Seismic swarms in Tricastin, lower Rhône Valley (France): review of historical and instrumental seismicity and models

Widespread Cenozoic volcanisms in the Arabian shield including &#8220;Harrats&#8221; have been referring to lithospheric thinning and/or mantle plume activity as a result of Red Sea rift-related extension.A fundamental key in understanding the deriving mechanism of these volcanic activities and its relationship to 2007-2009 seismic swarms required a reliable model of the present-day lithospheric thermo-chemical structure.In this work, we modeled crustal and lithospheric thickness variation as well as the variations in thermal, composition, seismic velocity, and density of the lithosphere beneath the Arabian shield within a thermodynamically self - consistent framework.The resulting thermal and density structures show large variations, revealing strong asymmetry between the Arabian shield and Arabian platform within the Arabian Plate.We model negative density anomalies associated with the hot mantle beneath Harrats, which coincides with the modelled lithosphere thinned (~ 65 km) as a result of the second stage of lithospheric thinning following the initial Red Sea extension.

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Numerical simulation of submarine landslide and generated tsunamis : Application to the Mayotte seismo-volcanic crisis

10.5194/egusphere-egu21-2854 ◽

2021 ◽

Author(s):

Pablo Poulain ◽

Anne Le Friant ◽

Rodrigo Pedreros ◽

Anne Mangeney ◽

Andrea Filippini ◽

...

Keyword(s):

Ground Deformation ◽

Numerical Models ◽

Morphological Data ◽

Submarine Landslides ◽

Submarine Slide ◽

Seismic Swarms ◽

Submarine Slides ◽

High Resolution Bathymetry ◽

The Impact ◽

The Waves

Since May 2018, Mayotte island has experienced an important seismic activity linked to the on-going sismo-volcanic crisis. The epicenters of the seismic swarms are located between 5 and 15 km east of Petite Terre for the main swarm, and 25 km east of Petite Terre for the secondary swarm. Although variations in the number of earthquakes and their distribution have been observed since the start of the eruption in early July 2018 [Lemoine A.(2020), Cesca et al.(2020)], a continuous seismicity persists and could generate several earthquakes of magnitudes close to M4 widely felt by the population. This recurrent seismicity could weaken the steep submarine slopes of Mayotte, as highlighted by the high resolution bathymetry data collected during the MAYOBS cruise in May 2019 (Feuillet et al.,submitted) and trigger submarine landslides with associated tsunamis.To address the hazards associated with such events, we analyzed morphological data to define 8 scenarios of potential submarine slides with volumes ranging from 11,25.106 to 800.106 m3 and we simulate the landslide dynamics and generated waves. We use two complementary numerical models: (i) the code HYSEA to simulate the dynamic of the submarine granular flows and the water wave generation, and (ii) the Boussinesq FUNWAVE- TVD model simulate the waves propagation and the inundation on Mayotte. The effect of the time at which the models are coupled is investigated.The most impacting submarine slide scenarios are located close to Petite Terre at a shallow depth. They can locally generate a sea surface elevation more than a meter in local areas especially at Petite Terre. The various simulations show that parts of the island are particularly sensitive to the risk of tsunamis. Indeed, some scenarios that does not cause significant coastal flooding still seems to cause significant hazards in these exposed areas. The barrier reef around Mayotte has a prominent role in controlling the wave propagation towards the island and therefore reducing the impact on land. It should be noted that the arrival of tsunamis on the coastline is not necessarily preceded by a retreat from the sea and the waves can reach the coasts of Mayotte very quicky (few minutes).&#160;Cesca, S., Letort, J., Razafindrakoto, H.N.T.&#160;et al.&#160;Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation.&#160;Nat. Geosci.&#160;13,&#160;87&#8211;93 (2020). https://doi.org/10.1038/s41561-019-0505-5Feuillet, N, Jorry, S. J., Crawford, W, Deplus, C. Thinon, I, Jacques, E. Saurel, J.M., Lemoine, A., Paquet, F., Daniel, R., Gaillot, A., Satriano, C., Peltier, A., Aiken, C., Foix, O., Kowalski, P., Laurent, A., Beauducel, F., Grandin, R., Ballu, V., Bernard, P., Donval, J.P., Geli, L., Gomez, J. Guyader, V., Pelleau, P., Rinnert, E., Bertil, D., Lemarchand, A., Van der Woerd, J.et al. (in rev). Birth of a large volcano offshore Mayotte through lithosphere-scale rifting, Nature.Anne Lemoine, Pierre Briole, Didier Bertil, Agathe Roull&#233;, Michael Foumelis, Isabelle Thinon, Daniel Raucoules, Marcello de&#160;Michele, Pierre Valty, Roser Hoste&#160;Colomer, The 2018&#8211;2019 seismo-volcanic crisis east of Mayotte, Comoros islands: seismicity and ground deformation markers of an exceptional submarine eruption,&#160;Geophysical Journal International, Volume 223, Issue 1, October 2020, Pages 22&#8211;44,&#160;https://doi.org/10.1093/gji/ggaa273

