The El Salvador and Philippines Tsunamis of August 2012: Insights from Sea Level Data Analysis and Numerical Modeling
We studied two tsunamis from 2012, one generated by the El Salvador earthquake of 27 August (Mw 7.3) and the other generated by the Philippines earthquake of 31 August (Mw 7.6), using sea level data analysis and numerical modeling. For the El Salvador tsunami, the largest wave height was observed in Baltra, Galapagos Islands (71.1 cm) located about 1,400 km away from the source. The tsunami governing periods were around 9 and 19 min. Numerical modeling indicated that most of the tsunami energy was directed towards the Galapagos Islands, explaining the relatively large wave height there. For the Philippines tsunami, the maximum wave height of 30.5 cm was observed at Kushimoto in Japan located about 2,700 km away from the source. The tsunami governing periods were around 8, 12 and 29 min. Numerical modeling showed that a significant part of the far-field tsunami energy was directed towards the southern coast of Japan. Fourier and wavelet analyses as well as numerical modeling suggested that the dominant period of the first wave at stations normal to the fault strike is related to the fault width, while the period of the first wave at stations in the direction of fault strike is representative of the fault length.
KeywordsTsunami earthquake DART tide gauge spectral analysis Fourier analysis wavelet analysis numerical modeling El Salvador earthquake Philippines earthquake
The sea level data used in this study were provided through the USA National Oceanographic and Atmospheric Administration (NOAA), and UNESCO Intergovernmental Oceanographic Commission (IOC). We express our sincere gratitude to our colleagues from the sea level data centers at both NOAA and IOC for their invaluable efforts regarding the preparation, processing and timely supply of sea level data which has greatly contributed to tsunami science in the last decade. Figure 1 was drafted using the GMT software (Wessel and Smith 1991). The wavelet package by Torrence and Compo (1998) was used in this study. This article benefitted from detailed and constructive reviews from two anonymous reviewers, for which we are sincerely grateful. We would like to thank Dr. Hermann Fritz (Georgia Institute of Technology, USA), the guest editor of this issue, for his assistance during the revision process of this article. This study was supported by the Alexander von Humboldt Foundation in Germany and the Japan Society for Promotion of Science (JSPS) in Japan.
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