Physics-based simulations are critical for understanding natural hazards. The increasing complexity of numerical codes requires benchmark exercises to verify that different computational methods yield consistent results when solving the same governing equations. Here, we present an open-access web platform designed for the verification of earthquake dynamic rupture, seismic cycle, and tsunami simulations. The platform architecture utilizes a modular, serverless backend on Amazon Web Services (AWS) to provide scalable file processing and visualization. A lightweight static web application provides a secure interface for uploading and managing results, while the browser-based data visualization enables interactive analysis of time series and surface grid data. By using structured JavaScript Object Notation (JSON) text files to define benchmark structures, the system remains fully extensible, allowing the addition of new scenarios without modifying the underlying software logic. The platform hosts the "The Tsunami Problem Versions" (TTPV) 1 & 2, two benchmarks for 3D fully coupled earthquake dynamic rupture and tsunami generation, and provides a framework for earthquake cycle models. This community resource aims to build trust in numerical simulations and facilitate long-term collaborative code verification as modeling software continues to evolve.

Hydrologic observations and experimental studies indicate that inelastic dilation from coseismic fault damage can cause substantial pore pressure reduction, yet most near-fault hydromechanical models ignore such inelastic effects. Here, we present a 3-D groundwater flow model incorporating the effects of inelastic dilation based on an earthquake dynamic rupture model with inelastic off-fault deformation, both on pore pressure and permeability enhancement. Our results show that inelastic dilation causes mostly notable depressurization within similar to 1 km off the fault at shallow depths (<3 km). We found agreement between our model predictions and recent field observations, namely that both sides of the fault can experience large-magnitude (similar to tens of meters) water level drawdowns. For comparison, simulations considering only elastic strain produced smaller water level changes (similar to several meters) and contrasting signs of water level change on either side of the fault. The models show that inelastic dilation is a mechanism for coseismic fault depressurization at shallow depths. While the inelastic dilation is a localized phenomenon which is most pronounced in the fault zone, the pressure gradients produced in the coseismic phase have a broader effect, increasing fluid migration back into the fault zone in the postseismic phase. We suggest field hydrologic measurements in the very-near-field (<1 km) of active faults could capture damage-related pore pressure signals produced by inelastic dilation, helping improve our understanding of fault mechanics and groundwater management near active faults.

Along-strike variations of sediment thickness and inelastic wedge deformation can significantly affect the variations of near-trench slip, seismic radiation, and tsunamigenesis along the Japan Trench. We present fully coupled models of dynamic rupture, ocean acoustic waves, and tsunami for the 2011 M-W 9.1 Tohoku-Oki earthquake to fully investigate the physics of tsunami generation and radiation fields, by extending a dynamic rupture model with wedge inelasticity (Ma, 2023). The fully coupled models, incorporating ocean compressibility, produce tsunami in good agreement with that from a dispersive shallow-water model, confirming the validity of both models. We show strong radiation of ocean acoustic and seismic waves caused by fast rupture velocity (similar to 3 km/s) and large near-trench slip south of 39 degrees N, dominated by elastic wedge response. However, north of 39 degrees N where sediment thickens in the northern Japan Trench, the inelastic wedge deformation excites tsunami efficiently with diminishing near-trench slip (<20 m), consistent with differential bathymetry observations, but causes slow rupture velocity (similar to 850 m/s) and significantly weaker radiation of ocean acoustic and seismic waves. Inelastic wedge deformation thus provides a self-consistent interpretation to both depletion in high-frequency radiation and large tsunami generation in the northern Japan Trench in this earthquake, which may challenge the use of ocean acoustic waves for robust tsunami early warning.

