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

Petrescu, Laura; Borleanu, Felix; Rădulian, Mircea; Ismail‐Zadeh, Alik; Maţenco, Liviu

doi:10.1016/j.tecto.2020.228688

Cited by 27 publications

(17 citation statements)

References 94 publications

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“…earthquake trigger). Stress patterns in the slab strongly suggest that the Vrancea seismic cluster would correspond to a zone of high stress concentrations associated with enhanced rock tearing 6 . The stress level is expected to be high due to both slab (un)bending and the geometrical complexity of the Carpathians, contrary to dehydration reactions, which should occur anywhere an oceanic slab is warming up.…”

Section: Introductionmentioning

confidence: 99%

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Dehydration-induced earthquakes identified in a subducted oceanic slab beneath Vrancea, Romania

Ferrand

Manea

2021

Sci Rep

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Vrancea, Eastern Romania, presents a significant intermediate-depth seismicity, between 60 and 170 km depth, i.e. pressures from 2 to 6.5 GPa. A debate has been lasting for decades regarding the nature of the seismic volume, which could correspond to the remnant of a subducted slab of Tethyan lithosphere or a delamination of the Carpathians lithosphere. Here we compile the entire seismicity dataset (≈ 10,000 events with 2 ≤ Mw ≤ 7.9) beneath Vrancea for P > 0.55 GPa (> 20 km) since 1940 and estimate the pressure and temperature associated with each hypocenter. We infer the pressure and temperature, respectively, from a depth-pressure conversion and from the most recent tomography-based thermal model. Pressure–temperature diagrams show to what extent these hypocentral conditions match the thermodynamic stability limits for minerals typical of the uppermost mantle, oceanic crust and lower continental crust. The stability limits of lawsonite, chloritoid, serpentine and talc minerals show particularly good correlations. Overall, the destabilization of both mantle and crustal minerals could participate in explaining the observed seismicity, but mantle minerals appear more likely with more convincing correlations. Most hypocentral conditions match relatively well antigorite dehydration between 2 and 4.5 GPa; at higher pressures, the dehydration of the 10-Å phase provides the best fit. We demonstrate that the Vrancea intermediate-depth seismicity is evidence of the current dehydration of an oceanic slab beneath Romania. Our results are consistent with a recent rollback of a W-dipping oceanic slab, whose current location is explained by limited delamination of the continental Moesian lithosphere between the Tethyan suture zone and Vrancea.

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Section: Introductionmentioning

confidence: 99%

“…1) is highly seismic [1][2][3] . In particular, and most surprisingly, the Vrancea region, located at the SE corner of the Carpathians, is characterized by a puzzling intermediate-depth high-seismicity body [4][5][6] , with the highest seismicity between 60 and 170 km depth (Fig. 2).…”

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confidence: 99%

Dehydration-induced earthquakes identified in a subducted oceanic slab beneath Vrancea, Romania

Ferrand

Manea

2021

Sci Rep

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“…Along its path towards NW from the Black Sea Basin to the SEC, the fault shows two segments with distinct seismic activities: (1) from the Black Sea Basin to the Danube River, and (2) from the Danube River to the NE edge of the Vrancea epicentral area. The first segment is less active with a stress regime of thrusting faulting [6,7], while the second segment displays a significant seismic activity with predominant strike-slip faulting along the major fault line and its satellites, oriented SE-NW. Towards the NW edge, where the PCF intersects the Peri-Carpathian Fault, the seismicity configuration becomes more complex (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Earthquake Source Properties of a Lower Crust Sequence and Associated Seismicity Perturbation in the SE Carpathians, Romania, Collisional Setting

et al. 2021

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Romanian seismicity is mainly confined to the Eastern Carpathians Arc bend (ECAB), where strong subcrustal earthquakes (magnitude up to 7.9) are generated in a narrow lithospheric body descending into the mantle. The seismic activity in the overlying crust is spread over a larger area, located mostly toward the outer side of the ECAB. It is significantly smaller than subcrustal seismicity, raising controversies about possible upper mantle-crust coupling. A significant earthquake sequence took place in the foreland of the ECAB triggered on 22 November 2014 by a mainshock of magnitude 5.7 (the greatest instrumentally recorded earthquake in this region) located in the lower crust. The mainshock triggered a significant increase in the number of small-magnitude events spread over an unusually large area in the ECAB. The paper’s goal is to compute the source parameters of the earthquakes that occurred during the aforementioned sequence, by empirical application of Green’s function and spectral ratio techniques. Fault plane solutions are determined using multiple methods and seismicity evolution at regional scale is investigated. Our results highlight a still active deformation regime at the edge of the EE Craton, while the source parameters reveal a complex fracture of the mainshock and a very high-stress drop.

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“…The earthquake hypocentres are localised in the mantle within a volume of about 110(deep) × 70 × 30 km 3 . These earthquakes are likely to be associated with tectonic stress releases within the relic part of the oceanic lithosphere descending beneath Vrancea (e.g., Petrescu et al, 2021). Geology, geodynamics, and seismicity of the Vrancea region were reviewed by Ismail-Zadeh et al (2012b).…”

Section: Carpathiansmentioning

confidence: 99%

Numerical Modelling of Lithospheric Block-and-Fault Dynamics: What Did We Learn About Large Earthquake Occurrences and Their Frequency?

Ismail‐Zadeh

Soloviev

2022

Surv Geophys

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Dynamics of lithospheric plates resulting in localisation of tectonic stresses and their release in large earthquakes provides important information for seismic hazard assessments. Numerical modelling of the dynamics and earthquake simulations have been changing our view about occurrences of large earthquakes in a system of major regional faults and about the recurrence time of the earthquakes. Here, we overview quantitative models of tectonic stress generation and stress transfer, models of dynamic systems reproducing basic features of seismicity, and fault dynamics models. Then, we review the thirty-year efforts in the modelling of lithospheric block-and-fault dynamics, which allowed us to better understand how the blocks react to the plate motion, how stresses are localised and released in earthquakes, how rheological properties of fault zones exert influence on the earthquake dynamics, where large seismic events occur, and what is the recurrence time of these events. A few key factors influencing the earthquake sequences, clustering, and magnitude are identified including lithospheric plate driving forces, the geometry of fault zones, and their physical properties. We illustrate the effects of the key factors by analysing the block-and-fault dynamics models applied to several earthquake-prone regions, such as Carpathians, Caucasus, Tibet-Himalaya, and the Sunda arc, as well as to the global tectonic plate dynamics.

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

Cited by 27 publications

References 94 publications

Dehydration-induced earthquakes identified in a subducted oceanic slab beneath Vrancea, Romania

Dehydration-induced earthquakes identified in a subducted oceanic slab beneath Vrancea, Romania

Earthquake Source Properties of a Lower Crust Sequence and Associated Seismicity Perturbation in the SE Carpathians, Romania, Collisional Setting

Numerical Modelling of Lithospheric Block-and-Fault Dynamics: What Did We Learn About Large Earthquake Occurrences and Their Frequency?

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