Results generated in this study are available for open access use to further discussions on the region.

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Low-magnitude seismic swarms in the Calabrian Arc (Italy)

Chiappetta,

La Rocca

2023

J Seismol

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Seismic swarms of low magnitude earthquakes occur frequently in the Calabrian Arc. During the last few years, several earthquakes of magnitude up to ML4.4 occurred both on land and offshore near the coast of Calabria. Some of them were followed by a sequence of tens to hundreds of smaller, well-clustered earthquakes that occurred during the following weeks or months. In other cases, swarms of low-magnitude earthquakes occur without a classical mainshock-aftershock evolution. In this work, we selected swarms that were well recorded by a high number of seismic stations to perform a detailed analysis consisting of the determination of the relative location and focal mechanism for as many earthquakes as possible. In some cases, the relative location allows to recognize the seismogenic fault and to distinguish the fault plane from the auxiliary plane of the focal mechanism solution. In other cases, the relative location unravels a small cloud of events that is not compatible with a unique fault plane, suggesting the occurrence of the swarm in highly fractured seismogenic volume. The relative hypocenter positions allow to estimate the size of the seismogenic volume, which is very small in most of the cases, often less than 1 km3. However, its extension is greater than the size computed for the mainshock rupture in many cases. The most common source mechanism is of normal type, but strike-slip and reverse kinematics are also found, in particular for swarms located offshore and near the coast. The temporal distribution of events does not show any evident migration of the sources, thus suggesting that the driving mechanism is not related with aseismic phenomena like fluid diffusion and stress waves.

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Encore Ubaye: Earthquake Swarms, Foreshocks, and Aftershocks in the Southern French Alps

Cited by 15 publications

References 24 publications

Tectonic stress regime in the 2003–2004 and 2012–2015 earthquake swarms in the Ubaye Valley, French Alps

Tectonic stress regime in the 2003–2004 and 2012–2015 earthquake swarms in the Ubaye Valley, French Alps

How Alpine seismicity relates to lithospheric strength

Low-magnitude seismic swarms in the Calabrian Arc (Italy)

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