One of the essential characteristics of earthquakes associated with large tsunami generation is the depletion of high-frequency radiation, which is not well understood by elastic dislocation theory and largely not accounted for in most rupture models of real events. We present fully coupled models of dynamic rupture, ocean acoustic waves, and tsunami for the 1896 Sanriku earthquake with wedge inelasticity. The inelastic wedge deformation due to thick sediment in the northern Japan Trench is shown to generate efficient short-wavelength seafloor uplift (>5 m), which is several times larger than the uplift by elastic dislocation models and generates impulsive tsunami that can have a large impact on the rugged Sanriku coast. Seismic moment due to inelastic wedge deformation has a reverse faulting focal mechanism with a steep plunge (>75 degrees) of T axis, reflecting high efficiency in tsunami generation. However, the inelastic deformation is a large energy sink, which causes slower rupture velocity, weaker radiation of ocean acoustic and seismic waves, and similar to 10 times lower moment-scaled radiated energy than those of elastic models, explaining nearly all the anomalous characteristics of this tsunami earthquake. The anti-plane off-fault shear stress in the mode III rupture direction, limited by yielding, plays an important role in the slow rupture velocity and energy radiation along strike. Ocean acoustic waves may not provide robust signals for tsunami early warning due to weak high-frequency radiation. Additionally, large, long-duration ground velocity pulses can naturally result from inelastic deformation. Plain Language Summary The 1896 Sanriku earthquake was one of the deadliest earthquakes in recorded Japanese history, well known for its anomalously large tsunami but weak ground shaking. It was classified as a tsunami earthquake. Similar anomalous characteristics were also observed in the northern Japan Trench in the 2011 M-W 9.1 Tohoku-Oki earthquake. The physics of large tsunamigenesis and weak ground shaking remains poorly understood. We explain these anomalous characteristics of the 1896 Sanriku earthquake by inelastic wedge deformation in fully coupled models of dynamic rupture, ocean acoustic waves, and tsunami. Inelastic deformation of thick wedge sediment in the northern Japan Trench is shown in the models to produce efficient short-wavelength tsunami with small shallow slip, slow rupture velocity, depletion in high-frequency radiation, and low moment-scaled radiated energy, accounting for nearly all the anomalous characteristics of this earthquake. Ocean acoustic waves may not provide robust early warning signals for tsunami. The physics shown in this work can have important implications for tsunami early warning and hazard assessment around the world.

One crucial yet unanswered question about the 2011 M-W 9.1 Tohoku-Oki earthquake and tsunami is what generated the largest tsunami (up to 40 m) along the Sanriku coast north of 39N without large slip near the trench. A minimalist dynamic rupture model with wedge plasticity is presented to address this issue. The model incorporates the important variation of sediment thickness along the Japan Trench into the Japan Integrated Velocity Structure Model (JIVSM). By revising a heterogeneous stress drop model, the dynamic rupture model with a standard rate-and-state friction law can explain the GPS, tsunami, and differential bathymetry data (within data uncertainties) with minimum tuning. The rupture is driven by a large patch of stress drop up to similar to 10 MPa near the hypocenter with significantly smaller stress drop (< 3 MPa) in the upper-10 km. The largest shallow slip reaches 75.67 m close to the trench north of hypocenter, which is caused by the large fault width, free surface, shallowly dipping fault geometry, and northwardly increasing sediment thickness, dominated by elastic off-fault response. North of large shallow slip zone, however, inelastic deformation of thick wedge sed-iments significantly controls the rupture propagation along trench, giving rise to slow rupture velocity (-850 m/ s), diminishing shallow slip, and efficient seafloor uplift. The short-wavelength inelastic uplift produces impulsive tsunami consistent with the observations off the Sanriku coast in terms of timing, amplitude, and pulse width. Wedge plasticity and variation of sediment thickness along the Japan Trench thus provides a self-consistent interpretation to the along-strike variation of near-trench slip and anomalous tsunami generation in the northern Japan Trench in this earthquake.

Inelastic off-fault deformation can lead to large tsunamigenesis in different tectonic settings. Here a mechanism for tsunami generation by strike-slip earthquakes that involves dynamic off-fault failure at restraining bends is presented. Dynamic rupture on a vertical strike-slip fault is modeled with undrained inelastic off-fault response incorporated by the Drucker-Prager yield criterion. I show that in a local transpressive stress regime dynamic off-fault failure at restraining bends produces significantly larger and more localized surface uplift than is produced by purely elastic dislocation models, resulting in a positive flower and coseismic pop-up structure. The larger uplift is due to frictional sliding with a thrust component on conjugate microfractures, modeled by inelastic deformation. The short-wavelength inelastic uplift, largely controlled by bend size, is shown to generate localized tsunami efficiently in a shallow bay by fully coupling dynamic rupture, ocean acoustic waves, and tsunami. Fully-coupled models also indicate that supershear rupture on a vertical planar strike-slip fault does not generate large tsunami as the large kinetic energy of supershear rupture is carried away by ocean acoustic waves. Dynamic off-fault failure at fault complexities, such as restraining bends and compressional stepovers, may need be urgently incorporated in the current tsunami hazard assessments in strike-slip environments.

Inelastic wedge deformation likely plays an important role in the generation of tsunami and ocean acoustic waves in accretionary subduction margins. In an elastic dislocation model, whether or not the fault breaks the trench has a significant effect on seafloor deformation and resulting tsunami. However, this boundary condition is less important when significant inelastic deformation in the overriding wedge occurs, because large seafloor uplift can occur with little or no slip at the trench. Here we incorporate wedge plasticity in fully coupled dynamic rupture and tsunami simulations for a buried fault in the Cascadia subduction zone with realistic fault geometry, bathymetry, and velocity structure. A linearized Eulerian approach is verified and used to simulate gravity waves in the ocean. Our coupled models show that the inelastic deformation of wedge sediments can significantly contribute to seafloor uplift, producing tsunami heights at least twice as large as in purely elastic simulations, whilst generating weaker ocean acoustic and seismic waves. Inelastic wedge deformation is therefore an important mechanism to consider in tsunami hazard assessment in the Cascadia subduction zone. These results have important implications for tsunami generation and early warning in accretionary and other sediment‐filled margins worldwide.

