The role of coseismic Coulomb stress changes in shaping the hard-link between normal fault segments

The mechanism and evolution of fault linkage is important in the growth and development of large faults. Here we investigate the role of coseismic stress changes in shaping the hard-links between parallel normal fault segments (or faults), by comparing numerical models of the Coulomb stress change from simulated earthquakes on two en echelon fault segments to natural observations of hard-linked fault geometry. We consider three simplified linking fault geometries: 1) fault bend; 2) breached relay ramp; and 3) strike-slip transform fault. We consider scenarios where either one or both segments rupture and vary the distance between segment tips. Fault bends and breached relay ramps are favoured where segments underlap, or when the strike-perpendicular distance between overlapping segments is less than 20% of their total length, matching all documented examples. Transform fault linkage geometries are preferred when overlapping segments are laterally offset at larger distances. Few transform faults exist in continental extensional settings, and our model suggests that propagating faults or fault segments may first link through fault bends or breached ramps before reaching sufficient overlap for a transform fault to develop. Our results suggest that Coulomb stresses arising from multi-segment ruptures or repeated earthquakes are consistent with natural observations of the geometry of hard-links between parallel normal fault segment

Hydrous oceanic crust hosts megathrust creep at low shear stresses

The rheology of the metamorphosed oceanic crust may be a critical control on megathrust strength and deformation style. However, little is known about the strength and deformation style of metamorphosed basalt. Exhumed megathrust shear zones exposed on Kyushu, SW Japan, contain hydrous metabasalts deformed at temperatures between ~300° and ~500°C, spanning the inferred temperature-controlled seismic-aseismic transition. Field and microstructural observations of these shear zones, combined with quartz grain-size piezometry, indicate that metabasalts creep at shear stresses <100 MPa at ~370°C and at shear stresses <30 MPa at ~500°C. These values are much lower than those suggested by viscous flow laws for basalt. The implication is that relatively weak, hydrous, metamorphosed oceanic crust can creep at low viscosities over a wide shear zone and have a critical influence on plate interface strength and deformation style around the seismic-aseismic transition

Subduction megathrust creep governed by pressure solution and frictional-viscous flow

Subduction megathrust slip speeds range from slow creep at plate convergence rates (centimetres per year) to seismic slip rates (metres per second) in the largest earthquakes on Earth. The deformation mechanisms controlling whether fast slip or slow creep occurs, however, remain unclear. Here, we present evidence that pressure solution creep (fluid-assisted stress driven mass transfer) is an important deformation mechanism in megathrust faults. We quantify megathrust strength using a laboratory-constrained microphysical model for fault friction, involving viscous pressure solution and frictional sliding. We find that at plate-boundary deformation rates, aseismic, frictional–viscous flow is the preferred deformation mechanism at temperatures above 100 °C. The model thus predicts aseismic creep at temperatures much cooler than the onset of crystal plasticity, unless a boundary condition changes. Within this model framework, earthquakes may nucleate when a local increase in strain rate triggers velocity-weakening slip, and we speculate that slip area and event magnitude increase with increasing spacing of strong, topographically derived irregularities in the subduction interface

Mid-crustal shear zone development under retrograde conditions: pressure–temperature–fluid constraints from the Kuckaus Mylonite Zone, Namibia

The Kuckaus Mylonite Zone (KMZ) forms part of the larger Marshall Rocks–Pofadder shear zone system, a 550 km-long, crustal-scale strike-slip shear zone system that is localized in high-grade granitoid gneisses and migmatites of the Namaqua Metamorphic Complex. Shearing along the KMZ occurred ca. 40 Ma after peak granulite-facies metamorphism during a discrete tectonic event and affected the granulites that had remained at depth since peak metamorphism. Isolated lenses of metamafic rocks within the shear zone allow the P–T–fluid conditions under which shearing occurred to be quantified. These lenses consist of an unsheared core that preserves relict granulite-facies textures and is mantled by a schistose collar and mylonitic envelope that formed during shearing. All three metamafic textural varieties contain the same amphibolite-facies mineral assemblage, from which calculated pseudosections constrain the P–T conditions of deformation at 2.7–4.2 kbar and 450–480 °C, indicating that deformation occurred at mid-crustal depths through predominantly viscous flow. Calculated T–MH2O diagrams show that the mineral assemblages were fluid saturated and that lithologies within the KMZ must have been rehydrated from an external source and retrogressed during shearing. Given that the KMZ is localized in strongly dehydrated granulites, the fluid must have been derived from an external source, with fluid flow allowed by local dilation and increased permeability within the shear zone. The absence of pervasive hydrothermal fractures or precipitates indicates that, even though the KMZ was fluid bearing, the fluid/rock ratio and fluid pressure remained low. In addition, the fluid could not have contributed to shear zone initiation, as an existing zone of enhanced permeability is required for fluid infiltration. We propose that, following initiation, fluid infiltration caused a positive feedback that allowed weakening and continued strain localization. Therefore, the main contribution of the fluid was to produce retrograde mineral phases and facilitate grain-size reduction. Features such as tectonic tremor, which are observed on active faults under similar conditions as described here, may not require high fluid pressure, but could be explained by reaction weakening under hydrostatic fluid pressure conditions

