Seismicity patterns in Vrancea and predictive features

Rădulian, Mircea; Popa, Mihaela; Carbunar, Octavian F.; Rogozea, Maria

doi:10.1556/ageod.43.2008.2-3.6

Cited by 13 publications

(5 citation statements)

References 11 publications

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“…The deep part of the Vrancea earthquake nest is confined to a narrow ~100 km(height) × 70 × 30 km volume in the upper mantle beneath the SE Carpathians (Fig. 1, Radulian et al, 2008) and releases the highest strain in continental Europe (Oncescu and Bonjer, 1997;Wenzel et al, 1999). Despite its remote location from the most active European collisional boundaries, the Vrancea earthquakes pose a significant seismic risk for the densely populated regions of Romania and neighbouring countries (e.g.…”

Section: Seismotectonics Of the Vrancea Regionmentioning

confidence: 99%

Tectonic regimes and stress patterns in the Vrancea Seismic Zone: Insights into intermediate-depth earthquake nests in locked collisional settings

et al. 2021

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Section: Seismotectonics Of the Vrancea Regionmentioning

confidence: 99%

Tectonic regimes and stress patterns in the Vrancea Seismic Zone: Insights into intermediate-depth earthquake nests in locked collisional settings

et al. 2021

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“…The subcrustal earthquakes are generated mainly in a confined and seismically active nest characterized by an extreme density of foci within a welldefined high velocity lithospheric body (e.g., MARTIN and WENZEL, 2006;RADULIAN et al, 2008;KOULAKOV et al, 2010). Events with magnitude M w [ 7 are generated here two to three times per century.…”

Section: Seismicity Patternsmentioning

confidence: 99%

New Seismic and Tomography Data in the Southern Part of the Harghita Mountains (Romania, Southeastern Carpathians): Connection with Recent Volcanic Activity

Popa

Rădulian

Szakács

et al. 2011

Pure Appl. Geophys.

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The southern part of the southeastern Carpathians represents the site of the most recent volcanic eruptions of the entire Carpathian-Pannonian region. The products of these eruptions range from 42 to 10 Ka radiocarbon ages in the South Harghita Mountains (high K calc-alkaline rocks with adakite-like features), and at 1.2-0.6 Ma K-Ar ages in the Perşani Mountains (alkali basalts). They were emplaced in a post-collisional regime. Ciomadul volcano is located at the southernmost part of the NW-SE oriented Cȃlimani-Gurghiu-Harghita range crossing the inner part of the southeastern Carpathians and in the rough proximity of the Vrancea seismic zone (at ca. 60 km toward NW). Its magma generation is attributed to geodynamic events closely related to the seismogenic area. A number of particular geophysical and geochemical features located in the study region, including (1) the abrupt attenuation of the seismic waves originating from the Vrancea intermediate-depth foci, (2) the most intense heat-flow anomaly in Romania, (3) the most prominent 3 He/ 4 He anomaly measured in natural ''postvolcanic'' gas emanations, are all in favor of the hypothesis of a still existing hot local magma chamber. Data acquired during recent seismic monitoring of the Vrancea zone and its neighborhoods suggest an enhancement of the local seismicity beneath the southern edge of the South Harghita Mts., both at crustal and subcrustal levels. At the same time, recent tomography images obtained using local earthquake data correlate well with the presence of a vertically extended low-velocity zone coming from the upper mantle to the assumed magmatic chambers located in the crust. The present data, supporting the presence of an active crustal magma chamber beneath Ciomadul, allow us to consider that future volcanic activity at this volcano cannot be discarded.

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“…In contrast with the eastern Carpathian branch, where the convergence of the plates seems to be currently inactive, complex active processes still take place beneath Vrancea in a very confined area. The brightest manifestation of this process is a cluster of intermediate seismicity beneath Vrancea in a narrow nearly vertical volume at depths below 60 km, which is clustered along a NE–SW direction [e.g., Wenzel et al , 1999; Radulian et al , 2008; Radulian and Popa , 1996]. Large intermediate‐depth events with magnitude M = 6.5 occur two to five times per century.…”

Section: Geotectonic Setting Of the Area And Previous Seismic Studiesmentioning

confidence: 99%

Delamination or slab detachment beneath Vrancea? New arguments from local earthquake tomography

Koulakov

Zaharia

Enescu

et al. 2010

Geochem Geophys Geosyst

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[1] Vrancea, located at the southeastern Carpathians Arc bend, is one of the areas in the Alpine-Himalayan belt that features strong earthquakes occurring at intermediate depths (60-200 km). In this study we investigated the crustal and lithospheric structure beneath the Vrancea seismic area using a local earthquake tomography approach. We used an updated and revised catalog, spanning from 1982 to 2006 that uses data from both permanent and temporary networks in the target area. Simultaneous tomographic inversion for the Vp and Vs anomalies and the Vp/Vs ratio and source locations was done using the LOTOS code. The reliability and robustness of the results were rigorously checked using various tests (e.g., by studying the role of different parameters on the results of the inversion, performing the inversion using random data subsets, and synthetic modeling). The tomography results clearly indicate the presence of a high-velocity material beneath Vrancea at a depth interval of about 60-200 km that coincides with the distribution of intermediate-depth seismicity. This result agrees generally with previous tomographic studies. We compare two scenarios leading to this structure: (1) subduction and slab detachment and (2) ''drop forming'' or delamination. The latter mechanism presumes that the thickening of the crust due to continent-continent collision causes transformation of the mafic lower crust into denser eclogite. This material accumulates until it reaches a critical mass, at which point it forms a large drop that begins to fall down. We propose that the high-velocity anomaly we observe in our tomogram might represent the descending eclogitic lower crust material enveloped by the entrained lithosphere. It is possible that a similar delamination process can be observed in other parts of the Alpine-Himalayan belt, such as in the Pamir Hindu-Kush area.

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Seismicity patterns in Vrancea and predictive features

Cited by 13 publications

References 11 publications

Tectonic regimes and stress patterns in the Vrancea Seismic Zone: Insights into intermediate-depth earthquake nests in locked collisional settings

Tectonic regimes and stress patterns in the Vrancea Seismic Zone: Insights into intermediate-depth earthquake nests in locked collisional settings

New Seismic and Tomography Data in the Southern Part of the Harghita Mountains (Romania, Southeastern Carpathians): Connection with Recent Volcanic Activity

Delamination or slab detachment beneath Vrancea? New arguments from local earthquake tomography

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