Optimal time alignment of tide‐gauge tsunami waveforms in nonlinear inversions: Application to the 2015 Illapel (Chile) earthquake. Issue 21 (15th November 2016)

• Record Type: Journal Article
• Authors: Romano, F.; Piatanesi, A.; Lorito, S.; Tolomei, C.; Atzori, S.; Murphy, S.
• Is Part Of: Geophysical research letters. Volume 43:Issue 21(2016)
• Page Start: 11, 226
• Page End: 11, 235
• Publication Date: 2016-11-15
• Subjects: tsunami -- inversion -- optimal time alignment -- subduction earthquakes; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL071310
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Tsunami waveform inversion is often used to retrieve information about the causative seismic tsunami source. Tide gauges record tsunamis routinely; however, compared to deep‐ocean sensor data, tide‐gauge waveform modeling is more difficult due to coarse/inaccurate local bathymetric models resulting in a time mismatch between observed and predicted waveforms. This can affect the retrieved tsunami source model, thus limiting the use of tide‐gauge data. A method for nonlinear inversion with an automatic optimal time alignment (OTA), calculated by including a time shift parameter in the cost function, is presented. The effectiveness of the method is demonstrated through a series of synthetic tests and is applied as part of a joint inversion with interferometric synthetic aperture radar data for the slip distribution of the 2015 Mw 8.3 Illapel earthquake. The results show that without OTA, the resolution on the slip model degrades significantly and that using this method for a real case strongly affects the retrieved slip pattern. Key Points: Optimal time alignment (OTA) overcomes known modeling issues of tsunami tide‐gauge records for source inversion Synthetic tests are used to illustrate and validate the new method showing how OTA significantly improves the retrieved source model With OTA method the tsunami source of the Illapel earthquake is displaced trenchward