Dynamic wedge failure produces short‐wavelength seafloor uplift efficiently with diminishing shallow slip on the plate interface, generating impulsive tsunami. For ria coasts with prevalent small‐wavelength bathymetric and geomorphologic features, such as the Sanriku coast of Japan, impulsive tsunami can be amplified to produce large runup. We model tsunami propagation and runup of the 1896 Sanriku tsunami by using the seafloor deformation from dynamic rupture models of Ma and Nie (2019) for a M W 8 earthquake with inelastic wedge deformation. The nonlinear Boussinesq equation is solved by a nested‐grid finite‐difference method with high‐resolution bathymetry data. We show that an inelastic deformation model with extensive wedge failure produces impulsive tsunami similar to those observed offshore the Sanriku coast in the 2011 Tohoku earthquake and generates large runup remarkably consistent with the 1896 Sanriku tsunami. As an alternative to previous models based solely on fault slip, we suggest that the impulsive tsunami and large runup along the Sanriku coast observed in the 2011 Tohoku earthquake can be explained by inelastic wedge deformation north of 38.5°N.

In areas of infrequent seismicity or where geologic structures (e.g., sedimentary basins) complicate seismic wave propagation, earthquake ground motion simulations provide one approach to improving the accuracy of ground motion predictions for seismic hazard analyses. However, most current methods for simulating earthquake ground motions ignore important features of the earthquake rupture and typically employ stochastic approaches at frequencies above ~1 Hz. Here, we worked towards improving methods for simulating earthquake ground motions for seismic hazard applications by forming a group modeling effort that incorporates dynamic features of the earthquake fault and rupture (e.g., through complex fault geometry, stress heterogeneity, etc...) that have been demonstrated from both observations and numerical simulations to affect resulting ground motions.

We test the amplitude of deconvolution‐based ambient field Green's functions in 3‐D numerical simulations of seismic wave propagation. We first simulate strongly scattered waves in a hypothetical 3‐D sedimentary basin with small‐scale heterogeneities, which provides an ideally random environment to test various approaches of extracting the amplitude of Green's functions, as the deterministic station‐to‐station Green's functions can be computed in the given velocity structure. Our second model computes the station‐to‐station Green's functions in the Community Velocity Model (S4.26) for Southern California and compares them with the Green's functions extracted from 1 year of ambient noise data. In both models, remarkable waveform similarity among different Green's functions is obtained. In the hypothetical basin model where the wavefield is nearly random, both the correlation‐ and deconvolution‐based Green's functions contain robust amplitude information. However, large‐amplitude biases are observed in the Green's functions extracted from ambient noise in Southern California, showing a strong azimuthal dependence. The deconvolution approach in general overestimates the amplitude along the direction of noise propagation but underestimates it in other azimuths. The correlation approach with temporal normalization and spectral whitening generates similar amplitude to the deconvolution in a wide azimuthal range. Our results corroborate that the inhomogeneous distribution of noise sources biases the amplitude of Green's functions. Carefully reducing these biases is necessary to use these ambient field Green's functions in the virtual earthquake approach.

Elastic dislocation models require large near‐trench slip to explain large tsunamigenesis, which is probably best exemplified in the 2011 M9 Tohoku earthquake. However, it is puzzling that the largest Tohoku tsunami heights occurred about 100 km north of the largest slip zone, where bathymetric surveys indicate no large slip at the trench or submarine landslides. Here we show that coseismic yielding of plentiful sediments in the northern Japan Trench margin can induce large inelastic uplift landward from the trench and diminish slip near the trench. The scarcity of sediments in the south leads to nearly elastic response with large slip at the trench and mostly horizontal seafloor displacement. Thus, the variations of sediments along the Japan Trench and sediment yielding can explain the puzzling variations of tsunamigenesis and near‐trench slip in this earthquake. Inelastic wedge deformation can be an important mechanism of tsunamigenesis in accretionary and other sediment‐filled plate margins.

