Megathrust earthquake occurrence is dependent on the physical properties and stress environments of convergent plate boundaries. Local and regional earthquakes may modulate the stress environment ...fractionally that affects the nucleation of next earthquakes. This study investigates the influence of precedent earthquakes on the induction of forthcoming earthquakes around the circum‐Pacific plate boundaries. We assess the global stress perturbation induced by 1,636 earthquakes combining 1,457 earthquakes with moment magnitudes greater than or equal to MW7.0 and 179 earthquakes with moment magnitudes MW6.4–6.9 in 1900–2020. We stack the induced Coulomb stress changes for optimally oriented reverse faults. The circum‐Pacific region is divided by eight subregions. The cumulative Coulomb stress changes reach up to the order of tens to hundreds of bar at the convergent plate boundaries. Descendant large earthquakes dominantly occurred in the regions with large lateral gradients of cumulative Coulomb stress changes induced by precedent earthquakes. The cumulative Coulomb stress changes for 120 years are comparable among subduction zones. The seismicity in subduction zones may depend on the strength of the stress field as well as the lateral gradient in the stress field. The instability and inhomogeneity in stress fields may play a major role in the nucleation of megathrust earthquakes.
Plain Language Summary
Great earthquakes produce significant damages over large areas. The timely identification of impending earthquakes is crucial for seismic hazard mitigation. We assess the stress induced from neighboring earthquakes for 120 years around the circum‐Pacific plate boundaries. Large earthquakes perturbed the stress fields. We analyze 1,636 earthquakes with moment magnitudes greater than or equal to 6.4 in 1900–2020. The cumulative Coulomb stress changes reach up to the order of tens to hundreds of bar at the plate boundaries. Large earthquakes followed in the regions with large lateral gradients of cumulative Coulomb stress changes induced by precedent earthquakes. Laterally heterogeneous stress fields may play an important role in nucleation of great earthquakes.
Key Points
The stress fields in subduction zones were highly perturbed by precedent large earthquakes
Descendant large earthquakes dominantly occur in the regions of high stress contrasts
The stress perturbation by precedent earthquakes may be a major factor controlling global seismicity
Layered lithium–nickel–cobalt–manganese oxide (NCM) materials have emerged as promising alternative cathode materials owing to their high energy density and electrochemical stability. Although high ...reversible capacity has been achieved for Ni‐rich NCM materials when charged beyond 4.2 V versus Li+/Li, full lithium utilization is hindered by the pronounced structural degradation and electrolyte decomposition. Herein, the unexpected realization of sustained working voltage as well as improved electrochemical performance upon electrochemical cycling at a high operating voltage of 4.9 V in the Ni‐rich NCM LiNi0.895Co0.085Mn0.02O2 is presented. The improved electrochemical performance at a high working voltage at 4.9 V is attributed to the removal of the resistive Ni2+O rock‐salt surface layer, which stabilizes the voltage profile and improves retention of the energy density during electrochemical cycling. The manifestation of the layered Ni2+O rock‐salt phase along with the structural evolution related to the metal dissolution are probed using in situ X‐ray diffraction, neutron diffraction, transmission electron microscopy, and X‐ray absorption spectroscopy. The findings help unravel the structural complexities associated with high working voltages and offer insight for the design of advanced battery materials, enabling the realization of fully reversible lithium extraction in Ni‐rich NCM materials.
Structural and electrochemical stabilization of Ni‐rich LiNixCoyMn1−x−yO2 (NCM) materials under high‐voltage battery operation is demonstrated. The improved electrochemical performance at a high working voltage at 4.9 V is attributed to the removal of the resistive Ni2+O rock‐salt surface layer, which stabilizes the voltage profile and improves retention of the energy density during electrochemical cycling.
The distance-dependent coseismic and postseismic displacements produced by the 2011 M
9.0 Tohoku-Oki megathrust earthquake caused medium weakening and stress perturbation in the crust around the ...Korean Peninsula, increasing the seismicity with successive M
5-level earthquakes at the outskirts of high seismicity regions. The average M
5-level occurrence rate prior to the megathrust earthquake was 0.15 yr
(0.05-0.35 yr
at a 95% confidence level), and the rate has increased to 0.71 yr
(0.23-1.67 yr
at a 95% confidence level) since the megathrust earthquake. The 2016 M
5-level midcrustal earthquakes additionally changed the stress field in adjacent regions, inducing the 15 November 2017 M
5.4 earthquake. The successive 2016 and 2017 moderate-size earthquakes built complex stress fields in the southeastern Korean Peninsula, increasing the seismic hazard risks in the regions of long-term stress accumulation. The increased seismic risks may continue until the medium properties and stress field are recovered.
