483 research outputs found

    SKS splitting in Southern Italy: anisotropy variations in a fragmented subduction zone.

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    In this paper we present a collection of good quality shear wave splitting measurements in Southern Italy. In addition to a large amount of previous splitting measurements, we present new data from 15 teleseisms recorded from 2003 to 2006 at the 40 stations of the CAT/SCAN temporary network. These new measurements provide additional constraints on the anisotropic behaviour of the study region and better define the fast directions in the southern part of the Apulian Platform. For our analysis we have selected wellrecorded SKS phases and we have used the method of Silver and Chan to obtain the splitting parameters: the azimuth of the fast polarized shear wave (φ) and delay time (ÎŽt). Shear wave splitting results reveal the presence of a strong seismic anisotropy in the subduction system below the region. Three different geological and geodynamic regions are characterized by different anisotropic parameters. The Calabrian Arc domain has fast directions oriented NNE–SSW and the Southern Apennines domain has fast directions oriented NNW–SSE. This rotation of fast axes, following the arcuate shape of the slab, is marked by a lack of resolved measurements which occurs at the transition zone between those two domains. The third domain is identified in the Apulian Platform: here fast directions are oriented almost N–S in the northern part and NNE–SSW to ENE–WSW in the southern one. The large number of splitting parameters evaluated for events coming from different back-azimuth allows us to hypothesize the presence of a depth-dependent anisotropic structure which should be more complicated than a simple 2 layer model below the Southern Apennines and the Calabrian Arc domains and to constrain at 50 km depth the upper limit of the anisotropic layer, at least at the edge of Southern Apennines and Apulian Platform. We interpret the variability in fast directions as related to the fragmented subduction system in the mantle of this region. The trench-parallel φ observed in Calabrian Arc and in Southern Apennines has its main source in the asthenospheric flow below the slab likely due to the pressure induced by the retrograde motion of the slab itself. The pattern of φ in the Apulian Platform does not appear to be the direct result of the rollback motion of the slab, whose influence is limited to about 100 km from the slab. The anisotropy in the Apulian Platform may be related to an asthenospheric flow deflected by the complicated structure of the Adriatic microplate or may also be explained as frozen-in lithospheric anisotropy

    Active deformation and shallow structure of the Wagner, Consag, and DelfĂ­n Basins, northern Gulf of California, Mexico

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    Oblique rifting began synchronously along the length of the Gulf of California at 6 Ma, yet there is no evidence for the existence of oceanic crust or a spreading transform fault system in the northern Gulf. Instead, multichannel seismic data show a broad shallow depression, ∌70 × 200 km, marked by active distributed deformation and six ∌10-km-wide segmented basins lacking well-defined transform faults. We present detailed images of faulting and magmatism based on the high resolution and quality of these data. The northern Gulf crust contains a dense (up to 18 faults in 5 km) complex network of mainly oblique-normal faults, with small offsets, dips of 60–80° and strikes of N-N30°E. Faults with seafloor offsets of tens of meters bound the Lower and two Upper DelfĂ­n Basins. These subparallel basins developed along splays from a transtensional zone at the NW end of the Ballenas Transform Fault. Twelve volcanic knolls were identified and are associated with the strands or horsetails from this zone. A structural connection between the two Upper DelfĂ­n Basins is evident in the switching of the center of extension along axis. Sonobuoy refraction data suggest that the basement consists of mixed igneous sedimentary material, atypical of mid-ocean ridges. On the basis of the near-surface manifestations of active faulting and magmatism, seafloor spreading will likely first occur in the Lower DelfĂ­n Basin. We suggest the transition to seafloor spreading is delayed by the lack of strain-partitioned and focused deformation as a consequence of shear in a broad zone beneath a thick sediment cover

    Illumination of the Crustal Structure in the Southern Apennines using Teleseismic Receiver Functions, CAT/SCAN Project