Significant shortening by pressure solution creep in the Dwyka diamictite, Cape Fold Belt, South Africa

The Dwyka diamictite preserves a record of horizontal shortening related to the development of the Cape Fold Belt at subgreenschist conditions. This shortening was accommodated by folding and thrust faulting, but pressure solution may also have contributed significantly to bulk deformation. Cleavage within the Dwyka group is, in the studied part of the Karoo Basin, subvertical to moderately south dipping, and approximately axial planar to regional folds. The cleavage is anastomosing, leading to the development of ‘tombstone cleavage’, and defined microscopically by thin seams of fine grained dark material. X-ray diffraction analyses show that the diamictite matrix is made up of quartz, feldspars, muscovite and chlorite. Element maps further indicate that the cleavage is defined predominantly by phyllosilicates and minor oxides, implying that it is made up of relatively insoluble material and hydrothermal alteration products. Overall, the cleavage therefore formed by dissolution and removal of mobile elements. This indicates that pressure solution likely accommodated a significant component of shortening during the Cape Orogeny, and provides an example of low temperature cleavage development during orogenesis

Foreldresamarbeid i hentesituasjoner

Selv om tema for oppgaven var tidlig ferdigstilt, brukte jeg lang tid på å formulere min problemstilling. Ved oppstart av prosjektet fant jeg en artikkel på forskning.no. Artikkelen er basert på en masteroppgave som omhandler henting i norske barnehager, skrevet av Kjersti Lønning Velde. Masteroppgaven tar for seg hvordan foreldrene opplever hentesituasjonen. Resultatene viser at det er stor variasjon i måten foreldrene blir møtt, hvor mye informasjon som formidles og hvor mye tid de ansatte bruker på samarbeidet (Strand, 2017). Artikkelen ble en inspirasjonskilde til min problemstilling. Jeg ønsket derimot å vinkle oppgaven mot personalet sin opplevelse av hentesituasjoner, nærmere bestemt barnehagelæreren. Dette ble en naturlig vinkling for meg, siden jeg snart er ferdig utdannet barnehagelærer. Jeg ønsker selv å bidra til å skape et godt foreldresamarbeid i hentesituasjoner i fremtiden. For å avgrense oppgaven har jeg valgt å fokusere på storbarnsavdelinger. Problemstillingen min ble som følger: ”Hvordan kan barnehagelæreren ved storbarnsavdelinger oppleve hentesituasjoner som en arena for foreldresamarbeid”.publishedVersionBDBAC490

Effekt av styrket pedagognorm på kvalitet i barnehagen

Den 1. august 2018 trådte en ny nasjonal pedagognorm for barnehage i kraft. Denne krever én barnehagelærer/pedagog per 14 barn, mot én pedagog per 18 barn (tidligere norm). Gjennom kvalitative intervju av fire personer som jobber på ulike nivå av barnehage, sammenlignes deres erfaringer med økt pedagogandel og deres oppfatninger av hvordan det påvirker kvaliteten i barnehagen. Alt i alt oppgir de økt kvalitet, men at det finnes begrensende strukturelle faktorer som gjør at de anser at full kvalitetsmessig uttelling ikke er oppnådd. Dette gjenspeiles i stor grad i tilgjengelig teori på feltet.A norm for increased teacher-to-child-ratio for Norwegian kindergarten came into force on August 1st, 2018. It calls for one teacher per 7 children under the age of 3, and one teacher per 14 children over the age of 3. The previous ratios were 1:9 and 1:18. Through qualitative interviews with four employees from different levels within the kindergarten system, I have collected and compared their experiences with and perceptions of how an increase in teacher- to-child-ratio affects the quality of kindergarten. All in all they report an increase in quality, but mention certain limiting structural factors which has them thinking the full potential for quality increase is not yet achieved. This is largely reflected in available literature on the subject

«Eg kan godt skjøne kvifor denne teksten er vanskeleg å forstå» Ein kvalitativ studie av korleis revisjonen av læreplanen i norsk frå 2013 kjem til uttrykk i ei eksamensoppgåve for 10. trinn våren 2016 og i 13 argumenterande elevtekstar

