Explore the vast range of titles available.

The human tragedy caused by the earthquake doublet on 6 February 2023 in Turkey and Syria is difficult to comprehend. While earthquake scientists are trying to understand this seismic event, its catastrophic impact highlights heightened risk in the entire region.

We present a dynamic rupture model of the 2016 M w 7.8 Kaikōura earthquake to unravel the event’s riddles in a physics-based manner and provide insight on the mechanical viability of competing hypotheses proposed to explain them. Our model reproduces key characteristics of the event and constraints puzzling features inferred from high-quality observations including a large gap separating surface rupture traces, the possibility of significant slip on the subduction interface, the non-rupture of the Hope fault, and slow apparent rupture speed. We show that the observed rupture cascade is dynamically consistent with regional stress estimates and a crustal fault network geometry inferred from seismic and geodetic data. We propose that the complex fault system operates at low apparent friction thanks to the combined effects of overpressurized fluids, low dynamic friction and stress concentrations induced by deep fault creep. The 2016 Kaikōura earthquake in New Zealand raised the discussion about how a complex fault system operates. Here the authors propose a dynamic rupture scenario that reproduces key characteristics of the event and show that the fault system works at low apparent friction.

Earthquake rupture speed can affect ground shaking and therefore seismic hazard. Seismological observations show that large earthquakes span a continuum of rupture speeds, from slower than Rayleigh waves up to P-wave speed, and include speeds that are predicted to be unstable by two-dimensional theory. This discrepancy between observations and theory has not yet been reconciled by a quantitative model. Here we present numerical simulations that show that long ruptures with oblique slip (both strike-slip and dip-slip components) can propagate steadily at various speeds, including those previously suggested to be unstable. The obliqueness of slip and the ratio of fracture energy to static energy release rate primarily control the propagation speed of long ruptures. We find that the effects of these controls on rupture speed can be predicted by extending the three-dimensional theory of fracture mechanics to long ruptures with oblique slip. This model advances our ability to interpret supershear earthquakes, to constrain the energy ratio of faults based on observed rupture speed and rake angle, and to relate the potential rupture speed and size of future earthquakes to the observed slip deficit along faults.Long fault ruptures that have both strike-slip and dip-slip components can propagate at a wide range of speeds, including those theoretically predicted to be unstable, according to numerical simulations.

Slow slip events occur worldwide and could trigger devastating earthquakes, yet it is still debated whether their moment-duration scaling is linear or cubic and a fundamental model unifying slow and fast earthquakes is still lacking. Here, we show that the rupture propagation of simulated slow and fast earthquakes can be predicted by a newly-developed three-dimensional theory of dynamic fracture mechanics accounting for finite rupture width, an essential ingredient missing in previous theories. The complete spectrum of rupture speeds is controlled by the ratio of fracture energy to energy release rate. Shear stress heterogeneity can produce a cubic scaling on a single fault while effective normal stress variability produces a linear scaling on a population of faults, which reconciles the debated scaling relations. This model provides a new framework to explain how slow slip might lead to earthquakes and opens new avenues for seismic hazard assessment integrating seismological, laboratory and theoretical developments. A new model elucidates the connections between silent earthquakes (\"slow slip events\") and regular ones by accounting for their finite rupture depth. It reconciles debated features of slow slip events and explains how they might lead to earthquakes.

One of the ultimate goals in landslide hazard assessment is to predict maximum landslide extension and velocity. Despite much work, the physical processes governing energy dissipation during these natural granular flows remain uncertain. Field observations show that large landslides travel over unexpectedly long distances, suggesting low dissipation. Numerical simulations of landslides require a small friction coefficient to reproduce the extension of their deposits. Here, based on analytical and numerical solutions for granular flows constrained by remote-sensing observations, we develop a consistent method to estimate the effective friction coefficient of landslides. This method uses a constant basal friction coefficient that reproduces the first-order landslide properties. We show that friction decreases with increasing volume or, more fundamentally, with increasing sliding velocity. Inspired by frictional weakening mechanisms thought to operate during earthquakes, we propose an empirical velocity-weakening friction law under a unifying phenomenological framework applicable to small and large landslides observed on Earth and beyond. Despite commonly occurring on Earth and other terrestrial bodies, mass wasting processes are poorly understood, hampering hazard assessment and mitigation. Lucas and colleagues propose a universal velocity-weakening friction law capable of describing the behaviour of small to large landslides.

