Temporal evolution of strain rate before the 2021 Mw 7.4 Maduo Earthquake.

The development of geodetic tools, such as Interferometric Synthetic Aperture Radar (InSAR), has revolutionized our exploration of earthquake physics and the assessment of seismic hazard. Over the past 20 years, InSAR has been increasingly used to determine the interseismic strain rate across major seismogenic faults. Strain derived from geodetically mapped crustal deformation rates serves as an indicator of a fault’s earthquake potential, in alignment with classical elastic rebound theory. However, InSAR observation periods are often relatively short compared to much longer large earthquake recurrence intervals. This raises questions about how well geodetic strain rates represent the long-term strain accumulation on faults. It is therefore critical to understand how strain rate evolves during the interseismic period. 

We observe the interseismic period prior to the 2021 Mw 7.4 Maduo Earthquake: a left-lateral strike-slip earthquake that ruptured a slow-moving fault approximately 70 km south of the major block-bounding East Kunlun fault in the Eastern Tibetan Plateau. Using six years of Sentinel-1 data, we explore the temporal evolution of strain rate over time. We derive eastward velocity and maximum shear strain rate for the six-year period prior to the Maduo earthquake, before segmenting the time-series and analysing strain rate with a two-year moving time window. Our results indicate that the geodetically derived strain rate may not be constant over the interseismic period, implying that strain may not accumulate at a fixed rate in the seismogenic crust. Additionally, strain rate on the seismogenic fault does not appear to accelerate prior to the Maduo earthquake, at least on the timescales resolvable by InSAR used in this study.