We review the recent researches of numerical simulations on faulting, which are interpreted in this paper as the evolution of the state of the fault plane and the evolution of fault structure. The theme includes the fault constitutive (friction) law, the properties of the gauge particles, the initial phase of the rupture, the dynamic rupture process, the interaction of the fault segments, the fault zone dynamics, and so on. Many numerical methods have been developed: boundary integral equation methods (BIEM), finite difference methods (FDM), finite or spectral element methods (FEM, SEM) as well as distinct element methods (DEM), discrete element methods (again DEM) or lattice solid models (LSM). The fault dynamics should be solved as a complex non-linear system, which shows multiple hierarchical structures on its property and behavior. The researches have progressively advanced since the 1990's both numerically and physically thanks to high performance computing environments. The interaction at small scales is modeled to provide a large scale property of the fault. The dynamic rupture has been actively studied especially for the effect on the fault geometry evolution or due to the existed fault structure. The (quasi-)static and the initial processes of the fault movement have been also explored in a seismic cycle. The effect of fluid or heat has been also taken into account in the mechanics. All these efforts help us to understand the phenomena and the unified understanding (simulation) over different spacio-temporal scales is more and more expected.
In this paper, we propose a stochastic dynamic model for earthquake rupture and suggest that the Langevin equation of frictions may be used for interpreting the slip distributions of rupture processes in earthquakes. The steady-state solution of the derived Langevin equation analytically attains the truncated exponential (TEX) distribution that is empirically characterized in many rupture models of earthquake events worldwide, as demonstrated by Thingbaijam and Mai (2016, https://doi.org/10.1785/0120150291). Our proposed stochastic dynamic faulting model for earthquake rupture intrinsically in…
Ruptures of the largest earthquakes can last between a few seconds and several minutes. An early assessment of the final earthquake size is essential for early warning systems. However, it is still unclear when in the rupture history this final size can be predicted. Here we introduce a probabilistic view of rupture evolution - how likely is the event to become large - allowing for a clear and well-founded answer with implications for earthquake physics and early warning. We apply our approach to real time magnitude estimation based on either moment rate functions or broadband teleseismic P ar…
Using 9-sets of different laboratory earthquake tests, we examined the nature of cracking under true triaxial stress conditions in the lithosphere . We found that 3D stress state can induce oblique nucleation of many fractures, forming final plane of complex polymodal faults. Our fully 3D experiments indicate unconventional fault nucleation with 2-3 times faster slip phase, implying a new slip-weakening mechanism for earthquakes in upper crust. In addition, We compared our observations of irregular cracks with typical anti-cracks signals in multi-anvil High Pressure and Temperature test. For t…
Earthquake ruptures dynamically activate coseismic off-fault damage around fault cores. Systematic field observation efforts have shown the distribution of off-fault damage around main faults, while numerical modeling using elastic-plastic off-fault material models has demonstrated the evolution of coseismic off-fault damage during earthquake ruptures. Laboratory scale micro-earthquake experiments have pointed out the enhanced high-frequency radiation due to the coseismic off-fault damage. However, the detailed off-fault fracturing mechanisms, subsequent radiation and its contribution to the o…
Large continental earthquakes activate multiple faults in a complex fault system, dynamically inducing co-seismic damage around them. The 2016 Mw 7.8 Kaikoura earthquake in the northern South Island of New Zealand has been reported as one of the most complex continental earthquakes ever documented1, which resulted in a distinctive on and off-fault deformation pattern. Previous geophysical studies confirm that the rupture globally propagated northward from epicenter. However, the exact rupture- propagation path is still not well understood because of the geometrical complexity, partly at sea, a…
Low-frequency earthquakes are a particular class of slow earthquakes that provide a unique source of information on the mechanical properties of a subduction zone during the preparation of large earthquakes. Despite increasing detection of these events in recent years, their source mechanisms are still poorly characterised, and the relation between their magnitude and size remains controversial. Here, we present the source characterisation of more than 10,000 low-frequency earthquakes that occurred during tremor sequences in 2012-2016 along the Nankai subduction zone in western Shikoku, Japan.…
