Machine Learning Can Predict the Timing and Size of Analog Earthquakes

Despite the growing spatiotemporal density of geophysical observations at subduction zones, predicting the timing and size of future earthquakes remains a challenge. Here we simulate multiple seismic cycles in a laboratory‐scale subduction zone. The model creates both partial and full margin ruptures, simulating magnitude M_w 6.2–8.3 earthquakes with a coefficient of variation in recurrence intervals of 0.5, similar to real subduction zones. We show that the common procedure of estimating the next earthquake size from slip‐deficit is unreliable. On the contrary, machine learning predicts well the timing and size of laboratory earthquakes by reconstructing and properly interpreting the spatiotemporally complex loading history of the system. These results promise substantial progress in real earthquake forecasting, as they suggest that the complex motion recorded by geodesists at subduction zones might be diagnostic of earthquake imminence

Penicillamine-related lichenoid dermatitis and utility of zinc acetate in a wilson disease patient with hepatic presentation, anxiety and spect abnormalities

Wilson disease is an autosomal recessive disorder of hepatic copper metabolism with consequent copper accumulation and toxicity in many tissues and consequent hepatic, neurologic and psychiatric disorders. We report a case of Wilson disease with chronic liver disease; moreover, in our patient, presenting also with high levels of state anxiety without depression, 99mTc-ECD- SPECT showed cortical hypoperfusion in frontal lobes, more marked on the left frontal lobe. During the follow-up of our patient, penicillamine was interrupted after the appearance of a lichenoid dermatitis, and zinc acetate permitted to continue the successful treatment of the patient without side-effects. In our case the therapy with zinc acetate represented an effective treatment for a Wilson disease patient in which penicillamine-related side effects appeared. The safety of the zinc acetate allowed us to avoid other potentially toxic chelating drugs; this observation is in line with the growing evidence on the efficacy of the drug in the treatment of Wilson disease. Since most of Wilson disease penicillamine-treated patients do not seem to develop this skin lesion, it could be conceivable that a specific genetic factor is involved in drug response. Further studies are needed for a better clarification of Wilson disease therapy, and in particular to differentiate specific therapies for different Wilson disease phenotypes

Dynamical effects of subducting ridges: Insights from 3-D laboratory models

We model the subduction of buoyant ridges and plateaus to study their effect on slab dynamics. Oceanic ridges parallel to the trench have a stronger effect on the process of subduction because they simultaneously affect a longer trench segment. Large buoyant slab segments sink more slowly into the asthenosphere, and their subduction result in a diminution of the velocity of subduction of the plate. We observe a steeping of the slab below those buoyant anomalies, resulting in smaller radius of curvature of the slab, that augments the energy dissipated in folding the plate and further diminishes the velocity of subduction. When the 3D geometry of a buoyant plateau is modelled, the dip of the slab above the plateau decreases, as a result of the larger velocity of subduction of the dense "normal" oceanic plate on both sides of the plateau. Such a perturbation of the dip of the slab maintains long time after the plateau has been entirely incorporated into the subduction zone. We compare experiments with the present-day subduction zone below South America. Experiments suggest that a modest ridge perpendicular to the trench such as the present-day Juan Fernandez ridge is not buoyant enough to modify the slab geometry. Already subducted buoyant anomalies within the oceanic plate, in contrast, may be responsible for some aspects of the present-day geometry of the Nazca slab at depth

Seamount Subduction and Megathrust Seismicity: The Interplay Between Geometry and Friction

Subducting seamounts are recognized as one of the key features influencing megathrust earthquakes. However, whether they trigger or arrest ruptures remains debated. Here, we use analog models to study the influence of a single seamount on megathrust earthquakes, separating the effect of topography from that of friction. Four different model configurations have been developed (i.e., flat interface, high and low friction seamount, low friction patch). In our models, the seamount reduces recurrence time, interseismic coupling, and fault strength, suggesting that it acts as a barrier: 80% of the ruptures concentrate in flat regions that surround the seamount and only smaller magnitude earthquakes nucleate above it. The low-friction zone, which mimics the fluid accumulation or the establishment of fracture systems in natural cases, seems to be the most efficient in arresting rupture propagation in our experimental setting

Back-arc strain in subduction zones: Statistical observations versus numerical modeling

