Upper mantle electrical resistivity structure beneath the Southwest Indian Ridge 37ºE

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月30日（金） 国立極地研究所 ３階ラウン

Framing safety of women in public transport: A media discourse analysis of sexual harassment cases in Bangladesh

This paper analyzes the role of print media in framing incidences of sexual harassment in public transport; particularly in the context of Bangladesh, where gender-based violence is highly prevalent in the public sphere. This article uses Douglas’ cultural theory to reflect on media practices and its institutional power to reframe the social problem through risk and blame attribution. We conducted a discourse analysis of 71 news articles extracted from four of the widely circulated and influential newspapers of Bangladesh. Our findings reveal that the hegemonic discourse of gender-based violence in public transport is systemic and/or primarily reliant on legal recourse. By contrast, discourses presenting sexual harassment as symptomatic of broader gender inequality is less frequent. Moreover, these media platforms belong to an assemblage of patriarchal social-power holders that collaborate with established law and order to facilitate a blame game, thereby relieving the same stakeholders of ownership and accountability. Given the power of news media in constructing meta-narratives of safety (and nudging policymakers), journalists must tread responsibly on issues of blame, women’s safety, and their rights to the city

Affects and assemblages of (un)safety among female bus commuters in Dhaka

By examining the lived experiences of 30 female bus commuters in Dhaka using in-depth qualitative approaches, this paper argues for an enhanced understanding of socio-cognitive undercurrents of gendered mobilities. By privileging a feminist-affective lens, and tracing the emotionally and politically charged everyday negotiations of space, power struggles, (dis) comfort, and encounters between gendered bodies, the paper contends that women’s agency to act and respond to harassment in public transport is contingent on multi-scalar assemblages comprising socio-technical infrastructures, lifestyles, cultural histories, personal dispositions and situated knowledge. Moreover, by applying assemblage thinking and affect theories in transport spaces, the study links discussions on gender, violence and mobility beyond the common economic tropes as is common in transport studies of the Global South

Devising gender-responsive transport policies in South Asia: Gender & Development

Over time, the transport sector has grown more cognisant of gender differences in planning and policy. Yet, extant literature on transport shows that challenges, such as sexual harassment of women still prevail. The value of this study is its contribution towards gender-responsive transport policies with a focus on women by highlighting (1) the spectrum of barriers that prevent women’s mobility across origin to destination journeys; and (2) construction of safety by using interventions and tools available to them, namely technology, women-only solutions, and infrastructural design. The findings are based on data from in-depth interviews with women participants in two Indian cities–Delhi and Kolkata. Drawing from our research, key policy suggestions include framing interventions in a rights-based manner, institutionalising gender-disaggregated data to inform interventions, and sensitising institutions such as the law enforcement on gender equity and women’s rights to the city. This research would be especially beneficial for regions in and beyond South Asia sharing similar contexts

Electromagnetic constraints on a melt region beneath the central Mariana back-arc spreading ridge

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q10017, doi:10.1029/2012GC004326.An electrical resistivity profile across the central Mariana subduction system shows high resistivity in the upper mantle beneath the back-arc spreading ridge where melt might be expected to exist. Although seismic data are equivocal on the extent of a possible melt region, the question arises as to why a 2-D magnetotelluric (MT) survey apparently failed to image any melt. We have run forward models and inversions that test possible 3-D melt geometries that are consistent with the MT data and results of other studies from the region, and that we use to place upper bounds on the possible extent of 3-D melt region beneath the spreading center. Our study suggests that the largest melt region that was not directly imaged by the 2-D MT data, but that is compatible with the observations as well as the likely effects of melt focusing, has a 3-D shape on a ridge-segment scale focused toward the spreading center and a resistivity of 100 Ω-m that corresponds to ∼0.1–∼1% interconnected silicate melt embedded in a background resistivity of ∼500 Ω-m. In contrast to the superfast spreading southern East Pacific Rise, the 3-D melt region suggests that buoyant mantle upwelling on a ridge-segment scale is the dominant process beneath the slow-spreading central Mariana back-arc. A final test considers whether the inability to image a 3-D melt region was a result of the 2-D survey geometry. The result reveals that the 2-D transect completed is useful to elucidate a broad range of 3-D melt bodies.TM and NS are supported by the scientific program of “TAIGA” (Trans-crustal Advection and In situ reaction of Global sub-seafloor Aquifer)” sponsored by the MEXT of Japan, and are also supported by the JSPS for Grant-In-Aid for Scientific Research (21244070). Participation in the Marianas experiment by RLE and ADC was supported by NSF grant OCE0405641.2013-04-2

