Based on 2D seismic profiles, multibeam and seabed grab cores acquired during the Garanti cruise in 2017, 1–5 km wide seabed giant polygons were identified in the Grenada basin, covering a total area ...of ∼55,000 km2, which is the largest area of outcropping polygonal faults (PF) ever found on Earth so far. They represent the top part of an active 700–1,200 m thick underlying polygonal fault system (PFS) formed due to the volumetric contraction of clay‐ and smectite‐rich sediments, initiated in the sub‐surface at the transition between the Early to Middle Pliocene. The short axes of the best‐fit ellipses obtained from a graphical center‐to‐center method were interpreted as the local orientation of a preferential contraction perpendicular to the creep deformation of slope sediments. In the North Grenada Basin, the polygons are relatively regular, but their short axes seem to be parallel to a N40°E extension recently evidenced in the forearc, possibly extending in the backarc, but not shown in the study area. They are most probably related to a progressive burial due to a homogeneous subsidence. In the South Grenada Basin, the polygons are more elongated and their axes are progressively rotating southeastward toward the depocenter, indicating a creep deformation toward the center of the basin created by a differential subsidence. Seabed polygons and underlying PF could thus be indicative of the deformation regime of shallow sediments related to main slopes controlled by two different basin architectures.
Key Points
Seabed giant polygons in the Grenada Basin cover the largest area (55,000 km2) ever found on Earth
The short axis of best‐fit ellipses of polygons may represent the orientation of the creep deformation of slope sediments
The north and south tectonic domains in the Grenada Basin are marked by major differences in the shape and orientation of seabed polygons
We report the INTernational Gamma-ray Astrophysics Laboratory (INTEGRAL) detection of the short gamma-ray burst GRB 170817A (discovered by Fermi-GBM) with a signal-to-noise ratio of 4.6, and, for the ...first time, its association with the gravitational waves (GWs) from binary neutron star (BNS) merging event GW170817 detected by the LIGO and Virgo observatories. The significance of association between the gamma-ray burst observed by INTEGRAL and GW170817 is 3.2 , while the association between the Fermi-GBM and INTEGRAL detections is 4.2 . GRB 170817A was detected by the SPI-ACS instrument about 2 s after the end of the GW event. We measure a fluence of (1.4 0.4 0.6) × 10−7 erg cm−2 (75-2000 keV), where, respectively, the statistical error is given at the 1 confidence level, and the systematic error corresponds to the uncertainty in the spectral model and instrument response. We also report on the pointed follow-up observations carried out by INTEGRAL, starting 19.5 hr after the event, and lasting for 5.4 days. We provide a stringent upper limit on any electromagnetic signal in a very broad energy range, from 3 keV to 8 MeV, constraining the soft gamma-ray afterglow flux to <7.1 × 10−11 erg cm−2 s−1 (80-300 keV). Exploiting the unique capabilities of INTEGRAL, we constrained the gamma-ray line emission from radioactive decays that are expected to be the principal source of the energy behind a kilonova event following a BNS coalescence. Finally, we put a stringent upper limit on any delayed bursting activity, for example, from a newly formed magnetar.
The Eocene tectonic evolution of the easternmost Caribbean Plate (CP) boundary, that is the Lesser Antilles subduction zone (LASZ), is debated. Recents works shed light on a peculiar period of ...tectonic duality in the arc/back‐arc regions. A compressional‐to‐transpressional regime occurred in the north, while rifting and seafloor spreading occurred in Grenada basin to the south. The mechanism for this strong spatial variation and its evolution through time has yet to be established. Here, using 3‐D subduction mechanical models, we evaluate whether the change in the trench‐curvature radius at the northeast corner of the CP could have modulated the duality. We assume asymmetrical CP boundaries at the north (from east to west: oblique subduction to strike‐slip) and at the south (subduction‐transform edge propagator‐like behavior). Regardless of the imposed trench curvature, the southern half of our modeled CP undergoes a NW‐to‐W‐oriented extension due to the tendency of the southernmost part of the South‐America oceanic slab to rollback. In contrast, the tectonic regime in the northeast corner of the CP depends on the trench‐curvature radius. A low radius promotes transtension‐to‐transpression, with a NE‐oriented compressive component of the principal stress. A high radius largely reduces the compressive component and promotes an extensional regime similar to that in the south. We thus propose that an initially low‐curvature radius of the NE‐LASZ triggered the tectonic N‐S duality in the Eocene and led to an ephemeral period of transpression/compression at the north. However, an additional mechanism might have been required to locally enhance compression.