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    Field geology, well data and seismic imaging have illuminated the upper crustal structure of the Southern Apennines. However, lack of control of the deep structure allows viable competing thin-skin and thick-skin models of the orogen. In thin-skin models the detachment decouples a stack of rootless nappes from the basement. In thick-skin models, basement is involved in the most recent phase of thrusting. To examine the deep crustal structure, we use the teleseismic recordings from the CAT/SCAN array, deployed in southern Italy from Dec. 2003-Oct. 2005. We use receiver functions processed into a Common Conversion Point stack to generate images of the crust. We image three main westward-dipping seismic-velocity discontinuities where P-to-S conversions occur. They correspond to velocity jumps at the Moho, the upper-lower crust boundary and sedimentary interfaces resulting from the contrast between clastic and carbonate strata with basement. The CCP image matches features from both thin-skin and thick skin model. The lateral continuity of the converters favors thin skin, but consistent interpretation across the image favors the thick skin. Overall, the results provide a better fit to the thick-skin interpretation. This suggests a change in structural style as the collision with Apulia halted motion. This model also implies considerably less Plio-Pleistocene shortening across the Apennines and a SE motion of the Calabrian Arc subparallel to the southern Apennines rather than a radial expansion of the Arc

    Process evaluation results from a school- and community-linked intervention: the Trial of Activity for Adolescent Girls (TAAG)

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    Process evaluation is a component of intervention research that evaluates whether interventions are delivered and received as intended. Here, we describe the process evaluation results for the Trial of Activity for Adolescent Girls (TAAG) intervention. The intervention consisted of four synergistic components designed to provide supportive school- and community-linked environments to prevent the decline in physical activity in adolescent girls. Process evaluation results indicate that the intervention components were delivered from intervention staff to teachers with high fidelity (84–97%) to the protocol and with lower fidelity (range: 18–93%) from teachers to students. Physical activity programs for girls, a unique feature of the TAAG intervention, increased from a mean of 10 programs per school to a mean of 16 and 15 in years 1 and 2, respectively, in intervention schools, with no change in control schools. These findings suggest that a multicomponent school- and community-based physical activity intervention can be delivered with fidelity and result in a middle school environment that supports physical activity for girls

    Steady late quaternary slip rate on the Cinarcik section of the North Anatolian fault near Istanbul, Turkey

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    The distribution of plate motion between multiple fault strands and how this distribution may evolve remain poorly understood, despite the key implications for seismic hazards. The North Anatolian Fault in northwest Turkey is a prime example of a multistranded continental transform. Here we present the first constraints on late Quaternary slip rates on its northern branch across the Cinarcik Basin in the eastern Marmara Sea. We use both deep penetration and high‐resolution multichannel seismic reflection data with a stratigraphic age model to show that a depocenter has persisted near the fault bend responsible for that transform basin. Successively older depocenters have been transported westward by fault motion relative to Eurasia, indicating a uniform right‐lateral slip rate of 18.5 mm/yr over the last 500,000 years, compared to overall GPS rates (23–24 mm/yr). Thus, the northern branch has slipped at a nearly constant rate and has accounted for most of the relative plate motion between Eurasia and Anatolia since ~0.5 Ma

    Results from the seismological component of CAT/SCAN, the Calabria-Apennine Tyrrhenian/Subduction-Collision-Accretion-Network

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    The Calabrian Arc is the final remnant of a Western Mediterranean microplate driven by rollback. The Calabrian-Apennine-Tyrrhenian/Subduction-Collision-Accretion Seismic Network (CAT/SCAN) was a passive seismic experiment to study of the Calabrian Arc and its transition to the southern Apennines. The follow up Calabrian Arc project added a multidisciplinary (seismology, geology, geomorphology, geochronology, GPS, etc.) approach to better understand the tectonics of southern Italy imaged by the CAT/SCAN experiment. Here we focus on the seismological results of the two projects. The CAT/SCAN land deployment consisted of three phases. The initial phase included an array of 39 broadband seismometers onshore, deployed during the winter of 2003/4. In September 2004, the array was reduced and in April 2005, the array was reduced once again. The field deployment was completed in October 2005. Offshore, 12 broadband Ocean Bottom Seismometers (OBSs) were deployed in the beginning of October 2004. However, only 1 was recovered normally while several others were recovered after being disturbed by trawling. The experiment goal was to determine the structure of the Calabrian subduction and southern Apennine collision systems and the structure of the transition from oceanic subduction in Calabria to continental collision in the southern Apennines.Published7922T. Tettonica attivaN/A or not JCRrestricte

