A new method of analysing pressure wave dependences is presented and tested against the published experimental data. Upon the results of examination of more than 90 rock samples, it was found that a significant portion of rocks ∼45 %) exhibit negative Poisson ratios at lower pressures. Such a significant number of naturally auxetic rocks suggests that the occurrence of negative Poisson ratios is not as exotic as assumed previously.

The influence of fluid injection on tectonic fault sliding and generation of seismic events was studied in the paper by a multi-degree-of-freedom rate-and-state friction model with a two-parametric friction law. The considered system could exhibit different types of motion. The main seismic activity could appear directly after the start of fluid injection or in the post-injection phase (after some days or months). Such an influence of injection on seismicity is observed in the real cases.

We use temperature maps of the solar corona for three regions and use a technique that separates multiple timescales and space scales to show that the small-scale temperature fluctuations appear more frequently prior to the occurrence of a solar flare, in comparison with the same region after the flare and with a quiet region. We find that, during the flare, energy flows from large to small scales and heat transport associated with a heat front is convective along and diffusive across the front.

The disappearance of Malaysia Airlines flight MH370 on 8 March 2014 is one of the great mysteries of our time. The most relevant aspect is that not a piece of debris was found during the intensive surface search carried out for roughly 2 months following the crash. By combining different ocean data with dynamical systems tools, we propose a revised search strategy by showing why debris could not have been expected in some targeted search areas and determining regions where debris could be.

The popular data assimilation technique known as the ensemble Kalman filter (EnKF) suffers from sampling errors due to the limited size of the ensemble. This deficiency is usually cured by inflating the sampled error covariances and by using localization. This paper further develops and discusses the finite-size EnKF, or EnKF-N, a variant of the EnKF that does not require inflation. It expands the use of the EnKF-N to a wider range of dynamical regimes.