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New U-Pb and 40Ar/39Ar ages integrated with geologic mapping and observations across the western Alaska Range constrain the distribution and tectonic setting of Cretaceous to Oligocene magmatism along an evolving accretionary plate margin in south-central Alaska. These rocks were emplaced across basement domains that include Neoproterozoic to Jurassic carbonate and siliciclastic strata of the Farewell terrane, Triassic and Jurassic plutonic and volcanic rocks of the Peninsular terrane, and Jurassic and Cretaceous siliciclastic strata of the Kahiltna assemblage. Plutonic rocks of different ages also host economic mineralization including intrusion-related Au, porphyry Cu-Mo-Au, polymetallic veins and skarns, and peralkaline intrusion-related rare-earth elements. The oldest intrusive suites were emplaced ca. 104-80 Ma into the Peninsular terrane only prior to final accretion. Deformation of the northern Kahiltna succession and underlying Farewell terrane occurred at ca. 97 Ma, and more widespread deformation ca. 80 Ma involved south-vergent folding and thrusting of the Kahiltna assemblage that records collisional accretion of the Peninsular-Wrangellia terrane and juxtaposition of sediment wedges formed on the inboard and outboard terranes. More widespread magmatism ca. 75-55 Ma occurred in two general pulses, each having distinct styles of localized deformation. Circa 75-65 Ma plutons were emplaced in a transpressional setting and stitch the accreted Peninsular and Wrangellia terranes to the Farewell terrane. Circa 65-55 Ma magmatism occurred across the entire range and extends for more than 200 km inboard from the inferred position of the continental margin. The Paleocene plutonic suite generally reflects shallower emplacement depths relative to older suites and is associated with more abundant andesitic to rhyolitic volcanic rocks. Deformation ca. 58-56 Ma was concentrated along two high-strain zones, the most prominent of which is 1 km wide, strikes east-northeast, and accommodated dextral oblique motion. Emplacement of widespread intermediate to mafic dikes ca. 59-51 Ma occurred before a notable magmatic lull from ca. 51-44 Ma reflecting a late Paleocene to early Eocene slab window. Magmatism resumed ca. 44 Ma, recording the transition from slab window to renewed subduction that formed the Aleutian-Meshik arc to the southwest. In the western Alaska Range, Eocene magmatism included emplacement of the elongate north-south Merrill Pass pluton and large volumes of ca. 44-37 Ma andesitic flows, tuffs, and lahar deposits. Finally, a latest Eocene to Oligocene magmatic pulse involved emplacement of a compositionally variable but spatially concentrated suite of magmas ranging from gabbro to peralkaline granite ca. 35-26 Ma, followed by waning magmatism that coincided with initiation of Yakutat shallow-slab subduction. Cretaceous to Oligocene magmatism throughout the western Alaska Range collectively records terrane accretion, translation, and integration together with evolving subduction dynamics that have shaped the southern Alaska margin since the middle Mesozoic. [ABSTRACT FROM AUTHOR]

We analyse seismic data collected from a short-term array deployment in the low seismicity area of Dunedin city, New Zealand. The addition of this temporary network to the permanent GeoNet national seismic network allows detection of earthquakes not captured by the GeoNet network. Using one of the newly detected earthquakes as a master event, we employ a template match-filter analysis to identify similar events in the area. Specifically, we record a cluster of micro-events at the northern extent of the Akatore Fault (<15 km from the city centre). A recent paleoseismic study has shown the Akatore Fault to have had multiple earthquake ruptures in the late Holocene after over 110 ka of quiescence, so the observed microseismicity is consistent with the fault being in a state of elevated activity. In contrast, other known faults in the area are quiescent with respect to both microseismicity and Holocene ruptures. The establishment of a permanent seismic array in and around Dunedin for the monitoring of microseismicity on the Akatore Fault and other local faults is warranted. [ABSTRACT FROM AUTHOR]

Abstract: Shallow slow slip events have been well documented offshore Gisborne at the northern Hikurangi subduction margin, New Zealand, and are associated with tectonic tremor downdip of the slow slip patch and increases in local microseismicity. Tremor and seismicity on the shallow subduction interface are often poorly resolved due to their distance from land‐based seismic and geodetic networks. To address this shortcoming, the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip experiment deployed 24 absolute pressure gauges and 15 ocean bottom seismometers on the seafloor above the Gisborne slow slip patch to investigate the spatial and temporal extent of slow slip and associated tremor and earthquake activity. We present a detailed spatiotemporal analysis of the seismic signatures of various interplate slip processes associated with the September/October 2014 Gisborne slow slip event. Tectonic tremor begins toward the end and continues after the geodetically constrained slow slip event and is localized in the vicinity of two subducted seamounts within and updip of the slow slip patch. The subsequent, rather than synchronous occurrence of tremor suggests that tremor may be triggered by stress changes induced by slow slip. However, Coulomb failure stress change models based on the slow slip distribution fail to predict the location of tremor, suggesting that seamount subduction plays a dominant role in the stress state of the shallow megathrust. This and the observed interplay of seismic and aseismic interplate slip processes imply that stress changes from slow slip play a secondary role in the distribution of associated microseismicity. [ABSTRACT FROM AUTHOR]