We consider a poro-elasto-plastic model of fault gouge and study its effects on the rupture dynamics of fractally rough faults. The model consists of a combined Mohr–Coulomb and end-cap yield surface in the gouge layer and allows compaction and dilatancy with undrained pore-pressure changes. We show that gouge compaction at restraining bends causes pore-pressure increase and allows rupture to propagate through segments that arrest rupture in the case with only the brittle failure off the fault. On the other hand, strengthening by undrained gouge dilatancy at releasing bends limits the tendency of supershear rupture from the case with only the brittle off-fault failure. Slip distributions and rupture velocities become more uniform due to the stabilizing tendency of the pore fluids in the fault gouge. The previously observed tendency for ruptures to accelerate and decelerate at releasing and restraining bends respectively can be reversed.

We describe a set of benchmark exercises that are designed to test if computer codes that simulate dynamic earthquake rupture are working as intended. These types of computer codes are often used to understand how earthquakes operate, and they produce simulation results that include earthquake size, amounts of fault slip, and the patterns of ground shaking and crustal deformation. The benchmark exercises examine a range of features that scientists incorporate in their dynamic earthquake rupture simulations. These include implementations of simple or complex fault geometry, off‐fault rock response to an earthquake, stress conditions, and a variety of formulations for fault friction. Many of the benchmarks were designed to investigate scientific problems at the forefronts of earthquake physics and strong ground motions research. The exercises are freely available on our website for use by the scientific community.

A dynamic earthquake model is validated by finding good agreement with an empirical ground-motion prediction equation (GMPE). The model replaces complex detailed deterministic processes on the nonplanar fault with a stochastic emergent law of stress on a planar fault. Initial stress on the fault plane is heterogeneous with a power-law spectrum that is self-similar. Rupture extent and moment are determined primarily by the specified lowest Fourier mode of initial stress. Higher modes are random with a self-similar spectrum that is tied to the amplitude of the lowest mode. Rupture stops naturally due to variation of initial stress. We calculate 10 random realizations with a velocity structure for a hard-rock site. The calculated mean response spectrum for M-w 7 at a distance of 10 km agrees with the GMPE of Boore et al. (2014) within 25% of one standard deviation at periods from 0.3 to 10 s. The agreement of the ground-motion spectral response levels depends on the spatial stress spectrum being correctly related to the amplitude of the lowest mode, so that it is a consistent self-similar model. There are no arbitrary parameters in the model other than those that determine moment and rupture length and width. The standard deviation of the calculated ground motion is a substantial fraction of that of the GMPE.

Fault gouge deformation likely plays a significant role in controlling the strength of mature, large‐displacement faults. Experiments show that intact gouge deforms in an overall ductile and stable manner, readily compacting, but dilates and experiences brittle failure under large strain rate. Inelastic gouge compaction and dilatancy are modeled here using a combined Mohr‐Coulomb and end‐cap yield criterion in a dynamic rupture model of a strike‐slip fault with strongly velocity‐weakening friction. We show that large shear stress concentration ahead of the rupture associated with the rupture front causes the gouge layer to compact (e.g., by structural collapse and comminution), leading to rapidly elevated pore pressure and significant weakening of the principal fault surface. Shortly after the rupture front passes, strong dilatancy during strength drop and rapid sliding reduces pore pressure and strengthens the fault, promoting slip pulses. Large strain localization in the gouge layer occurs as a result of rapid gouge dilatancy and strain softening. The combination of prerupture weakening from compaction and restrengthening from dilatancy hardening leads to a smaller‐strength drop, and limits the stress concentration outside the gouge layer. This leads to a reduction of inelastic shear strain in the damage zone, which is more consistent with geological observations and high‐speed frictional experiments. With the presence of well‐developed fault gouge, the strength of mature faults may be limited by end‐cap rather than Mohr‐Coulomb failure; thus, their frictional strengths are significantly smaller than Byerlee friction.

Dynamically induced Coulomb failure in the overriding wedge significantly affects energy radiation of shallow subduction earthquakes. For a wedge on the verge of failure, extensive fluid-assisted coseismic failure due to updip rupture causes significant seafloor uplift above a shallow dipping basal fault. The large inelastic uplift, greatly enhanced by the presence of free surface, significantly dilates the fault behind the rupture front during the rupture propagation, which reduces the effective normal stress and sliding friction on the fault, and increases the dynamic stress drop and slip velocity. As a result, slip-velocity time histories in the shallow section of the fault tend to have a ‘snail-like’ shape, leading to depletion of high frequencies in the slip velocity field and the resultant source time function. We also show that the failure in the wedge acts as a large energy sink (while contributing to seismic moment), giving rise to distributed heat generation (i.e., small heat flow anomaly across the fault), low moment-scaled radiated energy, slow rupture velocity, and small directivity, which provides a unifying interpretation for nearly all anomalous observations documented for shallow subduction earthquakes.