Off-fault deformation in regions of complex fault geometries: the 2013, Mw7.7, Baluchistan rupture (Pakistan)

Journal of Geophysical Research, Solid Earth
By: , and 



Observations of recent earthquake surface ruptures show that ground deformations include a localized component occurring on faults, and an off-fault component affecting the surrounding medium. This second component is also referred to as off-fault deformation (OFD). The localized component generally occurs on complex networks of faults that connect at depth onto a unique fault plane, whereas OFD consists of distributed fracturing and diffuse deformation of the bulk volume, and occurs over scales of hundreds of meters to kilometers around the faults. High-resolution optical image correlation presents a unique potential to characterize the complexity of the surface displacements, including on-fault displacements and OFDs. In this study, we used sub-pixel correlation of 0.5-m resolution optical images to measure the surface displacement field with a <20 cm accuracy for a 30-km long section of the 2013 Mw7.7 Baluchistan, Pakistan, rupture. Our results document significant variability in the fault displacements, associated with large proportions of OFD in regions of fault geometrical complexity. Conversely, in regions where the fault geometry is simple, surface deformation is entirely accommodated by the primary faults with 0% OFD. When combining the localized deformation on faults with the OFD, we show that the total surface displacement budget is constant along the strike of the rupture, despite strong variations observed in the rupture geometry. Based on this analysis, we propose an idealized scenario of earthquake surface deformation as a function of the rupture geometrical variations.

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Publication type Article
Publication Subtype Journal Article
Title Off-fault deformation in regions of complex fault geometries: the 2013, Mw7.7, Baluchistan rupture (Pakistan)
Series title Journal of Geophysical Research, Solid Earth
DOI 10.1029/2022JB024480
Volume 127
Issue 11
Year Published 2022
Language English
Publisher American Geophysical Union
Contributing office(s) Geologic Hazards Science Center
Description e2022JB024480, 19 p.
Country Pakistan
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