High-frequency (HF) seismic radiation of large earthquakes is approximately represented by P wave trains recorded at teleseismic distances. Observed envelopes of such signals look random and intermittent, suggesting non-trivial stochastic structure. Variogram and spectral analyses were applied to instant power calculated from band-filtered observed P-wave signals from eight large (Mw=7.6-9.2) earthquakes, with 8-30 records per event and eight non-overvlapping frequency bands analyzed (total frequency range 0.6-6.2 Hz, bandwidth 0.7 Hz). Estimates for both variograms and power spectra look line…
Despite the enormous efforts towards searching for precursors, no precursors have exhibited real predictive power with respect to an earthquake thus far. Seismogenic locked segments that can accumulate adequate strain energy to cause major earthquakes are very heterogeneous and less brittle; progressive failures of the locked segments with these properties can produce an interesting seismic phenomenon: a characteristic earthquake and a sequence of smaller subsequent earthquakes (pre-shocks) always arise prior to another characteristic earthquake within a well-defined seismic zone and its curre…
Frictional heat during earthquake rupture raises the pressure of fault zone fluids and affects the rupture process and its seismic radiation. Here, we investigate the role of two key parameters governing thermal-pressurization of pore fluids -- hydraulic diffusivity and shear-zone half-width -- on earthquake rupture dynamics, kinematic source properties and ground-motions. We conduct 3D strike-slip dynamic rupture simulations assuming a rate-and-state dependent friction law with strong velocity-weakening coupled to thermal-pressurization of pore fluids. Dynamic rupture evolution and ground-sha…
In this study, we have used point-source approximation with the premise that it is compatible with the rupture process of the predominant faulting geometry caused by the initiation of Shonbe seismic sequence. First, all recorded earthquakes during six months after the main shock, 2013 April 9th, in the vicinity of khaki anticline near Shonbe, are relocated with the probabilistic nonlinear method based on Bayesian inference. The synthetic test is done, with the exact distribution of real stations on hand. Thus, the proper value for the parameter that can explicitly affect the error results is c…
Fluid pressure and flow in the crust is a key parameter controlling earthquake physics. Since earthquake slip is linked to spatio-temporal localisation of deformation, it is expected that the localised fluid pressure around the fault plane could potentially impact the dynamic strength of the slipping fault zone. Coseismic fluid pressure drops have been inferred from field studies, notably in gold deposits which are thought to be formed by this process, but reliable quantitative predictions are still lacking. Here, experimental results are presented where local on- and off-fault fluid pressure …
Pulse-like ruptures arise spontaneously in many elastodynamic rupture simulations and seem to be the dominant rupture mode along crustal faults. Pulse-like ruptures propagating under steady-state conditions can be efficiently analysed theoretically, but it remains unclear how they can arise and how they evolve if perturbed. Using thermal pressurisation as a representative constitutive law, we conduct elastodynamic simulations of pulse-like ruptures and determine the spatio-temporal evolution of slip, slip rate and pulse width perturbations induced by infinitesimal perturbations in background s…
A major part of the seismicity striking the Mediterranean area and other regions worldwide is hosted in carbonate rocks. Recent examples are the destructive earthquakes of L'Aquila Mw 6.1 2009 and Norcia Mw 6.5 2016 in Central Italy. Surprisingly, within this region, fast (\approx 3km/s) and destructive seismic ruptures coexist with slow (maximum 10 m/s) and non-destructive rupture phenomena. Despite of its relevance for seismic hazard studies, the transitions from fault creep to slow and fast seismic rupture propagation are still poorly constrained by seismological and laboratory observations…
When a dynamic earthquake rupture propagates on a fault in the Earth's crust, the medium around the fault is dynamically damaged due to stress concentrations around the rupture tip. Recent field observations, laboratory experiments and canonical numerical models show the coseismic off-fault damage is essential to describe the coseismic off-fault deformation, rupture dynamics, radiation and overall energy budget. However, the numerical modeling of "localized" off-fault fractures remains a challenge mainly because of computational limitations and model formulation shortcomings. We thus developed…