    Vulnerability of low-arsenic aquifers to municipal pumping in Bangladesh

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    Sandy aquifers deposited >12,000 years ago, some as shallow as 30 m, have provided a reliable supply of low-arsenic (As) drinking water in rural Bangladesh. This study concerns the potential risk of contaminating these aquifers in areas surrounding the city of Dhaka where hydraulic heads in aquifers >150 m deep have dropped by 70 m in a few decades due to municipal pumping. Water levels measured continuously from 2012 to 2014 in 12 deep (>150 m), 3 intermediate (90-150 m) and 6 shallow (<90 m) community wells, 1 shallow private well, and 1 river piezometer show that the resulting drawdown cone extends 15-35 km east of Dhaka. Water levels in 4 low-As community wells within the 62-147 m depth range closest to Dhaka were inaccessible by suction for up to a third of the year. Lateral hydraulic gradients in the deep aquifer system ranged from 1.7 × 10-4 to 3.7 × 10-4 indicating flow towards Dhaka throughout 2012-2014. Vertical recharge on the edge of the drawdown cone was estimated at 0.21 ± 0.06 m/yr. The data suggest that continued municipal pumping in Dhaka could eventually contaminate some relatively shallow community wells

    Using estrus detection patches to optimally time insemination improved pregnancy risk in suckled beef cows enrolled in a fixed-time artificial insemination program

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    Citation: Hill, S. L., Grieger, D. M., Olson, K. C., Jaeger, J. R., Dahlen, C. R., Bridges, G. A., . . . Stevenson, J. S. (2016). Using estrus detection patches to optimally time insemination improved pregnancy risk in suckled beef cows enrolled in a fixed-time artificial insemination program. Journal of Animal Science, 94(9), 3703-3710. doi:10.2527/jas2016-0469A multilocation study examined pregnancy risk (PR) after delaying AI in suckled beef cows from 60 to 75 h when estrus had not been detected by 60 h in response to a 7-d CO-Synch + progesterone insert (CIDR) timed AI (TAI) program (d-7: CIDR insert concurrent with an injection of GnRH; d 0: PGF(2 alpha) injection and removal of CIDR insert; and GnRH injection at TAI [ 60 or 75 h after CIDR removal]). A total of 1,611 suckled beef cows at 15 locations in 9 states (CO, IL, KS, MN, MS, MT, ND, SD, and VA) were enrolled. Before applying the fixed-time AI program, BCS was assessed, and blood samples were collected. Estrus was defined to have occurred when an estrus detection patch was >50% colored (activated). Pregnancy was determined 35 d after AI via transrectal ultrasound. Cows (n = 746) detected in estrus by 60 h (46.3%) after CIDR removal were inseminated and treated with GnRH at AI (Control). Remaining nonestrous cows were allocated within location to 3 treatments on the basis of parity and days postpartum: 1) GnRH injection and AI at 60 h (early-early = EE; n = 292), 2) GnRH injection at 60 h and AI at 75 h (early-delayed = ED; n = 282), or 3) GnRH injection and AI at 75 h (delayed-delayed = DD; n = 291). Control cows had a greater (P < 0.01) PR (64.2%) than other treatments (EE = 41.7%, ED = 52.8%, DD = 50.0%). Use of estrus detection patches to delay AI in cows not in estrus by 60 h after CIDR insert removal (ED and DD treatments) increased (P < 0.05) PR to TAI when compared with cows in the EE treatment. More (P < 0.001) cows that showed estrus by 60 h conceived to AI at 60 h than those not showing estrus (64.2% vs. 48.1%). Approximately half (49.2%) of the cows not in estrus by 60 h had activated patches by 75 h, resulting in a greater (P < 0.05) PR than their nonestrous herd mates in the EE (46.1% vs. 34.5%), ED (64.2% vs. 39.2%), and DD (64.8% vs. 31.5%) treatments, respectively. Overall, cows showing estrus by 75 h (72.7%) had greater (P < 0.001) PR to AI (61.3% vs. 37.9%) than cows not showing estrus. Use of estrus detection patches to allow for a delayed AI in cows not in estrus by 60 h after removal of the CIDR insert improved PR to TAI by optimizing the timing of the AI in those cows