Investigating the Potential of Ridesharing to Reduce Vehicle Emissions

As urban populations grow, cities need new strategies to maintain a good standard of living while enhancing services and infrastructure development. A key area for improving city operations and spatial layout is the transportation of people and goods. While conventional transportation systems (i.e., fossil fuel based) are struggling to serve mobility needs for growing populations, they also represent serious environmental threats. Alternative-fuel vehicles can reduce emissions that contribute to local air pollution and greenhouse gases as mobility needs grow. However, even if alternative-powered vehicles were widely employed, road congestion would still increase. This paper investigates ridesharing as a mobility option to reduce emissions (carbon, particulates and ozone) while accommodating growing transportation needs and reducing overall congestion. The potential of ridesharing to reduce carbon emissions from personal vehicles in Changsha, China, is examined by reviewing mobility patterns of approximately 8,900 privately-owned vehicles over two months. Big data analytics identify ridesharing potential among these drivers by grouping vehicles by their trajectory similarity. The approach includes five steps: data preprocessing, trip recognition, feature vector creation, similarity measurement and clustering. Potential reductions in vehicle emissions through ridesharing among a specific group of drivers are calculated and discussed. While the quantitative results of this analysis are specific to the population of Changsha, they provide useful insights for the potential of ridesharing to reduce vehicle emissions and the congestion expected to grow with mobility needs. Within the study area, ridesharing has the potential to reduce total kilometers driven by about 24% assuming a maximum distance between trips less than 10 kilometers, and schedule time less than 60 minutes. For a more conservative maximum trip distance of 2 kilometers and passenger schedule time of less than 40 minutes, the reductions in traveled kilometers could translate to the equivalent of approximately 4.0 tons CO2 emission reductions daily

Upper mantle electrical resistivity structure beneath the central Mariana subduction system

Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 11 (2010): Q09003, doi:10.1029/2010GC003101.This paper reports on a magnetotelluric (MT) survey across the central Mariana subduction system, providing a comprehensive electrical resistivity image of the upper mantle to address issues of mantle dynamics in the mantle wedge and beneath the slow back-arc spreading ridge. After calculation of MT response functions and their correction for topographic distortion, two-dimensional electrical resistivity structures were generated using an inversion algorithm with a smoothness constraint and with additional restrictions imposed by the subducting slab. The resultant isotropic electrical resistivity structure contains several key features. There is an uppermost resistive layer with a thickness of up to 150 km beneath the Pacific Ocean Basin, 80–100 km beneath the Mariana Trough, and 60 km beneath the Parece Vela Basin along with a conductive mantle beneath the resistive layer. A resistive region down to 60 km depth and a conductive region at greater depth are inferred beneath the volcanic arc in the mantle wedge. There is no evidence for a conductive feature beneath the back-arc spreading center. Sensitivity tests were applied to these features through inversion of synthetic data. The uppermost resistive layer is the cool, dry residual from the plate accretion process. Its thickness beneath the Pacific Ocean Basin is controlled mainly by temperature, whereas the roughly constant thickness beneath the Mariana Trough and beneath the Parece Vela Basin regardless of seafloor age is controlled by composition. The conductive mantle beneath the uppermost resistive layer requires hydration of olivine and/or melting of the mantle. The resistive region beneath the volcanic arc down to 60 km suggests that fluids such as melt or free water are not well connected or are highly three-dimensional and of limited size. In contrast, the conductive region beneath the volcanic arc below 60 km depth reflects melting and hydration driven by water release from the subducting slab. The resistive region beneath the back-arc spreading center can be explained by dry mantle with typical temperatures, suggesting that any melt present is either poorly connected or distributed discontinuously along the strike of the ridge. Evidence for electrical anisotropy in the central Mariana upper mantle is weak.Japanese participation in the Marianas experiment was supported by Japan Society for the Promotion of Science for Grant-In-Aid for Scientific Research (15340149 and 12440116), Japan-U.S. Integrated Action Program and the 21st Century COE Program of Origin and Evolution of Planetary Systems, and by the Ministry of Education, Culture, Sports, Science, and Technology for the Stagnant Slab Project, Grant-in Aid for Scientific Research on Priority Areas (17037003 and 16075204). U.S. participation was supported by NSF grant OCE0405641. Australian support came from Flinders University. T. M. is supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Deep Ocean Exploration Institute

