Overlapping regions of coseismic and transient slow slip on the Hawaiian decollement

Earthquakes and slow slip are different faulting processes that release accumulated stress on different time scales. Despite nearly two decades of study, it is still unclear whether the same section of fault is capable of hosting both slow, aseismic and fast, seismic slip. Here, we jointly invert GPS, strong motion records, and empirically corrected tsunami waveforms for the 2018 M7.1 Hawai'i earthquake. Our inversion results suggest the earthquake had a slow rupture speed of 1.2 km/s with a maximum slip of similar to 3 m South-East of the hypocenter extending to the South-West through an area known to regularly host slow slip events. After exploring how the choice of fault geometry and regularization parameters affect the slip distributions of the earthquake and slow slip events we find strong evidence of overlap between the two. Additionally, we perform numerical modeling to simulate fast and slow slip behavior. Due to the homogeneity of the Hawaiian decollement differences in effective stress are likely an important factor that causes the diversity of slip. We find that an earthquake can completely penetrate into the slow slip zone provided the effective stress differences between fast and slow slip zones is large enough to facilitate this. Our results reinforce the idea that an individual section of fault is capable of hosting a variety of distinct slip behaviors. This is important for estimating earthquake rupture extent and for better ground motion and tsunami hazard assessment. (C) 2020 Elsevier B.V. All rights reserved.