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Interactions Between Shallow Slow Slip Events and Megathrust Earthquakes Based on 3D Dynamic Earthquake-Cycle Modeling

Description: 

Recent observations reveal that shallow slow slip events (SSEs) contribute to strain release at shallow subduction zone and may contribute to promoting shallow megathrust earthquakes. However, physics-based understanding of possible interactions between seismic and aseismic activities at shallow subduction zone is very limited. In this study, we use a 3D dynamic earthquake simulator, which captures both quasi-static (for SSEs) and dynamic (for megathrust earthquakes) slip on shallowly dipping subduction interfaces, to explore their interactions and implications for seismic and tsunami hazards. We construct a 3D subduction-zone model with two asperities of different strengths, including Z1 asperity of high normal stress and Z2 of low normal stress, embed within a conditionally stable zone on the subduction interface. We find that both SSEs and earthquakes can occur on this interface. SSEs occur mainly on the conditionally stable zone and dynamic ruptures can nucleate on asperities and propagate into the conditionally stable zone at slow speeds, generating tsunami earthquakes. There is a clear correlation between the size of an earthquake and SSE activities preceding it. Small earthquakes rupture only the low-strength asperity and stop near the boundary of the high-strength asperity, while large earthquakes rupture both asperities cascadingly. Before a large earthquake, multiple periodic SSEs occur near the high strength asperity Z1 during the interseismic period, which gradually load stress on Z1 to make it critically stressed until Z1 gets ruptured in a large earthquake. Before a small earthquake, the preceding interseismic period is quiet with very few SSEs. An SSE may or may not directly lead to nucleation of an earthquake, depending on whether a nearby asperity is ready for spontaneously dynamic failure. In addition, because of different SSE activities before small and large earthquakes, the coupling degree may change dramatically between different interseismic periods, so that coupling degree estimation based on a short period of observation (e.g. 20 years) may be biased.

Session: Numerical Modeling in Seismology: Developments and Applications

Type: Oral

Date: 4/20/2023

Presentation Time: 02:30 PM (local time)

Presenting Author: Qingjun Meng

Student Presenter: No

Invited Presentation: 

Authors