Structure of the SW Iberian Margin from Combined Wide-angle and Multichannel Seismic Reflection Data (FRAME Project)

<p>The SW Iberian Margin has a complex tectonic setting and crustal structure derived from a succession of rift events related to the opening of North Atlantic and Neotethys from the Mesozoic to the Lower Cretaceous, and to the subsequent convergence between Nubian and Eurasian plates from Lower Oligocene to present day. Neogene plate convergence led to the reactivation of pre-existing extensional faults originated during the Mesozoic rifting in a combination of thrust and strike-slip systems. Despite a slow convergence rate, these faults now represent a major regional seismological and tsunamigenic hazard, as demonstrated by the devastating 1755 Lisbon earthquake of M>8.5 and the ensuing tsunami. Thus, unveiling the lithospheric structure along the SW Iberian Margin is not only important to understand the different stages of rifting and compression, but also to characterize the distribution of major lithospheric-scale boundaries, currently active and potentially capable of generating great, destructive tsunamigenic earthquakes.</p><p>To this end, we use here a spatially coincident wide-angle seismic (WAS) and multichannel seismic (MCS) data set collected along a NW-SE ~320 km transect SW of São Vicente cape during the FRAME survey in 2018. WAS data were recorded by 24 ocean bottom seismometers and hydrophones (OBS/H) while the MCS data were recorded by a 6 km long, 480 channel streamer. From NW to SE, the transect runs from the Tagus Abyssal plain to the westernmost extension of the Gulf of Cadiz across four major thrust faults, namely, the Tagus Abyssal Plain fault, Marquês de Pombal fault, São Vicente fault, and Horseshoe fault.</p><p>We applied joint refraction and reflection travel-time tomography (TTT) using a combination of arrival times identified at both WAS and MCS recordings to invert for the 2D P-wave velocity (Vp) structure of the crust and uppermost mantle, as well as the geometry of the main structural boundaries identified as seismic reflectors: the top of the acoustic basement and the Moho. Combining WAS and MCS travel-times brings a remarkable increase in the resolution and accuracy of the structure of the upper layers (i.e. top of the basement) thanks to the huge increase of spatial sampling in the shallow parts of the crust provided  by MCS data as compared to WAS data alone.</p><p>The inverted model shows a Vp structure with abrupt lateral velocity and structural variations marked by a rough Top of Basement topography and sharp changes in crustal thickness. In the northernmost part of the model there is evidence of mantle exhumation. The Moho shallows beneath the NE continuation of the Horseshoe Basin and the Gorringe Bank, coinciding with the location of the Marquês de Pombal, São Vicente, and Horseshoe thrust faults. The inversion of deep seismic phases reveals the presence of four southwest dipping reflectors that sheds new light into the deep geometry these major regional thrust faults.</p>

GAPS IN THE ASPECTUAL PARADIGMS OF EXPERIENCER VERBS IN SERBIAN

The goal of this paper is to account for the gaps in the aspectual paradigms of experiencer verbs (verbs of emotion) in Serbian, i.e. to explain why certain verbs lack certain aspectual versions (imperfective, perfective or secondary imperfective). The proposed analysis ties the availability of aspectual forms to the thematic roles of participants in the situation denoted by the verb. Relying on Ramchand’s (2008) decompositional view of VP, it is assumed that there are two possible perfectivization options both of which depend on the presence of particular layers in VP structure and consequently particular thematic roles associated with those layers. The first perfectivization option is dependent upon the presence of the initiator argument (and InitP) while the second option is conditioned by the presence of the proper (affected) theme (or ResP). The lack of these two participants results in the systematic lack of perfective (the perfective gap). Secondary imperfective gaps are accounted for by the lack of true endpoint (the entailed endpoint of the resulting state, not just the situation denoted by the verb) while imperfective gaps are explained on a case-by-case basis appealing to the lack of lexicalization of certain verbal meanings or the fact that the verbal form is derived from a non-verbal stem.