We monitor dynamic rupture propagation during laboratory stick-slip experiments performed on saw-cut Westerly granite under upper crustal conditions (10-90 MPa). Spectral analysis of high-frequency acoustic waveforms provided evidence that energy radiation is enhanced with stress conditions and rupture velocity. Using acoustic recordings bandpass filtered to 400-800 kHz (7-14 mm wavelength) and highpass filtered above 800 kHz, we back projected high-frequency energy generated during rupture propagation. Our results show that the high-frequency radiation originates behind the rupture front duri…
Supershear Rupture Indicator in Near-fault Particle Motion
The Chinese University of Hong Kong（香港中文大学）；École Normale Supérieure, CNRS-UMR 8538, PSL Research University（巴黎高等师范学院，CNRS-UMR 8538，PSL研究大学）；Shenzhen Research Institute, The Chinese University of Hong Kong（香港中文大学深圳研究院）；Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong（香港中文大学环境、能源与可持续发展研究所）；Institute of Space and Earth Information Science, The Chinese University of Hong Kong（香港中文大学空间与地球信息科学研究所）；Bureau de Recherches Géologiques et Minières (BRGM)（法国地质与矿业研究局）
We compute a series of finite-source parameter inversions of the fault rupture of the 2004 Parkfield earthquake based on 1 Hz GPS records only. We confirm that some of the co-seismic slip at shallow depth (<5 km) constrained by InSAR data processing results from early post-seismic deformation. We also show 1) that if located very close to the rupture, a GPS receiver can saturate while it remains possible to estimate the ground velocity (~1.2 m/s) near the fault, 2) that GPS waveforms inversions constrain that the slip distribution at depth even when GPS monuments are not located directly above…
We show that the mesoscopic and transport characteristics of networks follow the same trends for the same type of the shear ruptures in terms of rupture speed while also comparing the results of three different friction experiments.The classified fronts obtained from a saw cut Westerly granite fault regarding friction network parameters show a clear separation into two groups indicating two different rupture fronts. With respect to the scaling of local ruptures durations with the networks parameters we show that the gap is related to the possibility of a separation between slow and regular fro…
California Institute of Technology（加州理工学院）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）
We present a novel approach for resolving modes of rupture directivity in large populations of earthquakes. A seismic spectral decomposition technique is used to first produce relative measurements of radiated energy for earthquakes in a spatially-compact cluster. The azimuthal distribution of energy for each earthquake is then assumed to result from one of several distinct modes of rupture propagation. Rather than fitting a kinematic rupture model to determine the most likely mode of rupture propagation, we instead treat the modes as latent variables and learn them with a Gaussian mixture mod…
Seismotectonics and Slip Behavior of a Submarine Plate Boundary Fault from Seismicity Repeaters and Tomography using a high-resolution earthquake catalog from machine learning
Most earthquake ruptures propagate at speeds below the shear wave velocity within the crust, but in some rare cases, ruptures reach supershear speeds. The physics underlying the transition of natural subshear earthquakes to supershear ones is currently not fully understood. Most observational studies of supershear earthquakes have focused on determining which fault segments sustain fully-grown supershear ruptures. Experimentally cross-validated numerical models have identified some of the key ingredients required to trigger a transition to supershear speed. However, the conditions for such a t…
The Mw 7.8 Kahramanmaraş Earthquake was larger and more destructive than what had been expected for the tectonic setting in Southeastern Turkey. By using near-field records we provide evidence for early supershear transition on the splay fault that hosted the nucleation and early propagation of the first rupture that eventually transitioned into the East Anatolian fault. The two stations located furthest from the epicenter show a larger fault parallel particle velocity component relative to the fault normal particle velocity component; a unique signature of supershear ruptures that has been id…
