Characterising complex surface ruptures in the 2013 Mw 7.7 Balochistan earthquake using three‐dimensional displacements

Journal article

We use satellite‐derived high‐resolution topography and ortho‐images, namely pre‐earthquake Advanced Land Observing Satellite World 3D data and post‐earthquake Pleiades data, to retrieve 3D displacements in the 2013 Balochistan, Pakistan earthquake. Previous studies of this earthquake have revealed many complex rupture patterns, such as off‐fault deformation (near‐field strike‐slip displacements smaller than the far‐field) and inelastic surface deformation (horizontal shortening on the surface significantly larger than that from simple elastic model). In this paper, we re‐analyse the complexities of surface ruptures in a systematic way using the newly‐derived 3D displacements. In doing so, we made use of the vertical component of the curl and the horizontal divergence of the displacement field. By comparing the off‐fault deformation and curl field along the rupture, we found curl is a good measure of the width of the deformation zone. The curl width ratio (CWR)– the ratio of the basic resolution of the curl field and curl width– was used to quantify the degree of surface slip localisation. When CWR ≥ 0.9, there is no or very little off‐fault deformation, whereas when CWR ≤ 0.6, surface deformation is almost 100% distributed. The distributed deformation observed is controlled by both the fault geometry and local material types. Despite the overall strike‐slip with some thrusting, the divergence shows localised extension or enhanced shortening in the near field due to fault geometric variations at a spatial scale of tens to hundreds of metres, consistent with the 3D displacements and geological interpretations.

Authors: Zhou, Y; Parsons, B; Walker, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Geophysical Union
• Journal: Journal of Geophysical Research
• Volume: 123
• Issue: 11
• Pages: 10,191-10,211
• Publication date: 2018-10-23
• Acceptance date: 2018-10-17
• DOI: 10.1029/2018JB016043
• EISSN: 2169-9356
• ISSN: 0148-0227
• Keywords: 3D displacements; 2013 Balochistan earthquake; complex surface ruptures