We investigated VP/VS changes in the upper crust of the Japanese islands after the 2011 MW9.0 Tohoku‐Oki megathrust earthquake. Abrupt VP/VS changes with azimuth‐dependent variations were observed ...after the megathrust earthquake. The VP/VS changes ranged between −0.0458 (±0.0012) and 0.0422 (±0.0033). Large localized VP/VS changes over regional distances suggested medium‐dependent deformation. Peak VP/VS changes were observed along paths subparallel or subperpendicular to the directions toward the megathrust earthquake. The VP/VS changes displayed characteristic 2θ variations as a function of the azimuth difference, suggesting azimuthal seismic anisotropy. The VP/VS ratio recovered gradually over time. Some regions presented permanent VP/VS changes. The azimuthal seismic anisotropy may have developed from preferential crack orientation as a consequence of the combined effects of lithospheric displacements and a depth‐dependent ambient stress field. It appears that recovery of the medium properties may take decades.
Plain Language Summary
We report a unique observation of azimuthal seismic anisotropy in the upper crust of Japanese islands, which was induced by the 2011 M9.0 Tohoku‐Oki megathrust earthquake. The azimuthal seismic anisotropy was caused by the direction‐dependent discriminative lithospheric displacement during the megathrust earthquake. We analyzed the traveltimes of local seismic waves and estimated the changes in Vp/Vs ratios after the megathrust earthquake. We observed the abrupt Vp/Vs changes after the megathrust earthquake. The Vp/Vs ratios recovered gradually with time for several years. This study may provide important information on the medium property changes after the megathrust earthquake and will be useful for mitigation of potential seismic hazards.
Key Points
Abrupt VP/VS changes occurred in the upper crust of the Japanese islands after the 2011 Tohoku‐Oki megathrust earthquake
Peak VP/VS changes developed along the paths subparallel or subperpendicular to the megathrust
Azimuthal seismic anisotropy developed due to the lithospheric displacements caused by the megathrust earthquake
α-Synuclein is a crucial element in the pathogenesis of Parkinson's disease (PD) and related neurological diseases. Although numerous studies have presented potential mechanisms underlying its ...pathogenesis, the understanding of α-synuclein-mediated neurodegeneration remains far from complete. Here, we show that overexpression of α-synuclein leads to impaired DNA repair and cellular senescence. Transcriptome analysis showed that α-synuclein overexpression led to cellular senescence with activation of the p53 pathway and DNA damage responses (DDRs). Chromatin immunoprecipitation analyses using p53 and γH2AX, chromosomal markers of DNA damage, revealed that these proteins bind to promoters and regulate the expression of DDR and cellular senescence genes. Cellular marker analyses confirmed cellular senescence and the accumulation of DNA double-strand breaks. The non-homologous end joining (NHEJ) DNA repair pathway was activated in α-synuclein-overexpressing cells. However, the expression of MRE11, a key component of the DSB repair system, was reduced, suggesting that the repair pathway induction was incomplete. Neuropathological examination of α-synuclein transgenic mice showed increased levels of phospho-α-synuclein and DNA double-strand breaks, as well as markers of cellular senescence, at an early, presymptomatic stage. These results suggest that the accumulation of DNA double-strand breaks (DSBs) and cellular senescence are intermediaries of α-synuclein-induced pathogenesis in PD.
Mitochondria are crucial for cellular energy metabolism and are involved in signaling, aging, and cell death. They undergo dynamic changes through fusion and fission to adapt to different cellular ...states. In this study, we investigated the effect of knocking out the dynamin 1-like protein (Dnm1l) gene, a key regulator of mitochondrial fission, in neural stem cells (NSCs) differentiated from Dnm1l knockout embryonic stem cells (Dnm1l−/− ESCs). Dnm1l−/− ESC-derived NSCs (Dnm1l−/− NSCs) exhibited similar morphology and NSC marker expression (Sox2, Nestin, and Pax6) to brain-derived NSCs, but lower Nestin and Pax6 expression than both wild-type ESC-derived NSCs (WT-NSCs) and brain-derived NSCs. In addition, compared with WT-NSCs, Dnm1l−/− NSCs exhibited distinct mitochondrial morphology and function, contained more elongated mitochondria, showed reduced mitochondrial respiratory capacity, and showed a metabolic shift toward glycolysis for ATP production. Notably, Dnm1l−/− NSCs exhibited impaired self-renewal ability and accelerated cellular aging during prolonged culture, resulting in decreased proliferation and cell death. Furthermore, Dnm1l−/− NSCs showed elevated levels of inflammation and cell stress markers, suggesting a connection between Dnm1l deficiency and premature aging in NSCs. Therefore, the compromised self-renewal ability and accelerated cellular aging of Dnm1l−/− NSCs may be attributed to mitochondrial fission defects.
