Along-dipping variations in fault geometry influencing shallow-slip-deficit during the 2021 MW7.4 Maduo earthquake

The shallow slip deficit (SSD) during strike-slip earthquakes raises a question of how the strain budget is accommodated over multiple cycles. However, the origin of variable SSD observed in different earthquakes is still under debate because each earthquake has its unique initial stress condition. Here, we derive the slip model of the 2021 M_W7.4 Maduo earthquake in Qinghai, China, using multi-track radar images. Our results revealed that, in contrast to the large SSD on segments close to the epicenter, a much smaller SSD was observed at the west terminus of the rupture, where aftershock distribution indicates that the fault changes dip direction at 6 km depth. The 2021 Maduo earthquake thus represents an extraordinary case of significant along-strike SSD variation. After accounting for interseismic, postseismic, and diffuse off-fault deformation, we find that this variation is likely contributed by the along-dipping geometrical variation, implying that a multi-segment earthquake may leave heterogeneous stress condition on the fault with different amounts of SSD.