Log in

Relevant bibliographies by topics / Seismogenic pseudotachylytes / Journal articles

Journal articles on the topic 'Seismogenic pseudotachylytes'

To see the other types of publications on this topic, follow the link: Seismogenic pseudotachylytes.

Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 25 journal articles for your research on the topic 'Seismogenic pseudotachylytes.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Hawemann, Friedrich, Neil S. Mancktelow, Sebastian Wex, Alfredo Camacho, and Giorgio Pennacchioni. "Pseudotachylyte as field evidence for lower-crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)." Solid Earth 9, no. 3 (May 9, 2018): 629–48. http://dx.doi.org/10.5194/se-9-629-2018.

Full text

Abstract:

Abstract. Geophysical evidence for lower continental crustal earthquakes in almost all collisional orogens is in conflict with the widely accepted notion that rocks, under high grade conditions, should flow rather than fracture. Pseudotachylytes are remnants of frictional melts generated during seismic slip and can therefore be used as an indicator of former seismogenic fault zones. The Fregon Subdomain in Central Australia was deformed under dry sub-eclogitic conditions of 600–700 °C and 1.0–1.2 GPa during the intracontinental Petermann Orogeny (ca. 550 Ma) and contains abundant pseudotachylyte. These pseudotachylytes are commonly foliated, recrystallized, and cross-cut by other pseudotachylytes, reflecting repeated generation during ongoing ductile deformation. This interplay is interpreted as evidence for repeated seismic brittle failure and post- to inter-seismic creep under dry lower-crustal conditions. Thermodynamic modelling of the pseudotachylyte bulk composition gives the same PT conditions of shearing as in surrounding mylonites. We conclude that pseudotachylytes in the Fregon Subdomain are a direct analogue of current seismicity in dry lower continental crust.

APA, Harvard, Vancouver, ISO, and other styles

2

Young, Erik M., Christie D. Rowe, and James D. Kirkpatrick. "Shear zone evolution and the path of earthquake rupture." Solid Earth 13, no. 10 (October 26, 2022): 1607–29. http://dx.doi.org/10.5194/se-13-1607-2022.

Full text

Abstract:

Abstract. Crustal shear zones generate earthquakes, which are at present unpredictable, but advances in mechanistic understanding of the earthquake cycle offer hope for future advances in earthquake forecasting. Studies of fault zone architecture have the potential to reveal the controls on fault rupture, locking, and reloading that control the temporal and spatial patterns of earthquakes. The Pofadder Shear Zone exposed in the Orange River in South Africa is an ancient, exhumed, paleoseismogenic continental transform which preserves the architecture of the earthquake source near the base of the seismogenic zone. To investigate the controls on earthquake rupture geometries in the seismogenic crust, we produced a high-resolution geologic map of the shear zone core mylonite zone. The core consists of ∼ 1–200 cm, pinch-and-swell layers of mylonites of variable mineralogic composition, reflecting the diversity of regional rock types which were dragged into the shear zone. Our map displays centimetric layers of a unique black ultramylonite along some mylonite interfaces, locally adding to thick composite layers suggesting reactivation or bifurcation. We present a set of criteria for identifying recrystallised pseudotachylytes (preserved earthquake frictional melts) and show that the black ultramylonite is a recrystallised pseudotachylyte, with its distribution representing a map of ancient earthquake rupture surfaces. Pseudotachylytes are most abundant on interfaces between the strongest wall rocks. We find that the geometry of lithologic interfaces which hosted earthquakes differs from interfaces lacking pseudotachylyte at wavelengths of ≳ 10 m. We argue that the pinch-and-swell structure of the mylonitic layering, enhanced by viscosity contrasts between layers of different mineralogy, is expected to generate spatially heterogeneous stress during viscous creep in the shear zone, which dictated the path of earthquake ruptures. The condition of rheologically layered materials causing heterogeneous stresses should be reasonably expected in any major shear zone, is enhanced by creep, and represents the pre-seismic background conditions through which earthquakes nucleate and propagate. This has implications for patterns of earthquake recurrence and explains why some potential geologic surfaces are favored for earthquake rupture over others.

