ALBERT

Description: The ocean is key to understanding societal threats including climate change, sea level rise, ocean warming, tsunamis, and earthquakes. Because the ocean is difficult and costly to monitor, we lack fundamental data needed to adequately model, understand, and address these threats. One solution is to integrate sensors into future undersea telecommunications cables. This is the mission of the SMART subsea cables initiative (Science Monitoring And Reliable Telecommunications). SMART sensors would “piggyback” on the power and communications infrastructure of a million kilometers of undersea fiber optic cable and thousands of repeaters, creating the potential for seafloor-based global ocean observing at a modest incremental cost. Initial sensors would measure temperature, pressure, and seismic acceleration. The resulting data would address two critical scientific and societal issues: the long-term need for sustained climate-quality data from the under-sampled ocean (e.g., deep ocean temperature, sea level, and circulation), and the near-term need for improvements to global tsunami warning networks. A Joint Task Force (JTF) led by three UN agencies (ITU/WMO/UNESCO-IOC) is working to bring this initiative to fruition. This paper explores the ocean science and early warning improvements available from SMART cable data, and the societal, technological, and financial elements of realizing such a global network. Simulations show that deep ocean temperature and pressure measurements can improve estimates of ocean circulation and heat content, and cable-based pressure and seismic-acceleration sensors can improve tsunami warning times and earthquake parameters. The technology of integrating these sensors into fiber optic cables is discussed, addressing sea and land-based elements plus delivery of real-time open data products to end users. The science and business case for SMART cables is evaluated. SMART cables have been endorsed by major ocean science organizations, and JTF is working with cable suppliers and sponsors, multilateral development banks and end users to incorporate SMART capabilities into future cable projects. By investing now, we can build up a global ocean network of long-lived SMART cable sensors, creating a transformative addition to the Global Ocean Observing System.

Description: Hundreds of submarine communication cables cross the world's oceans. Today, these cables are unaware of their environment. However, repeaters spaced at ~50 km intervals along them offer access to power and bandwidth, providing the opportunity to add sensor capability to future SMART cables (Science Monitoring And Reliable Telecommunications), a concept advanced by a Joint Task Force of the International Telecommunication Union, the World Meteorological Organization and the Intergovernmental Oceanographic Commission of UNESCO1. Two NASA workshops focused on applications in climate research and oceanography2. In the workshop described here, research scientists, practitioners from earthquake observatories and tsunami warning centers, and engineers discussed potential applications of SMART cables for earthquake and tsunami early warning and reviewed existing approaches and how they can benefit from SMART cables. They also considered what possibilities exist in research on Earth structure, the physics of earthquakes, and tsunami excitation and propagation. According to current planning, a first generation of SMART cables will be equipped with a simple instrumentation package containing accelerometers, pressure gauges and temperature sensors in order to make the sensor package simple and able to withstand the rough deployment conditions in standard cable-laying operations. Most destructive tsunamis are triggered by great earthquakes along the plate boundary faults in subduction zones. Their offshore location makes quick detection and assessment of their tsunamigenic potential a real challenge using land-based networks. The DART system of ocean bottom pressure detectors can detect ocean-crossing tsunamis but sensors are too sparse and too far from shore to be much help in local warning. Dedicated submarine cables present another real-time solution but come with a hefty price tag. Thus a comprehensive coverage of all endangered subduction zones is out of reach, particularly in the developing world. Already a few cables crossing the Pacific can reduce the time-to-detection of potentially tsunamigenic earthquakes along the Ring of Fire by ~20%, and the detection of the actual tsunami wave would be reduced by a similar fraction. With trench-parallel cables even larger improvements are possible. The continuous high sampling rates possible in a cable allow separation of tsunami and seismic wavefields, allowing reliable tsunami measurements in the near field. Wide science benefits are expected from the faithful recordings of offshore earthquakes as well as from the vastly improved coverage of the ocean basins from even a small number of SMART cables.

Description: We report the detection of sixteen binary systems from the Anglo-Australian Planet Search. Solutions to the radial velocity data indicate that the stars have companions orbiting with a wide range of masses, eccentricities and periods. Three of the systems potentially contain brown-dwarf companions while another two have eccentricities that place them in the extreme upper tail of the eccentricity distribution for binaries with periods less than 1000 d. For periods up to 12 years, the distribution of our stellar companion masses is fairly flat, mirroring that seen in other radial velocity surveys, and contrasts sharply with the current distribution of candidate planetary masses, which rises strongly below 10  M J . When looking at a larger sample of binaries that have FGK star primaries as a function of the primary star metallicity, we find that the distribution maintains a binary fraction of ~43 ± 4 per cent between –1.0 and +0.6 dex in metallicity. This is in stark contrast to the giant exoplanet distribution. This result is in good agreement with binary formation models that invoke fragmentation of a collapsing giant molecular cloud, suggesting that this is the dominant formation mechanism for close binaries and not fragmentation of the primary star's remnant protoplanetary disc.

