151HIGHLIGHTS 2020

Dynamic earthquake rupture in the lower crust, A. Petley-Ragan (a), Y. Ben-Zion (b), F. Renard (a,c), H. Austrheim (a), B. Ildefonse (d) and B. Jamtveit (a), Sci. Adv. 5, eaaw0913 (2019);

https://doi.org/10.1126/sciadv.aaw0913. (a) The Njord Centre, University of Oslo (Norway) (b) Department of Earth Sciences, University of Southern California, Los

Angeles (USA) (c) University Grenoble Alpes, University Savoie Mont Blanc, Grenoble (France) (d) Géosciences Montpellier, University of Montpellier (France)

[1] B. Jamtveit et al., Nature, 556, 487-493 (2018). [2] B. Jamtveit et al., J. Geophys. Res. 124, 7725-7755 (2019).

RECOIL-INDUCED ASYMMETRIES IN ELECTRON EMISSION PATTERNS OF N2

Photoelectrons exert a recoil onto the atom or molecule from which they are ejected. This work shows that this recoil, together with non-dipole effects, qualitatively changes the observed angular distribution of photoelectrons with respect to the molecular fragmentation, and massively breaks the two-fold symmetries one would expect for photoelectron emission from a symmetric molecule like N2.

PRINCIPAL PUBLICATION AND AUTHORS

REFERENCES

to volume strain during pulverisation typically produces a grain size distribution with a steeper power law exponent than what results through a grinding and tear process that is dominated by shear stress.

Together, 2D electron microscopy imaging and 3D µ-CT imaging of the rock samples have unravelled the mechanics of rock damage associated with this fossil earthquake from the lower crust of the Caledonian mountain chain. The results demonstrate that the Earth s lower crust is a strong material, in which high tectonic stress can be released through earthquakes [2].

Fig. 133: a) Electron back-scattered diffraction (EBSD-) map of a sheared and fragmented garnet in the cataclasite

zone shown in Figure 132. Right inset displays the grain size distribution expressed as the probability density function (PDF) with associated power law exponents.

b) EBSD-map of a fragmented garnet crystal in the wall rock damage zone shown in Figure 132a. Inset as in (a).

Both EBSD images use inverse pole figure colouring in relation to a horizontal x-vector.

Electron emission in the frame of the molecule is studied using molecular frame photoelectron angular distributions (MFPADs), a well-established tool to investigate molecular potentials and perform orbital imaging of electronic states as the emitted photoelectron is scattered by the molecular potential when it

emerges. Due to the availability of high-intensity, high-energy light sources such as beamline ID31, fully differential photoionisation experiments, and thus, measurements of MFPADs, become feasible at photon energies of several tens of keV. At those photon energies, the often-invoked dipole and Born-Oppenheimer approximations,