APA, Harvard, Vancouver, ISO, and other styles

3

Ferré, Eric C., Joseph L. Allen, and Aiming Lin. "Pseudotachylytes and seismogenic friction: an introduction to current research." Tectonophysics 402, no. 1-4 (June 2005): 1–2. http://dx.doi.org/10.1016/j.tecto.2005.03.013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

O’Hara, Kieran D., and Frank E. Huggins. "A Mössbauer study of pseudotachylytes: redox conditions during seismogenic faulting." Contributions to Mineralogy and Petrology 148, no. 5 (October 28, 2004): 602–14. http://dx.doi.org/10.1007/s00410-004-0622-y.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Morozov, Yu A., M. A. Matveev, A. I. Smulskaya, and A. L. Kulakovskiy. "Two genetic types of pseudotachylytes." Доклады Академии наук 484, no. 5 (May 16, 2019): 589–94. http://dx.doi.org/10.31857/s0869-56524845589-594.

Full text

Abstract:

The study of two varieties of pseudotachylytes (PST) in granitoids of the Riphean complex on the Barents Sea coast of the Kola Peninsula (Rybachii and Srednii peninsulas) and in metapsammite of the Paleoproterozoic complex in the Northern Ladoga region by a few independent analytical methods has made it possible to establish that they belong to different genetic forms, such as mechanically crushed rocks and melting products, respectively. As for the melting differences, we have given a detailed description of the mineral and material transformations of the original rock into the PST glass matrix and obtained evidence for the initial melting out of the micaceous eutectics with its subsequent shift to the granite type. The conclusion has been made on the most likely formation of molten PST due to frictional rock melting under rapid rise of its blocks from a depth of 12–15 km to the crustal surface (less than 3 km) along the faults of presumably seismogenic nature. It is suggested that crushing and frictional melting can be complementary, rather than mutually exclusive processes, and the formation of molten PST is commonly preceded by the mechanical rock crushing stage.

APA, Harvard, Vancouver, ISO, and other styles

6

Ujiie, K. "Dynamics of Earthquake Faulting in Subduction Zones: Inference from Pseudotachylytes and Ultracataclasites in an Ancient Accretionary Complex." Scientific Drilling SpecialIssue (November 1, 2007): 92–93. http://dx.doi.org/10.5194/sd-specialissue-92-2007.

Full text

Abstract:

The fault rocks in ancient accretionary complexes exhumed from seismogenic depths may provide an invaluable opportunity to examine the mechanisms and mechanics of seismic slip in subduction thrusts and splay faults. In order to understand the dynamics of earthquake faulting in subduction zones, we analyzed pseudotachylytes and ultracataclasites from the Shimanto accretionary complex in southwest Japan. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.s01.21.2007" target="_blank">10.2204/iodp.sd.s01.21.2007</a>

APA, Harvard, Vancouver, ISO, and other styles

7

Allanic, C., C. Sue, M. Burkhard, and M. Cosca. "A paleo-seismogenic Lepontine dome? New insights from pseudotachylytes-generating faults." Geochimica et Cosmochimica Acta 70, no. 18 (August 2006): A9. http://dx.doi.org/10.1016/j.gca.2006.06.031.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Karson, Jeffrey A., C. Kent Brooks, Michael Storey, and Malcolm S. Pringle. "Tertiary faulting and pseudotachylytes in the East Greenland volcanic rifted margin: Seismogenic faulting during magmatic construction." Geology 26, no. 1 (1998): 39. http://dx.doi.org/10.1130/0091-7613(1998)026<0039:tfapit>2.3.co;2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Piccardo, G. B., G. Ranalli, and L. Guarnieri. "Seismogenic Shear Zones in the Lithospheric Mantle: Ultramafic Pseudotachylytes in the Lanzo Peridotite (Western Alps, NW Italy)." Journal of Petrology 51, no. 1-2 (November 6, 2009): 81–100. http://dx.doi.org/10.1093/petrology/egp067.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Kohút, Milan, and Sarah C. Sherlock. "Tracing the Initiation of the Tribeč Mountain Exhumation by Laser-Probe 40Ar/39Ar Dating of Seismogenic Pseudotachylytes (Western Carpathians, Slovakia)." Journal of Geology 124, no. 2 (March 2016): 255–65. http://dx.doi.org/10.1086/684443.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Altenberger, U., G. Prosser, A. Grande, C. Günter, and A. Langone. "A seismogenic zone in the deep crust indicated by pseudotachylytes and ultramylonites in granulite-facies rocks of Calabria (Southern Italy)." Contributions to Mineralogy and Petrology 166, no. 4 (June 19, 2013): 975–94. http://dx.doi.org/10.1007/s00410-013-0904-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Rasskazov, Sergei, Irina Chuvashova, Tatyana Yasnygina, Elena Saranina, Nikolay Gerasimov, Youseph Ailow, and Yi-Min Sun. "Tectonic Generation of Pseudotachylytes and Volcanic Rocks: Deep-Seated Magma Sources of Crust-Mantle Transition in the Baikal Rift System, Southern Siberia." Minerals 11, no. 5 (May 2, 2021): 487. http://dx.doi.org/10.3390/min11050487.

