Coseismic Deformation Analysis of Qinghai Maduo Ms 7.4 Earthquake Based on Optical Remote Sensing and SAR Images

Objectives An Ms 7.4 earthquake occurred in Maduo, Qinghai Province,China on May 22, 2021, which is a rare powerful earthquake that occurred in Bayan Har block in recent years, it is essential to study the characteristics of its coseismic deformation field.

Methods Based on Sentinel-2 and Landsat 8 images before and after Maduo earthquake, east-west and south-north two-dimensional coseismic deformation fields were obtained by optical pixel offset tracking (POT). Interferometric synthetic aperture radar (InSAR)was utilized to obtain line of sight (LOS) coseismic deformation based on Sentinel-1 ascending and descending images, and synthetic aperture radar (SAR) POT was utilized to obtain range and azimuth directions coseismic deformation of the earthquake, meanwhile, 3D coseismic deformation field of this earthquake is calculated, moreover, the results of coseismic deformation field extracted are compared and verified.

Results The experimental results show that coseismic deformation field characteristics of Maduo earthquake based on optical and SAR images are great consistent. Maduo earthquake is a typical left-lateral strike-slip event, the coseismic deformation is dominated by east-west horizontal movements, and the seismogenic fault is Jiangcuo fault. Based on optical images, it is obtained that east-west and north-south deformations of the earthquake are about ±1.60 m and ±0.60 m,respectively. Based on SAR images, the maximum LOS uplift and subsidence of ascending are about 1.29 m and -1.12 m, and descending are about 1.15 m and -1.26 m. In the 3D coseismic deformation field, the east-west deformation is about -2.00 m to 1.70 m, north-south deformation is mainly concentrated in -1.00 m to 0.50 m, and it moves alternately up and down along both sides of the fault zone in vertical direction, the deformation is about ±0.3 m. The magnitude of deformation values on north side of the earthquake is larger than that on south side. Branch ruptures are shown at the end of the southeast (34.48°N, 99.04°E) and northwest (34.76°N, 97.61°E) of the surface rupture, and south side of Eling Lake (34.74°N, 97.75°E), and aftershock sequence is distributed near these branch ruptures.

Conclusions InSAR and POT technologies complement each other, which provide an effective way to obtain the complete coseismic deformation field, and multi-platform, high-resolution optical and SAR images provide important datasets.