Tomographic inversion of OBS converted shear waves:case study of profile EW6 in the Dongsha area

Studies of converted S-wave data recorded on the ocean bottom seismometer(OBS)allow for the estimation of crustal S-wave velocity,from which is further derived the Vp/Vs ratio to constrain the crustal lithology and geophysical properties.Constructing a precise S-wave velocity model is important for deep structural research,and inversion of converted S-waves provides a potential solution.However,the inversion of the converted S-wave remains a weakness because of the complexity of the seismic ray path and the inconsistent conversion interface.In this study,we introduced two travel time correction methods for the S-wave velocity inversion and imaged different S-wave velocity structures in accordance with the corresponding corrected S-wave phases using seismic data of profile EW6 in the northeastern South China Sea(SCS).The two inversion models show a similar trend in velocities,and the velocity difference is<0.15 km/s(mostly in the range of 0–0.1 km/s),indicating the accuracy of the two travel time correction methods and the reliability of the inversion results.According to simulations of seismic ray tracing based on different models,the velocity of sediments is the primary influencing factor in ray tracing for S-wave phases.If the sedimentary layer has high velocities,the near offset crustal S-wave refractions cannot be traced.In contrast,the ray tracing of Moho S-wave reflections was not significantly impacted by the velocity of the sediments.The two travel time correction methods have their own advantages,and the application of different approaches is based on additional requirements.These works provide an important reference for future improvements in converted S-wave research.

Submarine volcanism in the southern margin of the South China Sea

Submarine volcanism is widely developed in the South China Sea(SCS).However,the characteristics,distribution,and genesis of submarine volcanoes in the southern margin of the SCS remain obscure.In this study,we analyzed the characteristics of submarine volcanoes and identified a total of 43 submarine volcanoes in the southern margin of the SCS,based on a newly acquired 310-km seismic reflection profile,along with previous 45 multi-channel seismic(MCS)profiles,petrological results from volcanic rocks sampled by dredging and drilling,nearby ocean bottom seismometer(OBS)wide-angle seismic profiles,and gravity and magnetic data.The study ascertains that most of these volcanoes are located in fault-block belts and graben-horst zones with strong crustal stretching and thinning.These volcanoes exhibit positive high-amplitude external seismic reflections,weak and chaotic internal seismic reflections,and are accompanied by local deformation of the surrounding sedimentary strata.Meanwhile,they have higher positive gravity anomalies and higher magnetic anomalies than the background strata.The petrological dating results show that volcanic ages are primarily in the Pliocene-Pleistocene,with geochemical characteristics indicating dominance of oceanic island basalt(OIB)-type alkali-basalts.Extensional faults have obviously spatial correspondence with post-spreading volcanism,suggesting these faults may provide conduits for submarine volcanism.The high-velocity bodies(HVBs)in the lower crust and magma underplating exist in the southern SCS,which could provide a clue of genesis for submarine volcanism.The inference is that the intensity of post-spreading volcanism in the southern margin might be affected by stretching faults,crustal thinning and magma underplating.

IL-13/IL-13RA2 signaling promotes colorectal cancer stem cell tumorigenesis by inducing ubiquitinated degradation of p53

Cancer stem cells(CSCs)are considered tumor-initiating cells and the main drivers of disease progression.Targeting these rare cancer cells,however,remains challenging with respect to therapeutic benefit.Here,we report the up-regulation of IL-13RA2 expression in colorectal cancer(CRC)tissues and spheroid cells.The expression of IL-13RA2 was positively correlated with canonical stemness markers in CRC.We further demonstrated that the level of IL-13 was up-regulated in the serum of CRC patients.Biologically,recombinant IL-13(rIL13)stimulation promoted the sphere formation,proliferation,and migration of CRC cells in vitro and enhanced tumorigenesis in vivo.This phenotype could be reversed by knocking down IL-13RA2.Mechanistically,IL-13 activated autophagy by inducing LC3I/LC3II transformation in CRC-CSCs,which was crucial for the biological functions of IL-13.We further demonstrated that IL-13RA2 acted as a modular link of the E3 ligase UBE3C and the substrate p53 protein,enhancing the interaction of UBE3C and p53,thereby inducing the K48-linked ubiquitination of p53.In conclusion,the IL-13/IL-13RA2 signaling cascade promotes CRC-CSC self-renewal and tumorigenesis by inducing p53 ubiquitination,adding an important layer to the connection between IL-13 and p53,which can be translated into novel targeted therapies.

Hyperextended crustal structure of the Qiongdongnan Basin and subsequent magmatic influence from the Hainan mantle plume

The Qiongdongnan Basin(QDNB)is a rift basin located in the extension direction of the oceanic ridge of the Northwest Subbasin of the South China Sea.This basin is surrounded by Late Cenozoic Ocean Island Basalts(OIBs)magmatism associated with the putative Hainan mantle plume.However,how the Hainan mantle plume has affected the QDNB has not been studied in detail.To reveal the crustal structure of the QDNB and the possible influence of the Hainan mantle plume,we conducted a wide-angle seismic exploration from Hainan Island across the QDNB to the Xisha Block,and obtained the crustal structure by travel-time tomography.The results show that the crustal stretching factors of the Northern and Southern Rises of the QDNB are estimated to be 1.3-2.0,indicating slight or moderate crustal thinning.Whereas,the crustal stretching factor in the Central Depression of the QDNB is estimated to be more than 3.0,which means that the crust has been hyperextended.Controlled by two detachment faults(F2 and F11),the upper and lower crust show brittle and ductile thinning,respectively.Three anomalous low-velocity conduits penetrating the crystalline crust are developed in the Songnan Uplift and the Southern Rise of the QDNB.Their P-wave velocities are 5.5-6.0 km s^(−1),which are significantly lower than those of the surrounding crust(6.0-6.8 km s^(−1)).The Late Cenozoic magmatic intrusions(e.g.,sills and dikes)and hydrothermal activities can be observed in the sedimentary strata above these low-velocity conduits.We interpret that the low-velocity conduits might be the crustal magmatic footprints of the Hainan mantle plume,due to the correlated distributions of OIB-type magmatism,the magmatic intrusion patterns,the deep structure of the Hainan mantle plume and the high heat flow of 95 mW m^(−2).Thus,we propose that the crustal structure of the QDNB is the product of crustal hyperextension in the rifting stage and subsequently affected by the Hainan mantle plume magmatism.This study provides a typical case for understanding the influence of a mantle plume on the continental crust with pre-existing rift structures.