Unified algebraic treatment of resonance

Energy resonance in scattering is usually investigated either directly in the complex energy plane (E-plane) or indirectly in the complex angular momentum plane (L-plane). Another formulation complementing these two approaches was introduced recently. It is an indirect algebraic method that studies resonances in a complex charge plane (Z-plane). This latter approach will be generalized to provide a unified algebraic treatment of resonances in the complex E-, L-, and Z-planes. The complex scaling (rotation) method will be used in the development of this approach. The resolvent operators (Green's functions) are formally defined in these three spaces. Bound states spectrum and resonance energies in the E-plane are mapped onto a discrete set of poles of the respective resolvent operator on the real line of the L- and Z-planes. These poles move along trajectories as the energy is varied. A finite square integrable basis is used in the numerical implementation of this approach. Stability of poles and trajectories against variation in all computational parameters is demonstrated. Resonance energies for a given potential are calculated and compared with those obtained by other studies.Comment: 15 pages, 1 Table, 7 Figures (6 are snapshots of videos

Density and P‐wave velocity structure beneath the Paraná Magmatic Province: Refertilization of an ancient lithospheric mantle

We estimate density and P‐wave velocity perturbations in the mantle beneath the southeastern South America plate from geoid anomalies and P‐wave traveltime residuals to constrain the structure of the lithosphere underneath the Paraná Magmatic Province (PMP) and conterminous geological provinces. Our analysis shows a consistent correlation between density and velocity anomalies. The P‐wave speed and density are 1% and 15 kg/m3 lower, respectively, in the upper mantle under the Late Cretaceous to Cenozoic alkaline provinces, except beneath the Goiás Alkaline Province (GAP), where density (+20 kg/m3) and velocity (+0.5%) are relatively high. Underneath the PMP, the density is higher by about 50 kg/m3 in the north and 25 kg/m3 in the south, to a depth of 250 − 300 km. These values correlate with high‐velocity perturbations of +0.5% and +0.3%, respectively. Profiles of density perturbation versus depth in the upper mantle are different for the PMP and the adjacent Archean São Francisco (SFC) and Amazonian (AC) cratons. The Paleoproterozoic PMP basement has a high‐density root. The density is relatively low in the SFC and AC lithospheres. A reduction of density is a typical characteristic of chemically depleted Archean cratons. A more fertile Proterozoic and Phanerozoic subcontinental lithospheric mantle has a higher density, as deduced from density estimates of mantle xenoliths of different ages and composition. In conjunction with Re‐Os isotopic studies of the PMP basalts, chemical and isotopic analyses of peridodite xenoliths from the GAP in the northern PMP, and electromagnetic induction experiments of the PMP lithosphere, our density and P‐wave speed models suggest that the densification of the PMP lithosphere and flood basalt generation are related to mantle refertilization. Metasomatic refertilization resulted from the introduction of asthenospheric components from the mantle wedge above Proterozoic subduction zones, which surrounded the Paraná lithosphere. The high‐density PMP lithosphere is presently gravitationally unstable and prone to delamination.Key Points:Density and P‐wave velocity in the lithospheric mantle beneath the Paraná Magmatic Province are highHigh density precludes a depleted cratonic lithosphere and indicates refertilized lithospheric mantleBasalt magmatism suggests refertilized mantle with asthenospheric components from mantle wedgePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/1/ggge21079-sup-0003-2016GC006369-fs02.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/2/ggge21079-sup-0004-2016GC006369-fs03.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/3/ggge21079-sup-0002-2016GC006369-fs01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/4/ggge21079_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134193/5/ggge21079.pd

Direct inversion of S-P differential arrival-times for Vp/Vs ratio in SE Asia

Open Access via Jisc Wiley agreementPeer reviewedPublisher PD

Crustal structure of the Kermadec arc from MANGO seismic refraction profiles

Three active-source seismic refraction profiles are integrated with morphological and potential field data to place the first regional constraints on the structure of the Kermadec subduction zone. These observations are used to test contrasting tectonic models for an along-strike transition in margin structure previously known as the 32°S boundary. We use residual bathymetry to constrain the geometry of this boundary and propose the name Central Kermadec Discontinuity (CKD). North of the CKD, the buried Tonga Ridge occupies the forearc with VP 6.5–7.3 km s-1 and residual free-air gravity anomalies constrain its latitudinal extent (north of 30.5°S), width (110 ± 20 km) and strike (~005° south of 25°S). South of the CKD the forearc is structurally homogeneous down-dip with VP 5.7–7.3 km s-1. In the Havre Trough backarc, crustal thickness south of the CKD is 8-9 km, which is up-to 4 km thinner than the northern Havre Trough and at least 1 km thinner than the southern Havre Trough. We suggest that the Eocene arc did not extend along the current length of the Tonga-Kermadec trench. The Eocene arc was originally connected to the Three Kings Ridge and the CKD was likely formed during separation and easterly translation of an Eocene arc substrate during the early Oligocene. We suggest that the first-order crustal thickness variations along the Kermadec arc were inherited from before the Neogene and reflect Mesozoic crustal structure, the Cenozoic evolution of the Tonga-Kermadec-Hikurangi margin and along-strike variations in the duration of arc volcanism