Full text

Abstract:

Volcanic rocks from deep-seated sources of the crust-mantle transition (CMT) are geochemically distinguished from those of ocean island basalts (OIB). Here, we report geochemical data on tectonic pseudotachylytes from the Main Sayan Fault (MSF) and volcanic rocks from the Kamar-Stanovoy Zone of Hot Transtension (KSZHT) that represent the deep-seated CMT magmatic sources in the central part of the Baikal Rift System (BRS). The tectonic generation of the KSZHT magmas between 18.1 and 11.7 Ma is compared with present-day seismogenic deformations in the middle-upper crust of the South Baikal Basin and adjacent Tunka Valley, where strong earthquakes are distributed along the Main Sayan and Primorye sutures of the Siberian paleocontinent. From a detail seismic tomography model and geological evidence, we infer that the KSZHT crust–mantle magmatic processes were due to delamination and lamination of a thickened root part of the South Baikal Orogen existed in the Late Cretaceous and Paleogene. In addition, we identify similar deep-seated CMT sources for melts erupted in the past 17 Ma from a delaminated root part of the East Hangay Orogen and adjacent Orkhon-Selenga Saddle in the southwestern BRS. We suggest that both in the central and in the southwestern BRS, the deep-seated CMT magma sources designate cooperative pull-to-axis and convergent effects created in the Japan-Baikal Geodynamic Corridor and in the Indo-Asian interactional region, respectively.

APA, Harvard, Vancouver, ISO, and other styles

13

Prando, Francesca, Luca Menegon, Mark Anderson, Barbara Marchesini, Jussi Mattila, and Giulio Viola. "Fluid-mediated, brittle–ductile deformation at seismogenic depth – Part 2: Stress history and fluid pressure variations in a shear zone in a nuclear waste repository (Olkiluoto Island, Finland)." Solid Earth 11, no. 2 (April 8, 2020): 489–511. http://dx.doi.org/10.5194/se-11-489-2020.

Full text

Abstract:

Abstract. The microstructural record of fault rocks active at the brittle–ductile transition zone (BDTZ) may retain information on the rheological parameters driving the switch in deformation mode and on the role of stress and fluid pressure in controlling different fault slip behaviours. In this study we analysed the deformation microstructures of the strike-slip fault zone BFZ045 in Olkiluoto (SW Finland), located in the site of a deep geological repository for nuclear waste. We combined microstructural analysis, electron backscatter diffraction (EBSD), and mineral chemistry data to reconstruct the variations in pressure, temperature, fluid pressure, and differential stress that mediated deformation and strain localization along BFZ045 across the BDTZ. BFZ045 exhibits a mixed ductile–brittle deformation, with a narrow (<20 cm thick) brittle fault core with cataclasites and pseudotachylytes that overprint a wider (60–100 cm thick) quartz-rich mylonite. Mylonitic deformation took place at 400–500 ∘C and 3–4 kbar, typical of the greenschist facies metamorphism at the base of the seismogenic crust. We used the recrystallized grain size piezometry for quartz to document a progressive increase in differential stress, from ca. 50 to ca. 120 MPa, towards the shear zone centre during mylonitization and strain localization. Syn-kinematic quartz veins formed along the mylonitic foliation due to transiently high pore fluid pressure (up to lithostatic value). The overprint of the veins by dynamic recrystallization and mylonitic creep is further evidence of the occurrence of brittle events under overall ductile conditions. We propose a conceptual model in which the ductile–brittle deformation cycle was controlled by transient oscillations in fluid pressure and progressively higher differential stress, possibly occurring in a narrowing shear zone deforming towards the peak strength of the crust at the BDTZ.

