Variations in the distribution of magma in the lower crust and at the Moho beneath the East Pacific Rise at 9°-10°N

Measurements of the seafloor deformation under ocean waves (compliance) reveal an asymmetric lower crustal partial melt zone (shear velocity less than 1.8 km/s) beneath the East Pacific Rise axis between 9° and 10°N. At 9°48′N, the zone is less than 8 km wide and is centered beneath the rise axis. The zone shifts west of the rise axis as the rise approaches the westward-stepping 9°N overlapping spreading center discontinuity and is anomalously wide at the northern tip of the discontinuity. The ratio of the compliance determined shear velocity to the compressional velocities (estimated by seismic tomography) suggests that the melt is well-connected in high-aspect ratio cracks rather than in isolated sills. The shear and compressional velocities indicate less than 18% melt in the lower crust on average. The compliance measurements also reveal a separate lower crustal partial melt zone 10 km east of the rise axis at 9°48′N and isolated melt bodies near the Moho beneath four of the 39 measurement sites (three on-axis and one off-axis). The offset of the central melt zone from the rise axis correlates strongly with the offset of the overlying axial melt lens and the inferred center of mantle melting, but its shape appears to be controlled by crustal processes.     

Mapping river bathymetries: Evaluating topobathymetric LiDAR survey

Advances in topobathymetric LiDARs could enable rapid surveys at sub-meter resolution over entire stream networks. This is the first step to improving our knowledge of riverine systems, both their morphology and role in ecosystems. The Experimental Advanced Airborne Research LiDAR B (EAARL-B) system is one such topobathymetric sensor, capable of mapping both terrestrial and aquatic systems. Whereas the original EAARL was developed to survey littoral areas, the new version, EAARL-B, was also designed for riverine systems but has yet to be tested. Thus, we evaluated the ability of EAARL-B to map bathymetry and floodplain topography at sub-meter resolution in a mid-size gravel-bed river. We coupled the EAARL-B survey with highly accurate field surveys (0.03 m vertical accuracy and approximately 0.6 by 0.6 m resolution) of three morphologically distinct reaches, approximately 200 m long 15 m wide, of the Lemhi River (Idaho, USA). Both point-to-point and raster-to-raster comparisons between ground and EAARL-B surveyed elevations show that differences (ground minus EAARL-B surveyed elevations) over the entire submerged topography are small (root mean square error, RMSE, and median absolute error, M, of 0.11 m), and large differences (RMSE, between 0.15 and 0.38 m and similar M) are mainly present in areas with abrupt elevation changes and covered by dense overhanging vegetation. RMSEs are as low as 0.03 m over paved smooth surfaces, 0.07 m in submerged, gradually varying topography, and as large as 0.24 m along banks with and without dense, tall vegetation. EAARL-B performance is chiefly limited by point density in areas with strong elevation gradients and by LiDAR footprint size (0.2 m) in areas with topographic features of similar size as the LiDAR footprint. © 2018 John Wiley & Sons, Ltd.     

New insights on the relative contributions of coastal processes and tectonics to shore platform development following the Kaikōura earthquake

We describe the immediate impact of the 14 November 2016 Kaikōura magnitude 7.8 (Mw) earthquake on shore platforms and cliffs around Kaikōura Peninsula. The earthquake caused an instantaneous uplift of ~1.01 m of the peninsula. We resurveyed seven profiles previously used for erosion monitoring and observed changes in the configuration of the shoreline. The coseismic uplift has fundamentally changed the process regime operating on the platforms and altered the future trajectory of shore platform and cliff development. Our observations highlight the interplay of waves, weathering, biology and tectonics. At this location tectonism strongly modulates the process regime, driving instantaneous changes in morphology and altering rates and patterns of erosion. Finally, the uplift of the Kaikōura coast has implications for changing resilience to climate change and sea level rise. Copyright © 2017 John Wiley & Sons, Ltd.     