Approximately 50% of new HIV infections in the US occur in teenagers, with African American females making up a disproportionate number. The purpose of this study was to identify factors that could encourage delaying sexual debut. Twenty-eight African American mothers and their early adolescent daughters were recruited from four inner-city community centers. Seven separate focus groups were conducted for mothers and daughters using principles of Participatory Action Research. Four codes emerged from the data: social norms regarding sex, males, self-esteem, and family structure. These codes support the importance of an intervention to facilitate sexual communication between a mother and her daughter. [ABSTRACT FROM AUTHOR]

Organoiron polymers are one of the most well-examined classes of metal-containing polymers in light of their diverse structures, properties and applications. In this review, organoiron polymers are classified according to their structural make-up. The synthesis and characterization of oligomers and polymers containing dienes and cyclobutadiene rings coordinated to iron tricarbonyl moieties are described. This is followed by a thorough investigation of ferrocene-based polymers. The ferrocenyl units are found in the polymer main and side chains, and a wide variety of these organoiron polymers and their properties is reviewed. Polymers containing cyclopentadienyliron tricarbonyl complexes in their backbones and side chains are also described. Cationic η6-arene-η5-cyclopentadienyliron complexes have been incorporated into polymeric materials where the iron moieties are pendent to the main or side chains. The final class of organoiron polymers includes the iron-acetylides; these polymers are unique amongst the other examples described in this review since the iron complexes are σ-bonded to the organic backbones of the polymers. [Copyright &y& Elsevier]

This article shows that a new chiroptical molecular switch that operates in a dual mode, both photochemically and electrochemically, based on changes in the electronic state rather than in the configuration of the chiral molecule can be realized. Interconversion of the two bistable chiral forms can result from responses of the chiral molecules to external stimuli such as heat, light, pressure, chemicals, magnetic and electric fields. Photomodulation is the most common method and utilizes photoisomerization reactions of a variety of chromophores. Electrochemically modulated chiroptical switches, although less known, can operate in principle based on detection of the chiroptical properties of the two redox forms of the molecule.

We present the first paleoseismic investigation of the Hyde Fault, one of a series of north-east striking reverse faults within the Otago range and basin province in southern New Zealand. Surface traces of the fault and associated geomorphology were mapped using a lidar digital elevation model and field investigations. Trenches were excavated at two sites across fault scarps on alluvial fan surfaces. The trenches revealed stratigraphic evidence for four surface-rupturing earthquakes. Optically stimulated luminescence dating constrains the timing of these events to around 47.2 ka (37.5–56.7 ka at 95% confidence), 34.6 ka (24.7–46.4 ka), 23.5 ka (19.7–27.3 ka) and 10.5 ka (7.9–13.1 ka). We obtain a mean inter-event time of 12.4 kyr (2.3–23.9 kyr at 95% confidence) and the slip rate is estimated to be 0.22 mm/yr (0.15–0.3 mm/yr). We do not find evidence to suggest that earthquake recurrence on the Hyde Fault is episodic, in contrast to other well-studied faults within Otago, suggesting diverse recurrence styles may co-exist in the same fault system. This poses challenges for characterising the seismic hazard potential of faults in the region, particularly when paleoearthquake records are limited to the most recent few events. [ABSTRACT FROM AUTHOR]

We present new Sr, Nd, Hf and Pb isotope data for Early Miocene shoshonitic and high-K lavas dredged from seamounts in the South Fiji Basin, southwest Pacific Ocean. Our analyses provide a useful reference dataset for this distinctive compositional suite. The shoshonitic lavas formed in an intra-oceanic back-arc basin setting and are broadly coeval with nearby arc and back-arc basin lavas. Further work in the region will be needed before the tectonic implications of the shoshonitic and high-K lavas are fully understood. [ABSTRACT FROM AUTHOR]

