期刊
GEOPHYSICAL JOURNAL INTERNATIONAL
卷 227, 期 2, 页码 1143-1167出版社
OXFORD UNIV PRESS
DOI: 10.1093/gji/ggab259
关键词
Numerical modelling; Earthquake hazards; Site effects; Wave propagation
资金
- Beca Doctorado Nacional Conicyt [21130082]
- TIDES COST Action [ES1401]
- NERC [NE/N011791/1]
This study investigates the effects of topography and basins on seismic wave amplification following an earthquake, showing that both factors can significantly increase the amplitude and duration of ground motion. While there is good agreement between real and synthetic seismic waveforms at lower frequencies, the fit deteriorates at higher frequencies due to unresolved 3-D velocity heterogeneity.
During earthquakes, structural damage is often related to soil conditions. Following the 2014 April 1 M-w 8.1 Iquique earthquake in Northern Chile, damage to infrastructure was reported in the cities of Iquique and Alto Hospicio. In this study, we investigate the causes of site amplification in the region by numerically analysing the effects of topography and basins on observed waveforms in the frequency range 0.1-3.5 Hz using the spectral element method. We show that topography produces changes in the amplitude of the seismic waves (amplification factors up to 2.2 in the frequency range 0.1-3.5 Hz) recorded by stations located in steep areas such as the ca. 1-km-high coastal scarp, a remarkable geomorphological feature that runs north-south, that is parallel to the coast and the trench. The modelling also shows that secondary waves probably related to reflections from the coastal scarp propagate inland and offshore, augmenting the duration of the ground motion and the energy of the waveforms by up to a factor of three. Additionally, we find that, as expected, basins have a considerable effect on ground motion amplification at stations located within basins and in the surrounding areas. This can be attributed to the generation of multiple reflected waves in the basins, which increase both the amplitude and the duration of the ground motion, with an amplification factor of up to 3.9 for frequencies between 1.0 and 2.0 Hz. Comparisons between real and synthetic seismic waveforms accounting for the effects of topography and of basins show a good agreement in the frequency range between 0.1 and 0.5 Hz. However, for higher frequencies, the fit progressively deteriorates, especially for stations located in or near to areas of steep topography, basin areas, or sites with superficial soft sediments. The poor data misfit at high frequencies is most likely due to the effects of shallow, small-scale 3-D velocity heterogeneity, which is not yet resolved in seismic images of our study region.
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