Coseismic and early postseismic deformation due to the 2021 M7.4 Maduo
(China) earthquake
Abstract
Key Points: • We use Sentinel-1 Synthetic Aperture Radar (SAR) data to
derive a finite fault model for the 2021 M7.4 Maduo (Qinghai, China)
earthquake • The along-strike averaged coseismic slip has a maximum at
depth of 3-4 km, with an amplitude of ∼2.5 m. • Up to ∼0.1 m of
afterslip occurred on the fault trace in the first month following the
earthquake. Abstract The 2021 Maduo earthquake ruptured a 150 km-long
left-lateral fault in the northeast Tibet. We used Synthetic Aperture
Radar data collected by the Sentinel-1A/B satellites within days of the
earthquake to derive a finite fault model and investigate the details of
slip distribution with depth. We generated coseismic interferograms and
pixel offsets from different look directions corresponding to the
ascending and descending satellite orbits. At the eastern end the
rupture bifurcated into two sub-parallel strands, with larger slip on
the northern strand. Inversions of coseismic displacements show maximum
slip to the east of the epicenter. The averaged coseismic slip has a
peak at depth of 3-4 km, similar to slip distributions of a number of
shallow strike-slip earthquakes. Postseismic observations over several
weeks following the Maduo earthquake reveal surface slip with amplitude
up to 0.1 m that at least partially eliminated the coseismic slip
deficit in the uppermost crust. Plain language summary A large
earthquake occurred in a remote area of northeast Tibet (Qinghai
Province, China) on May 21, 2021. The earthquake produced a 150 km-long
rupture with surface offsets up to several meters. We used data
collected by orbiting satellites to map motions of the Earth’s surface
that occurred during and shortly after the earthquake. The measured
surface displacements were used to constrain the rupture geometry and
slip distribution at depth. Best-fitting models suggest that rupture
occurred on a sub-vertical fault steeply dipping to the north, with most
of slip occurring to the east of the earthquake epicenter. The maximum
coseismic slip occurred in the uppermost crust, in the depth interval of
3-4 km below the Earth’s surface. A decrease in the fault offsets toward
the Earth’s surface is likely caused by an increased frictional
resistance of the shallow layer to rapid coseismic slip. Satellite
observations made in the first month after the earthquake reveal that
the shallow part of the fault is slowly catching up with a deeper part
to make up for the difference in the amount of slip produced during the
earthquake.