Softening of thermoelectric generators facilitates conformal contact with arbitrary-shaped heat sources, which offers an opportunity to realize self-powered wearable applications. However, existing ...wearable thermoelectric devices inevitably exhibit reduced thermoelectric conversion efficiency due to the parasitic heat loss in high-thermal-impedance polymer substrates and poor thermal contact arising from rigid interconnects. Here, we propose compliant thermoelectric generators with intrinsically stretchable interconnects and soft heat conductors that achieve high thermoelectric performance and unprecedented conformability simultaneously. The silver-nanowire-based soft electrodes interconnect bismuth-telluride-based thermoelectric legs, effectively absorbing strain energy, which allows our thermoelectric generators to conform perfectly to curved surfaces. Metal particles magnetically self-assembled in elastomeric substrates form soft heat conductors that significantly enhance the heat transfer to the thermoelectric legs, thereby maximizing energy conversion efficiency on three-dimensional heat sources. Moreover, automated additive manufacturing paves the way for realizing self-powered wearable applications comprising hundreds of thermoelectric legs with high customizability under ambient conditions.
Reduced graphene oxide/alumina composite powders were prepared by mixing of graphene oxides and aluminum ions at the molecular-level. It was found that the composite consolidated from the powders ...showed that reduced graphene oxide were homogeneously dispersed and strongly bonded with the alumina matrix by oxygen atoms presenting at reduced graphene oxide/alumina interfaces. Both the hardness and the toughness of the composites were enhanced simultaneously by the addition of reduced graphene oxide, which act as bridges to restrain the propagation of cracks in the alumina matrix. It is clarified that graphenes can be utilized as promising reinforcements for enhancement in mechanical properties of ceramic materials when the molecular-level mixing process is applied.
Major earthquakes in continental regions may cause significant damage. Preexisting fault system across megacity receives high attention for possible seismic damages. Earthquake occurrence mechanism ...is important to assess the geohazard potentials. Continental‐scale Quaternary fault system is developed across the Seoul metropolitan area where the population is the largest in the Korean Peninsula. Historical seismic‐damage records suggest potential seismic hazards in the Seoul metropolitan area. We investigate the fault motions and spatial distribution of earthquakes in the Seoul metropolitan area using a matched‐filter technique that is based on stacked waveform crosscorrelation functions among densely‐deployed seismic stations. The analysis detects 1103 earthquakes that include 360 events with magnitudes (ML) of −0.6 to 2.0 around the Chugaryeong fault and 34 events with magnitudes of −0.5 to 2.7 around Wangsukcheon, Pocheon, and Yeseonggang faults. The seismicity suggests a set of near‐vertical subparallel (or orthogonal) faults that develop from the major faults. A major fault system behaves as a backbone structure that makes branch faults develop, producing seismicity including major earthquakes. The backbone structure may control the fault development that conforms to the ambient stress field. The backbone faults may play a role to increase geohazard potentials.
Plain Language Summary
The Seoul metropolitan area is the most populated region in the Korean Peninsula. Historical seismic damage records and major Quaternary faults suggest high seismic hazard potentials in the region. The identification of earthquake‐spawning faults is crucial for seismic hazard mitigation. We illuminate the earthquake‐spawning faults from micro to small earthquakes in the Seoul metropolitan. We perform a matched‐filter analysis to find earthquakes in adjacent locations of reported events. Recently‐deployed temporary dense seismic stations allow us to detect microearthquakes in high ambient‐noise environments of the megacity. We detect 1103 earthquakes that include 360 events with magnitudes (ML) of −0.6 to 2.0 around the Chugaryeong fault and 34 events with magnitudes (ML) of −0.5 to 2.7 around Wangsukcheon, Pocheon, and Yeseonggang faults. The earthquake distribution suggests the presence of active near‐vertical subparallel or conjugate faults along the major Quaternary faults that may behave as backbones of earthquake‐spawning faults.
Key Points
Micro to small earthquakes occur around Quaternary faults in the Seoul metropolitan area
Subvertical strike‐slip faults develop along the Quaternary faults, responding to the ambient stress field
Clustered earthquakes occur along conjugate or subparallel faults
The earthquakes in the western East Sea (Sea of Japan) mostly occur in the continental margin off the east coast of the Korean Peninsula. The seismic hazard potentials in and around the western Ease ...Sea are studied based on analyses of tectonic structures, seismicity features, earthquake source properties, Coulomb stress changes, and strong ground motions. The earthquake source mechanisms suggest that paleo-rifting structures in the western East Sea were activated by the current stress field. A low stress cumulation rate results in the occurrence of earthquakes with long recurrence intervals. The background seismicity suggests that earthquakes with magnitudes
M
w
5.0, 6.0, and 7.0 may occur within every
∼
44,
∼
336, and
∼
2550 years at 95 % confidence level. The spatial distribution of earthquakes changes with time. Most earthquakes are clustered within
∼
60 km from the coast. The seismicity analysis indicates an apparent increase of moderate-size (
M
w
3–5) earthquakes since the 2011
M
w
9.0 Tohoku-Oki megathrust earthquake. Static stress changes by moderate-size inland earthquakes induce offshore events. The seismicity and Coulomb stress changes suggest high seismic potentials around the western margin of the Ulleung basin. Earthquakes with magnitudes
M
w
6.0–7.0 in the western East Sea may produce peak ground accelerations of 0.2 g within the distance of
∼
40–80 km, which includes the coastal regions.
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