Do Shallow Slip Deficits Reflect Fault Structural Maturity or Modeling Choices? A Comparative Analysis of Tibetan Strike‐Slip Earthquakes

Abstract

InSAR‐constrained finite fault slip models are often used to characterize fault geometries and slip distributions of large continental earthquakes. A common feature of these models is a decrease in slip near the surface, commonly expressed as a percentage shallow slip deficit (SSD). This often does not seem to be accommodated interseismically and its causes are still debated, with some studies attributing large deficits to off‐fault deformation along structurally immature faults. We explore this hypothesis through a survey of ten, well‐documented strike‐slip earthquakes from the Tibetan Plateau which occurred on faults that sample a wide spectrum of structural maturity. We collate published SSD values and also compute our own, modified “effective shallow slip deficit” based on the total (on‐ and off‐fault) surface offsets from optical imagery, where available. For the 2021 7.4 Maduo and 2022 6.6 Menyuan earthquakes, we assess the consistency of 10–13 independently modeled slip distributions by comparing them with each other. Slip models vary the most in the uppermost 1 km and around fault bends and other geometrical complexities, leading to large ranges in SSD of 0%–88% (for Maduo) and 0%–51% (for Menyuan). This highlights the need to scrutinize slip models carefully before considering shallow slip deficits. The influence from modeling choices, together with factors such as fault roughness and near‐surface geology, obscures any simple relationship between shallow slip deficits and fault structural maturity for large strike‐slip earthquakes on the Tibetan plateau.