Geologic map with symbols.
Map of damage (rock fractures) around the Longmenshan fault zone, China. The red lines on this simplified geological map show the surface rupture of the 2008 magnitude 7.9 Wenchuan earthquake. The red star and USGS focal mechanism show the epicenter. The color-filled circles represent the amount of damage that scientists measured around the fault. The red circles are where the pre-existing rock damage was intense prior to the earthquake, whereas green circles show where there was little damage. Credit: Wu et al. [2024], Figure 1
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Geophysical Research Letters

When earthquakes break the Earth’s surface, they create surface ruptures along existing faults that are surrounded by damage zones. These damage zones are made of rocks that have fractured during past earthquakes. It is unclear how this pre-existing damage affects future earthquake ruptures. Some contend that more damage prevents energy from being stored and therefore damage inhibits earthquake rupture. Others argue that damage weakens the fault and leads to more earthquake slip.

Wu et al. [2024] measured the pre-existing damage around the surface rupture of the 2008 Mw7.9 Wenchuan earthquake in China. This unique data set allows a rare comparison between earthquake slip and pre-existing fracture damage. The data show an anti-correlation between the amount of fracture damage and the amount of near-surface slip in the earthquake. In other words, the study shows that, in this earthquake, existing damage inhibited slip.

The study implies that, as a fault accumulates near-surface damage, it may also (assuming the damage does not heal) reduce the amount of near-surface slip that can occur in future earthquakes. This also has implications for assessing hazard as the future slip distribution may be related to the distribution of existing damage – a hypothesis to be tested in additional locations.

Citation: Wu, C. H., Cui, P., Klinger, Y., Tan, X. B., Yi, S. J., & Li, Y. S. (2024). Pre-existing off-fault damage can impede coseismic on-fault slip. Geophysical Research Letters, 51, e2024GL111198. https://doi.org/10.1029/2024GL111198

—Åke Fagereng, Associate Editor, Geophysical Research Letters

Text © 2024. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.