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Abstract The 205 Ma Rochechouart impact structure (France) is characterized by various impactite formations overlying the Hercynian crystalline basement. New constraints from downhole logging and surface electrical resistivity measurements along >100 m long profiles reveal that the top melt‐bearing breccia layer is more conductive and porous than the underlying melt‐poor breccia layer. The stratigraphy within the impactite and the transition with the basement are irregular at small (∼1–10 m) and medium (>100 m) scales, with vertical amplitude up to 40–50 m. At larger scale (>1 km), audio‐magnetotelluric observations are able to map the lateral and vertical extent of fracturing/brecciation in the basement, reaching 200 m below the surface nearby Chassenon, in the northern part of the structure. Our results also unveil that the impactite deposits and the brecciated basement of the Rochechouart impact structure may have been shifted laterally and vertically during the modification stage of the impact event through displacements of megablocks, which may be associated with the collapse of a central uplift.

Abstract Meteorites contain records of past magnetic fields in the form of natural remanent magnetization (NRM). A key property of meteorite magnetization that provides information about its origin is its dependence on spatial scale. In particular, understanding how the mean remanent magnetization varies from the scale of meteorites to the global scale of their parent bodies would aid in the interpretation of spacecraft magnetometry data. However, the vast majority of meteorite samples whose remanent magnetization have been measured have sizes

Abstract Microscopic billow-like wavy folds have been observed along slip planes of the Nojima active fault, southwest Japan. The folds are similar in form to Kelvin–Helmholtz (KH) instabilities occurring in fluids, which implies that the slip zone underwent “lubrication” such as frictional melting or fluidization of fault gouge materials. If the temperature range for generation of the billow-like wavy folds can be determined, we can constrain the physical properties of fault gouge materials during seismic slip. Here, we report on rock magnetic studies that identify seismic slip zones associated with the folds, and their temperature rises during ancient seismic slips of the Nojima active fault. Using a scanning magneto-impedance magnetic microscope and a scanning superconducting quantum interference device microscope, we observed surface stray magnetic field distributions over the folds, indicating that the folds and slip zones are strongly magnetized. This is due to the production of magnetite through thermal decomposition of antiferromagnetic or paramagnetic minerals in the gouge at temperatures over 350 °C. The presence of micrometer-sized finely comminuted materials in the billow-like wavy folds, along with our rock magnetic results, suggests that frictional heating-induced fluidization was the driving mechanism of faulting. We found that the existence of the magnetized KH-type billow-like wavy folds supports that the low-viscosity fluid induced by fluidization after frictional heating decreased the frictional strength of the fault slip zone. Graphical abstract .

A valveless micro pump, utilizing a multi-layer thin film NdFeB/Ta permanent magnet (TFPM), is presented. The micro pump consists of a diaphragm actuator, comprising a TFPM, 6µm in thickness and 3 mm in diameter, which is bonded to a membrane made of polydimethylsiloxane (PDMS) of about 80µm in thickness, together with a pump chamber and a pair of diffuser elements. TFPM is sputtered on a 50µm thick Nb sheet. The diffuser elements are used to generate a one-way fluid flow. The chamber is made of acryl plates. UV negative film resist is used to bond the different layers. Compared to sinusoidal driving signal with same amplitude, a square driving signal can generate a higher flow rate. Applying a square wave voltage, ±7.5V in amplitude, the pump flow rate attains 130µL/min at a frequency of 15Hz. The flow rate is highly dependent on frequency and driving signal type. Diaphragm displacement, pump frequency is measured and analyzed.