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Papal Legates against the Albigensians: The Debts of the Church of Valence (1215–1250)

Traditio ◽

10.1017/s0362152900001677 ◽

2013 ◽

Vol 68 ◽

pp. 259-276

Author(s):

D. Dudley Stutz

Keyword(s):

Middle Ages ◽

Thirteenth Century ◽

Detailed Treatment ◽

Northern Portion ◽

Rhone Valley ◽

The Church ◽

The Middle Ages

In 1232 Pope Gregory IX (r. 1227–41) imposed a tenth of episcopal revenues on prelates of Occitania to subsidize the church of Valence, which owed 10,000 poundstournoisto various bankers of Vienne, Rome, Lyons, and Siena. In 1865 B. Hauréau first noted the event when he edited one of the main documents in theGallia christianavolume concerning the ecclesiastical province of Vienne. With the publication of Gregory IX's register from 1890–1908 most of the facts of the tax were more widely available. In 1910 Ulysse Chevalier briefly mentioned the tax in his monograph on the long tenure of John of Bernin, archbishop of Vienne (r. 1218–66). In 1913, Heinrich Zimmermann cited Hauréau's text in a note in his detailed treatment of early thirteenth-century papal legations. Recently Alain Marchandisse reviewed eight of the eleven papal letters pertaining to the tax in his study of William of Savoy (d. 1239) as bishop-elect of Liège. These scholars provided no reason for the debt or why the papacy would take such measures to ensure payment. Perhaps they did not study this tax further because a church indebted to moneylenders is not in itself surprising. It appears that the church of Valence acquired the debt, very large compared to the church's income, when bishop-elect William of Savoy (r. 1225–39) waged war against Adhémar II of Poitiers-Valentinois, count of the Valentinois (r. 1189–1239). Struggles between bishops and the local nobility occurred on a regular basis throughout the Middle Ages, so what in this unimportant Rhone-valley diocese interested the pope enough to impose taxes on prelates of Occitania over twenty years to ensure payment of this debt? Adhémar II faithfully supported Raymond VI (r. 1194–1222) and Raymond VII (r. 1222–49) of Saint-Gilles, counts of Toulouse, throughout their struggle with the papacy during and following the Albigensian crusades. Adhémar II was also their vassal for the Diois, which borders the Valentinois on the southeast and comprised the northern portion of the marquisate of Provence. These lands had been reserved for the church in the Treaty of Meaux-Paris (1229), which ended the Albigensian crusades. Thus William of Savoy as bishop-elect of Valence defended the papacy's claims on the marquisate of Provence, which the papacy deemed part of the larger struggle between the Roman church and the counts of Toulouse. The facts on the nature of the debts and the steps the papacy took to aid the diocese show that the local struggle between the bishop of Valence and the count of the Valentinois embodied a part of the larger struggle between the papacy and the counts of Toulouse over the marquisate of Provence, which began as early as 1215.

