We observe the nucleation phase of in‐plane ruptures in laboratory. show that is composed two distinct phases, a quasi‐static and an acceleration stage, followed by dynamic propagation. propose empirical model which describes rupture length evolution: The described exponential growth while inverse power law time. transition from to accelerating related critical length, scales inversely with normal stress accordance theoretical predictions, surfacic power, may be intrinsic property interface....

Abstract In this study we use the precursory acoustic emission (AE) activity during nucleation of stick‐slip instability as a proxy to investigate foreshock occurrence prior natural earthquakes. We report on three experiments performed cylindrical samples Indian metagabbro under upper crustal stress conditions (30–60 MPa). AEs were continuously recorded by eight calibrated sensors experiments. Seismological parameters (moment magnitude, corner frequency and stress‐drop) detected (−8.8 ≤ M w...

Natural fault systems exhibit a complex interplay of factors that govern the nucleation, propagation, and arrest ruptures. Among these factors, distribution initial stress stands out as key driver rupture dynamics, influencing size, recurrence interval, spatial characteristics seismic events. The system size further contributes to complexity cycle. This study investigates how heterogeneous conditions shape cycle long experimental fault.We reproduce frictional ruptures on biaxial direct shear...

Abstract In this study we explore experimentally the effects of fault heterogeneity on rupture nucleation. We conducted friction experiments between two polycarbonate plates, with a periodically heterogeneous interface. The propagation is monitored an ultra‐fast video camera by taking advantage photo‐elastic properties material used. show that nucleation process does not always consists monotonic growth velocity. Instead, front advances alternation slow and fast episodes accelerates until it...

Abstract Fluid‐induced stress perturbations in the crust at seismogenic depths caused by sources such as tidal or seasonal loading may trigger earthquakes. We investigate role of small periodic pore pressure ( P p ) perturbation rupture nucleation performing laboratory triaxial creep experiments on Fontainebleau sandstone, saturated water, under sinusoidal variations. Results show that recorded acoustic emissions (AEs) correlate with rock approaches failure. More interestingly, AEs occur...

This study is devoted to the experimental investigation of interaction a propagating rupture with one or several mechanical heterogeneities. We developed friction laboratory experiment where soft elastic solid slides past rigid flat plate. The system coupled an original medical imaging technique, ultrasound speckle interferometry, that allows observing dynamics as well emitted shear wavefield into body. compare for homogeneous interface and three cases heterogeneous sliding surfaces: (1)...

Abstract Fluids are pervasive in the Earth's crust and saturate fractures faults. The combination of fluids gouge layers developing along faults can generate different viscosities. Such viscous were found to influence reactivation, frictional stability faults, eventually dynamics propagating earthquake ruptures. We reproduced laboratory earthquakes on analog material (PMMA) study lubricant fault stability, rupture nucleation, propagation under mixed lubrication conditions. Experiments...

Ultrafast ultrasonic speckle interferometry, an imaging technique derived from elastography, is used to follow the dynamic of interface failure in a friction experiment. Experimental results that characterise two slipping regimes are presented: slow slip regime associated with depinning events at and supershear rupture emission Mach waves fronts. These discussed light geophysical observations made scale Earth on dynamics active faults.

Abstract [1] We address the problem of modeling dynamic rupture on multiscale heterogeneous faults in 3D. Under assumption slip-weakening friction, we numerically construct effective friction laws that integrate effects small-scale heterogeneity during rupture. This homogenization process is based description initial phase by dominant unstable spectral mode. Its dynamics influenced geometry fault, static heterogeneities and law. first define a periodic model, introducing distribution...

SUMMARY An unusual seismic activity has recently occurred in the Gripp valley, located central part of French Pyrenees. Since spring 2020, two new swarms appeared, clearly outside usual location seismicity this area. On 20 September almost concomitantly with activation second swarm, a hole suddenly opened bed local river, Adour de Payolle. This drained water from which dried up over 500 m. We follow and study spatial temporal evolution these clusters, using four temporary stations deployed...

Decades of seismological observations have highlighted the variability foreshock occurrence prior to natural earthquakes, making thus difficult track how earthquakes start. Here, we report on three stick-slip experiments performed cylindrical samples Indian metagabbro under upper crustal stress conditions (30-60 MPa). Acoustic emissions (AEs) were continuously recorded by 8 calibrated acoustic sensors during experiments. Seismological parameters detected AEs (-8.8 <= Mw -7 ) follow...

SUMMARY Well-constrained earthquake depth estimations are important for seismic hazard determination. As local networks of the East-African Rift usually too sparse reliable estimations, we used detections pP and sP phase arrivals (the so-called phases) at teleseismic distance to constrain depths in this region. We rely on a fully automatic Cepstral analysis approach, first validated global scale using ISC-EHB catalogue, then applied seismicity. investigated 9575 earthquakes from magnitude 2...

Abstract In seismology, the rupture mechanisms of an earthquake, a glacier stick‐slip and landslide are not directly observed, but inferred from surface measurements. contrast, laboratory experiments can illuminate near field effects. The reflects mechanism is highly attenuated in case real‐world data. We image elastic wave‐field nucleating non‐invasively its near‐field with ultrasound speckle correlation. Our imaging yields particle velocity full shear wave at source location inside 3D...

Abstract We investigate the interaction between two rupture fronts as they propagate toward each other and ultimately collide. This phenomenon was observed during laboratory experiments conducted on poly methyl methacrylate. Subsequently, we used numerical simulations to elucidate key aspects of these observations draw broader conclusions. Our findings indicate that collision generates interface waves along sliding at Rayleigh wave speed. Additionally, interact with starting stopping S‐wave...

SUMMARY An accurate magnitude estimation is necessary to properly evaluate seismic hazard, especially in low moderate seismicity areas such as Metropolitan France. However, magnitudes of small earthquakes are subject large uncertainties caused by major high-frequency propagation effects which generally not considered. To address this issue, we developed a method separate source, attenuation and site parameters from the elastic radiative transfer modelling full energy envelopes seismograms....

We apply shear wave elastography, a medical imaging technique that uses ultrafast ultrasound to analyze rupture nucleation. In order better understand friction and processes which are responsible for earthquake nucleation, we build laboratory experiment reproduces the stick-slip behavior of seismic fault soft elastic materials. The process is generated by controlling driving slab through motor in synchronization with acquisition system. As an analog asperity on fault, patch sand grains...