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  • 1
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    Aseismic slip transients emerge spontaneously in three-dimensional rate and state modeling of subduction earthquake sequences (2005)
    In:  J. Geophys. Res., Kunming, China, Inst. f. Theoret. Geodäsie, vol. 110, no. B8, pp. 771-785, pp. B08307, (ISSN: 1340-4202)
    Details
    Publication Date: 2005
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Friction ; Subduction zone ; Modelling ; Creep observations and analysis ; Three dimensional ; Seismicity ; JGR
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Isolated cases of remote dynamic triggering in Canada detected using cataloged earthquakes combined with a matched-filter approach (2015)
    Wiley
    Details
    Publication Date: 2015-06-04
    Description: Here we search for dynamically triggered earthquakes in Canada following global mainshocks between 2004 and 2014 with M S 〉 6, depth 〈 100 km, and estimated peak ground velocity 〉 0.2 cm/s. We use the Natural Resources Canada (NRCan) earthquake catalog to calculate β-statistical values in 1°×1° bins in 10-day windows before and after the mainshocks. The statistical analysis suggests triggering may occur near Vancouver Island, along the border of the Yukon and Northwest Territories, in western Alberta, western Ontario, and the Charlevoix seismic zone. We also search for triggering in Alberta where denser seismic station coverage renders regional earthquake catalogs with lower completeness thresholds. We find remote triggering in Alberta associated with three mainshocks using a matched-filter approach on continuous waveform data. The increased number of local earthquakes following the passage of mainshock surface waves suggests local faults may be in a critically stressed state.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    MicroRNA-155 Regulates ROS Production, NO Generation, Apoptosis and Multiple Functions of Human Brain Microvessel Endothelial Cells Under Physiological and Pathological Conditions (2015)
    Wiley
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    Publication Date: 2015-05-27
    Description: The microRNA-155 (miR155) regulates various functions of cells. Dysfunction or injury of endothelial cells (ECs) plays an important role in the pathogenesis of various vascular diseases. In this study, we investigated the role and potential mechanisms of miR155 in human brain microvessel endothelial cells (HBMECs) under physiological and pathological conditions. We detected the effects of miR155 silencing on ROS production, NO generation, apoptosis and functions of HBMECs at basal and in response to oxidized low density lipoprotein (ox-LDL). Western blot and q-PCR were used for analyzing the gene expression of epidermal growth factor receptor (EGFR)/ extracellular regulated protein kinases (ERK)/ p38 mitogen-activated protein kinase (p38 MAPK), phosphatidylinositol-3-kinase (PI3K) and serine/threonine kinase(Akt), activated caspase-3 and intercellular adhesion molecule-1 (ICAM-1). Results showed that under both basal and challenge situations: 1) Silencing of miR155 decreased apoptosis and reactive oxygen species (ROS) production of HBMECs, whereas, promoted nitric oxide (NO) generation. 2) Silencing of miR155 increased the proliferation, migration and tube formation ability of HBMECs, while decreased cell adhesion ability. 3) Gene expression analyses showed that EGFR/ ERK/ p38 MAPK and PI3K/Akt were increased and that activated caspase-3 and ICAM-1 mRNA were decreased after knockdown of miR155. In conclusion, knockdown of miR155 could modulate ROS production, NO generation, apoptosis and function of HBMECs via regulating diverse gene expression, such as caspase-3, ICAM-1 and EGFR/ERK/p38 MAPK and PI3K/Akt pathways. This article is protected by copyright. All rights reserved
    Electronic ISSN: 0091-7419
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Published by Wiley
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  • 4
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    Spatiotemporal evolution of slow slip events in a non-planar fault model for northern Cascadia subduction zone (2016)
    Wiley
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    Publication Date: 2016-08-02
