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TitleA crustal focal mechanism catalog for northern Chile: initial results
AuthorHerrera, C; Cassidy, J FORCID logo; Dosso, S E; Block, W; Sippl, C
SourceSSA 2020 Annual Meeting ; 2020 p. 1 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20190359
PublisherSeismological Society of America
MeetingSeismological Society of America 2020 Annual Meeting; Albuquerque, NM; US; April 27-30, 2020
DocumentWeb site
Mediaon-line; digital
File formathtml; pdf
AreaAndes; Chile
Lat/Long WENS -84.0000 -56.0000 -18.0000 -24.0000
Subjectsgeophysics; structural geology; Science and Technology; Nature and Environment; seismology; earthquakes; earthquake risk; seismic risk; seismicity; earthquake magnitudes; seismological network; seismic waves; amplitude spectra; bedrock geology; structural features; faults; tectonic setting; subduction zones; structural trends; stress analyses; Nazca Subduction Zone; 2001 Mw 6.3 Aroma Earthquake
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2020 04 01
AbstractChile experiences considerable seismic hazard from interplate, intraplate and crustal earthquakes. Due to their large magnitudes and frequent occurrence in the Nazca subduction zone, interplate and intraplate earthquakes have been widely studied with broadband and strong motion networks. However, the smaller-magnitude crustal seismicity has been studied much less, and the lack of sufficiently dense seismic networks over most of the country makes comprehensive studies of crustal events very challenging.
In northern Chile, the interseismic gap since the last giant thrust earthquake in 1877 has motivated the deployment of several temporary and permanent seismic networks since the early 2000s, thus providing new opportunities to carry out seismological studies in the area, especially between latitudes 18°S and 24°S.
We select more than 800 ML greater than or equal to 3.0 crustal earthquakes that occurred between 2005 and 2018, reported in two recently-published earthquake catalogs for the area, and calculate their focal mechanisms using P-wave polarities and S/P amplitude ratios from broadband and short-period waveform data recorded by local stations.
Our initial results show a variety of faulting geometries, with some trends becoming evident. Several offshore crustal events show north-south strike with thrust mechanisms, indicating strong influence of the main plate subduction. However, several onshore events near 21°S show a clear east-west strike, with north-south horizontal pressure axes, which may indicate the existence of additional local tectonic features in compressive regime. Further inland, persistent seismicity occurs in the Andes mountains in a small area near latitude 19.7°S, which could be related to the 2001 Mw 6.3 Aroma crustal earthquake.
Our compilation of crustal-earthquake results for northern Chile can provide clues to local and regional faulting patterns, and serve as a basis for crustal stress mapping studies in the region.
Summary(Plain Language Summary, not published)
This study examines the earthquake-generating stress field along the entire subduction zone of Chile. This is accomplished by determining the focal mechanism (rupture style) of recent well-recorded earthquakes. The goal is to map the stress field in Chile, for applications in the (similar) subduction zone in southwestern British Columbia, to better assess earthquake hazards in Canada.

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