Abstract
The 2017 Jiuzhaigou Ms 7.0 earthquake occurred on the northeastern margin of the Tibetan Plateau, with no noticeable rupture surface recognized. We characterized the pre-seismic deformation of the earthquake from GPS (Global Positioning System) data at eight continuous and 73 campaign sites acquired over the 2009–2017 period. With respect to the Eurasian plate, the velocity field showed a noticeable decrease, from west of the epicenter of the Jiuzhaigou earthquake to the western edge of the Longmenshan fault, in the southeast direction. The total northwest west–southeast east shortening rate in the vicinity of the epicentral area was in the range of 1.5 mm/y to 3.1 mm/y. With a GPS velocity transect across the Huya fault (HYF), where the epicenter was located, we estimated the activity of the HYF, showing a dominant left-lateral slip rate of 3.3 ± 0.2 mm/y. We calculated strain rates using a spherical wavelet-based multiscale approach that solved for the surface GPS velocity according to multiscale wavelet basis functions while accounting for spatially variable spacing of observations. Multiscale components of the two-dimensional strain rate tensor showed a complex crustal deformation pattern. Our estimates of strain rate components at the scale of seven and eight revealed extensional strain rate on the northern extension of the HYF. The Jiuzhaigou earthquake occurred at the buffer zone between extensional and compressional deformation, and with significant maximum shear rates being 100–140 nanostrain/y. In addition, a maximum shear strain rate of 60–120 nanostrain/y appeared around the epicenter of the 2013 Ms 6.6 Minxian–Zhangxian earthquake. These findings imply that inherent multiscale strain rates could be separated to identify strain accumulation related to medium- and large-sized earthquakes.
Highlights
The ongoing collision between the Indian and Eurasian plates has caused the eastward extrusion of the Tibetan Plateau and the uplift of Tibet [1,2]
Previous studies claimed that the uplift of Eastern Tibetan Plateau is due to the thickening of brittle crust [3,4] related to thrust fault rooted in the lithosphere with large amounts of slip
What was the strain pattern prior to the recent Ms 7.0 Jiuzhaigou earthquake? Is there any relationship between spatial strain buildup and seismic activities in this region? In this study, we explored the pre-seismic strain based on the GPS observations spanning from 2009 to 2017 and employed a multiscale spherical wavelet approach to calculate strain rate fields, as well as analyzed the correlation between crustal strain and seismicity
Summary
The ongoing collision between the Indian and Eurasian plates has caused the eastward extrusion of the Tibetan Plateau and the uplift of Tibet [1,2]. Some researchers argued that a lower crustal flow (channel flow) [5,6], in which low-viscosity material in the lower crust flows outward from the interior of the Plateau and inflates the crust in Eastern Tibet, is responsible for the low-rate east–west shortening across the mountains and within the Sichuan Basin. In both models, Tibet was regarded as moving eastward with respect to the Sichuan Basin across the northeastern borderland of Remote Sens. Previous studies showed the present-day crustal motion in this region was predominantly southeastward extrusion of the Eastern Tibetan Plateau with respect to the stable Sichuan Basin, part of the South China block (Figure 1). What was the strain pattern prior to the recent Ms 7.0 Jiuzhaigou earthquake? Is there any relationship between spatial strain buildup and seismic activities in this region? In this study, we explored the pre-seismic strain based on the GPS observations spanning from 2009 to 2017 and employed a multiscale spherical wavelet approach to calculate strain rate fields, as well as analyzed the correlation between crustal strain and seismicity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