Microseismicity of the Mid-Atlantic Ridge at 7°S-8°15′S and at the Logatchev Massif oceanic core complex at 14°40′N-14°50′N

Lithospheric formation at slow spreading rates is heterogeneous with multiple modalities, favoring symmetric spreading where magmatism dominates or core complex and inside corner high formation where tectonics dominate. We report microseismicity from three deployments of seismic networks at the Mid-Atlantic Ridge (MAR). Two networks surveyed the MAR near 7 degrees S in the vicinity of the Ascension transform fault. Three inside corner high settings were investigated. However, they remained seismically largely inactive and major seismic activity occurred along the center of the median valley. In contrast, at the Logatchev Massif core complex at 14 degrees 45N seismicity was sparse within the center of the median valley but concentrated along the eastern rift mountains just west of the serpentine hosted Logatchev hydrothermal vent field. To the north and south of the massif, however, seismic activity occurred along the ridge axis, emphasizing the asymmetry of seismicity at the Logatchev segment. Focal mechanisms indicated a large number of reverse faulting events occurring in the vicinity of the vent field at 3-5 km depth, which we interpret to reflect volume expansion accompanying serpentinization. At shallower depth of 2-4 km, some earthquakes in the vicinity of the vent field showed normal faulting behavior, suggesting that normal faults facilitates hydrothermal circulation feeding the vent field. Further, a second set of cross-cutting faults occurred, indicating that the surface location of the field is controlled by local fault systems

In-situ evidence for dextral active motion at the Arabia-India plate boundary

International audienceThe Arabia-India plate boundary--also called theOwen fracture zone--is perhaps the least-known boundary among large tectonic plates1-6. Although it was identified early on as an example of a transform fault converting the divergent motion along the Carlsberg Ridge to convergent motion in the Himalayas7, its structure and rate of motion remains poorly constrained. Here we present the first direct evidence for active dextral strike-slip motion along this fault, based on seafloor multibeam mapping of the Arabia-India-Somalia triple junction in the northwest Indian Ocean. There is evidence for 12km of apparent strike-slip motion along the mapped segment of the Owen fracture zone, which is terminated to the south by a 50-km-wide pull-apart basin bounded by active faults. By evaluating these new constraints within the context of geodetic models of global plate motions, we determine a robust angular velocity for the Arabian plate relative to the Indian plate that predicts 2-4mmyr−1 dextral motion along the Owen fracture zone. This transformfault was probably initiated around 8 million years ago in response to a regional reorganization of plate velocities and directions8-11, which induced a change in configuration of the triple junction. Infrequent earthquakes of magnitude 7 and greater may occur along the Arabia-India plate boundary, unless deformation is in the formof aseismic creep

Role of endogenous and exogenous female sex hormones in arthritis and osteoporosis development in B10.Q-ncf1*/* mice with collagen-induced chronic arthritis

<p>Abstract</p> <p>Background</p> <p>Collagen-induced arthritis (CIA) is an often-used murine model for human rheumatoid arthritis (RA). Earlier studies have shown potent anti-arthritic effects with the female sex hormone estradiol and the selective estrogen receptor modulator (SERM) raloxifene in CIA in DBA/1-mice. B10.Q-ncf1^*/*mice are B10.Q mice with a mutated Ncf1 gene. In B10.Q-ncf1^*/*mice, CIA develops as a chronic relapsing disease, which more accurately mimics human RA. We investigated the role of endogenous and exogenous sex steroids and raloxifene in the course of this model of chronic arthritis. We also examined whether treatment would prevent the development of inflammation-triggered generalized osteoporosis.</p> <p>Methods</p> <p>Female B10.Q-ncf1^*/*mice were sham-operated or ovariectomized, and CIA was induced. 22 days later, when 30% of the mice had developed arthritis, treatment with raloxifene, estradiol or vehicle was started, and the clinical disease was evaluated continuously. Treatment was continued until day 56 after immunization. At termination of the experiment (day 73), bone mineral density (BMD) was analyzed, paws were collected for histological examination, and sera were analyzed for markers of cartilage turnover and pro-inflammatory cytokines.</p> <p>Results</p> <p>Raloxifene and estradiol treatment, as well as endogenous estrogen, decreased the frequency of arthritis, prevented joint destruction and countered generalized osteoporosis. These effects were associated with lower serum levels of the pro-inflammatory cytokine IL-6.</p> <p>Conclusions</p> <p>This is the first study to show that raloxifene and estradiol can ameliorate established erosive arthritis and inflammation-triggered osteoporosis in this chronic arthritis model. We propose that treatment with raloxifene could be a beneficial addition to the treatment of postmenopausal RA.</p

