Yu Zhou is a doctoral student at the University of Oxford, working under the supervision of Barry Parsons and Richard Walker.
Very high resolution satellites provide low cost means of measuring ground height changes
Light detection and ranging (LiDAR) surveys from aircraft have been a valuable tool for determining vertical offsets in earthquakes, but so far their relatively high cost and low availability has limited their applicability.
New generations of very high resolution (VHR) satellites such as Pleiades provide an alternative means of measuring surface topography with precision down to tens of centimetres, at a much lower cost.
To demonstrate how Pleiades stereo imagery can determine height changes of less than a metre, we acquired data for the area around the epicentre of the El Mayor-Cucapah 2010 earthquake (just south of the US-Mexico border) which has also been covered by both pre- and post-earthquake LiDAR surveys.
By establishing differences between the 1 m ground resolution Pleiades imagery and the pre-earthquake, 5 m ground resolution LiDAR data, we mapped the vertical component of slip in the 2010 earthquake (Figure 1). Our results were comparable to a previous study that used the post-earthquake LiDAR data (Oskin et al., 2012).
The Pleiades stereo imagery also allowed us to resolve a current controversy about the 2013 Mw 7.7 Balochistan earthquake. Previous studies have argued that the fault kinematics switch between strike-slip and dip-slip motion in successive earthquakes (Avouac et al., 2014; Barnhart et al., 2015).
However, by determining the vertical component of motion on the 200+ km long Hoshab fault for the first time, we found that the oblique motion in the 2013 earthquake is typical of this fault. A constant ratio of vertical to horizontal motion over multiple earthquakes (Figure 2) suggests that the Hoshab fault has experienced the same style of faulting throughout the Late Quaternary.
The Balochistan earthquake provides an example of distributed faulting in a remote and inaccessible area that has been made amenable to detailed near-field investigation by the new generation of very high-resolution satellite stereo imagery.
References
Zhou, Y., Parsons, B., Elliott, J., Barisin, I., Walker, R. (in prep.) Assessing the ability of Pleiades stereo imagery to determine height changes in earthquakes: a case study for the El Mayor-Cucapah epicentral area, Journal of Geophysical Research.
Zhou, Y., Elliott, J., Parsons, B., Walker, R. (in review) The 2013 Balochistan earthquake: an extraordinary or completely ordinary event?, Geophysical Research Letters.
Barnhart, W., Briggs, R., Reitman, N., Gold, R., Hayes, G. (2015) Evidence for slip partitioning and bimodal slip behaviour on a single fault: Surface slip characteristics of the 2013 Mw 7.7 Balochistan, Pakistan earthquake, Earth and Planetary Science Letters, 420, 1–11. doi:10.1016/j.epsl.2015.03.027
Avouac, J.-P., Ayoub, F., Wei, S., Ampuero, J.P., Meng, L., Leprince, S., Jolivet, R., Duputel, Z., Helmberger, D. (2014) The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault, Earth and Planetary Science Letters, 391, 128–134. doi:10.1016/j.epsl.2014.01.036
Parsons, B., Zhou, Y., Elliott, J., Barisin I., Walker, R. (2014) Assessing the Ability of Pleiades Stereo Imagery to Determine Height Changes in Earthquakes: A Case Study for the El Mayor–Cucapah Epicentral Area, (EP43E-08) AGU, San Francisco, USA, 15-19 December.
Oskin, M. E., Arrowsmith, J.R., Corona, A.H., Elliott, A.J., Fletcher, J.M., Fielding, E.J., Gold, P.O., Garcia, J.J.G., Hudnut, K. W., Liu-Zeng, J., Teran, O.J. (2012) Near-field deformation from the El Mayor–Cucapah earthquake revealed by differential LIDAR, Science, 335 (6069), 702–705. doi:10.1126/science.1213778