Key Points
The trench curvature at the northeast Caribbean plate affects the back‐arc tectonic regime in models of the Lesser Antilles subduction zone
A low‐radius of curvature induces a strong north‐south variation in the stress field, and may have favored a transpressive regime at north
A high‐radius of curvature reduces the spatial variation in the tectonic regime and induces NW‐to‐E‐oriented extension from north to south
System scalability is fundamental for large-scale quantum computers (QCs) and is being pursued over a variety of hardware platforms. For QCs based on trapped ions, architectures such as the quantum ...charge-coupled device (QCCD) are used to scale the number of qubits on a single device. However, the number of ions that can be hosted on a single quantum computing module is limited by the size of the chip being used. Therefore, a modular approach is of critical importance and requires quantum connections between individual modules. Here, we present the demonstration of a quantum matter-link in which ion qubits are transferred between adjacent QC modules. Ion transport between adjacent modules is realised at a rate of 2424 s
and with an infidelity associated with ion loss during transport below 7 × 10
. Furthermore, we show that the link does not measurably impact the phase coherence of the qubit. The quantum matter-link constitutes a practical mechanism for the interconnection of QCCD devices. Our work will facilitate the implementation of modular QCs capable of fault-tolerant utility-scale quantum computation.
Strain partitioning related to oblique plate convergence has long been debated in Northern Lesser Antilles. Geophysical data acquired during the ANTITHESIS cruises highlight that the sinistral ...strike‐slip Bunce Fault develops along the vertical, long, and linear discontinuity between the sedimentary wedge and a more rigid backstop. The narrowness of the 20‐ to 30‐km‐wide accretionary wedge and its continuity over ~850 km is remarkable. The Bunce Fault extends as far south as 18.5°N where it anastomoses within the accretionary prism where the sharp increase in convergence obliquity possibly acts as a mechanical threshold. Surface traces related to subducting seamounts suggest that 80% of the lateral component of the convergent motion is taken up by internal deformation within the accretionary prism and by the Bunce Fault. The absence of crustal‐scale, long‐term tectonic system south of the Anegada Passage casts doubt upon the degree of strain partitioning in the Northern Lesser Antilles.
Plain Language Summary
Lithospheric plates are frequently bounded by subduction zones where oceanic plates underthrust overriding plates. In most cases, this convergence is oblique to the margin, its resulting tectonic deformation is generally due to margin‐normal and margin‐parallel components of the plate convergence vector. At the Northern Lesser Antilles, the North American Plate subducts beneath the Caribbean Plate with oblique convergence increasing from Guadeloupe to Virgin Islands. This study aims to analyze and resolve the tectonic deformation along this margin. We acquired marine geophysical data during ANTITHESIS cruises (2014–2016) to image the seafloor and the crustal structure. We place a particular emphasis on the strike‐slip Bunce Fault, which extends over ~850 km, including a newly discovered 350‐km segment, 20–30 km landward from the trench. Although long strike‐slip faults have already been observed at oblique subduction zones, the proximity of the Bunce Fault to the trench is unprecedented. We conclude that the mechanical discontinuity between the sedimentary wedge and a more rigid backstop and the sharp increase in obliquity is likely to control the location of the trench‐parallel, strike‐slip deformation north of the Anegada Passage when strain partitioning to the south may be small or taken up in more diffuse pattern.