    Description: Slow slip events (SSEs) are identified as the quasi-stable fault deformation in the deep transition zone from locked to continuous sliding in many subduction zones. In the well-instrumented Cascadia margin, a class of Mw6.0 slow slip events arise beneath Port Angeles every ∼14 months, as inferred from two decades of continuous geodetic monitoring. The along-strike bending of the incoming oceanic plate beneath north Washington is a unique geometric feature whose influence on slow slip processes is still unknown. Here we incorporate a realistic fault geometry of northern Cascadia in the framework of rate- and state-dependent friction law, to simulate the spatiotemporal evolution of slow slip events on a non-planar subduction fault. The modeled SSEs capture the major characteristics revealed by GPS observations. The central 150km-long fault segment beneath Port Angeles acts as a repetitive slip patch, where SSEs appear every ∼1.5 years with a maximum slip of ∼2.5 cm. Two minor slip patches with smaller areas and cumulative slips straddle this central slip patch. The along-strike segmentation of slow slip is inversely related to the local fault dip and strike angles of the slow slip zone, suggesting strong geometrical control on the slow slip process. This correlation holds even after removing the effect of W / h ∗ , ratio between velocity-weakening SSE fault width and characteristic nucleation size. Besides the GPS-detectable fast-spreading phase, we find that each SSE cycle consists of deep pre-SSE preparation and post-SSE relaxation phases, which may be the driving mechanism for the deep inter-ETS tremor activity discovered in Cascadia.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Joint analysis of the 2014 Kangding, southwest China, earthquake sequence with seismicity relocation and InSAR inversion (2015)
    Wiley
    Details
    Publication Date: 2015-04-19
    Description: Over 1000 earthquakes struck the northwest of Kangding on the Xianshuihe fault in southwest China between November 22 and 29, 2014, including two largest events of Mw 5.9 and Mw 5.6. The hypocenters of 799 relocated earthquakes suggest that two independent mainshock–aftershock sub-sequences occurred on the Selaha and Zheduotang branches of the Xianshuihe fault, respectively. Fault slip inversion results from one InSAR interferogram (09/26/2014-12/05/2014) show that the Mw 5.9 mainshock produced a maximum slip of ~0.47 m at the depth of ~9 km. However, there is no distinct slip associated with the Mw 5.6 mainshock. The InSAR determined moment is 2.36 × 10 18  N m with a rigidity of 30 GPa, equivalent to Mw 6.2, which is about two-fold the total seismic moment of all the recorded earthquakes during the InSAR time span. This large discrepancy between geodetic and seismic moment estimates indicates that there was probably rapid aseismic afterslip in the two weeks following the Mw 5.9 mainshock. The released seismic energy of this earthquake sequence is far less than the accumulated strain energy since the 1955  M earthquake on the same fault branch, which implies that the seismic risk on the Selaha-Kangding segment of the Xianshuihe fault remains high.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    m6A facilitates hippocampus-dependent learning and memory through YTHDF1 (2018)
    Springer Nature
    In: Nature
    Details
    Publication Date: 2018
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 7
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    Poroelastic Stress Triggering of the December 2013 Crooked Lake, Alberta, Induced Seismicity Sequence (2016)
    Wiley
    Details
    Publication Date: 2016-08-13
    Description: The Crooked Lake area in Central Alberta, Canada, became seismically active in December 2013 with a sequence of earthquakes Mw2.0 and higher. The earthquakes are suspected to be induced by hydraulic fracturing in nearby horizontal wells due to their strong spatiotemporal correlation. To investigate the physical mechanism of the induced seismicity near Crooked Lake, we calculate stress and pore pressure perturbations resulting from high-rate multi-stage fluid injection in the framework of linear poroelasticity. The calculated perturbations are used for seismic risk analysis based on the Coulomb failure criterion. Results show that most seismicity is within a positive Coulomb stress change regime, indicating failure is promoted by injection of fluid . By comparing Coulomb stress results for different parameter settings, we show that elastic response of the solid matrix, instead of fluid diffusion, is more likely the dominant factor for the induced earthquakes shortly after fluid injection.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Geodetic imaging of potential seismogenic asperities on the Xianshuihe-Anninghe-Zemuhe fault system, southwest China, with a new 3D viscoelastic interseismic coupling model (2015)
    Wiley
    Details
    Publication Date: 2015-02-05