Characterization of the in situ magnetic architecture of oceanic crust (Hess Deep) using near-source vector magnetic data

Marine magnetic anomalies are a powerful tool for detecting geomagnetic polarity reversals, lithological boundaries, topographic contrasts, and alteration fronts in the oceanic lithosphere. Our aim here is to detect lithological contacts in fast-spreading lower crust and shallow mantle by characterizing magnetic anomalies and investigating their origins. We conducted a high-resolution, near-bottom, vector magnetic survey of crust exposed in the Hess Deep “tectonic window” using the remotely operated vehicle (ROV) Isis during RRS James Cook cruise JC21 in 2008. Hess Deep is located at the western tip of the propagating rift of the Cocos-Nazca plate boundary near the East Pacific Rise (EPR) (2°15′N, 101°30′W). ROV Isis collected high-resolution bathymetry and near-bottom magnetic data as well as seafloor samples to determine the in situ lithostratigraphy and internal structure of a section of EPR lower crust and mantle exposed on the steep (~20°dipping) south facing slope just north of the Hess Deep nadir. Ten magnetic profiles were collected up the slope using a three-axis fluxgate magnetometer mounted on ROV Isis. We develop and extend the vertical magnetic profile (VMP) approach of Tivey (1996) by incorporating, for the first time, a three-dimensional vector analysis, leading to what we here termed as “vector vertical magnetic profiling” approach. We calculate the source magnetization distribution, the deviation from two dimensionality, and the strike of magnetic boundaries using both the total field Fourier-transform inversion approach and a modified differential vector magnetic analysis. Overall, coherent, long-wavelength total field anomalies are present with a strong magnetization contrast between the upper and lower parts of the slope. The total field anomalies indicate a coherently magnetized source at depth. The upper part of the slope is weakly magnetized and magnetic structure follows the underlying slope morphology, including a “bench” and lobe-shaped steps, imaged by microbathymetry. The lower part of the slope is strongly magnetized, with a gradual reduction in amplitude from east to west across the slope. Surface morphology and recent drilling results indicate that the slope has been affected by mass wasting, but the observation of internally coherent magnetization distributions within the upper and lower slopes suggest that the disturbance is surficial. We attribute the spatial differences in magnetization distribution to the combination of changes in in situ lithology and depth to the source. These survey lines document the first magnetic profiles that capture the gabbro-ultramafic and possibly dike-gabbro boundaries in fast-spreading lower crust

Faulting and volcanism in the axial valley of the slow-spreading center of the Mariana back arc basin from Wadatsumi side-scan sonar images

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q05006, doi:10.1029/2004GC000881.We analyzed in detail the geology of the median valley floor of the Mariana Basin slow-spreading ridge using sea surface geophysical data and a high-resolution deep-tow side-scan sonar survey over one spreading segment. Analysis of surface magnetic data indicates highly asymmetric accretion, with the half-spreading rate on the western side of the basin being two to three times larger than on the eastern side. Surface magnetic and reflectivity data together suggest that asymmetric spreading is accomplished through eastward ridge jumps of ∼10 km of amplitude. Deep-tow backscatter data indicate along-axis variations of the volcanic processes with the emplacement of smooth and hummocky flows at the segment center and end, respectively. This variation likely relates to changes in the effusion rate due to the deepening or even disappearance of the magma chamber toward the segment end. Concerning tectonic processes, we find a power law distribution of the fractures, with an exponent of 1.74. This suggests that within the inner valley floor, fracture growth prevails over fracture nucleation and coalescence and that fractures accommodate less than 8% of the strain. According to our calculation based on a ratio of 0.02 to 0.03 between the vertical displacement and the length of faults, the amount of tectonic strain accommodated in the inner valley floor would consistently be ∼1.1–3.4%. Data also show two distinct sets of fractures. One trend is parallel to the rift direction at the segment center (∼N160°E) and perpendicular to the plate separation direction. Another set trends ∼17° oblique to this direction (∼N175°E) and is located over the eastern part of the valley, in the vicinity of a major bounding fault also trending ∼N175°E, that is, obliquely to the direction of plate motion. We modeled the stress field near a major fault that is oblique to the regional stress field associated with plate separation using a three-dimensional boundary element approach. We found that the orientation of the predicted fissuring near the oblique fault is locally rotated by ∼15° due to a flexure of the bending plate close to this fault.The KR03-12 cruise was funded by both JAMSTEC and ORI. This research was supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the United States Geological Survey