Field evidence for fluid facilitated fracturing and Dissolution-Precipitaion creep explains observed off-fault tremor and continuous deformation: Field examples from the Alpine Fault, New Zealand

<div> <p>Geophysical observations show that the Alpine Fault in New Zealand is characterised by mid-crustal off-fault recurring tremor events and off-fault regions of continuous deformation. While geodesy indicates that deformation is distributed across the South Island, evidence from the rock record shows deformation accommodated in a region within several km from the fault. This zone is characterized by a 100-300 m wide mylonitised central fault zone and an approximately 8--10km, wide deformation region marked by the presence of Alpine foliation. Magnetotelluric surveys of the Southern Alps indicate a mid-crustal, high signal area coinciding with the location of the recurring tremors.  </p> </div><div> <p>While the mylonites and their associated mechanisms have been extensively studied in the field area, the wider off-fault deformation region has not had the same scrutiny. In the latter region, we observe frequent layer parallel, folded and crosscutting quartz veins. Quartz vein orientation and geometries are consistent with fracturing in the presence of fluid within an overall tectonic stress regime. The observed overprinting of older veins by younger vein generations, as well as their successive reorientations, indicate recurring fracturing within a continuously deforming region. Quantitative analysis of vein geometries including their width and displacement shows that vein formation may trigger the observed mid-crustal tremor signal. Microstructural signatures within the host rock are consistent with dissolution-precipitation creep as the main deformation mechanism in the host rock and pre-existing veins.  </p> </div><div> <p>In summary, according to field evidence both geophysically observed transient and continuous deformation take place in the presence of fluid and occur contemporaneously. This implies that strain accommodation in the host rock facilitated by dissolution-precipitation creep is insufficient; consequently, stress is build-up over time triggering intermittent fracturing.  </p> </div>

Cumulants of Jack symmetric functions and b-conjecture (extended abstract)

International audience Goulden and Jackson (1996) introduced, using Jack symmetric functions, some multivariate generating series ψ(x, y, z; t, 1 + β) that might be interpreted as a continuous deformation of the rooted hypermap generating series. They made the following conjecture: coefficients of ψ(x, y, z; t, 1+β) are polynomials in β with nonnegative integer coefficients. We prove partially this conjecture, nowadays called b-conjecture, by showing that coefficients of ψ(x, y, z; t, 1 + β) are polynomials in β with rational coefficients. Until now, it was only known that they are rational functions of β. A key step of the proof is a strong factorization property of Jack polynomials when α → 0 that may be of independent interest.

Modeling of the Dec 24, 2018 eruptive intrusion at Etna volcano by data of multi-disciplinary continuous deformation networks (CGPS, borehole strainmeters and tiltmeters)

<p>In the previous EGU 2019 we presented the different data acquired by the multi-disciplinary deformation networks during the eruption of Etna on 24 December 2018, when the volcano was suddenly penetrated by a violent dyke intrusion. An eruptive fissure opened and continued to propagate southward for more than 10 hours. The situation created the fear of possible serious consequences of feeding a lava flow even at medium-low altitudes, therefore potentially hazardous for the villages and infrastructures located there. However, the propagation stopped and lava flows finished on 25 December.</p><p>In this updated study we present the effort made to model the complex eruptive process characterized by two attempts of intrusion. We inferred a first dyke starting from the sea level depth with an increasing of its dimension in the shallower part. Successively and until the early hours of 25 December, we revealed a second attempt of intrusion characterized by a dyke with a powerful opening with respect to the first dyke but that, fortunately, did not reach the free surface. We describe how different types of continuous deformation data provide complementary information on the ongoing process allowing us to model the fast intrusive process. In particular, the high-precision borehole instruments (strainmeters and tiltmeters) provided a robust early warning; the displacement field measured by high-rate GPS allowed obtaining an early but also reliable model of the source. Finally, the integration of all the continuous data constrained a more detailed and complete model and its time evolution able to represent the complex process leading to this flank eruption.</p><p> </p>

Topologies of Organization: Space in Continuous Deformation

This paper offers to extend existing discussions about the socio-material production of organizational space through the concept of topology. It does so by: (1) connecting the concept of topology to existing approaches to spatial organization that emphasize its socio-material and open-ended emergence; (2) theorizing organizational space as being in constant deformation across different topological shapes; and (3) exploring this in an empirical example that juxtaposes a management meeting with its interruption. The empirical material is collected through the method of shadowing managers at a Danish school. Theoretically, the paper argues that the shaping of space is contingent upon dis/continuities between (non)human agencies. The topological deformation of space testifies to the continuous but under-acknowledged work provided by (non)human agencies to both achieve and challenge the stability of organizational space. It further situates the boundary between inside and outside as a transient condition. This renders spatial matters such as scale and size situational achievements. Topology thus implies that we cannot in advance scale organization into micro and macro spatialities, and further, foregrounds the inherent dis/organization of space.