    Description: We use GPS and InSAR measurements to image the spatial variation of interseismic coupling on the Xianshuihe-Anninghe-Zemuhe (XAZ) fault system. A new 3D viscoelastic interseismic deformation model is developed to infer the rotation and strain rates of blocks, postseismic viscoelastic relaxation, and interseismic slip deficit on the fault surface discretized with triangular dislocation patches. The inversions of synthetic data show the optimal weight ratio and smoothing factor are both 1. The successive joint inversions of geodetic data with different viscosities reveal six potential fully coupled asperities on the XAZ fault system. Among them, the potential asperity between Shimian and Mianning, which does not exist in the case of 10 19 Pa s, is confirmed by the published micro-earthquake depth profile. Besides, there is another potential partially coupled asperity between Daofu and Kangding with a length scale up to 140 km. All these asperity sizes are larger than the minimum resolvable wavelength. The minimum and maximum slip deficit rates near the Moxi town are 7.0 and 12.7 mm/yr respectively. Different viscosities have little influence on the roughness of the slip deficit rate distribution and the fitting residuals, which probably suggests that our observations cannot provide a good constraint on the viscosity of the middle-lower crust. The calculation of seismic moment accumulation on each segment indicates the Songlinkou-Selaha (S4), Shimian-Mianning (S7), and Mianning-Xichang (S8) segments are very close to the rupture of characteristic earthquakes. However, the confidence level is confined by sparse near-fault observations.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Discriminating induced seismicity from natural earthquakes using moment tensors and source spectra (2016)
    Wiley
    Details
    Publication Date: 2016-01-28
    Description: Earthquake source mechanisms and spectra can provide important clues to aid in discriminating between natural and induced events. In this study, we calculate moment tensors and stress drop values for eight recent induced earthquakes in the Western Canadian Sedimentary Basin with magnitudes between 3.2 and 4.4, as well as a nearby magnitude 5.3 event that is interpreted as a natural earthquake. We calculate full moment tensor solutions by performing a waveform-fitting procedure based on a 1-D transversely isotropic velocity model. In addition to a dominant double-couple (DC) signature that is common to nearly all events, most induced events exhibit significant non-double-couple components. A parameter sensitivity analysis indicates that spurious non-DC components are negligible if the signal to noise ratio (SNR) exceeds 10 and if the 1-D model differs from the true velocity structure by less than 5%. Estimated focal depths of induced events are significantly shallower than the typical range of focal depths for intraplate earthquakes in the Canadian Shield. Stress drops of the eight induced events were estimated using a generalized spectral-fitting method and fall within the typical range of 2 to 90 MPa for tectonic earthquakes. Elastic moduli changes due to the brittle damage production at the source, presence of multiple intersecting fractures, dilatant jogs created at the overlapping areas of multiple fractures, or non-planar pre-existing faults may explain the non-DC components for induced events.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Frictional behavior of oceanic transform faults and its influence on earthquake characteristics (2012)
    Wiley
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    Publication Date: 2012-04-26
    Description: We use a three-dimensional strike-slip fault model in the framework of rate and state-dependent friction to investigate earthquake behavior and scaling relations on oceanic transform faults (OTFs). Gabbro friction data under hydrothermal conditions are mapped onto OTFs using temperatures from (1) a half-space cooling model, and (2) a thermal model that incorporates a visco-plastic rheology, non-Newtonian viscous flow and the effects of shear heating and hydrothermal circulation. Without introducing small-scale frictional heterogeneities on the fault, our model predicts that an OTF segment can transition between seismic and aseismic slip over many earthquake cycles, consistent with the multimode hypothesis for OTF ruptures. The average seismic coupling coefficient χ is strongly dependent on the ratio of seismogenic zone width W to earthquake nucleation size h*; χ increases by four orders of magnitude as W/h* increases from ∼1 to 2. Specifically, the average χ = 0.15 ± 0.05 derived from global OTF earthquake catalogs can be reached at W/h* ≈ 1.2–1.7. Further, in all simulations the area of the largest earthquake rupture is less than the total seismogenic area and we predict a deficiency of large earthquakes on long transforms, which is also consistent with observations. To match these observations over this narrow range of W/h* requires an increase in the characteristic slip distance dc as the seismogenic zone becomes wider and normal stress is higher on long transforms. Earthquake magnitude and distribution on the Gofar and Romanche transforms are better predicted by simulations using the visco-plastic model than the half-space cooling model.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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