Accurate Depth Determination for Moderate‐Magnitude Earthquakes Using Global Teleseismic Data

The determination of accurate source depths for globally observed earthquakes has long been one of the most problematic issues in earthquake source seismology. The optimal method for constraining the depths of teleseismically observed earthquakes is through the identification of near‐source surface reflections—depth phases. However, observing such phases is complicated by the relatively small amplitude of these arrivals compared to the background noise, particularly for earthquakes with Mw < 5.5. In this study, I present a methodology for leveraging the recent expansion in global seismic network coverage to enhance the identification of coherent depth phases through an automated stacking routine using a globally distributed array. While depth solutions for each individual depth phase are often nonunique, the identification of potential depths across multiple different phases, where each shows the correct distance‐dependent delay, provides a robust way to semiautomatically determine the source depth of an earthquake. I present a range of examples for the processing routine developed, along with an example for its regional application, to the North Chilean subduction zone. The technique presented offers an opportunity to improve depth estimates for earthquakes down to Mw4.9 and, requiring significantly less analyst input than other techniques offering a similar resolution, has the potential to be applied to large earthquake data sets

Upper- and mid-mantle interaction between the Samoan plume and the Tonga-Kermadec slabs

Mantle plumes are thought to play a key role in transferring heat from the core\u2013mantle boundary to the lithosphere, where it can significantly influence plate tectonics. On impinging on the lithosphere at spreading ridges or in intra-plate settings, mantle plumes may generate hotspots, large igneous provinces and hence considerable dynamic topography. However, the active role of mantle plumes on subducting slabs remains poorly understood. Here we show that the stagnation at 660 km and fastest trench retreat of the Tonga slab in Southwestern Pacific are consistent with an interaction with the Samoan plume and the Hikurangi plateau. Our findings are based on comparisons between 3D anisotropic tomography images and 3D petrological-thermo-mechanical models, which self-consistently explain several unique features of the Fiji\u2013Tonga region. We identify four possible slip systems of bridgmanite in the lower mantle that reconcile the observed seismic anisotropy beneath the Tonga slab (VSH4VSV) with thermo-mechanical calculations

Asperities and barriers on the seismogenic zone in North Chile: state-of-the-art after the 2007 Mw 7.7 Tocopilla earthquake inferred by GPS and InSAR data

The Mw 7.7 2007 November 14 earthquake had an epicentre located close to the city of Tocopilla, at the southern end of a known seismic gap in North Chile. Through modelling of Global Positioning System (GPS) and radar interferometry (InSAR) data, we show that this event ruptured the deeper part of the seismogenic interface (30–50 km) and did not reach the surface. The earthquake initiated at the hypocentre and was arrested ~150 km south, beneath the Mejillones Peninsula, an area already identified as an important structural barrier between two segments of the Peru–Chile subduction zone. Our preferred models for the Tocopilla main shock show slip concentrated in two main asperities, consistent with previous inversions of seismological data. Slip appears to have propagated towards relatively shallow depths at its southern extremity, under the Mejillones Peninsula. Our analysis of post-seismic deformation suggests that small but still significant post-seismic slip occurred within the first 10 d after the main shock, and that it was mostly concentrated at the southern end of the rupture. The post-seismic deformation occurring in this period represents ~12–19 per cent of the coseismic deformation, of which ~30–55 per cent has been released aseismically. Post-seismic slip appears to concentrate within regions that exhibit low coseismic slip, suggesting that the afterslip distribution during the first month of the post-seismic interval complements the coseismic slip. The 2007 Tocopilla earthquake released only ~2.5 per cent of the moment deficit accumulated on the interface during the past 130 yr and may be regarded as a possible precursor of a larger subduction earthquake rupturing partially or completely the 500-km-long North Chile seismic gap