International audience1] Recent statistical analysis by Lallemand et al. (2008) of subduction zone parameters revealed that the back-arc deformation mode depends on the combination between the subducting (nu(sub)) and upper (nu(up)) plate velocities. No significant strain is recorded in the arc area if plate kinematics verifies nu(up) = 0.5 vsub - 2.3 (cm/a) in the HS3 reference frame. Arc spreading ( shortening) occurs if nu(up) is greater ( lower) than the preceding relationship. We test this statistical law with numerical models of subduction, by applying constant plate velocities far away from the subduction zone. The subducting lithosphere is free to deform at all depths. We quantify the force applied on the two converging plates to sustain constant surface velocities. The simulated rheology combined viscous (non-Newtonian) and brittle behaviors, and depends on water content. The influence of subduction rate vs is first studied for a fixed upper plate. After 950 km of convergence ( steady state slab pull), the transition from extensional to compressive stresses in the upper plate occurs for vs similar to 1.4 cm/a. The effect of upper plate velocity is then tested at constant subduction rate. Upper plate retreat ( advance) with respect to the trench increases extension ( compression) in the arc lithosphere and increases ( decreases) the subducting plate dip. Our modeling confirms the statistical kinematic relationship between vsub and nu(up) that describes the transition from extensional to compressive stresses in the arc lithosphere, even if the modeled law is shifted toward higher rates of upper plate retreat, using our set of physical parameters ( e. g., 100 km thick subducting oceanic plate) and short- term simulations. Our results make valid the choice of the HS3 reference frame for assessing plate velocity influence on arc tectonic regime. The subduction model suggests that friction along the interplate contact and the mantle Stokes reaction could be the two main forces competing against slab pull for upper mantle subductions. Besides, our simulations show that the arc deformation mode is strongly time dependent

A Multidisciplinary Approach to Earthquake Research: Implementation of a Geochemical Geographic Information System for the Gargano Site, Southern Italy

A priority task for correct environmental planning is to evaluate Natural Hazards, especially in highly populated areas. In particular, thorough investigations based on different Earth Science techniques must be addressed for the Seismic Hazard Assessment (SHA) in tectonically active areas. Not only the management but also the multidisciplinary analysis of all the SHA-related data sets is best performed using a Geographic Information System. In this paper we show how a researchoriented GIS is built and used in a practical case. The Geochemical Geographic Information System (G2IS) was developed and applied to the Gargano promontory (southern Italy) in the framework of an EC research project, the Geochemical Seismic Zonation (GSZ) Project. This multidisciplinary – multiscaling powerful tool is described in its structure, updating procedures and manipulation techniques. Preliminary results are presented on the detection of geochemically active fault zones and their correlation with remote sensing data and other evidences of seismogenic structures.Published255-278JCR Journalreserve

Assessing the volcanic hazard for Rome. 40Ar/39Ar and In-SAR constraints on the most recent eruptive activity and present-day uplift at Colli Albani Volcanic District

We present new 40Ar/39Ar data which allow us to refine the recurrence time for the most recent eruptive activity occurred at Colli Albani Volcanic District (CAVD) and constrain its geographic area. Time elapsed since the last eruption (36 kyr) overruns the recurrence time (31 kyr) in the last 100 kyr. New interferometric synthetic aperture radar data, covering the years 1993–2010, reveal ongoing inflation with maximum uplift rates (>2 mm/yr) in the area hosting the most recent (<200 ka) vents, suggesting that the observed uplift might be caused by magma injection within the youngest plumbing system. Finally, we frame the present deformation within the structural pattern of the area of Rome, characterized by 50 m of regional uplift since 200 ka and by geologic evidence for a recent (<2000 years) switch of the local stress-field, highlighting that the precursors of a new phase of volcanic activity are likely occurring at the CAVD

Archaeoseismology: Methodological issues and procedure

Archaeoseismic research contributes important data on past earthquakes. A limitation of the usefulness of archaeoseismology is due to the lack of continuous discussion about the methodology. The methodological issues are particularly important because archaeoseismological investigations of past earthquakes make use of a large variety of methods. Typical in situ investigations include: (1) reconstruction of the local archaeological stratigraphy aimed at defining the correct position and chronology of a destruction layer, presumably related to an earthquake; (2) analysis of the deformations potentially due to seismic shaking or secondary earthquake effects, detectable on walls; (3) analysis of the depositional characteristics of the collapsed material; (4) investigations of the local geology and geomorphology to define possible natural cause(s) of the destruction; (5) investigations of the local factors affecting the ground motion amplifications; and (6) estimation of the dynamic excitation, which affected the site under investigation. Subsequently, a 'territorial' approach testing evidence of synchronous destruction in a certain region may delineate the extent of the area struck by the earthquake. The most reliable results of an archaeoseismological investigation are obtained by application of modern geoarchaeological practice (archaeological stratigraphy plus geological–geomorphological data), with the addition of a geophysical-engineering quantitative approach and (if available) historical information. This gives a basic dataset necessary to perform quantitative analyses which, in turn, corroborate the archaeoseismic hypothesis. Since archaeoseismological investigations can reveal the possible natural causes of destruction at a site, they contribute to the wider field of environmental archaeology, that seeks to define the history of the relationship between humans and the environment. Finally, through the improvement of the knowledge on the past seismicity, these studies can contribute to the regional estimation of seismic hazard