Rockfish in Puget Sound: An ecological history of exploitation

In Puget Sound, WA (USA), rockfish (Sebastes spp.) have significantly declined in abundance, with multiple petitions to list individual species under the Endangered Species Act. In order to better understand the ecological legacy of rockfish fishing to the Puget Sound ecosystem, the local history of rockfish exploitation was reviewed, focusing on the socioeconomic forces and management decisions which influenced the trajectory of landings. Rockfish have always been harvested for human consumption in the region, but over time exploitation patterns have changed from an opportunistic subsistence activity by indigenous peoples, to a year-round target of commercial and recreational interests. Annual commercial and recreational harvests together peaked (almost 400 mt) in the early 1980s as anglers’ attitudes changed, gear technology improved, rockfish became more familiar to the market, human population increased, and agency programs promoted fisheries to sustain employment. Rockfishes were generally not managed intensely or with conservation goals in mind until the late 1980s, in part due to scientific shortcomings and a lack of resources. By the time management actions were deemed necessary, the greatest harvest had already occurred. However, the low intrinsic productivity of most rockfish species suggests that the legacy of fishing will remain for years to come. As managers strive to restore the integrity and resilience of Puget Sound, they must realize the significance of historical fishery removals to the ecosystem and use the proper social and economic incentives to drive individual behavior toward these ecosystem goals.     

The use of local indicators of spatial association to improve LiDAR-derived predictions of potential amphibian breeding ponds

We examined whether spatially explicit information improved models that use LiDAR return signal intensity to discriminate in-pond habitat from terrestrial habitat at 24 amphibian breeding ponds. The addition of Local Indicators of Spatial Association (LISA) to LiDAR return intensity data significantly improved predictive models at all ponds, reduced residual error by as much as 74%, and appeared to improve models by reducing classification errors associated with types of in-pond vegetation. We conclude that LISA statistics can help maximize the information content that can be extracted from time resolved LiDAR return data in models that predict the occurrence of small, seasonal ponds.      

Development of the HEFT and NuSTAR focusing telescopes

Hard X-ray/soft gamma-ray astrophysics is on the verge of a major advance with the practical realization of technologies capable of efficiently focusing X-rays above 10 keV. Hard X-ray focusing telescopes can achieve orders of magnitude improvements in sensitivity compared to the instruments based on coded apertures and collimated detectors that have traditionally been employed in this energy band. Compact focal planes enable high-performance detectors with good spectral resolution to be employed in efficient, low-background configurations. We have developed multilayer coated grazing incidence optics and solid state Cadmium Zinc Telluride focal plane systems for the High Energy Focusing Telescope (HEFT) balloon-borne experiment, and for the Nuclear Spectroscopic Telescope Array (NuSTAR) Small Explorer satellite. In this paper we describe the technologies, telescope designs, and performance of both experiments.     

Distinguishing Carbonate Reservoir Pore Facies with Nuclear Magnetic Resonance Measurements

  Characterization of carbonate rocks may involve identifying the important pore types which are present. In the past, this task has required detailed petrographic analysis of many core samples. Here, we describe a method which uses nuclear magnetic resonance (NMR) measurements to reduce the amount of petrographic analysis needed for porosity typing of carbonate reservoir rocks. For a rock sample which has been measured with NMR, our method decomposes the log(T₂) spectrum into at most three Gaussian-shaped components and gives a set of nine parameters. Two characteristic quantities having geological significance are extracted from the nine parameters. Values of the two quantities are compared with a reference set, established from samples having both NMR and petrographic evaluations of porosity types. We use a Bayesian approach to the classification of the dominant porosity type. Tests of our method on 103 samples show a correct prediction in 60 to 90 percent of the samples. The lower success rate was obtained for samples with five porosity types from three fields; the higher success rate obtained with samples with three porosity types from one well. The use of geologically significant quantities extracted from the decomposition gives comparable success rate to those obtained using a standard, non-geological approach such as canonical variates.     

"The Bush is No More": Insights on Institutional Change and Natural Resource Availability in Rural South Africa

The past decade has brought substantial transition to South Africa. The introduction of democracy in 1994 has yielded important political and socioeconomic transformations affecting millions of people. Here, we explore the impact of institutional and structural changes on the availability and management of fuelwood, a key natural resource in rural South Africa. As in other developing regions, many households depend on natural resources for both sustenance and energy needs. Drawing on qualitative data from 32 interviews, our objective is to describe, from the perspective of the respondents, (1) resource scarcity, (2) the underlying causes of resource scarcity, (3) the role of traditional authority in managing resources, and (4) strategies used by community members in the face of resource scarcity. The results have important implications for the well-being of both social and natural systems in many transitional, rural developing societies.