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TitleGround motion evaluation along the Chilean subduction zone: variability and possible causes
AuthorHerrera, C; Cassidy, J FORCID logo; Dosso, S E; Bastias, N; Onur, T
SourceAmerican Geophysical Union Fall Meeting 2019, abstracts; S31B-05, 2019 p. 1 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20190301
PublisherAmerican Geophysical Union
MeetingAmerican Geophysical Union Fall Meeting 2019; San Francisco, CA; US; December 9-13, 2019
DocumentWeb site
Mediaon-line; digital
File formathtml; pdf
Lat/Long WENS -74.0000 -66.0000 -18.0000 -26.0000
Lat/Long WENS -76.0000 -66.0000 -28.0000 -38.0000
Lat/Long WENS -76.0000 -70.0000 -40.0000 -46.0000
Subjectsgeophysics; tectonics; Nature and Environment; Science and Technology; Health and Safety; seismology; earthquakes; subduction zones; seismicity; models; earthquake catalogues; earthquake magnitudes; Chilean subduction zone; Nazca Plate
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2019 12 01
AbstractThe study and prediction of ground motions produced by moderate to large earthquakes is one of the key components for engineering seismology and seismic hazard assessments. In this context, Ground Motion Prediction Equations (GMPE) are models that predict the ground motion intensity at a given site, based on earthquake source, path and site effects parameters. These models can be used as a reference framework to evaluate observed ground motions in a specific region.
The Chilean section of the Nazca plate subduction under South America is one of the most seismically active regions in the world, where at least one significant earthquake with damaging ground motions occurs every 10 years. To monitor the seismicity, new digital seismic stations are continually being deployed, thus providing opportunities for strong ground motion studies.
In this work, we analyze ground motion variability along the Chilean subduction zone. We divide the country in to three regions (north, center and south) that are analyzed separately. We compile an interface earthquake catalog for each region, and infer site condition parameters for the newer stations deployed in Chile. Nationwide, we obtain more than 5400 strong motion observations from 375 recent 4.0 less than or equal to Mw less than or equal to 8.8 earthquakes, and compare these observations with an empirical GMPE developed with Chilean data.
We find a good overall fit of the GMPE in north and central Chile, with the best fit in central Chile. By analyzing between-event residuals, we find a clear increase of short-period ground-motion energy with depth in these two regions, with a sharper contrast in central Chile. The events showing larger ground motions at short periods are located in areas of low interseismic coupling, similar to recent findings in Japan, suggesting a frictional related origin. Southern Chile shows less frequent seismicity and has not been considered for GMPE development. Observations in this region are generally over-predicted by the GMPE. We propose that future GMPEs should include corrections for depth, and include data from Southern Chile, since recent studies have proposed a reawakening of significant seismicity since the 1960 Mw 9.5 Valdivia earthquake, starting with the 2016 Mw 7.6 Chiloé earthquake in the region.
Summary(Plain Language Summary, not published)
This research uses seismic recordings of recent subduction zone earthquakes along the Chilean margin to examine the variation in ground shaking through the region. We compare our results with shaking predictions currently used in building codes in both Chile and Canada (Cascadia subduction zone). We find good agreement with the Canadian models, but that variations in Chile (from north to south) are significant, and ground motion prediction equations in southernmost Chile would benefit from updates using these new datasets.

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