Incremental growth of normal faults: Insights from a laser-equipped analog experiment

International audienceWe conducted a laser-equipped analog experiment aimed at quasi-continuously monitoring the growth of a dense population of normal faults in homogeneous conditions. To further understand the way geological faults progressively gain in slip and length as they accumulate more strain, we measured with great precision the incremental slip and length changes that the analog faults sustain as they grow. These measurements show that the analog faults share common features with the natural ones. In particular, during their growth, the faults develop and maintain cumulative slip profiles that are generally triangular and asymmetric. The growth takes place through two distinct phases: an initial, short period of rapid lateral lengthening, followed by a longer phase of slip accumulation with little or no lengthening. The incremental slip is found to be highly variable in both space (along the faults) and time, resulting in variable slip rates. In particular, ‘short- and long-term' slip rates are markedly different. We also find that slip measurements at local points on fault traces do not contain clear information on the slip increment repeat mode. Finally, while the fault growth process is highly heterogeneous when considered at the scale of a few slip events, it appears homogeneous and self-similar at longer time scales which integrate many slip increments. This is likely to be the result of a feedback between stress heterogeneities and slip development. The long-term scale homogeneity also implies that the long-term faulting process is primarily insensitive to the short-term heterogeneities that are rapidly smoothed or redistributed. We propose a new conceptual scenario of fault growth that integrates the above observations and we suggest that faults grow in a bimodal way as a result of a self-driven and self-sustaining process

Inherited Ocean-Continent Transition zones in deeply subducted terranes: Insights from Alpine Corsica

In the Schistes Lustrés of Alpine Corsica (France) serpentinized mantle rocks are associated with continental basement and meta-volcanic/-sedimentary cover rocks. The relationships among these different lithologies are especially well exposed in the Monte San Petrone unit, where Alpine metamorphism reached lawsonite-eclogite conditions. The contact between serpentinites and slivers of continental basement, relatively flat-lying over several kilometers, is characterized by evidence of cataclastic deformation pre-dating Alpine High-Pressure ductile fabrics. The serpentinite/continental basement pair is stratigraphically overlain by metasediments with a typical Jurassic-Cretaceous supra-ophiolitic lithostratigraphy, with metaradiolarites passing upward to marbles and calcschists. Noticeably, no evidence of cataclastic deformation is found in metasediments. These observations indicate that the lithostratigraphy of the Monte San Petrone unit was established during a pre-Alpine polyphase evolution, which culminated in extensive brittle deformation along a flat-lying detachment fault prior to the deposition of Jurassic sediments. We suggest that the inferred Mesozoic extensional tectonics were related to the opening of the Western Tethys. The Mesozoic architecture of the Monte San Petrone area, which is typical of an Ocean-Continent Transition (OCT) zone, was preserved despite Alpine deformation and metamorphism, when the different lithologies (i.e. meta-ophiolites, continent-derived rocks and metasediments) underwent a common metamorphic evolution, culminating at T=490-550. °C and P=2.2-2.6. GPa. Similar tectono-stratigraphic associations are observed in other high-pressure terranes of Alpine Corsica, suggesting that inherited OCT-type domains may be common in Alpine-type orogens. © 2011 Elsevier B.V

Geomorphology of the southernmost Longitudinal Valley fault: Implications for evolution of the active suture of eastern Taiwan

In order to understand fully the deformational patterns of the Longitudinal Valley fault system, a major structure along the eastern suture of Taiwan, we mapped geomorphic features near the southern end of the Longitudinal Valley, where many well‐developed fluvial landforms record deformation along multiple strands of the fault. Our analysis shows that the Longitudinal Valley fault there comprises two major strands. The Luyeh strand, on the west, has predominantly reverse motion. The Peinan strand, on the east, has a significant left‐lateral component. Between the two strands, late Quaternary fluvial sediments and surfaces exhibit progressive deformation. The Luyeh strand dies out to the north, where it steps to the east and joins the Peinan strand to become the main strand of the reverse sinistral Longitudinal Valley fault. To the south, the Luyeh strand becomes an E‐W striking monocline. This suggests that the reverse motion on the Longitudinal Valley system decreases drastically at that point. The Longitudinal Valley fault system is therefore likely to terminate abruptly there and does not seem to connect to any existing structure further to the south. This abrupt structural change suggests that the development of the Longitudinal Valley suture occurs through discrete structural “jumps,” rather than by a continuous northward maturation

The effect of illustrations on patient comprehension of medication instruction labels

BACKGROUND: Labels with special instructions regarding how a prescription medication should be taken or its possible side effects are often applied to pill bottles. The goal of this study was to determine whether the addition of illustrations to these labels affects patient comprehension. METHODS: Study participants (N = 130) were enrolled by approaching patients at three family practice clinics in Toronto, Canada. Participants were asked to interpret two sets of medication instruction labels, the first with text only and the second with the same text accompanied by illustrations. Two investigators coded participants' responses as incorrect, partially correct, or completely correct. Health literacy levels of participants were measured using a validated instrument, the REALM test. RESULTS: All participants gave a completely correct interpretation for three out of five instruction labels, regardless of whether illustrations were present or not. For the two most complex labels, only 34–55% of interpretations of the text-only version were completely correct. The addition of illustrations was associated with improved performance in 5–7% of subjects and worsened performance in 7–9% of subjects. CONCLUSION: The commonly-used illustrations on the medication labels used in this study were of little or no use in improving patients' comprehension of the accompanying written instructions