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TitleSource parameters of the Mw 5.7 Pica crustal earthquake in northern Chile
AuthorHerrera, C; Cassidy, J FORCID logo; Dosso, S E; Dettmer, J; Rivera, E; Ruiz, S; Vasyura-Bathke, H
SourceSeismological Research Letters vol. 94, issue 1, 2022 p. 100-112,
Alt SeriesNatural Resources Canada, Contribution Series 20210521
PublisherSeismolgical Society of America
File formatpdf
AreaPica; Chile
Lat/Long WENS -72.0000 -67.0000 -18.5000 -23.5000
SubjectsScience and Technology; Nature and Environment; seismology
Illustrationslocation maps; cross-plots; tables; charts; diagrams
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2022 09 12
AbstractOn September 10th, 2008, a MW 5.7 crustal earthquake occurred under the Central Valley of northern Chile, near the town of Pica, at a depth of ~33 km. We find this earthquake to be a high stress-drop, reverse-oblique event that generated unusually high ground accelerations of up to 0.67 g. Overall, its observed ground motion intensities are considerably larger than those predicted by ground motion models, particularly at short periods. The source properties inferred through waveform modeling indicate reverse-oblique fault motion on a ~75 km2 plane dipping to the NE, which is corroborated by the located aftershock distribution. Stress drop values of the mainshock and larger aftershocks were estimated through S-wave spectrum modeling, with values up to ~250 MPa for the mainshock. The event occurred in a cold section of the continental crust under the Central Valley, and its fault kinematics and orientation are consistent with the dominant style of faulting and stress field under the neighboring Coastal Cordillera. Although our recurrence analysis shows that crustal events in the region occur at a lower rate than interplate and intraplate events, crustal events of similar or higher magnitude than the Pica earthquake have occurred, on average, approximately once every three years in northern Chile, which could pose an important hazard to nearby populations or critical infrastructure.
Summary(Plain Language Summary, not published)
In this article we examine one of the largest (and best-recorded) crustal earthquakes in northern Chile. We examine the type of rupture, the location and depth, aftershock patterns, and relationship with local geology. The ground motions show higher than expected shaking, and have implications for improving earthquake hazard models in northern Chile. Results of this study also have applications in northern Cascadia - which is also an active subduction zone with a similar subduction geometry and types of earthquakes.

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