APA, Harvard, Vancouver, ISO, and other styles

14

Kendrick, J. E., Y. Lavallée, K. U. Hess, S. De Angelis, A. Ferk, H. E. Gaunt, D. B. Dingwell, and R. Leonhardt. "Seismogenic frictional melting in the magmatic column." Solid Earth Discussions 5, no. 2 (October 16, 2013): 1659–86. http://dx.doi.org/10.5194/sed-5-1659-2013.

Full text

Abstract:

Abstract. Lava dome eruptions subjected to high extrusion rates commonly evolve from endogenous to exogenous growth and limits to their structural stability hold catastrophic potential as explosive eruption triggers. In the conduit, strain localisation in magma, accompanied by seismogenic failure, marks the onset of brittle magma ascent dynamics. The rock record of exogenous dome structures preserves vestiges of cataclastic processes (Cashman et al., 2008; Kennedy and Russell, 2011) and of thermal anomalies (Kendrick et al., 2012), key to unravelling subsurface processes. Here, a combined structural, thermal and magnetic investigation of a shear band crosscutting a large block erupted in 2010 at Soufrière Hills volcano (SHV) reveals evidence of faulting and frictional melting within the magmatic column. The mineralogy of this pseudotachylyte vein offers confirmation of complete recrystallisation with an isothermal remanent magnetisation signature that typifies local electric currents in faults. The pseudotachylyte presents an impermeable barrier, which is thought to have influenced the degassing pathway. Such melting events may be linked to the step-wise extrusion of magma accompanied by repetitive long-period (LP) drumbeat seismicity at SHV (Neuberg et al., 2006). Frictional melting of SHV andesite in a high velocity rotary shear apparatus highlights the small slip distances (< 15 cm) required to bring 800 °C magma to melting point at upper conduit stress conditions (10 MPa). We conclude that frictional melting is an inevitable consequence of seismogenic, conduit-dwelling magma fracture during dome building eruptions and that it may have an important influence on magma ascent dynamics.

APA, Harvard, Vancouver, ISO, and other styles

15

White, Joseph Clancy. "Paradoxical pseudotachylyte – Fault melt outside the seismogenic zone." Journal of Structural Geology 38 (May 2012): 11–20. http://dx.doi.org/10.1016/j.jsg.2011.11.016.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Kendrick, J. E., Y. Lavallée, K. U. Hess, S. De Angelis, A. Ferk, H. E. Gaunt, P. G. Meredith, D. B. Dingwell, and R. Leonhardt. "Seismogenic frictional melting in the magmatic column." Solid Earth 5, no. 1 (April 9, 2014): 199–208. http://dx.doi.org/10.5194/se-5-199-2014.

Full text

Abstract:

Abstract. Lava dome eruptions subjected to high extrusion rates commonly evolve from endogenous to exogenous growth and limits to their structural stability hold catastrophic potential as explosive eruption triggers. In the conduit, strain localisation in magma, accompanied by seismogenic failure, marks the onset of brittle magma ascent dynamics. The rock record of exogenous dome structures preserves vestiges of cataclastic processes and thermal anomalies, key to unravelling subsurface processes. Here, a combined structural, thermal and magnetic investigation of a shear band crosscutting a large block erupted in 2010 at Soufrière Hills volcano (SHV) reveals evidence of faulting and frictional melting within the magmatic column. The mineralogy of this pseudotachylyte vein offers confirmation of complete recrystallisation, altering the structure, porosity and permeability of the material, and the magnetic signature typifies local electric currents in faults. Such melting events may be linked to the step-wise extrusion of magma accompanied by repetitive long-period (LP) drumbeat seismicity at SHV. Frictional melting of Soufrière Hills andesite in a high velocity rotary shear apparatus highlights the small slip distances (< 15 cm) thought to be required to bring 800 °C magma to melting point at upper conduit stress conditions (10 MPa). We conclude that frictional melting is a common consequence of seismogenic magma fracture during dome building eruptions and that it may govern the ascent of magma in the upper conduit.

