Strain Threshold for the Formation of Coseismic Surface Rupture

The 2021 M-w 7.4 Maduo earthquake (eastern Tibetan Plateau), with a surface deformation zone that is characterized by multiple distinct surface rupture segments separated by segments with no surface ruptures, provides an excellent opportunity to constrain the strain threshold (minimum strain) for the formation of surface ruptures. Through sub-pixel correlation of pre- and post-event SPOT-6/7 satellite images (pixel = 1.5 m), we derive surface displacement and shear-strain fields of the Maduo earthquake. By quantifying the minimum shear strain along the surface rupture segments and the maximum shear strain along the segments with no surface ruptures, we estimate a rupture strain threshold, which ranges from 0.8% to 1.8% and appears to decrease with structural maturity of the causative fault. This threshold is generally consistent with a rupture strain limit (0.5%-1.5%) of intact rocks from laboratory measurements, and is higher than a commonly-assumed strain threshold (0.5%) for inelastic deformation.

Automated summary

The 2021 M-w 7.4 Maduo earthquake in the eastern Tibetan Plateau had a surface deformation zone characterized by multiple distinct surface rupture segments and segments with no surface ruptures. By analyzing satellite images, surface displacement and shear-strain fields were derived, revealing a rupture strain threshold ranging from 0.8% to 1.8%. This threshold, which decreases with the fault's structural maturity, is generally consistent with laboratory measurements of intact rocks and higher than the commonly-assumed strain threshold for inelastic deformation (0.5%).