Recent GPS observations show that slow slip events in south central Alaska are segmented along-strike. In this project, we review several mechanisms that might contribute to this kind of segmentation, suggesting that the subducted Yakutat Plateau might be main reason. We then use numerical simulations in the framework of rate-and-state friction with a non-planar fault geometry, aiming to understand which parameters are required to vary along-strike to recreate the segmentation. The simulations reproduced key observations such as the interval, duration, magnitude, propagation speed, and moment-area scaling of slow slip events in this region. In most cases, these two segments rupture independently but occasionally rupture together. Results show that the segmentation is most likely related to the along-strike variation of effective normal stress on the fault plane. Receiver function modeling based on seismic data show little along-strike variation of Vp/Vs ratio on the fault zone, suggesting little along-strike change of pore-pressure. Then the difference in effective normal stress would come from difference of normal stress from overburden structure and the extra buoyancy from the subducted Yakutat Plateau, with a larger contribution from the later. Our work implies that a structural anomaly will have a long-lived effect on the slip behavior of a subduction zone and might be a driving factor on slow slip event segmentation.
For haotian Li: fig1_AK