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Föhrenverjüngung: Plastizität und Akklimatisation in einem trockeneren Klima

Schweizerische Zeitschrift fur Forstwesen ◽

10.3188/szf.2018.0269 ◽

2018 ◽

Vol 169 (5) ◽

pp. 269-278

Author(s):

Barbara Moser ◽

Christoph Bachofen ◽

Thomas Wohlgemuth

Keyword(s):

Scots Pine ◽

Natural Regeneration ◽

Common Garden ◽

Forest Steppe ◽

Short Time Scale ◽

Summer Drought ◽

Spring Precipitation ◽

Pine Regeneration ◽

A Minor ◽

Rhone Valley

Pine regeneration: plasticity and acclimation in a dryer climate Increasing summer drought might limit the natural regeneration of Scots pine stands at low elevations of the Rhone valley. Common garden experiments at the forest-steppe ecotone have shown that emergence and establishment of Scots pine primarily depend on spring precipitation and, to a minor degree, on summer drought and rising temperatures. Scots pine seedlings acclimated rapidly to drought periods by favouring root to shoot growth. In the second year, the saplings were already adapted to drought so that most of them survived an extended spring and summer drought, as recorded at Sion twelve times during the last 154 years. Only an extreme summer drought – no water from June to September – killed 14.7% of the Scots pine saplings. Surprisingly, they were even able to acclimate to such extreme drought events: after the same extreme summer drought in the third year, mortality dropped below 5%. In general, the Scots pine was very plastic, i.e. seedlings and saplings changed their phenotype depending on environmental conditions. But we also found genetic adaptation: Scots pine originating from regions with pronounced summer drought, including populations from lower elevations in the Rhone valley, produced more biomass than those from moister regions in all treatment combinations. Black pine reacted similarly to the treatments like Scots pine, but it grew faster and more saplings survived the first extreme summer drought. These results show that Scots pine from low elevations of the Rhone valley is one of the most drought-tolerant provenances in Europe. Thanks to its high phenotypic plasticity and the ability of seedlings and saplings to acclimate to drought on a short time scale, natural regeneration of Scot pine at low elevations of the Rhone valley is likely to occur also under future conditions, but maybe less frequent than today.

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200-m-deep earthquake swarm in Tricastin (lower Rhône Valley, France) accounts for noisy seismicity over past centuries

Terra Nova ◽

10.1111/j.1365-3121.2009.00875.x ◽

2009 ◽

Vol 21 (3) ◽

pp. 203-210 ◽

Cited By ~ 10

Author(s):

François Thouvenot ◽

Liliane Jenatton ◽

Jean-Pierre Gratier

Keyword(s):

Earthquake Swarm ◽

Deep Earthquake ◽

Rhone Valley

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Temporal evolution of relative seismic velocity in the Golf of Corinth - Greece.

10.5194/egusphere-egu21-15222 ◽

2021 ◽

Author(s):

Estelle Delouche ◽

Laurent Stehly

Keyword(s):

Lower Crust ◽

Seismic Noise ◽

Seismic Velocity ◽

Temporal Evolution ◽

Velocity Variation ◽

Extension Rate ◽

Fluid Migration ◽

Seismic Stations ◽

Gulf Of Corinth ◽

Seismic Swarms

Our aim is to monitor the temporal evolution of the crust in Greece, with a particular focus on the Gulf of Corinth. &#160;Indeed, Greece is one of the most exposed country to earthquakes in Europe. The Gulf of Corinth, &#160;is known for its fast extension rate of about 15 mm/yr in the western part and 10mm/yr in the eastern part. This fast extension is associated with recurrent seismic swarms and by a few destructive earthquakes. This seismicity is likely the result of a combination of multiple driving processes including fluid migration at depth.In the present work, we use seismic noise recorded from 2010 to 2020 by all seismic stations deployed in Greece, and in particular by the dense Corinth Rift Laboratory network, to compute the seismic velocity variation (dv/v) in several subregions. By comparing the result obtained at different periods, we are able to distinguish the temporal evolution of the upper, mid and lower crust. This temporal evolution is compared to the seismicity of the Gulf of Corinth.

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Swell-Triggered Seismicity at the Near-Front Damage Zone of the Ross Ice Shelf

Seismological Research Letters ◽

10.1785/0220200478 ◽

2021 ◽

Author(s):

Richard C. Aster ◽

Bradley P. Lipovsky ◽

Hank M. Cole ◽

Peter D. Bromirski ◽

Peter Gerstoft ◽

...