Key Points
ANTITHESIS cruises highlight the SE extent of the Bunce Fault where it anastomoses in the prism at the change of obliquity of convergence
The sinistral strike‐slip Bunce Fault develops along a rheological discontinuity at the prism backstop at 30 km from the trench
A synthesize of structures resulting from strain partitioning observed in the Greater and Northern Lesser Antilles is proposed
Oblique collision of buoyant provinces against subduction zones frequently results in individualizing and rotating regional‐scale blocks. In contrast, the collision of the Bahamas Bank against the ...Northeastern Caribbean Plate increased the margin convexity triggering forearc fragmentation into small‐scale blocks. This deformation results in a prominent sequence of V‐shaped basins that widens trenchward separated by elevated spurs, in the Northern Lesser Antilles (NLA, i.e., Guadeloupe to Virgin Island). In absence of deep structure imaging, various competing models were proposed to account for this Basins‐and‐Spurs System. However, high‐resolution bathymetric and deep multichannel seismic data acquired during cruises ANTITHESIS 1‐3, reveal a drastically different tectonic evolution of the NLA Forearc.
During Eocene‐Oligocene time, the Caribbean Northeastern Boundary accommodated the Bahamas Bank collision and the subsequent margin convex bending by major left‐lateral strike‐slip faults systems in the Greater Antilles and by trench‐parallel extension along N40°–90°‐trending normal faults in the NLA. Block rotations, forearc fracturing, and V‐shaped valleys opening went along with this tectonic phase, which ends up with tectonic uplifts and an earliest‐middle Miocene regional emersion phase. Post middle Miocene regional subsidence and tectonic extension in the forearc are partly accommodated along the newly imaged N300°‐trending, 200‐km‐long normal Tintamarre Faults Zone. This drastic subsidence phase reveals vigorous margin basal erosion, which likely generated the synchronous westward migration of the volcanic arc. Thus, unlike widely accepted previous theoretical models, the NE‐SW faulting and the prominent V‐shaped valleys result from a past and sealed tectonic phase related to the margin bending and subsequent blocks rotation.
Key Points
The N. Lesser Antilles has undergone Eocene‐Oligocene NW‐SE extention and post mid Miocene NE‐SW extension separated by a regional emersion
Fault‐bounded V‐Shaped valleys result from past and sealed NW‐SE extention due to Bahamas Bank collision, margin bending, and blocks rotation
Drastic post mid Miocene subsidence and synchronous westward migration of the volcanic arc reveal vigorous subduction‐related margin erosion
The BOLERO-2 study previously demonstrated that adding everolimus (EVE) to exemestane (EXE) significantly improved progression-free survival (PFS) by more than twofold in patients with ...hormone-receptor-positive (HR+), HER2-negative advanced breast cancer that recurred or progressed during/after treatment with nonsteroidal aromatase inhibitors (NSAIs). The overall survival (OS) analysis is presented here.
BOLERO-2 is a phase III, double-blind, randomized international trial comparing EVE 10 mg/day plus EXE 25 mg/day versus placebo (PBO) + EXE 25 mg/day in postmenopausal women with HR+ advanced breast cancer with prior exposure to NSAIs. The primary end point was PFS by local investigator assessment; OS was a key secondary end point.
At the time of data cutoff (3 October 2013), 410 deaths had occurred and 13 patients remained on treatment. Median OS in patients receiving EVE + EXE was 31.0 months 95% confidence interval (CI) 28.0–34.6 months compared with 26.6 months (95% CI 22.6–33.1 months) in patients receiving PBO + EXE (hazard ratio = 0.89; 95% CI 0.73–1.10; log-rank P = 0.14). Poststudy treatments were received by 84% of patients in the EVE + EXE arm versus 90% of patients in the PBO + EXE arm. Types of poststudy therapies were balanced across arms, except for chemotherapy (53% EVE + EXE versus 63% PBO + EXE). No new safety concerns were identified.
In BOLERO-2, adding EVE to EXE did not confer a statistically significant improvement in the secondary end point OS despite producing a clinically meaningful and statistically significant improvement in the primary end point, PFS (4.6-months prolongation in median PFS; P < 0.0001). Ongoing translational research should further refine the benefit of mTOR inhibition and related pathways in this treatment setting.
NCT00863655.
At subduction zones, fluid circulation and elevated pore pressure are key factors controlling the seismogenic behavior along the plate interface by reducing absolute fault strength, increasing the ...time return of high magnitude co-seismic rupture and favoring aseismic slip. The Lesser Antilles is an end-member subduction zone where the slow subduction of numerous trans-oceanic fracture zones and patches of pervasively fractured, hydrated and serpentinized exhumed mantle rocks increase the water input. Heat-flow variations measured in the trench and the forearc during the Antithesis 1 cruise reveal heat advection by fluid circulation and shed a new light onto the thermal control of seismicity location in the subduction zone.
