Analysis and Characterization of the Energy and Amplitude Evolution of Tsunami Records of Recent Near-field Events in Chile and its Link with Characteristics of Seismic Source and Topobathymetry
Abstract
Recent tsunamis observed along the Chilean coast brought new evidence on the hydrodynamic control exercised by the topobathymetry regarding tsunami energy, at the shelf and the embayment scales. The generation of reflected waves and edge waves, together with the amplification and decay of tsunami waves is a consequence of this. These topobathymetric controls have been widely studied in terms of the natural modes and energetic periods, but not the structure of the temporal variations of the energy contained in the sea surface records.
In this work, we characterize tsunami records along the coast of Chile, for recent events in the near-field generated by subduction earthquakes. The events of Antofagasta 1995, Maule 2010, Pisagua 2014, Illapel 2015, and Valparaíso 2017 are selected to carry out this study. Nine coastal stations with different geometrical features are selected for the analysis, covering more than 2,400 kilometers of coast almost equally spaced between latitudes 18.4ºS and 39.9ºS. The different characteristics of the events in terms of magnitudes, energy release, and relative position of seismic sources and coastal stations, allow analysing the resulting signals by event and by station. Thus, tsunami records are studied incorporating the temporal dimension. We use wavelet analysis and temporal variations of the moving root mean square tsunami amplitudes (MRMS). Among the parameters that are of interest, which are related to the seismic source and the topobathymetric characteristics, we analyze: i) the rate of energy growth by frequency bands, ii) the rate of energy decay by bands of frequency, iii) the characteristic times to reach the energy peaks by frequency bands, in addition to other parameters defined in previous works, such as the energy peaks and natural modes. Based on this analysis, some hypotheses are advanced, which would explain the observed behaviour. Particularly, for disaster mitigation purpose, it is important to understand and quantify the characteristic times required to reach the maximum wave height and to pass below a hazard threshold; This knowledge is essential to determine the time window in which tsunami evacuation alerts should be active.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNH33A..05Q
- Keywords:
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- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDS;
- 4333 Disaster risk analysis and assessment;
- NATURAL HAZARDS;
- 4341 Early warning systems;
- NATURAL HAZARDS;
- 4564 Tsunamis and storm surges;
- OCEANOGRAPHY: PHYSICAL