ИСТИНА

The effect of fault rupture dynamics in the earthquake source on tsunami generation has been actively studied in recent years for real [e.g. 1] and hypothetical [e.g. 2,3] events. The purpose of this study is to investigate the effect of rupture dynamics on the generation of the 2015 Illapel tsunami. The Illapel event was chosen for consideration because (1) most of papers devoted to the reconstruction of the source of this earthquake emphasize the importance of the fault rupture dynamics [4]; (2) a large amount of observational data is available; and (3) preliminary analysis in terms of total tsunami energy has shown that the dynamics of the formation of the permanent bottom deformation in this very event significantly affects tsunami generation [5]. To reconstruct the dynamic bottom deformation, we used the dynamic Finite Fault Model earthquake source from the USGS database. Based on this earthquake source, using Okada formulas and the superposition principle, we created static and quasi dynamic bottom deformations (i.e. without seismic waves). For the created deformations, we performed numerical simulations of tsunamis using the JAGURS [6] and CPTM [7] models. Numerical tsunami simulation shows that the consideration of dynamic parameters leads to a redistribution of tsunami amplitudes in space. The maximum values of tsunami amplitude along the entire coast are approximately the same for the dynamic (5.54 m) and static sources (5.78 m). But at some points along the coast, the dynamic source produces a larger tsunami amplitude (by 2.18 m in absolute value), while at other points, the static source produces a larger tsunami amplitude (by 1.32 m in absolute value). It is also found that the use of the dynamic source leads to saturation of the signal with high-frequency components, the intensity of which weakens with distance from the source. All the results obtained will be interpreted based on the basic mechanisms of tsunami amplification caused by the dynamics of bottom deformation. The JAGURS model is based on two-dimensional nonlinear Boussinesq dispersive equations in spherical coordinates, while the CPTM model is based on three-dimensional compressible fluid potential theory equations, which require much longer computation times. A comparison of the tsunami height time series calculated with the use of JAGURS and CPTM models showed that the difference between them is small (NRMSD is less than 12%) and manifests itself mainly in the short-wave disturbances following the leading tsunami wave. 1.Le Gal M., Violeau D., Ata R., Wang, X. (2018). Shallow water numerical models for the 1947 gisborne and 2011 Tohoku-Oki tsunamis with kinematic seismic generation. // Coastal Engineering, 139, 1-15. 2.Fukutani Y., Suppasri A., Imamura F. (2015). Stochastic analysis and uncertainty assessment of tsunami wave height using a random source parameter model that targets a Tohoku-type earthquake fault. //Stochastic Environmental Research and Risk Assessment, 29, 1763-1779. 3.Williamson A., Melgar D., Rim D. (2019). The effect of earthquake kinematics on tsunami propagation. //Journal of Geophysical Research: Solid Earth, 124(11), 11639-11650. 4.Satake K., Heidarzadeh M. (2017). A review of source models of the 2015 Illapel, Chile earthquake and insights from tsunami data // The Chile-2015 (Illapel) Earthquake and Tsunami, 1-9. 5.Sementsov K.A., Tanioka Y., Nosov M.A., Kolesov S.V. (2023) Tsunami amplitude amplification due to the dynamics of the bottom deformation: case studies of real events // JpGU Meeting 21-26 May, 2023 6.Baba T., Takahashi N., Kaneda Y., Ando K., Matsuoka D., Kato T. (2015). Parallel implementation of dispersive tsunami wave modeling with a nesting algorithm for the 2011 Tohoku tsunami // Pure and Applied Geophysics, 172, 3455-3472. 7.Nosov M. A., Kolesov S. V. (2019). Combined numerical model of tsunami // Mathematical Models and Computer Simulations. 11. –№. 5. –P. 679-689.