APA, Harvard, Vancouver, ISO, and other styles

17

Bonnet, G., P. Agard, S. Angiboust, P. Monié, M. Fournier, B. Caron, and J. Omrani. "Structure and metamorphism of a subducted seamount (Zagros suture, Southern Iran)." Geosphere 16, no. 1 (November 21, 2019): 62–81. http://dx.doi.org/10.1130/ges02134.1.

Full text

Abstract:

Abstract Millions of seamounts on modern and past seafloor end up being subducted, and only small pieces are recovered in suture zones. How they are metamorphosed and deformed is, however, critical to understand how seamount subduction can impact subduction zone geometry, fluid circulation or seismogenic conditions, and more generally to trace physical conditions along the subduction boundary. Since geophysical studies mostly reach the shallowest subducted seamounts and miss internal structures due to low resolution, there is a high need for fossil seamount exposures. We herein report on a fully exposed, 3D example of seamount that we discovered in the Siah Kuh massif, Southern Iran. Through a series of sections across the whole massif and the combination of magmatic-metamorphic-sedimentary petrological data, we document several distinct stages associated with seamount build-up on the seafloor and with subduction. In particular, we constrain different stages of metamorphism and associated mineralogy, with precise conditions for subduction-related metamorphism around 250 °C and 0.7 GPa, in the middle of the seismogenic zone. Extensive examination of the seismogenic potential of the Siah Kuh seamount reveals that it was not a large earthquake asperity (despite the report of a rare example of cm-scale, high-pressure pseudotachylyte in this study), and that it possibly behaved as a barrier to earthquake propagation. Finally, we discuss the nature of high-pressure fluid circulation preserved in this seamount.

APA, Harvard, Vancouver, ISO, and other styles

18

Wang, Lifeng, and Sylvain Barbot. "Excitation of San Andreas tremors by thermal instabilities below the seismogenic zone." Science Advances 6, no. 36 (September 2020): eabb2057. http://dx.doi.org/10.1126/sciadv.abb2057.

Full text

Abstract:

The relative motion of tectonic plates is accommodated at boundary faults through slow and fast ruptures that encompass a wide range of source properties. Near the Parkfield segment of the San Andreas fault, low-frequency earthquakes and slow-slip events take place deeper than most seismicity, at temperature conditions typically associated with stable sliding. However, laboratory experiments indicate that the strength of granitic gouge decreases with increasing temperature above 350°C, providing a possible mechanism for weakening if temperature is to vary dynamically. Here, we argue that recurring low-frequency earthquakes and slow-slip transients at these depths may arise because of shear heating and the temperature dependence of frictional resistance. Recurring thermal instabilities can explain the recurrence pattern of the mid-crustal low-frequency earthquakes and their correlative slip distribution. Shear heating associated with slow slip is sufficient to generate pseudotachylyte veins in host rocks even when fault slip is dominantly aseismic.

APA, Harvard, Vancouver, ISO, and other styles

19

OBATA, Masaaki, and Tadamasa UEDA. "A Finding of Ultramafic Mylonitic Pseudotachylyte and Its Seismogenic Significance: Toward a Better Understanding of Seismogenic Processes in the Mantle." Journal of Geography (Chigaku Zasshi) 120, no. 3 (2011): 439–51. http://dx.doi.org/10.5026/jgeography.120.439.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Allen, Joseph L., and Colin A. Shaw. "Seismogenic structure of a crystalline thrust fault: fabric anisotropy and coeval pseudotachylyte–mylonitic pseudotachylyte in the Grizzly Creek Shear Zone, Colorado." Geological Society, London, Special Publications 359, no. 1 (2011): 135–51. http://dx.doi.org/10.1144/sp359.8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Sullivan, Walter A., and Emma J. O’Hara. "A natural example of brittle-to-viscous strain localization under constant-stress conditions: a case study of the Kellyland fault zone, Maine, USA." Geological Magazine 159, no. 3 (November 15, 2021): 421–40. http://dx.doi.org/10.1017/s0016756821001035.