A Cognitive Study of the NP+de(的)+VP Structure in Mandarin

The article presents a cognitive account of the NP+de(的) +VP structure in Mandarin. By making its syntactic functions and cognitive motivations explicit, it shows that the relationship between the constituents of the structure is subject-predicate rather than modifier-head as claimed by previous studies. Based on the new proposals that the structure is exocentric and the particle de is a nominalizing infix, the article offers a possible solution for the long-debated contradiction between the overall nominal functions of the structure and its constituents’ verbal part of speech. We conclude that a cognitive linguistic approach to analyzing structures in Mandarin can be useful in producing a picture of the formation of the structures and revealing how they are cognitively motivated. This study contributes to the development of cognitive studies on Chinese grammar and sheds light on Chinese language instruction in the long run.

Deep mantle structure and origin of Cenozoic intraplate volcanoes in Indochina, Hainan and South China Sea

Summary Cenozoic basalts with ages ranging from 28.5 Ma to < 0.1 Ma are widely distributed in the Indochina block, the South China Sea basin, and the Leiqiong area in South China including the Leizhou Peninsula and the northern Hainan Island, which form the southeastern Asian basalt province (SABP). These Cenozoic basalts share common petrological and geochemical characteristics. However, the origin of the Cenozoic intraplate volcanism in the SABP is still a controversial issue. In this work we apply a novel technique of multiscale global tomography to study the whole-mantle 3-D P-wave velocity (Vp) structure beneath the SABP. Our results show that low-Vp anomalies prevail in the whole mantle beneath the SABP. Although the strongest low-Vp zones exist beneath Hainan, significant low-Vp anomalies are also visible in the mantle beneath other parts of the SABP. These low-Vp anomalies appear somehow independent, rather than deriving from a single plume. We deem that a cluster of plumes rather than a single plume existed in the Cenozoic and may still exist now in the mantle beneath the SABP, though the Hainan plume may be the strongest one. A geochemical study suggested that the Hainan plume upwelling might be slowing down and close to exhausting its source zone. This geochemical inference is supported by our tomographic images showing that the low-Vp zones under Hainan are weak and intermittent in the lower mantle (∼700–2889 km depths). The low-Vp zones in the mantle beneath other SABP Cenozoic volcanoes are also weak, suggesting that those mantle plumes, if any, are also dying or already dead. As compared with a strong single plume, each member in a plume cluster should be small and weak, and so hard to exist long. The SABP is surrounded by subduction zones. The hot mantle upwelling beneath the SABP might be caused by collapsing of subducted slabs down to the lowermost mantle.

French clitic climbing as periphrasis

Summary In this article, we propose a treatment of French clitic climbing as an instance of morphological periphrasis. In particular we reexamine the evidence in favour of argument composition and a flat VP structure with tense auxiliaries (Abeillé & Godard, 2002) and show (i) that the V (vs. VP) status of the complement does not strictly correlate with the possibility of clitic climbing, (ii) that transparency in bounded dependencies transcends the class of argument composition verbs, and (iii) that a flat VP structure complicates the treatment of modification and coordination. Adopting an approach in terms of periphrastic realisation along the lines of Bonami (2015), we provide a treatment of the climbing facts that does full justice to the limited mobility and their morphologically bound status (Miller, 1992) without having to rely on a flat VP structure. Finally, we show that the pronominalisation and extraction facts can be dealt with in a uniform fashion by way of constraints on canonical vs. non-canonical argument realisation.

