Role of mantle flow in Nubia-Somalia plate divergence

Present-day continental extension along the East African Rift System (EARS) has often been attributed to diverging sublithospheric mantle flow associated with the African Superplume. This implies a degree of viscous coupling between mantle and lithosphere that remains poorly constrained. Recent advances in estimating present-day opening rates along the EARS from geodesy offer an opportunity to address this issue with geodynamic modeling of the mantle-lithosphere system. Here we use numerical models of the global mantle-plates coupled system to test the role of present-day mantle flow in Nubia-Somalia plate divergence across the EARS. The scenario yielding the best fit to geodetic observations is one where torques associated with gradients of gravitational potential energy stored in the African highlands are resisted by weak continental faults and mantle basal drag. These results suggest that shear tractions from diverging mantle flow play a minor role in present-day Nubia-Somalia divergence.This work was supported by NSF award EAR-0538119 to E.C. D.S.S. was supported by NSF graduate research fellowship EAR-2009052513. G.I. acknowledges support from the Ringwood Fellowship at the Australian National University

Burnout in Medical Assistants in Primary Care: Can Mindfulness be a Solution?

Burnout is described as feelings associated with emotional exhaustion, depersonalization of patients, and a loss of sense of personal accomplishment and it is unique to healthcare workers. Current research highlights this condition among physicians, nurses, and mid-level providers; however, insufficient research exists regarding the effects of burnout on medical assistants. Research led to mindfulness as a possible solution defined as an intentional regulation of attention and awareness of the present moment. This project sought to see if mindfulness practices could be utilized to mitigate the effects of burnout in medical assistants. It was hypothesized that mindfulness could be a solution. This project featured a pretest/posttest quasi-experimental research design. The seven participants were medical assistants from three different clinics, part of an eight-clinic primary care network. Each of the sites was given a mindfulness activity for participants to complete during their working shift for 10 minutes. The practices were journaling, meditation, or going outside. The researcher gave participants the Maslach Burnout Inventory and Areas of Worklife Survey as pre- and postintervention tests. Paired t tests were conducted, results were analyzed in Excel, and p-values were calculated. Though there was a difference in the pretest and posttest scores for the depersonalization and personal accomplishment subscales, results show that mindfulness activities showed a statistically significant impact in the area of emotional exhaustion and workload

On the evaluation of some three-body variational integrals

Stable recursive relations are presented for the numerical computation of the integrals $$\int d{\bf r}_1 d{\bf r}_2 r_1^{l-1} r_2^{m-1} r_{12}^{n-1} \exp{\{-\alpha r_1 -\beta r_2 -\gamma r_{12}\}}$$ ($l$, $m$ and $n$ integer, $\alpha$, $\beta$ and $\gamma$ real) when the indices $l$, $m$ or $n$ are negative. Useful formulas are given for particular values of the parameters $\alpha$, $\beta$ and $\gamma$.Comment: 12 pages, 1 figure (PS) and 3 tables. Old figures 2 and 3 replaced by Tables I and III. A further table added. Paper enlarged giving some tips on the convergence of quadrature

A New Paradigm for Large Earthquakes in Stable Continental Plate Interiors

Large earthquakes within stable continental regions (SCR) show that significant amounts of elastic strain can be released on geological structures far from plate boundary faults, where the vast majority of the Earth's seismic activity takes place. SCR earthquakes show spatial and temporal patterns that differ from those at plate boundaries and occur in regions where tectonic loading rates are negligible. However, in the absence of a more appropriate model, they are traditionally viewed as analogous to their plate boundary counterparts, occuring when the accrual of tectonic stress localized at long-lived active faults reaches failure threshold. Here we argue that SCR earthquakes are better explained by transient perturbations of local stress or fault strength that release elastic energy from a pre-stressed lithosphere. As a result, SCR earthquakes can occur in regions with no previous seismicity and no surface evidence for strain accumulation. They need not repeat, since the tectonic loading rate is close to zero. Therefore, concepts of recurrence time or fault slip rate do not apply. As a consequence, seismic hazard in SCRs is likely more spatially distributed than indicated by paleoearthquakes, current seismicity, or geodetic strain rates