In the Northern Lesser Antilles, heat-flow anomalies, negative in the trench and positive in the forearc, reveal a ventilated fluid circulation with downward percolation of cold fluids at the sediment-starved, pervasively fractured trench and upward discharge of warm fluids through the Tintamarre Fault Zone in the forearc. In contrast, in the Central Lesser Antilles, a positive heat-flow anomaly at the trench and the accretionary wedge is typical of an insulated fluid circulation where warm fluids invade the plate interface flowing updip from the subduction depths up to the trench.
The investigated margin segments correspond with a very low number of interplate thrust earthquakes, illustrating the frequent statement that fluids in subduction zones tend to reduce the interplate coupling, favor slow to aseismic slip behavior, and increase the time return of large seismic events. Moreover, the location of intraslab, and supraslab earthquakes at depth beneath the Central Lesser Antilles suggest a close relation to temperature-related dehydration reactions.
•Vigorous fluid circulations occur in the Lesser Antilles subduction zone.•Heat-flow anomalies reveal ventilated and insulated fluid circulation in the Northern and Central Lesser Antilles respectively.•Warm fluid upward migration through the Tintamarre fault zone occur in the forearc at the Northern Lesser Antilles.•Seismicity locations in the Central Lesser Antilles suggest close relationship to temperature-related dehydration reactions.•Evidence of fluid circulation supports existing theory of very low interplate coupling.
The influence of the highly oblique plate convergence at the northern Lesser Antilles onto the margin strain partitioning and deformation pattern, although frequently invoked, has never been clearly ...imaged. The Anegada Passage is a set of basins and deep valleys, regularly related to the southern boundary of the Puerto Rico‐Virgin Islands (PRVI) microplate. Despite the publications of various tectonic models mostly based on bathymetric data, the tectonic origin and deformation of this Passage remains unconstrained in the absence of deep structure imaging. During cruises Antithesis 1 and 3 (2013–2016), we recorded the first deep multichannel seismic images and new multibeam data in the northern Lesser Antilles margin segment in order to shed a new light on the structure and tectonic pattern of the Anegada Passage. We image the northeastern extent of the Anegada Passage, from the Sombrero Basin to the Lesser Antilles margin front. Our results reveal that this northeastern segment is an EW trending left‐stepping en échelon strike‐slip system that consists of the Sombrero and Malliwana pull‐apart basins, the Malliwana and Anguilla left‐lateral faults, and the NE‐SW compressional restraining bend at the Malliwana Hill. Reviewing the structure of the Anegada Passage, from the south of Puerto Rico to the Lesser Antilles margin front, reveals a polyphased tectonic history. The Anegada Passage is formed by a NW‐SE extension, possibly related to the rotation or escape of PRVI block due to collision of the Bahamas Bank. Currently, it is deformed by an active WNW‐ESE strike‐slip deformation associated to the shear component of the strain partitioning resulting from the subduction obliquity.
Key Points
New bathymetric and seismic data highlight the deformation pattern of the northern Lesser Antilles active margin
The Anegada Passage is a NE‐SW trending past structure which is opened by NW‐SE extension due to the collision of the Bahamas Bank
Strain partitioning, related to the plate convergence obliquity, currently deforms the Anegada Passage by a WNW‐ESE shear strain.
A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon-oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive (56)Ni ...(refs 1-3). After the explosion, the decay chain from (56)Ni to (56)Co to (56)Fe generates γ-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of (56)Co lines at energies of 847 and 1,238 kiloelectronvolts and a γ-ray continuum in the 200-400 kiloelectronvolt band from the type Ia supernova 2014J in the nearby galaxy M82. The line fluxes suggest that about 0.6 ± 0.1 solar masses of radioactive (56)Ni were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10,000 ± 3,000 kilometres per second. The observed γ-ray properties are in broad agreement with the canonical model of an explosion of a white dwarf just massive enough to be unstable to gravitational collapse, but do not exclude merger scenarios that fuse comparable amounts of (56)Ni.
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