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How Often Do Subduction Interfaces and Overriding Upper-Plate Faults Rupture in the Same Earthquake (Or Close Enough in Time to Be the Same Situation)?

Description: 

Many global cities such as Anchorage, Karachi (Pakistan), Guayaquil (Ecuador) and Wellington (New Zealand) are located in strain-partitioned environments. For these cities, the worst-case-scenario earthquake might be a joint rupture of the subduction zone and one or more upper-plate faults. For example, the worst-case-scenario earthquake for Wellington would be a joint rupture of the southern Hikurangi interface and the southern Wellington Fault: the first would pose a tsunami hazard, the second would rupture lifelines, and both would cause strong shaking. However, the likelihoods and characteristics of joint ruptures are not particularly well understood, as there are only a handful of well-known cases of them (among which are the 1964 M=9.2 Alaska, 1855 M=8.2 Wairarapa and 2016 M=7.8 Kaikoura earthquakes). In applications of physics-based earthquake simulators to New Zealand within the RNC national science challenge programme, joint subduction/upper-plate ruptures occur frequently (e.g., Shaw et al., 2022), but it is uncertain how much this behaviour is controlled by modelling assumptions and details of model setup. To ground-truth the earthquake simulators, we look at the largest recorded subduction earthquakes around the world and examine how many of them also involved slip on upper-plate faults, or were closely followed by large upper-plate aftershocks. We also examine potential interactions between subduction-interface and upper-plate seismicity in Hikurangi earthquake sequences in 1961 and 1990. Finally, we note that both cosesismic and early aftershock triggering of upper plate faults, as commonly seen in simulators, have significant consequencs for event response and emergency management systems stress testing.

Session: Illuminating Complex, Multiplet Earthquake Sequences at Kahramanmaras (Turkiye), Herat (Afghanistan), and Beyond - II

Type: Oral

Date: 5/2/2024

Presentation Time: 11:15 AM (local time)

Presenting Author: Chris

Student Presenter: No

Invited Presentation: 

Authors