The speed at which an earthquake rupture propagates affects its energy balance and ground shaking impact. Dynamic models of supershear earthquakes, which are faster than the speed of shear waves, often start at subshear speed and later run faster than Eshelby’s speed. Here we present robust evidence of an early and persistent supershear rupture at the sub-Eshelby speed of the 2018 magnitude 7.5 Palu, Indonesia, earthquake. Slowness-enhanced back-projection of teleseismic data provides a sharp image of the rupture process, along a path consistent with the surface rupture trace inferred by subpixel correlation of synthetic-aperture radar and satellite optical images. The rupture propagated at a sustained velocity of 4.1 km s–1 from its initiation to its end, despite large fault bends. The persistent supershear speed is further validated by seismological evidence of far-field Rayleigh Mach waves. The unusual features of this earthquake probe the connections between the rupture dynamics and fault structure. An early supershear transition could be promoted by fault roughness near the hypocentre. Steady rupture propagation at a speed unexpected in homogeneous media could result from the presence of a low-velocity damaged fault zone.Supershear rupture speed occurred at the devastating 2018 magnitude 7.5 Palu earthquake, Indonesia, according to back-projection of teleseismic data.

Faults are unlocked by earthquakes. Analysis of seismic data from the 2015 Nepal earthquake shows that only part of the Main Himalayan Thrust fault was unzipped by the quake, leaving much of the fault locked and ready to slip in a future event.

Tsunami earthquakes occur in the shallow parts of subduction megathrust interfaces, which are often in contact with the accretionary wedge. Here, by conducting dynamic rupture simulations, we investigate how an accretionary wedge affects the rupture process of tsunami earthquakes and the resulting ground motions. We constructed a dynamic source model of the 2010 Mentawai tsunami earthquake (Mw 7.8), constrained by the slip distribution obtained by a source inversion analysis. The model reproduces the basic observed features of the event, including its recorded ground motions and its inferred slow rupture speed. The simulation results also show that seismic wave energy is efficiently trapped inside the accretionary wedge, which contributes to our understandings of the observation that tsunami earthquakes produce weaker ground motions than regular earthquakes of the same magnitude.

The 2011 Mw 9 Tohoku‐Oki earthquake, recorded by over 1000 near‐field stations and multiple large‐aperture arrays, is by far the best recorded earthquake in the history of seismology and provides unique opportunities to address fundamental issues in earthquake source dynamics. Here we conduct a high resolution array analysis based on recordings from the USarray and the European network. The mutually consistent results from both arrays reveal rupture complexity with unprecedented resolution, involving phases of diverse rupture speed and intermittent high frequency bursts within slow speed phases, which suggests spatially heterogeneous material properties. The earthquake initially propagates down‐dip, with a slow initiation phase followed by sustained propagation at speeds of 3 km/s. The rupture then slows down to 1.5 km/s for 60 seconds. A rich sequence of bursts is generated along the down‐dip rim of this slow and roughly circular rupture front. Before the end of the slow phase an extremely fast rupture front detaches at about 5 km/s towards the North. Finally a rupture front propagates towards the south running at about 2.5 km/s for over 100 km. Key features of the rupture process are confirmed by the strong motion data recorded by K‐net and KIK‐net. The energetic high frequency radiation episodes within a slow rupture phase suggests a patchy image of the brittle‐ductile transition zone, composed of discrete brittle asperities within a ductile matrix. The high frequency is generated mainly at the down‐dip edge of the principal slip regions constrained by geodesy, suggesting a variation along dip of the mechanical properties of the mega thrust fault or their spatial heterogeneity that affects rise time. Key Points Low and high frequency earthquake slip can be spatially complementary A single earthquake can involve a diversity of rupture styles The deeper portions of a megathrust fault are rheologically heterogeneous

Earthquakes are destructive natural hazards with damage capacity dictated by rupture speeds. Traditional dynamic rupture models predict that earthquake ruptures gradually accelerate to the Rayleigh wave speed with some of them further jumping to stable supershear speeds above the Eshelby speed (~ 2 times S wave speed). However, the 2018 M w 7.5 Palu earthquake, among several others, significantly challenges such a viewpoint. Here we generate spontaneous shear ruptures on laboratory faults to confirm that ruptures can indeed attain steady subRayleigh or supershear propagation speeds immediately following nucleation. A self-similar analysis of dynamic rupture confirms our observation, leading to a simple model where the rupture speed is uniquely dependent on a driving load. Our results reproduce and explain a number of enigmatic field observations on earthquake speeds, including the existence of stable subEshelby supershear ruptures, early onset of supershear ruptures, and the correlation between the rupture speed and the driving load. Earthquake rupture speeds significantly impact seismic hazards. Here, authors report laboratory earthquake experiments reproducing early and stable subEshelby supershear ruptures, and unlocking the correlation between rupture speed and driving load.