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We present a detailed survey on the ongoing destabilization process of the Mosul dam. The dam is located on the Tigris river and is the biggest hydraulic structure in Iraq. From a geological point of view the dam foundation is unstable due to the underlying geology that is formed by alternate and variable strata of highly soluble materials such as gypsum, anhydrite, marl and limestone. Here we present the first comprehensive multi-sensor cumulative deformation map for the dam generated from space-based synthetic aperture radar (SAR) measurements from the Italian constellation COSMO-SkyMed and the European Sentinel-1a satellite. We compared 2014-2016 data to an historic dataset spanning 2004-2010 acquired with the Envisat ASAR sensor. We found that deformation was rapid during 2004-2010, slowed down in 2012-2014, and restarted in August 2014 when grouting operations stopped due to the temporary capture of the dam by the self proclaimed Islamic State in Iraq and Syria (ISIS). We took advantage of the availability of data from multiple SAR satellites to infer the deformation at the dam in great spatial and temporal detail and shed new light on the processes of the ongoing destabilization. This study highlights how new constellations of SAR sensors together with the availability of historical datasets are leading to important advances in deformation monitoring of small scale geologic and manmade features. SECTION 1.

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Although still little used in practice, the non-linear time-history (NlTH) analysis is the most powerful method to design new earthquake-resistant buildings. This kind of analysis may even help the designer to assess the seismic performance of existing buildings and suitably plan their retrofit. With reference to a pre-seismic-code r/c building and to a suite of Italian spectrum-consistent earthquakes, the paper highlights the advantages of adopting NlTH analyses to evidence critical features in the seismic response of existing buildings and to assess in advance the effectiveness of their retrofit strategy. To this purpose, the behaviour of the retrofitted building should be suitably modelled. This paper shows how this can be done when carbon fibre reinforced polymer is used to strengthen the critical sections. Two advanced finite element programmes are adopted in parallel to carry out the numerical analyses: SAP2000 and SeismoStruct. The differences involved in the numerical model are discussed and the main advantages of a three-step procedure based on the NlTH approach are evidenced.

The paper shows that the rigid-plastic oscillator can be used to evaluate the maximum plastic displacement of any elastic-plastic oscillator under any earthquake. Motivated by this result a rigid-plastic response spectrum is introduced, which provides an easy method to calculate the maximum plastic displacement of a rigid-plastic oscillator for any given earthquake. Such a spectrum is easier to construct than the elastic-plastic response spectrum or the classical elastic one. By means of appropriate formulas presented in the paper, the rigid-plastic response spectrum can be used to determine a realistic upper bound to the maximum plastic displacement of any elastic-plastic oscillator under the given earthquake.

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