I 2013 vart læreplanen i norsk Kunnskapsløftet frå 2006 revidert (Utdanningsdirektoratet). Revisjonen førte mellom anna med seg at sjangernemningar, som til dømes artikkel, diskusjonsinnlegg og formelt brev, vart fjerna frå kompetansemåla. I staden inneheld kompetansemåla i den reviderte læreplanen teksttypar; kreative, informative, reflekterande og argumenterande tekstar. Endringa baserer seg på ei funksjonell og kontekstuell skriveopplæring, kor føremål og mottakar er løfta fram som viktig grunnlag for tekstskaping. Føremålet med denne studien er å sjå på korleis intensjonen bak læreplanrevisjonen kjem til uttrykk i eksamensoppgåve A2 frå hovudmålsettet for 10. trinn våren 2016, samt studera korleis intensjonen bak endringane kjem til uttrykk i 13 elevtekstar som svarar på denne oppgåva. Argumenterande tekstar står sentralt i analysane. Dette kvalitative forskingsprosjektet analyserer først Oppgåve A2 med utgangspunkt i Otnes (2014) (2015) &amp; Iversen (Otnes &amp; Iversen, 2016) sine termar for kategorisering av skriveoppgåver. Som verktøy for å analysera elevtekstane har eg kombinert to modellar knytt til argumentasjon. Først har eg gjennomført ein analyse av tekstkomponentar i ein problem-løysing-struktur ut frå Tirkkonen-Condit (1985) sin teori. Vidare har eg gjennomført ein analyse av den grunnleggjande argumentasjonen i teksten med utgangspunkt i Toulmin (2003) sin argumentasjonsmodell. Kombinasjonen av analysemodellar gir to innfallsvinklar til same tekstmateriale, og dermed ulike perspektiv på korleis eleven oppfattar og responderer på oppgåveformuleringa. Studien har konstatert at læreplanrevisjonen kjem til uttrykk i eksamensoppgåva. Prosjektet gir innsyn i korleis ei skriveoppgåve som legg opp til overtydande skrivehandling materialiserer seg i tekstar med argumenterande superstruktur og fleire argumenterande trekk. Samstundes belyser studien at ei informasjonsrik oppgåve med detaljerte instruksar og kontekstinnrammingar er svært styrande for korleis elevar løyser oppgåva. Elevane ser ut til å ta funksjonelle val i høve til oppgåveinstruksen, men noko av utfordringa ligg i at oppgåva gir så spesifikke bestillingar at det ikkje er så mange reelle val att for eleven å ta. Elevane i utvalet får synt lesekompetanse og sjølvstendig kunnskap om lesing og lesestrategiar, men dei får ikkje eit stort rom til å syna at dei er funksjonelle skrivarar med kompetanse i tekstoppbygging og tekststruktur.In 2013 the curriculum in Norwegian, Kunnskapsløftet from 2006 (Utdanningsdirektoratet), was revised. The revision entailed that genres such as articles, opinion pieces and formal letters were removed from the competence aims. The competence aims in the revised curriculum instead uses creative, informative, reflecting and argumentative texts. The revision was based on a functional and contextual view on writing where purpose and recipient are seen as important elements in text writing. The purpose of this project is to analyse how the intention behind the curriculum revision was expressed in “Oppgåve A2” from the Year 10 final exam in the spring of 2016. In addition, 13 student answers to “Oppgåve A2” were used to study how the intention behind the curriculum revision was reflected in their answers. Argumentative texts are central to the analysis. In this qualitative research project, the first objective was to analyse “Oppgåve A2”. The terms used for categorizing the writing tasks are borrowed from Otnes (2014) (2015) &amp; Iversen (Otnes &amp; Iversen, 2016). In the second objective two different argumentative analysis tools have been used in order to analyse the student texts. The first part of this study consists of an analysis of the text components in a problem-solution structure from the theory of Tirkkonen-Condit (1985). The second part of this study used the argumentation model of Toulmin (2003) to analyse the fundamental argumentation in the texts. This combination of the two models provides two different angles to the same text material, and therefore different perspectives to how the students understand and respond to the writing task. The results presented in this thesis shows that the curriculum revision is reflected in “Oppgåve A2”. The project also shows how a writing task, which asks for persuasive writing, results in texts with an argumentative superstructure and several argumentative characteristics. At the same time, the study illustrates that a task that is rich in information, with detailed instructions and contextualisation, is very influential in how students solve the task. The students seem to make functional decisions according to the instructions, but some of the challenge lies in the task giving orders that are so specific that there are not any real choices left for the students to make. The students in the selection get to showcase their knowledge about reading and reading strategies, but they are not given much room to demonstrate their skills as competent writers.Erfaringsbasert masteroppgåve i undervisning med fordjupning i norskVID-MAUNORNORMAU65