The 2019 $Mw$ 6.4 and 7.1 Ridgecrest, California, earthquake sequence (July 2019) ruptured consecutively a system of high‐angle strike‐slip cross faults (northeast‐ and northwest‐trending) within 34 hr. The complex rupture mechanism was illuminated by seismological and geodetic data, bringing forward the issue of the interdependency of the two fault systems both at depth and at the surface, and of its effect on the final surface displacement pattern. Here, we use high‐resolution (WorldView and Pleiades) optical satellite image correlation to measure the near‐fault horizontal and vertical surface displacement fields at 0.5 m ground resolution for the two earthquakes. We point out significant differences with previous geodetic‐ and geologic‐based measurements, and document the essential role of distributed faulting and diffuse deformation in producing the observed surface displacement patterns. We derive strain fields from the horizontal displacement maps, and highlight the predominant role of rotation and shear strain in the surface rupture process. We discuss the segmentation of the rupture based on the fault geometry and along‐strike slip variations. We also image several northeast‐trending faults with similar orientation to the deeply embedded shear fabric identified in aftershock studies, and show that these cross faults are present all along the rupture, including at a scale <100 m. Finally, we compare our results to kinematic slip inversions, and show that the surface diffuse deformation is primarily associated with areas of shallow slip deficit; however, this diffuse deformation cannot be explained using elastic modeling. We conclude that inelastic processes play an important role in contributing to the total surface deformation associated with the 2019 Ridgecrest sequence.

We use remote sensing observations to document surface deformation caused by the 2025 M _w 7.7 Mandalay earthquake. This event is a unique case of an extremely long (~510 km) and sustained supershear rupture probably favored by the rather smooth and continuous geometry of this section of the structurally mature Sagaing Fault. The seismic rupture involved the locked portion of the fault over its entire depth extent (0 to 13 km) with a remarkably uniform slip distribution that averages 3.3 m, and an average stress drop of 4.7 MPa. No shallow-slip deficit is observed. The rupture extent challenges usual scaling laws relating earthquake magnitude, fault length, and slip. The fault ruptured along a known seismic gap that last ruptured in 1839 and tailed off into sections that ruptured during large earthquakes in 1930 and 1946. The amplitude and spatial distribution of fault slip in the 2025 event conform only approximatively to the slip-predictable model and the segmentation inferred from the fault geometry and past ruptures. Plausible sequences of earthquakes with variable magnitude, segmentation, and return periods, including events similar to the 2025 earthquake are produced in quasidynamic simulations using a simplified but nonplanar fault geometry. Based on this simulation, M _w >7.5 events return irregularly with an interevent time of ~141 y on average and a SD of ~40 y. The simulation is consistent with the historical seismicity and with the maximum magnitude ~M _w 7.9 and return period (~250 y) derived from moment conservation. Data assimilation into such simulations could provide a way for time-dependent hazard assessment in the future.

Earthquake ruptures produce fault slip and kilometer‐wide diffuse deformation of the host rocks. However, the origin of the diffuse deformation and its role in the rupture process are debated. We produce a refined slip model for the 2019 Ridgecrest, California, earthquakes, and analyze the relations between down‐dip rupture process, and surface diffuse deformation. We show that the decrease in coseismic slip toward the ground surface, also known as shallow slip deficit (SSD), correlates with the occurrence of diffuse deformation at the surface, which is not accounted for by models assuming elastic host rocks. Hence, we suggest that a significant part of the SSD in earthquake source models could be interpreted as a proxy for shallow diffuse inelastic deformation around faults. Revisiting earthquake source models for 28 continental earthquakes, we discuss the controlling parameters of the SSD and diffuse deformation, and propose a conceptual model of the near‐field coseismic surface deformation.

The amount and spatial distribution of surface displacement that occurs during an earthquake are critical information to the understanding of the earthquake source and rupture processes. However, the earthquake surface displacement occurs over wide regions, includes multiple components that affect the ground surface at different spatial scales, and is challenging to characterize. In this study, we assess the effect of optical imagery and topography data resolution on the measurement of the earthquake surface displacement when using optical image cross‐correlation (OIC) techniques. Results show that the average noise in the output displacement maps linearly increases with decreasing image resolution, resulting in greater uncertainties in mapping surface fault geometry and associated displacement. Consequently, we observe, on average, a decrease by a factor ∼0.7–0.8 of the measured horizontal displacement when using 10 m compared to 0.5 m resolution imagery. Our analysis suggests that optical images of resolution of ≤1 m are necessary to accurately capture the complexity of the ground change. Sub‐meter vertical accuracy for the digital surface/elevation model is also required to perform accurate image orthorectification and OIC, which is better achieved in high‐resolution stereo optical imagery compared to existing global topography data. Sub‐meter resolution and stereo configurations are thus required for both the pre‐and the post‐earthquake periods to measure the full 3D near‐fault displacement field, including the vertical component using Digital Surface Model difference methods. Together, these results highlight the measurement needs for improving the observation of earthquake surface displacement toward the development of future Earth surface topography and topography change observing systems.