Comparison of coseismic near‐field and off‐fault surface deformation patterns of the 1992 M w 7.3 Landers and 1999 M w 7.1 Hector Mine earthquakes: Implications for controls on the distribution of surface strain

Subpixel correlation of preevent and postevent air photos reveal the complete near‐field, horizontal surface deformation patterns of the 1992 M w 7.3 Landers and 1999 M w 7.1 Hector Mine ruptures. Total surface displacement values for both earthquakes are systematically larger than “on‐fault” displacements from geologic field surveys, indicating significant distributed, inelastic deformation occurred along these ruptures. Comparison of these two data sets shows that 46 ± 10% and 39 ± 22% of the total surface deformation were distributed over fault zones averaging 154 m and 121 m in width for the Landers and Hector Mine events, respectively. Spatial variations of distributed deformation along both ruptures show correlations with the type of near‐surface lithology and degree of fault complexity; larger amounts of distributed shear occur where the rupture propagated through loose unconsolidated sediments and areas of more complex fault structure. These results have basic implications for geologic‐geodetic rate comparisons and probabilistic seismic hazard analysis. Hector Mine near‐field surface deformation measured from air photo correlation is compared to Landers deformation (Milliner et al., 2015) Landers and Hector Mine had significant distributed deformation 46% and 39% over average fault widths of 154 m and 121 m, respectively Field measurements underestimate fault slip due to distributed strain thus affecting empirical scaling laws and geologic slip rates