Elif Oral , Huihui Weng, Jean Paul Ampuero 

The impact of earthquakes can be severely aggravated by cascading secondary hazards.
The 2018 Mw 7.5 Palu, Indonesia earthquake led to devastating tsunamis and landslides, while triggered submarine landslides possibly contributed substantially to generate the tsunami. The rupture was supershear over most of its length, but its speed was unexpectedly low, between the S-wave velocity Vs and Eshelby’s speed sqrt(Vs), an unstable speed range in conventional theory. Here, we investigate whether dynamic rupture models including a low-velocity fault zone (LVFZ) can reproduce such steady, slow supershear rupture. We then examine numerically how this peculiar feature of the Palu earthquake could have affected the near-field ground motion and thus the secondary hazards. Our findings suggest that the presence of a LVFZ can explain the slowness of the rupture and may have mitigated the near-field ground motion and induced landslides in Palu.