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  1. Free, publicly-accessible full text available May 1, 2024
  2. Abstract On 19 September 2022, a major earthquake struck the northwestern Michoacán segment along the Mexican subduction zone. A slip model is obtained that satisfactorily explains geodetic, teleseismic, and tsunami observations of the 2022 event. The preferred model has a compact large-slip patch that extends up-dip and northwestward from the hypocenter and directly overlaps a 1973 Mw 7.6 rupture. Slip is concentrated offshore and below the coast at depths from 10 to 30 km with a peak value of ∼2.9 m, and there is no detected coseismic slip near the trench. The total seismic moment is 3.1×1020  N·m (Mw 7.6), 72% of which is concentrated in the first 30 s. Most aftershocks are distributed in an up-dip area of the mainshock that has small coseismic slip, suggesting near-complete strain release in the large-slip patch. Teleseismic P waveforms of the 2022 and 1973 earthquakes are similar in duration and complexity with high cross-correlation coefficients of 0.68–0.98 for long P to PP signal time windows, indicating that the 2022 earthquake is a quasi-repeat of the 1973 earthquake, possibly indicating persistent frictional properties. Both the events produced more complex P waveforms than comparable size events along Guerrero and Oaxaca, reflecting differences in patchy locking of the Mexican megathrust. 
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    Free, publicly-accessible full text available April 1, 2024
  3. ABSTRACT The largest earthquake since 1954 to strike the state of Nevada, United States, ruptured on 15 May 2020 along the Monte Cristo range of west-central Nevada. The Mw 6.5 event involved predominantly left-lateral strike-slip faulting with minor normal components on three aligned east–west-trending faults that vary in strike by 23°. The kinematic rupture process is determined by joint inversion of Global Navigation Satellite Systems displacements, Interferometric Synthetic Aperture Radar (InSAR) data, regional strong motions, and teleseismic P and SH waves, with the three-fault geometry being constrained by InSAR surface deformation observations, surface ruptures, and relocated aftershock distributions. The average rupture velocity is 1.5  km/s, with a peak slip of ∼1.6  m and a ∼20  s rupture duration. The seismic moment is 6.9×1018  N·m. Complex surface deformation is observed near the fault junction, with a deep near-vertical fault and a southeast-dipping fault at shallow depth on the western segment, along which normal-faulting aftershocks are observed. There is a shallow slip deficit in the Nevada ruptures, probably due to the immature fault system. The causative faults had not been previously identified and are located near the transition from the Walker Lane belt to the Basin and Range province. The east–west geometry of the system is consistent with the eastward extension of the Mina Deflection of the Walker Lane north of the White Mountains. 
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  4. Abstract

    On 29 July 2021, anMW8.2 thrust‐faulting earthquake ruptured offshore of the Alaska Peninsula within the rupture zone of the 1938MW8.2 earthquake. The spatiotemporal distribution of megathrust slip is resolved by jointly inverting regional and teleseismic broadband waveforms along with co‐seismic static and high‐rate GNSS displacements. The primarily unilateral rupture expanded northeastward, away from the rupture zone of the 22 July 2020MW7.8 Shumagin earthquake. Large slip extends along approximately 175 km, spanning about two third of the estimated 1938 aftershock zone, with well‐bounded depth from 20 to 40 km, and up to 8.6 m slip near the hypocenter. The rupture terminated in the eastern portion of the 1938 aftershock zone in a region of very large geodetic slip deficit where peak slip appears to have occurred in the 1938 rupture. The 2021 and 1938 events do not have similar slip distributions and do not indicate persistent asperities.

     
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  5. Abstract

    The eastern portion of the Shumagin gap along the Alaska Peninsula ruptured in anMW7.8 thrust earthquake on 22 July 2020. The megathrust fault space‐time slip history is determined by joint inversion of regional and teleseismic waveform data along with co‐seismic static Global Navigation Satellite System (GNSS) displacements. The rupture expanded westward and along‐dip from the hypocenter, located adjacent to the 1938MW8.2 Alaska earthquake, with slip and aftershocks extending into the gap about 180 to 205 km, respectively, at depths from 15 to 40 km. The deeper half of ~75% of the Shumagin gap experienced faulting. However, the patchy slip is significantly less than possible accumulated slip since the region's last major rupture in 1917, compatible with geodetic seismic‐coupling estimates of 10‐40% beneath the Shumagin Islands. The rupture terminated in the western region of very low seismic coupling. There was a regional decade‐scale decrease in b‐value prior to the 2020 event.

     
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  6. Abstract

    A vigorous shallow earthquake sequence along the southern coast of Puerto Rico commenced on 28 December 2019 in a region with little prior large seismicity. The largest event in the sequence (MW = 6.4), struck on 7 January 2020 and involved normal faulting. It produced extensive damage in southern Puerto Rico and power disruption across the island. Nearby strong ground motions and static offsets from GPS stations along with teleseismic recordings are inverted for the kinematic rupture process of the mainshock. The ~15‐km‐long rupture is spatially concentrated, with most slip between 3 and 13 km deep and peak slip of ~1.6 m. The static stress drop is high, ~19 MPa, with the rupture locating in the eastern section of a ~30‐km‐long band of seismicity bisected by a near‐orthogonal lineation. Complex faulting and high stress in the intraplate region appears to be responsible for the high earthquake productivity.

     
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  7. Abstract

    On 4 and 6 July 2019, two large strike‐slip earthquakes withW‐phase moment magnitudesMWW6.5 (foreshock) andMWW7.1 (mainshock) struck the Eastern California Shear Zone, northeast of Ridgecrest. The faulting geometry and kinematic coseismic slip distribution of both events are determined by jointly inverting seismological and geodetic observations guided by aftershock and surface rupture locations. The foreshock ruptured two orthogonal faults with a prominent L‐shaped geometry with maximum slip of ~1.1 m on the NE‐SW segment. The mainshock faulting extended NW‐SE along several primary fault segments that straddle the foreshock slip. The surface rupture and slip model indicate mostly near‐horizontal strike‐slip motion with maximum slip of ~3.7 m, but there is a localized vertical dip‐slip motion. Both the foreshock and mainshock ruptures terminate in regions of complex surface offsets. High aftershock productivity and low rupture velocity may be the result of rupture of a relatively immature fault system.

     
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  8. Abstract

    Crystal phase control still remains a challenge for the precise synthesis of 2D layered metal dichalcogenide (LMD) materials. The T′ phase structure has profound influences on enhancing electrical conductivity, increasing active sites, and improving intrinsic catalytic activity, which are urgently needed for enhancing hydrogen evolution reaction (HER) activity. Theoretical calculations suggest that metastable T′ phase 2D Sn1−xWxS2alloys can be formed by combining W with 1T tin disulfide (SnS2) as a template to achieve a semiconductor‐to‐metallic transition. Herein, 2D Sn1−xWxS2alloys with varyingxare prepared by adjusting the molar ratio of reactants via hydrothermal synthesis, among which Sn0.3W0.7S2displays a maximum of concentration of 81% in the metallic phase and features a distorted octahedral‐coordinated metastable 1T′ phase structure. The obtained 1T′‐Sn0.3W0.7S2has high intrinsic electrical conductivity, lattice distortion, and defects, showing a prominently improved HER catalytic performance. Metallic Sn0.3W0.7S2coupled with carbon black exhibits at least a 215‐fold improvement compared to pristine SnS2. It has excellent long‐term durability and HER activity. This work reveals a general phase transition strategy by using T phase materials as templates and merging heteroatoms to achieve synthetic metastable phase 2D LMDs that have a significantly improved HER catalytic performance.

     
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