Viti Levu, Fiji, provides one of the best exposed Phanerozoic analogues for the formation of juvenile continental crust in an intra-oceanic setting. Tonalites and trondhjemites are present in several large (75–150 km2) adjacent, mid-Cenozoic plutons. We report major and trace element data including rare earth element (REE) and high-precision high field strength element (HFSE) compositions, new Hf-Nd-Sr-Pb isotope data, and zircon U/Pb-ages, O-Hf isotopes, and trace elements, from five different plutons. The Eocene Yavuna pluton and the Miocene Colo plutons are mainly composed of tonalites and trondhjemites and represent the exposed middle crust of the former Vitiaz island arc. The plutons can be divided into three suites. One suite is light REE (LREE) depleted with some trace element ratios lower than average normal mid-ocean ridge basalts (N-MORB). A second suite has flat REE patterns similar to local island arc basalts. Both suites occur near the coast of Viti Levu, include a wide compositional spectrum from gabbro to tonalite, and can be produced mostly by fractional crystallization of mafic precursor melts. The third suite is characterized by LREE enrichments with higher La N /Yb N (2.3–4.9), higher Zr/Y (4.3–7.1), and lower Nb/Ta (9.6–12.4). They occur closer to the center of the island and are bimodal trondhjemite-gabbro intrusions. These characteristics are consistent with formation mostly by partial melting of mafic crust. Trace element modeling shows that the trace element ratios of the third suite can be produced by 10–20 % melting of the mafic crust in the presence of residual amphibole, resulting in the retention of the medium REE (MREE) and diagnostic trace element ratios including low Nb/Ta and high Zr/Y. Geochemical similarities of the LREE enriched suite to typical "low"-pressure Archean tonalites-trondhjemites-granodiorites (TTGs) imply a common petrogenetic origin and similar mechanisms for the generation of juvenile Archean and modern differentiated crust by partial melting of mafic crust with residual amphibole. In modern oceanic arcs, genetically unrelated felsic plutonic as well as volcanic rocks co-exist, and in this regard, the Fijian plutons accompany major tectonic disruptions to arc processes. [ABSTRACT FROM AUTHOR]

Many types of slow earthquakes have been discovered at subduction zones around the world. However, the physical process of these slow earthquakes is not well understood. To monitor offshore slow earthquakes, a marine seismic and geodetic experiment was conducted at the Hikurangi subduction margin from May 2014 to June 2015. During this experiment, a large slow slip event (Mw 6.8) occurred directly beneath the ocean bottom seismometer (OBS) network. In this study, S‐wave splitting and polarization analysis methods, which have been previously used on onshore data to investigate tremor and anisotropy, are applied to continuous OBS waveform data to identify tremors that are too small to detect by the envelope cross correlation method. Continuous tremor activity with stable polarization directions is detected at the end of the 2014 slow slip event and continued for about 2 weeks. The tremors are generated around a southwest bend in the slow slip contours and at the landward edge of a subducted seamount. Our findings corroborate a previous interpretation, based on burst‐type repeating earthquakes and intermittent tremor, that localized slow slip and tremor around the seamount was triggered by fluid migration following the large plate boundary slow slip event and indicate tremor occurred continuously rather than as isolated and sporadic individual events. Plain Language Summary: Slow earthquakes and tremor are characterized by slow fault rupture. Their generation mechanism has not been well understood. The slow earthquake itself does not cause damage but may inform forecasts of large earthquakes that could cause strong ground shaking or tsunamis. A large slow slip event occurred on the Hikurangi subduction plate boundary, offshore New Zealand, in 2014 directly beneath a temporary ocean bottom seismometer network. We applied new methods to this data to detect and characterize an earthquake tremor signal. The methods determine the polarization of the wave emanating from the tremor and the fast direction of the anisotropic subsurface structure through which the tremor wave propagates. These parameters enable us to detect small amplitude tremors and to determine their spatial and temporal distribution. We observed continuous tremor activity for about 2 weeks duration while the slow slip event was waning. This tremor activity occurred over a mapped subducted seamount and on the plate boundary, which likely experienced large stress changes due to the slow slip event. Our results are consistent with previous studies that used different methods on the same data, which indicate that the tremor activity in the vicinity of the seamount was triggered by fluid migration. Key Points: S‐wave splitting and polarization analyses of continuous offshore data detect small amplitude tremor activityTremor activity with stable polarization direction started near the end of the 2014 Gisborne slow slip event (SSE) and was continuous for about 2 weeksTremor activity occurred around the landward edge of the subducted seamount and was triggered by fluid migration following the SSE [ABSTRACT FROM AUTHOR]