Full text

Abstract:

AbstractThis article integrates field, powder X-ray diffraction and microstructural data to constrain deformation mechanisms in and the rheology of granite-derived fault rocks exposed along the SE side of the crustal-scale, strike-slip Kellyland fault zone. Deformation in this area of the Kellyland fault zone localized during cooling and is marked by (1) foliated granite, (2) a ∼50 m wide band of pulverized foliated granite, (3) a ∼2.8 m wide breccia zone hosting coeval shear zones, and (4) a >100 m wide ultramylonite zone. The earliest fabric in the foliated granite is defined by elongated quartz grains, and quartz dislocation creep was the rate-controlling deformation mechanism. Seismogenic deformation initiated when recorded flow stresses reached 96–104 MPa at temperatures of 400–450 °C and is marked by coeval pulverization and formation of breccia. Interseismic viscous creep at similar flow stresses is recorded by mutual cross-cutting relationships between breccia-hosted shear zones, brittle fractures and pseudotachylyte. Field and microstructural observations indicate that breccia-hosted shear zones are low-strain equivalents of the >100 m wide ultramylonite zone, and seismogenic deformation abated as the ultramylonite formed. The rheology of ultramylonites was governed by grain-size-sensitive creep at 112–124 MPa flow stresses. Hence, from the onset of seismogenesis, the Kellyland fault zone was likely a constant-stress system wherein the rate-controlling mechanism shifted from episodic seismogenic slip and interseismic viscous creep to steady state grain-size-sensitive creep in ultramylonites derived from brittle fault rocks. Flow stresses recorded by these rocks also imply that the whole zone was relatively weak if the brittle–viscous transition and uppermost viscous zone are the strongest part of the crust.

APA, Harvard, Vancouver, ISO, and other styles

22

Proctor, B. P., D. A. Lockner, J. B. Lowenstern, and N. M. Beeler. "Conversion of Wet Glass to Melt at Lower Seismogenic Zone Conditions: Implications for Pseudotachylyte Creep." Geophysical Research Letters 44, no. 20 (October 21, 2017): 10,248–10,255. http://dx.doi.org/10.1002/2017gl075344.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Prante, Mitchell R., and James P. Evans. "Pseudotachylyte and Fluid Alteration at Seismogenic Depths (Glacier Lakes and Granite Pass Faults, Central Sierra Nevada, USA)." Pure and Applied Geophysics 172, no. 5 (November 28, 2014): 1203–27. http://dx.doi.org/10.1007/s00024-014-0989-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Price, Nancy A., Scott E. Johnson, Christopher C. Gerbi, and David P. West. "Identifying deformed pseudotachylyte and its influence on the strength and evolution of a crustal shear zone at the base of the seismogenic zone." Tectonophysics 518-521 (January 2012): 63–83. http://dx.doi.org/10.1016/j.tecto.2011.11.011.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Dunkel, Kristina G., Xin Zhong, Paal Ferdinand Arnestad, Lars Vesterager Valen, and Bjørn Jamtveit. "High transient stress in the lower crust: Evidence from dry pseudotachylytes in granulites, Lofoten Archipelago, northern Norway." Geology, September 23, 2020. http://dx.doi.org/10.1130/g48002.1.

Full text

Abstract:

Seismic activity below the standard seismogenic zone is difficult to investigate because the geological records of such earthquakes, pseudotachylytes, are typically reacted and/or deformed. Here, we describe unusually pristine pseudotachylytes in lower-crustal granulites from the Lofoten Archipelago, northern Norway. The pseudotachylytes have essentially the same mineralogical composition as their host (mainly plagioclase, alkali feldspar, orthopyroxene) and contain microstructures indicative of rapid cooling, i.e., feldspar microlites and spherulites and “cauliflower” garnets. Mylonites are absent, both in the wall rocks and among the pseudotachylyte clasts. The absence of features recording precursory ductile deformation rules out several commonly invoked mechanisms for triggering earthquakes in the lower crust, including thermal runaway, plastic instabilities, and downward propagation of seismic slip from the brittle to the ductile part of a fault. The anhydrous mineralogy of host and pseudotachylytes excludes dehydration-induced embrittlement. In the absence of such weakening mechanisms, stress levels in the lower crust must have been transiently high.

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!