1. Excitation of Back‐Arc Tsunamis From Megathrust Ruptures: Theory and Application to the Sea of Japan.
- Author
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Salaree, Amir and Huang, Yihe
- Subjects
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TSUNAMI warning systems , *THRUST faults (Geology) , *TSUNAMIS , *SEISMIC waves , *SENDAI Earthquake, Japan, 2011 , *BACK-arc basins - Abstract
Large megathrust ruptures can create notable tsunamis in tectonic back‐arc basins as was documented during the 2011 Tohoku earthquake in the Sea of Japan. We present a physical analysis of the excitation of back‐arc tsunamis by extending the fore‐arc deformation field from the earthquake centroid into the back‐arc basin and identify fault dip as the main geometrical contributor to the propagation of these events. As such, our theoretical model along with a large number of numerical simulations reveal that the dominant period of back‐arc tsunamis is different from that of the fore‐arc waves and thus they are a new class of tsunamis. Through numerical simulations and analysis of data from the 2011 Tohoku event, we show that a combination of near‐ to intermediate‐field horizontal and vertical deformation as well as transient surface waves is necessary to reconstruct the back‐arc propagation. We find that while seismic surface waves can affect coastal tsunami amplitudes in the back‐arc, their effect comes second to that of the horizontal component of deformation as manifested via bathymetric gradient. We then simulate back‐arc tsunamis and the hazard in the Sea of Japan from several potential future earthquake scenarios in the Japan Trench and Nankai Trough. Our results show that the coseismic excitation of back‐arc tsunamis can result in considerable waves close to 1 m in the Sea of Japan, near the Niigata Prefecture from megathrust earthquakes. Plain Language Summary: The 2011 Japan earthquake created a large tsunami in the Pacific Ocean. But it also made a moderate tsunami in the Sea of Japan, on the far side of the Japanese islands. We call these waves Back‐arc tsunamis and study their properties by looking at the contributions of various earthquake aspects including earthquake size, depth, fault geometry, and seismic surface waves, to the generation of these tsunamis. Our work shows that contrary to regular tsunamis, the hazard from back‐arc tsunamis is affected by the fault dip angle (how steep the fault is). We also find that large earthquakes in eastern Japan can create relatively large back‐arc tsunamis (with wave heights exceeding 1 m) in the Sea of Japan. Key Points: We present theoretical and numerical models of back‐arc tsunamis produced by megathrust earthquakesAmong source parameters, seismic moment and fault dip angles determine the dominant period and the spread of back‐arc tsunamisBack‐arc tsunamis from Japan Trench rupture scenarios can reach amplitudes >1 m in the Sea of Japan, and should be included in hazard models [ABSTRACT FROM AUTHOR]
- Published
- 2023
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