African Americans make up the greater proportion of AIDS cases in adolescent girls but little is understood about the development of sexual risk behaviors during the early adolescent years. This article will explore ecological factors influencing adolescent sexual risk behaviors. In the focus groups, which were conducted using 28 African American mothers and their early adolescent daughters, 2 major themes emerged: exposure and support systems. Mothers described the impact community had on their daughters and how monitoring and support systems worked together to control exposure. The girls detailed the different ways they were impacted by the community. Attitudes the girls adopted from their exposures resulted in risk-taking behaviors or a determination to positively impact the community. Community was shown to be the context of the acquisition of sexual knowledge and attitudes. These findings support the development of interventions to address the impact of community on the participation of sexual risk behaviors. [ABSTRACT FROM AUTHOR]

Recent epidemiological trends in HIV/AIDS have helped draw attention to minority adolescents as especially high risk for HIV acquisition. Research shows the importance of maternal-child closeness and sexual communication in decreasing adolescent risk behaviors. The information, motivation, behavioral skills model (IMB) formed the framework for this pilot study whose purpose was to examine the informational and motivational antecedents of heterosocial risks in African American middle-school-aged girls and the maternal influence on these risks. Thirty-nine mother-daughter dyads participated, of whom 54% were impoverished. The girls' intent to stay safe, perceived social norms, and closeness to mother were negatively correlated with reported participation in potentially risky situations. Early interventions may enhance mother-daughter bonding, increasing sexual communication, and decreasing girls' participation in risky behaviors. This pilot study provides direction regarding testing of the IMB model in studies focused on early adolescent behaviors and mother-daughter interactions. [ABSTRACT FROM AUTHOR]

• Shear wave splitting used to measure crustal anisotropy during a slow slip event. • Fast azimuth variations near subducted seamount suggest structural control. • Temporal variations in Vp/Vs and delay time suggest some stress or fluid control. In September 2014, a five week long slow slip event (SSE) occurred near Gisborne at the northern Hikurangi subduction zone, New Zealand, and was recorded by offshore instruments deployed by the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) project. Up to 25 cm of slip occurred directly below the HOBITSS array. We calculate shear wave splitting (SWS) and V P / V S ratios for event-station pairs on HOBITSS ocean bottom seismometers and onshore GeoNet seismic stations to determine the relationship in time and space between slow slip and these seismic properties. Spatial averaging of SWS fast azimuths yields trench-perpendicular fast azimuths in some areas, suggesting that compressive stress from plate convergence closes microcracks and controls anisotropy in the upper-plate. Variations from the trench perpendicular directions are observed near a subducting seamount, with directions closely resembling fracture and fault patterns created by subducting seamounts previously observed in both laboratory and field experiments. Temporal variations in fast azimuths are observed at three stations, two of which are located above the seamount, suggesting measurable variations in stress orientations. During the SSE, median V P / V S measurements across all offshore stations increase from 1.817 to 1.894 and SWS delay times decrease from 0.178 s to 0.139 s (both changes are significant within 95% confidence intervals). Temporal variations in V P / V S and delay time are consistent with fluid pressurization below a permeability barrier and movement of fluids during the rupture of a slow-slip patch. [ABSTRACT FROM AUTHOR]

We use a prestack depth migration reflection image and magnetic anomaly data across the northern Hikurangi subduction zone, New Zealand, to constrain plate boundary structure and geometry of a subducting seamount in a region of shallow slow slip and recent International Ocean Discovery Program drilling. Our 3‐D model reveals the subducting seamount as a SW‐NE striking, lozenge‐shaped ridge approximately 40 km long and 15 km wide, with relief up to 2.5 km. This seamount broadly correlates with a 20‐km‐wide gap separating two patches of large (>10 cm) slow slip and the locus of tectonic tremor associated with the September–October 2014 Gisborne slow slip event. Largest slow slip magnitudes occurred where the décollement is underlain by a 3.0‐km‐thick zone of highly reflective subducting sediments. Wave speeds within this zone are 7% lower than adjacent and overlying strata, supporting the view that high fluid pressures within subducting sediments may facilitate shallow slow slip along the north Hikurangi margin. Plain Language Summary: Using a suite of geophysical data from the northern Hikurangi margin, New Zealand, we determine the location and geometry of a subducting seamount on the subducting Pacific Plate and establish its spatial relationship with slow slip and tremor that occurred on the plate boundary in September–October 2014. We infer that slow slip appears to occur preferentially where there are sediments with high fluid pressure in pore fluids subducting adjacent to the seamount but is reduced above the seamount itself. This observation has implications for understanding what physical conditions contribute to spatial variation in frictional properties of the plate interface that may control fault slip behavior on large, plate boundary subduction thrusts. Key Points: Seismic images reveal Hikurangi margin accretionary wedge architecture and seismic velocity distributionMagnetic anomaly modeling shows seismic tremor focused on the landward flanks and downdip of subducting seamountsStructural heterogeneity of the plate interface may influence the distribution of slow slip and tremor [ABSTRACT FROM AUTHOR]