    Locked and loading megathrust linked to active subduction beneath the Indo-Burman Ranges

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    The Indo-Burman mountain rangesmarkthe boundary between the Indian and Eurasian plates, north of the Sumatra–Andaman subduction zone. Whether subduction still occurs along this subaerial section of the plate boundary, with 46mm/yr of highly oblique motion, is contentious. About 21mm/yr of shear motion is taken up along the Sagaing Fault, on the eastern margin of the deformation zone. It has been suggested that the remainder of the relative motion is taken up largely or entirely by horizontal strike-slip faulting and that subduction has stopped. Here we present GPS measurements of plate motions in Bangladesh, combined with measurements from Myanmar and northeast India, taking advantage of a more than 300 km subaerial accretionary prism spanning the Indo-Burman Ranges to the Ganges–Brahmaputra Delta. They reveal 13–17mm/yr of plate convergence on an active, shallowly dipping and locked megathrust fault. Most of the strike-slip motion occurs on a few steep faults, consistent with patterns of strain partitioning in subduction zones. Our results strongly suggest that subduction in this region is active, despite the highly oblique plate motion and thick sediments. We suggest that the presence of a locked megathrust plate boundary represents an underappreciated hazard in one of the most densely populated regions of the world

    The process evaluation of it\u27s your move!, an Australian adolescent community-based obesity prevention project

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    BackgroundEvidence on interventions for preventing unhealthy weight gain in adolescents is urgently needed. The aim of this paper is to describe the process evaluation for a three-year (2005-2008) project conducted in five secondary schools in the East Geelong/Bellarine region of Victoria, Australia. The project, \u27It\u27s Your Move!\u27 aimed to reduce unhealthy weight gain by promoting healthy eating patterns, regular physical activity, healthy body weight, and body size perception amongst youth; and improve the capacity of families, schools, and community organisations to sustain the promotion of healthy eating and physical activity in the region.MethodsThe project was supported by Deakin University (training and evaluation), a Reference Committee (strategic direction, budgetary approval and monitoring) and a Project Management Committee (project delivery). A workshop of students, teachers and other stakeholders formulated a 10-point action plan, which was then translated into strategies and initiatives specific to each school by the School Project Officers (staff members released from teaching duties one day per week) and trained Student Ambassadors. Baseline surveys informed intervention development. Process data were collected on all intervention activities and these were collated and enumerated, where possible, into a set of mutually exclusive tables to demonstrate the types of strategies and the dose, frequency and reach of intervention activities.ResultsThe action plan included three guiding objectives, four on nutrition, two on physical activity and one on body image. The process evaluation data showed that a mix of intervention strategies were implemented, including social marketing, one-off events, lunch time and curriculum programs, improvements in infrastructure, and healthy school food policies. The majority of the interventions were implemented in schools and focused on capacity building and healthy eating strategies as physical activity practices were seen by the teachers as already meeting students\u27 needs.ConclusionsWhile substantial health-promoting activities were conducted (especially related to healthy eating), there remain further opportunities for secondary schools to use a whole-of-school approach through the school curriculum, environment, policies and ethos to improve healthy eating, physical activity and healthy body perceptions in youth. To achieve this, significant, sustained leadership will be required within the education sector generally and within schools specifically.<br /
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