On 7–8 January, 2025, the Eaton fire destroyed >9,000 structures and >40 km2 of forest in the northeastern region of the Los Angeles metropolitan area, California. Building damage was primarily assessed through ground investigations, a process that took several weeks due to hazardous conditions and the difficulty of accessing burnt areas. This study presents a novel approach for post-disaster damage assessment using sub-meter resolution satellite optical imagery. The Eaton fire is a good test case study as it benefits from ground-truth data collected during field surveys and subsequent airborne LiDAR acquisitions. The proposed approach utilizes stereo pairs of optical satellite images to reconstruct the 3D ground surface geometry before and after the event, enabling the detection of elevation changes across the affected regions. Results reveal meter-scale elevation differences associated with both collapsed structures and burned vegetation, spanning urban areas and the adjacent Angeles National Forest. This technique leverages established photogrammetric and post-processing methods, making it reproducible and adaptable to various disasters and geographic areas. The ultimate goal is to offer a rapid, high-resolution satellite-based solution for damage mapping.
\nWe use remote sensing observations to document surface deformation caused by the 2025 Mw 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, Mw >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 ~Mw 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.
", "doi": "10.1073/pnas.2514378122", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences", "publication_date": "2025-08-11", "series_number": "33", "volume": "122", "issue": "33", "pages": "e2514378122" } ]