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Distributed acoustic Sensing (DAS) data collected along a 30 km length of telecommunications fiber crossing the Alpine Fault near Haast enable analysis of interactions between fluvioglacial and seismotectonic processes. Here we use DAS recordings of 25 earthquakes to probe near‐surface structure beneath the Haast river valley. For each earthquake, delayed P‐ and S‐wave arrivals incompatible with a regional velocity model are observed at common locations. We show using a planar slab model that these delayed arrivals are proportional to the thickness of subjacent low‐velocity structures. 3D ray‐tracing reveals basin‐like low‐velocity features of approximately ∼1–4 km width and 200–650 m depth, consistent with independent seismic and gravity measurements collected along partly co‐located lines. We infer these low‐velocity structures to be sediment‐filled erosional basins that may exacerbate ground shaking in large earthquakes. The method developed here is general and highlights the potential of dense DAS measurements to provide high‐resolution subsurface characterization.

To address the seat shaking issue of a certain vehicle model under high-speed conditions, this article utilizes the TPA method, starting from the “source-path-response” perspective. By comparing with benchmark vehicles’ lateral parameters, it confirms the abnormal vibration frequency of the seat as 12Hz in the Z direction. Through real vehicle testing, the validity of this approach is verified, providing clear optimization solutions and improvement suggestions for subsequent vehicle NVH design.

Many chemical methods have been developed to favor a particular product in transformations of compounds that have two or more reactive sites. We explored a different approach to site selectivity using vibrational strong coupling (VSC) between a reactant and the vacuum field of a microfluidic optical cavity. Specifically, we studied the reactivity of a compound bearing two possible silyl bond cleavage sites—Si–C and Si–O, respectively—as a function of VSC of three distinct vibrational modes in the dark. The results show that VSC can indeed tilt the reactivity landscape to favor one product over the other. Thermodynamic parameters reveal the presence of a large activation barrier and substantial changes to the activation entropy, confirming the modified chemical landscape under strong coupling.

Scientists are rushing to study the tiny plastic specks that are in marine animals — and in us. Scientists are rushing to study the tiny plastic specks that are in marine animals — and in us. Credit: Will Parson/Chesapeake Bay Program Microplastics from the Magothy River are pictured at the laboratory of Dr. Lance Yonkos at the University of Maryland.

Periodic driving of a quantum system can enable new topological phases with no analog in static systems. In this paper, we systematically classify one-dimensional topological and symmetry-protected topological (SPT) phases in interacting fermionic and bosonic quantum systems subject to periodic driving, which we dub Floquet SPTs (FSPTs). For physical realizations of interacting FSPTs, many-body localization by disorder is a crucial ingredient, required to obtain a stable phase that does not catastrophically heat to infinite temperature. We demonstrate that 1D bosonic and fermionic FSPT phases are classified by the same criteria as equilibrium phases but with an enlarged symmetry group G˜ , which now includes discrete time translation symmetry associated with the Floquet evolution. In particular, 1D bosonic FSPTs are classified by projective representations of the enlarged symmetry group H2(G˜,U(1)) . We construct explicit lattice models for a variety of systems and then formalize the classification to demonstrate the completeness of this construction. We advocate that a prototypical Z2 bosonic FSPT may be realized by very simple Hamiltonians of the type currently available in existing cold atoms and trapped ion experiments.

We consider a clean quantum system subject to strong periodic driving. The existence of a dominant energy scale,hDx, can generate considerable structure in an effective description of a system that, in the absence of the drive, is nonintegrable and interacting, and does not host localization. In particular, we uncover points of freezing in the space of drive parameters (frequency and amplitude). At those points, the dynamics is severely constrained due to the emergence of an almost exact, local conserved quantity, which scars the entire Floquet spectrum by preventing the system from heating up ergodically, starting from any generic state, even though it delocalizes over an appropriate subspace. At large drive frequencies, where a naïve Magnus expansion would predict a vanishing effective (average) drive, we devise instead a strong-drive Magnus expansion in a moving frame. There, the emergent conservation law is reflected in the appearance of the “integrability” of an effective Hamiltonian. These results hold for a wide variety of Hamiltonians, including the Ising model in a transverse field in any dimension and for any form of Ising interaction. The phenomenon is also shown to be robust in the presence of two-body Heisenberg interactions with any arbitrary choice of couplings. Furthermore, we construct a real-time perturbation theory that captures resonance phenomena where the conservation breaks down, giving way to unbounded heating. This approach opens a window on the low-frequency regime where the Magnus expansion fails.

The discovery of slow earthquakes has revolutionized the field of earthquake seismology. Defining the locations of these events and the conditions that favor their occurrence provides important insights into the slip behavior of tectonic faults. We report on a family of recurring slow-slip events (SSEs) on the plate interface immediately seaward of repeated historical moment magnitude (M w) 8 earthquake rupture areas offshore of Japan. The SSEs continue for days to several weeks, include both spontaneous and triggered slip, recur every 8 to 15 months, and are accompanied by swarms of low-frequency tremors. We can explain the SSEs with 1 to 4 centimeters of slip along the megathrust, centered 25 to 35 kilometers (km) from the trench (4 to 10 km depth). The SSEs accommodate 30 to 55% of the plate motion, indicating frequent release of accumulated strain near the trench.

Investigating slow earthquake activity in subduction zones provides insight into the slip behavior of megathrusts, which can provide important clues about the rupture extent of future great earthquakes. Using the S-net ocean-bottom seismograph network along the Japan Trench, we mapped a detailed distribution of tectonic tremors, which coincided with very-low-frequency earthquakes and a slow slip event. Compiling these and other related observations, including repeating earthquakes and earthquake swarms, we found that the slow earthquake distribution is complementary to the Tohoku-Oki earthquake rupture. We used our observations to divide the megathrust in the Japan Trench into three along-strike segments characterized by different slip behaviors. We found that the rupture of the Tohoku-Oki earthquake, which nucleated in the central segment, was terminated by the two adjacent segments.

Examining the reliquefaction resistance of sand deposits is more challenging due to the complex interplay of several factors that may increase or decrease the resistance. This resulted in severe limitations in understanding the reliquefaction mechanism of sand deposits subjected to repeated shaking events. The present study attempted to overcome this limitation by examining the reliquefaction resistance using 1-g shaking table experiments. A total of 65 shakings were performed on saturated Solani sand with varying acceleration amplitude, dynamic frequency, shaking duration, and relative density of the sand specimen. All the above factors were experimented with three different shaking patterns (incremental, uniform and decremental) and independent events. For each shaking event, generation and dissipation of excess pore pressure, soil subsidence, and relative density variations were presented. The beneficial effect of seismic preshaking were applicable in partially liquefied soils that were subjected to incremental shaking pattern. On the other hand, contrary results were reported for uniform and decremental shaking patterns, where the later found to be more damaging. The state of the soil (partially or completely liquefied) governs the reliquefaction resistance, as the beneficial effect of preshaking was applicable only in partially liquefied soils, irrespective of the shaking pattern. Whereas complete liquefaction disturbs the structure of existing sand specimens and results in reduced reliquefaction resistance for future seismic events.