Self-avoiding fractional Brownian motion - The Edwards model

In this work we extend Varadhan's construction of the Edwards polymer model to the case of fractional Brownian motions in $\R^d$, for any dimension $d\geq 2$, with arbitrary Hurst parameters $H\leq 1/d$.Comment: 14 page

Seismically invisible fault zones: Laboratory insights into imaging faults in anisotropic rocks

Phyllosilicate‐rich rocks which commonly occur within fault zones cause seismic velocity anisotropy. However, anisotropy is not always taken into account in seismic imaging and the extent of the anisotropy is often unknown. Laboratory measurements of the velocity anisotropy of fault zone rocks and gouge from the Carboneras fault zone in SE Spain indicate 10–15% velocity anisotropy in the gouge and 35–50% anisotropy in the mica‐schist protolith. Greater differences in velocity are observed between the fast and slow directions in the mica‐schist rock than between the gouge and the slow direction of the rock. This implies that the orientation of the anisotropy with respect to the fault is key in imaging the fault seismically. For example, for fault‐parallel anisotropy, a significantly greater velocity contrast between fault gouge and rock will occur along the fault than across it, highlighting the importance of considering the foliation orientation in design of seismic experiments

Hydrologically-driven crustal stresses and seismicity in the New Madrid Seismic Zone

The degree to which short-term non-tectonic processes, either natural and anthropogenic, influence the occurrence of earthquakes in active tectonic settings or ‘stable’ plate interiors, remains a subject of debate. Recent work in plate-boundary regions demonstrates the capacity for long-wavelength changes in continental water storage to produce observable surface deformation, induce crustal stresses and modulate seismicity rates. Here we show that a significant variation in the rate of microearthquakes in the intraplate New Madrid Seismic Zone at annual and multi-annual timescales coincides with hydrological loading in the upper Mississippi embayment. We demonstrate that this loading, which results in geodetically observed surface deformation, induces stresses within the lithosphere that, although of small amplitude, modulate the ongoing seismicity of the New Madrid region. Correspondence between surface deformation, hydrological loading and seismicity rates at both annual and multi-annual timescales indicates that seismicity variations are the direct result of elastic stresses induced by the water load

The Calabrian Arc subduction complex in the Ionian Sea: Regional architecture, active deformation, and seismic hazard

We analyzed the structure and evolution of the external Calabrian Arc (CA) subduction complex through an integrated geophysical approach involving multichannel and single‐channel seismic data at different scales. Pre‐stack depth migrated crustal‐scale seismic profiles have been used to reconstruct the overall geometry of the subduction complex, i.e., depth of the basal detachment, geometry and structural style of different tectonic domains, and location and geometry of major faults. High‐resolution multichannel seismic (MCS) and sub‐bottom CHIRP profiles acquired in key areas during a recent cruise, as well as multibeam data, integrate deep data and constrain the fine structure of the accretionary wedge as well as the activity of individual fault strands. We identified four main morpho‐structural domains in the subduction complex: 1) the post‐Messinian accretionary wedge; 2) a slope terrace; 3) the pre‐Messinian accretionary wedge and 4) the inner plateau. Variation of structural style and seafloor morphology in these domains are related to different tectonic processes, such as frontal accretion, out‐of-sequence thrusting, underplating and complex faulting. The CA subduction complex is segmented longitudinally into two different lobes characterized by different structural style, deformation rates and basal detachment depths. They are delimited by a NW/SE deformation zone that accommodates differential movements of the Calabrian and the Peloritan portions of CA and represent a recent phase of plate re‐organization in the central Mediterranean. Although shallow thrust‐type seismicity along the CA is lacking, we identified active deformation of the shallowest sedimentary units at the wedge front and in the inner portions of the subduction complex. This implies that subduction could be active but aseismic or with a locked fault plane. On the other hand, if underthrusting of the African plate has stopped recently, active shortening may be accommodated through more distributed deformation. Our findings have consequences on seismic hazard, since we identified tectonic structures likely to have caused large earthquakes in the past and to be the source regions for future events