Keyword(s):

Lamb Waves ◽

Time Windows ◽

Damage Zone ◽

Austral Summer ◽

Dominant Frequency ◽

Theoretical Development ◽

Ice Shelf ◽

Background Rate ◽

Ross Ice Shelf ◽

Seismic Swarms

Abstract Ocean swell interacting with Antarctic ice shelves produces sustained (approximately, 2×106 cycles per year) gravity-elastic perturbations with deformation amplitudes near the ice front as large as tens to hundreds of nanostrain. This process is the most energetically excited during the austral summer, when sea ice-induced swell attenuation is at a minimum. A 2014–2017 deployment of broadband seismographs on the Ross Ice shelf, which included three stations sited, approximately, 2 km from the ice front, reveals prolific swell-associated triggering of discrete near-ice-front (magnitude≲0) seismic subevents, for which we identify three generic types. During some strong swell episodes, subevent timing becomes sufficiently phase-locked with swell excitation, to create prominent harmonic features in spectra calculated across sufficiently lengthy time windows via a Dirac comb effect, for which we articulate a theoretical development for randomized interevent times. These events are observable at near-front stations, have dominant frequency content between 0.5 and 20 Hz, and, in many cases, show highly repetitive waveforms. Matched filtering detection and analysis shows that events occur at a low-background rate during all swell states, but become particularly strongly excited during large amplitude swell at rates of up to many thousands per day. The superimposed elastic energy from swell-triggered sources illuminates the shelf interior as extensional (elastic plate) Lamb waves that are observable more than 100 km from the ice edge. Seismic swarms show threshold excitation and hysteresis with respect to rising and falling swell excitation. This behavior is consistent with repeated seismogenic fracture excitation and growth within a near-ice-front damage zone, encompassing fracture features seen in satellite imagery. A much smaller population of distinctly larger near-front seismic events, previously noted to be weakly associated with extended periods of swell perturbation, likely indicate calving or other larger-scale ice failures near the shelf front.

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Trade-offs between deep (magmatic) and shallow (hydrological) forcings on volcanic unrest at La Soufrière de Guadeloupe (Lesser Antilles)

10.5194/egusphere-egu21-8761 ◽

2021 ◽

Author(s):

David Jessop ◽

Roberto Moretti ◽

Séverine Moune ◽

Vincent Robert

Keyword(s):

Time Series ◽

Hydrothermal System ◽

Temporal Variations ◽

Temperature Record ◽

Trade Offs ◽

External Forcings ◽

Seismic Swarms ◽

Long Time ◽

Deep Activity

Fumarolic gas composition and temperature record deep processes that generate and transfer heat and mass towards the surface. &#160;These processes are a result of the emplacement, degassing and cooling of magma and the overturning of the above hydrothermal system. &#160;A reasonable expectation, and too often an unproved assumption, is that fumarole temperatures and the deep heat sources vary on similar timescales. &#160;Yet signals from deep and shallow processes have vastly different temporal variations.&#160; This indicates that signals arising from deep activity may be masked or modified by intervening hydrothermal processes, such as fluid-groundrock reactions in which secondary minerals play a major role. &#160;Clearly, this complicates the interpretation of the signals such as the joint variation of fumarole vent temperature and geochemical ratios in terms of what is occurring at depth. &#160;So what do the differences between the timescales governing deep and shallow processes tell us about the intervening transport mechanisms?At the volcanic dome of La Soufri&#232;re de Guadeloupe, the Observatoire Volcanologique et Sismologique de la Guadeloupe has performed weekly-to-monthly in-situ vent gas sampling over many years. &#160;These analyses reliably track several geochemical species ratios over time, which provide important information about the evolution of deep processes. &#160;Vent temperature is measured as part of the in-situ sampling, giving a long time series of these measurements. &#160;Here, we look to exploit the temporal variations in these data to establish the common processes, and also to determine why these signals differ. &#160;By fitting sinusoids to the gas-ratio time series we find that several of the deep signals are strongly sinusoidal. &#160;For example, the He/CH4 and CO2/CH4 ratios, which involve conservative components and mark the injection of deep and hot magmatic fluids, oscillate on a timescale close to 3 years. We also analyse the frequency content of the temperature measurements since 2011 and find that such long signals are not seen. &#160;This may be due to internal buffering by the hydrothermal system, but other external forcings are also present. &#160;From these data we build up a more informed model of the heat-and-mass supply chain from depth to the surface. &#160;This will potentially allow us to predict future unrest (e.g. thermal crises, seismic swarms), and distinguish between sources of unrest.

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