Does a Damaged‐Fault Zone Mitigate the Near‐Field Impact of Supershear Earthquakes?—Application to the 2018 7.5 Palu, Indonesia, Earthquake

Abstract

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 slow for a supershear event, between the S wave velocity VS and Eshelby's speed 2VS, an unstable speed range in conventional theory. Here, we investigate whether dynamic rupture models including a low‐velocity fault zone can reproduce such a steady supershear rupture with a relatively low speed. 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 low‐velocity fault zone can explain the unexpected rupture speed and may have mitigated the near‐field ground motion and the induced landslides in Palu.

Anatomy of Strike Slip Fault Tsunami-genesis

“…Our results suggest that strike slip faults, unlike what is typically assumed (16,54,55), may cause large tsunamis without the need to trigger underwater landslides. These results are based on numerical simulations of simple dynamic rupture scenarios on planar faults traversing a bay with idealized and smooth geometry.…”

Continuum of earthquake rupture speeds enabled by oblique slip

“…speed of this earthquake assumes the presence of a low velocity fault zone25 , which remains to be confirmed by local fault studies. The 2013 Mw6.7 Okhotsk deep earthquake9 and…”

Fault‐Zone Damage Promotes Pulse‐Like Rupture and Back‐Propagating Fronts via Quasi‐Static Effects

“…Our anti‐plane results can be transferred to in‐plane slip by replacing μ with μ /(1 − ν ), where ν is Poisson's ratio. However, in‐plane dynamical models can promote additional slip complexity, for instance transitions to supershear rupture speed which are relevant for the interpretation of past earthquakes (Huang et al, 2016; Oral et al, 2020).…”