[1] Earth's subducting plates move 3-4 times faster than its overriding plates, but it remains unclear whether these contrasting plate speeds are caused by additional pull from subducting slabs or by increased viscous drag on the lithosphere-asthenosphere boundary beneath deeply-protruding continental roots. To investigate the relative importance of plausible controls, we predicted global patterns of plate motions using numerical models that incorporate the influence of subducting slabs, convective mantle flow, and continental roots. From the mantle convection models, we computed a set of dynamically consistent plate velocities by balancing forces that drive and resist the motion of each plate. When deep continental roots anchor to the sub-asthenospheric upper mantle, the calculated patterns of plate motions are close to the observations if only $20% of (excess) upper mantle slab weight contributes to the slab pull force. However, this small contribution causes plates to move too slowly on average unless mantle viscosity is a factor of $2 lower than expected from post-glacial rebound. In contrast, we show that predicted and observed plate motions are more easily reconciled if even the deepest continental roots are underlain by a low-viscosity layer and at least half of (excess) upper mantle slab weight contributes to the slab pull force. This preferred scenario agrees with recent seismological evidence for a global asthenosphere and previously proposed mechanisms for partial decoupling of slabs from surface plates.Components: 8500 words, 5 figures.

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Abstract. We used a thermal model of an iron core to calculate magnetodynamo evolution in Earth-mass rocky planets to determine the sensitivity of dynamo lifetime and intensity to planets with different mantle tectonic regimes, surface temperatures, and core properties. The heat flow at the core-mantle boundary (CMB) is derived from numerical models of mantle convection with a viscous/pseudo-plastic rheology that captures the phenomenology of plate-like tectonics. Our thermal evolution models predict a longlived (∼8 Gyr) field for Earth and similar dynamo evolution for Earth-mass exoplanets with plate tectonics. Both elevated surface temperature and pressure-dependent mantle viscosity reduce the CMB heat flow but produce only slightly longer-lived dynamos (∼8-9.5 Gyr). Single-plate ("stagnant lid") planets with relatively low CMB heat flow produce long-lived (∼10.5 Gyr) dynamos. These weaker dynamos can cease for several billions of years and subsequently reactivate due to the additional entropy production associated with inner core growth, a possible explanation for the absence of a magnetic field on present-day Venus. We also show that dynamo operation is sensitive to the initial temperature, size, and solidus of a planet's core. These dependencies would severely challenge any attempt to distinguish exoplanets with plate tectonics and stagnant lids based on the presence or absence of a magnetic field.

Seismic tomography is providing mounting evidence for large scale compositional heterogeneity deep in Earth's mantle, and also the diverse geochemical and isotopic signatures observed in oceanic basalts suggest that the mantle is not chemically homogeneous. Isotopic studies on Archean rocks indicate that mantle inhomogeneity may have existed for most of the Earth's history. One important component may be recycled oceanic crust, residing at the base of the mantle. We investigate, by numerical modeling, if such reservoirs may have been formed in the early Earth, before plate tectonics (and subduction) were possible, and how they have survived -and evolved -since then. During Earth's early evolution, thick basaltic crust may have sunk episodically into the mantle in short but vigorous diapiric resurfacing events. These sections of crust may have resided at the base of the mantle for very long times. Entrainment of material from the enriched reservoirs thus produced may account for EM and HIMU signatures in oceanic basalts, whereas deep subduction events may have shaped and replenished deep mantle reservoirs. Our modeling shows that (1) convective instabilities and resurfacing may have produced deep enriched mantle reservoirs prior to the era of plate tectonics, that (2) such formation is qualitatively consistent with the geochemical record showing multiple distinct OIB sources, and that (3) reservoirs thus produced may be stable for billions of years.

Methods to improve the operational efficiency of a water supply network by early detection of anomalies are investigated by making use of the data streams from multiple sensor locations within the network. The water supply network is a demonstration site of Vitens, a Dutch water company that has several district metering areas where flow, pressure, electrical conductance and temperature are measured and logged online. Three different machine learning approaches are tested for their feasibility to detect anomalies. In the first approach, day-dependent support vector regression (SVR) models are trained for predicting the measurement signals and compared to straightforward models using mean and median estimates, respectively. Using SVRs or the averaged data as real-time pattern recognizers on all available signals, large leakages can be detected. The second approach utilizes adaptive orthogonal projections and reports an event when the number of hidden variables required to describe the streaming data to a user-defined degree (energy-level threshold) increases. As a third approach, (unsupervised) clustering techniques are applied to detect anomalies and underlying patterns from the raw data streams. Preliminary results indicate that the current dataset is too limited in the amount of events and patterns to harness the potential of these techniques.