Three dimensional crustal Vp structure beneath the Pearl River Estuary from joint onshore-offshore seismic experiment

<p>The Pear River Estuary (PRE) area is located in the northern margin of South China Sea (SCS), which is a typical rifted passive continental margin between the South China Block and SCS Basin. The Littoral Fault Zone (LFZ) crossing the PRE is an important seismogenic and boundary fault. Strong earthquakes occurred in both the west and east segments. While, the middle segment of the LFZ in PRE area is lack of large earthquake and possibly a seismic gap. Imaging the fine structure of the PRE area is helpful to understand the background of the spatial heterogeneity of seismicity. To explore the crustal structure of the PRE area, we carried an active-source experiment in July 2015. During the experiment, an airgun array composed of four individual airguns with total volume of 6000 in<sup>3</sup> mounted on SCSIO’s R/V Shiyan II was used as the seismic source. A total of 12200 shots were fired every 300 meters along 10 NW and 3 NE-trending shooting profiles. Six dynamite sources with a charge range from 1000 to 2500 kg were also shot on the land. During the experiment, 431 receivers including 29 ocean bottom seismographs (OBS), 256 short period seismometers, and 146 broadband seismometers were available. We manually picked Pg arrivals from the airgun and dynamite sources. We calculated a minimum 1D velocity model by VELEST. We then obtained the upper crust Vp structure using three-dimensional seismic tomography. Our preliminary result reveals that the Vp is consistent with local geological settings. There are low velocity anomaly beneath the LFZ and obvious velocity anomalies across the NW- and NE-trending active faults, which maybe potential threat to the Greater Bay Area.</p>

Interaction between interplate fault topography and tsunamigenic structures at the subduction zone offshore West Mexico

<p>The megathrust topography is key in conditioning the structural integrity of the overriding plate, and thus, the generation of tsunamigenic structures. Our objective is to investigate the Rivera subduction zone, offshore the Mexican Pacific coast, known for hosting large megathrust tsunamigenic earthquakes (Mw > 7.5), and where little is known regarding the distribution of tsunamigenic structures along the margin. Our working hypothesis is that there is an interaction between the megathrust relief at the surface of the subducted slab (Rivera Plate) and the existence of tsunamigenic structures in the above unsubducted plate (North America). To investigate this interaction, we used seismic methods to characterize the variations of the physical properties of the overriding plate, generally related to tectonic (faults) structures that are sources of tsunamis, with the reliefs of the deeper subducted plate obtained with the same method. Here, we use spatially coincident 2D multichannel seismic (MCS, 5.85 km long-streamer) and active marine wide-angle seismic (WAS) data acquired during the TSUJAL survey in 2014 offshore west of Mexico to measure structural variations of the overriding plate and the megathrust interface. We have jointly inverted refracted and reflected travel-times (TT) from both MCS and WAS data to constrain the P-wave velocity (Vp) structure of the overriding plate and the geometry of the megathrust. Before the inversion and to increase the amount of refracted TT we have applied the downward continuation technique to MCS field data allowing to better image the refracted waves in the records. MCS data has a higher spatial sampling than OBS data, which translates into a higher density sampling of the refracted waves and hence the tomographic resolution. Therefore, the resulting tomographic model displays small-scale velocity structure variations of the overriding plate and the megathrust relief that would not be resolved with TT from OBS data only. We used further refracted and reflected TT from OBS data to constrain the Vp structure of the subducting oceanic plate and the geometry of the oceanic Moho. The inverted megathrust interface obtained with the tomography shows clear topographic features in its shallow portion (<~10 km from the trench). Such topographic variations are smaller than the average size of seamounts of the Rivera plate, but they are similar to the seafloor fabric generated by a relict East Pacific Rise segment identified west of the trench in the bathymetry map of the region. Time-migrated images were also obtained after processing the MCS data to constrain the tectonic framework of the shallow subduction zone regardless of the tomographic models. The seismic sections reveal the lack of an extensive accretionary prism, implying that subduction-erosion dominates the structure of the margin in this region. Integrating all the data results, we find that megathrust highs correlate with low-velocity anomalies, suggesting the presence of fluids, and correlate with the presence of extensional faults in the overriding plate as well. This correlation demonstrates the control that megathrust topography exerts on the formation of tsunamigenic structures along the Rivera plate boundary.</p>