The nature of the high-speed rupture or the main shock of the Burridge-Knopoff spring-block model in two dimensions obeying the rate-and-state dependent friction law is studied by means of extensive computer simulations. It is found that the rupture propagation in larger events is highly anisotropic and irregular in shape on longer length scales, although the model is completely uniform and the rupture-propagation velocity is kept constant everywhere at the rupture front. The manner of the rupture propagation sometimes mimics the successive ruptures of neighboring "asperities" observed in real…
Coupling of rupture processes in solids with waves also propagating in fluids is a prominent phenomenon arising during tectonic earthquakes. It is executed here in a single `monolithic' model which can asymptotically capture both damageable solids (rocks) and (visco-)elastic fluids (outer core or oceans). Both ruptures on pre-existing lithospheric faults and a birth of new faults in compact rocks are covered by this model, together with emission and propagation of seismic waves, including, e.g., reflection of S-waves and refraction of P-waves on the solid-fluid interfaces. A robust, energy con…
Based on waveform data from a profile of aftershocks following the north-south trace of the June 28, 1992 Landers rupture across the Mojave desert, we construct a new velocity model for the Mojave region which features a thin, slow crust. Using this model, we obtain source parameters, including depth and duration, for each of the aftershocks in the profile, and in addition, any significant (M>3.7) Joshua Tree--Landers aftershock between April, 1992 and October, 1994 for which coherent TERRAscope data were available. In all, we determine source parameters and stress-drops for 45 significant (M_…
Friction and fault surface evolution are critical aspects in earthquake studies. We present the preliminary result from a novel experimental approach that combines rotary shear testing with X-ray micro-computed tomography ($μ$CT) technology. An artificial fault was sheared at small incremental rotational steps under the normal stress of 2.5 MPa. During shearing, mechanical data including normal force and torque were measured and used to calculate the friction coefficient. After each rotation increment, a $μ$CT scan was conducted to observe the sample structure. The careful and quantitative $μ$…
Although our existing one-dimensional (1D) model provides a successful quantitative description of rupture events, a 1D description is somewhat limited. We therefore derive a two-dimensional (2D) model which allows us to investigate characteristics of earthquakes (EQs) and slow slip events (SSEs) that are only apparent in a second dimension. We find that the leading edge of an EQ rupture in the direction of the global shear stress (x-direction) is wider in the plane of the crustal fault (y-direction) than the trailing edge. The direction of the slip velocity is primarily in the x-direction. EQ…
We have developed a model that describes the major characteristics of a rupture, ranging from regular earthquakes (EQs) to slow slip events (SSEs), including episodic tremor and slip (ETS). Previous model predictions, while accurate, are based on a highly idealized initial stress distribution and a simple velocity-dependent expression for friction. The full scope of the model has, therefore, not been fully demonstrated. Further developments, presented here, include more physically realistic treatments of both the initial conditions and friction. Model predictions are: (1) The type of a seismic…
University of Memphis（孟菲斯大学）；Alan Turing Institute（艾伦·图灵研究所）
Simulating dynamic rupture propagation is challenging due to the uncertainties involved in the underlying physics of fault slip, stress conditions, and frictional properties of the fault. A trial and error approach is often used to determine the unknown parameters describing rupture, but running many simulations usually requires human review to determine how to adjust parameter values and is thus not very efficient. To reduce the computational cost and improve our ability to determine reasonable stress and friction parameters, we take advantage of the machine learning approach. We develop two …
Joint Analysis of Shannon and Tsallis Entropy and GRACE-FO driven Equivalent Water Height Anomalies for Pre- and Post-Rupture Monitoring: An Example of the 2023 Mw = 7.8 Kahramanmaraş Earthquake, Türkiye
Farhangian University（法尔干大学）；The University of Tokyo（东京大学）；Arak University of Technology（阿拉克理工大学）
Usual inversion for earthquake source parameters from tsunami wave data incorporates subjective elements. Noisy and possibly insufficient data also results in instability and non-uniqueness in most deterministic inversions. Here we employ the satellite altimetry data for the 2004 Sumatra-Andaman tsunami event to invert the source parameters. Using a finite fault model that represents the extent of rupture and the geometry of the trench, we perform a non-linear joint inversion of the slips, rupture velocities and rise times with minimal a priori constraints. Despite persistently good waveform f…