Description: Since its discovery, Euparkeria capensis has been a key taxon for understanding the early evolution of archosaurs. The braincase of Euparkeria was described based on a single specimen, but much uncertainty remained. For the first time, all available braincase material of Euparkeria is re-examined using micro-computed tomography scanning. Contrary to previous work, the parabasisphenoid does not form the posterior border of the fenestra ovalis in lateral view, but it does bear a dorsal projection that forms the anteroventral half of the fenestra. No bone pneumatization was found, but the lateral depression of the parabasisphenoid may have been pneumatic. We propose that the lateral depression likely corresponds to the anterior tympanic recess present in crown archosaurs. The presence of a laterosphenoid is confirmed for Euparkeria . It largely conforms to the crocodilian condition, but shows some features which make it more similar to the avemetatarsalian laterosphenoid. The cochlea of Euparkeria is elongated, forming a deep cochlear recess. In comparison with other basal archosauromorphs, the metotic foramen is much enlarged and regionalized into vagus and recessus scalae tympani areas, indicating an increase in its pressure-relief mechanism. The anterior semicircular canal is extended and corresponds to an enlarged floccular fossa. These aspects of the braincase morphology may be related to the development of a more upright posture and active lifestyle. They also indicate further adaptations of the hearing system of Euparkeria to terrestriality.

Description: The Doppler measurements of stars are diluted and distorted by stellar activity noise. Different choices of noise models and statistical methods have led to much controversy in the confirmation of exoplanet candidates obtained through analysing radial velocity data. To quantify the limitation of various models and methods, we compare different noise models and signal detection criteria for various simulated and real data sets in the Bayesian framework. According to our analyses, the white noise model tend to interpret noise as signal, leading to false positives. On the other hand, the red noise models are likely to interpret signal as noise, resulting in false negatives. We find that the Bayesian information criterion combined with a Bayes factor threshold of 150 can efficiently rule out false positives and confirm true detections. We further propose a Goldilocks principle aimed at modelling radial velocity noise to avoid too many false positives and too many false negatives. We propose that the noise model with R HK -dependent jitter is used in combination with the moving average model to detect planetary signals for M dwarfs. Our work may also shed light on the noise modelling for hotter stars, and provide a valid approach for finding similar principles in other disciplines.

Description: Turbidite sandstones and related deposits commonly contain deformation structures and remobilized sediment that might have resulted from post-depositional modification such as downslope creep (e.g. slumping) or density-driven loading by overlying deposits. However, we consider that deformation can occur during the passage of turbidity currents that exerted shear stress on their substrates (whether entirely pre-existing strata, sediment deposited by earlier parts of the flow itself or some combination of these). Criteria are outlined here, to avoid confusion with products of other mechanisms (e.g. slumping or later tectonics), which establish the synchronicity between the passage of overriding flows and deformation of their substrates. This underpins a new analytical framework for tracking the relationship between deformation, deposition and the transit of the causal turbidity current, through the concept of kinematic boundary layers. Case study examples are drawn from outcrop (Miocene of New Zealand, and Apennines of Italy) and subsurface examples (Britannia Sandstone, Cretaceous, UK Continental Shelf). Example structures include asymmetric flame structures, convolute lamination, some debritic units and injection complexes, together with slurry and mixed slurry facies. These structures may provide insight into the rheology and dynamics of submarine flows and their substrates, and have implications for the development of subsurface turbidite reservoirs.

Description: 〈span〉〈div〉ABSTRACT〈/div〉I review the unusual swarm of 50 earthquakes, Mw 5.2–5.4, which occurred at Kīlauea caldera between May and August 2018. Given the strong similarity in published source mechanisms derived by centroid moment tensor (CMT) methods, I stacked the 〈span〉P〈/span〉 waves from a global distribution of stations from local to antipodal distances. The composite source mechanism is consistent with a normal planar fault striking 335° NNW, dipping 78° W, with a rake nearly −90°. The differences between the composite source and waveform‐derived sources are due in part to the choice of source depth, seismic velocity, and rigidity beneath Kīlauea summit. Antipodal 〈span〉PKIKP〈/span〉 observations of the bottom of the source are derived from stacked data from three Global Seismographic Network (GSN) stations at ∼175°Δ in southern Africa. The stacked 〈span〉PKIKP〈/span〉 displacement data show dilatational first motions, apparently inconsistent with proposed piston models of the volcano–earthquake activity for comparable swarms observed in the Galapagos, Miyakejima, and Iceland. As recognized in these prior studies, the vertical‐〈span〉P〈/span〉 compensated linear vector dipole (CLVD) moment tensor solutions likely result from arcuate faults, which collectively circumscribe the caldera. The interevent times of the swarm sequence are not random; rather, the time interval between events increases by ∼1/2  hr for each earthquake.〈/span〉