Shear Fault Formation in Granite Under High and Transient Co‐Seismic Strain Rates Unveiled by Ultra‐Fast X‐Ray Imaging

Kinematics and Dynamics of Normal Faults in Southern Tibet: Insights From the 2025 Mw 7.1 Dingri Earthquake

Normal faults in southern Tibet have long suffered from limited ground‐based seismic and geodetic observations, constraining our understanding of both interseismic and coseismic processes and their interactions. The 2025 Mw 7.1 Dingri earthquake provides an opportunity to address these gaps. Here, we integrate interseismic slip deficit rate inversion, finite‐fault slip analyses, and 3D dynamic rupture simulations constrained by geodetic and seismic data to investigate fault behavior. The earthquake ruptured two asperities, with a shallow slip gap located above the hypocentral region, and exhibited a slow initiation followed by rapid strain release. A fault bend may have arrested the southward rupture, while the northward termination appears to have been controlled by a low slip deficit rate barrier. The shallow slip gap above the hypocenter may represent a high‐strength segment requiring elevated fracture energy for rupture initiation, resulting in the relatively slow rupture onset during the event. These results indicate that geometric complexity and heterogeneity of on‐fault stress and strength jointly governed the normal faulting. In addition, we quantified seismic moment accumulation rates on 132 normal faults in southern Tibet, finding that the accumulated moments over 500 years correspond to earthquakes of Mw 5.3–7.2. However, geometric and stress‐strength heterogeneities may reduce the likelihood of large cascading ruptures compared to large block‐bounding strike‐slip and thrust faults. Overall, our findings highlight rupture complexities of the Dingri earthquake, while underscoring substantial seismic hazards posed by rift systems in southern Tibet.

The 2024 Mw4.8 New Jersey Intraplate Earthquake: Preferential Rupture of an Immature Fault in Frictionally Unstable Basement Rocks

Dynamic Rupture and Near-Fault Ground-Motion Simulation of the 1973 MS7.6 Luhuo, China, Earthquake

The 1973 MS7.6 Luhuo earthquake is the most representative strike-slip event in the Xianshuihe fault zone, yet published source models differ markedly, and the mechanism that arrested its rupture near Renda remains poorly understood. Using spectral-element dynamic rupture simulations with a nonplanar fault geometry, three-dimensional velocity model, and depth-dependent initial stress field, we test whether fault geometry or inherited stress heterogeneity controlled the termination. Our results show that N75° W is the optimal maximum principal stress orientation, yielding surface offsets, a bilateral rupture mode, and an intensity pattern consistent with observations. Fault geometry alone cannot explain the termination: continuous and dipping faults rupture completely, and a 1 km stepover at Renda blocks the rupture jump yet leaves minor slip on the secondary fault. Introducing the 1923 Daofu earthquake stress change as a low-stress barrier instead terminates rupture near Renda, and simulated magnitude, offsets, and intensity then agree with observations. A compliant damage zone raises coseismic slip and lowers the moment magnitude while contracting the meizoseismal zone, whereas topography barely alters the rupture but appreciably modulates ground motion. These findings demonstrate that inherited stress heterogeneity, rather than fault geometry, can be the primary control on rupture arrest and can inform seismic hazard assessment for the Sichuan-Yunnan fault system.

The 2024 Mw 7.3 Hualien Earthquake Sequence: Aftershock-Constrained Fault Geometry and Static Stress Triggering Analysis

The 2024 Mw 7.3 Hualien earthquake represents a significant seismic event in a highly complex tectonic setting, providing a critical opportunity to constrain complex fault geometries and evaluate stress triggering mechanisms. We compiled a high-resolution aftershock catalog of 23,748 events from continuous seismic waveforms recorded over three months. This catalog systematically documents the spatiotemporal evolution of the 2 April 2024 Mw 7.3 Hualien mainshock and its aftershocks. The aftershock distribution outlines a conjugate fault system composed of the east-dipping Longitudinal Valley fault and the west-dipping Central Range fault, with clear depth-dependent variations in geometry. The seismicity front expanded as a logarithmic function of time, consistent with afterslip-driven migration of the Hualien earthquake sequence. The aftershocks predominantly occurred around and outside of the high-slip periphery, consistent with stress reduction within high-slip areas and stress concentration at the periphery and gradient zones of the high-slip area. Coulomb stress calculations further suggest that static stress transfer from the mainshock contributed to the occurrence of several major aftershocks. These results highlight the role of stress interactions in controlling aftershock distribution and provide constraints on postseismic hazard assessment in eastern Taiwan.

cavitation as a mechanism for nucleating earthquakes at the base of the seismogenic zone

Transmission of Seismic Waves With Tensile Components Across Cemented Rock Discontinuities Exhibiting Tension‐Softening Behavior

Fault slip involves not only shear but also tensile motions, causing repeated opening and closure of fault‐zone discontinuities. This cyclic deformation progressively changes the mechanical stiffness, fundamentally impacting seismic wave transmission. However, most existing analytical models neglect tensile components. This study develops a unified analytical framework combining the established Barton‐Bandis (BB) model for compressive deformation with a proposed inverse hyperbolic‐linear (iHL) model to describe tensile loading and unloading behaviors of cemented rock fractures. Integrating this model into a displacement discontinuity model and method of characteristics, we present the analytical solution that simultaneously accounts for compression‐hardening and tension‐softening effects on stress wave propagation. The BB‐iHL model uses an effective stiffness evolving dynamically with the instantaneous stress state, enabling quantitative prediction of stress wave transmission during earthquake cycles. Validation against split Hopkinson pressure and tension bar experiments confirms the model's ability to reproduce more realistic wave propagation. Results demonstrate that tensile stiffness degradation strongly influences wave transmission coefficients, particularly at low frequencies and amplitudes, and that ignoring tensile effects underestimates transmitted energy and waveform complexity. A case study based on seismic data from the 2008 Wenchuan earthquake illustrates the potential of the proposed framework for analyzing field‐scale seismic wave transmission. These findings underscore the critical role of tensile deformation in fault‐zone dynamics and highlight the proposed model as a tool for more accurate seismic wave modeling and earthquake hazard assessment.