Maria C. Neves

Software for slip-tendency analysis in 3D: A plug-in for Coulomb

Slip-tendency analysis is a valuable tool in fault reactivation evaluation and seismic hazard assessment as it provides a means of quantifying the slip potential on mapped or suspected faults in a known or inferred stress field. We developed an interactive graphic tool to perform slip-tendency analysis. The application is written in MATLAB in the form of plug-ins for COULOMB, a graphic-rich deformation and stress change open-source software. In addition to identifying the faults most prone to reactivation, we compute and plot synthetic focal mechanisms from the direction and sense of likely slip. This allows compatibility between focal mechanisms and geological structures to be verified. Both individual faults and fault networks can be considered in three dimensions. The potential for slip depends on the prevailing stress field, the fault surface orientation and the coefficient of friction. These parameters are given interactively in a Windows environment. The application thus offers an easy-to-use graphical interface with the possibility of fast parameter modification and 3D visualization of the results.

Modellus: Interactive computational modelling to improve teaching of physics in the geosciences

Many aspects of modern research and other professional activities in the geosciences require advanced knowledge about mathematical physics models and scientific computation methods and tools. In-depth meaningful learning of such knowledge skills is a difficult cognitive process which involves developing strong background knowledge of physics, mathematics and scientific computation appropriately contextualised in the geosciences themes. In this paper we describe an interactive engagement teaching approach that is based on Modellus, a freely available computer software system allowing (1) mathematical modelling ranging from explorative to expressive modelling, (2) the introduction of scientific computation without requiring the development of a working knowledge of programming and (3) the simultaneous manipulation and analysis of several different model representations, namely, tables, graphs and animations with interactive objects having properties defined in a visible and modifiable mathematical model. As examples of application, with insights for the development of other activities in a wide range of geosciences courses, we discuss a set of interactive computational modelling activities for introductory meteorology we have implemented in undergraduate university courses.

Impact of sea-level rise on earthquake and landslide triggering offshore the Alentejo margin (SW Iberia)

Earthquakes and submarine landslides are recurrent and widespread manifestations of fault activity offshore SW Iberia. The present work tests the effects of sea-level rise on offshore fault systems using Coulomb stress change calculations across the Alentejo margin. Large-scale faults capable of generating large earthquakes and tsunamis in the region, especially NE–SW trending thrusts and WNW–ESE trending dextral strike-slip faults imaged at basement depths, are either blocked or unaffected by flexural effects related to sea-level changes. Large-magnitude earthquakes occurring along these structures may, therefore, be less frequent during periods of sea-level rise. In contrast, sea-level rise promotes shallow fault ruptures within the sedimentary sequence along the continental slope and upper rise within distances of <100 km from the coast. The results suggest that the occurrence of continental slope failures may either increase (if triggered by shallow fault ruptures) or decrease (if triggered by deep fault ruptures) as a result of sea-level rise. Moreover, observations of slope failures affecting the area of the Sines contourite drift highlight the role of sediment properties as preconditioning factors in this region.