| Titre | The Mw 5.7 Pica earthquake: a crustal event in northern Chile with large ground accelerations and stress drop |
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| Auteur | Herrera, C; Cassidy, J F ; Dosso, S E; Dettmer, J; Rivera, E; Ruiz, S; Vasyura-Bathke, H |
| Source | Seismological Research Letters vol. 93, no. 2B, 2022 p. 1255-1256 |
| Image |  |
| Année | 2022 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20210550 |
| Éditeur | Seismological Society of America |
| Réunion | Seismological Society of America Technical Sessions; Bellevue; US; avril 19-23, 2022 |
| Document | publication en série |
| Lang. | anglais |
| Media | numérique; en ligne |
| Formats | pdf |
| Lat/Long OENS | -69.3833 -69.3667 -20.4667 -20.4833 |
| Sujets | secousses séismiques; mouvements de la croûte |
| Programme | Géoscience pour la sécurité publique Risques géologique du tremblement de terre |
| Diffusé | 2022 04 19 |
| Résumé | (disponible en anglais seulement)
Important crustal earthquakes in Chile are less frequent compared with interplate and intraplate events. However, even moderate-magnitude onshore crustal events
can pose a major hazard due to their closer proximity to population centers. We study the rupture properties of a Mw 5.7 crustal earthquake that occurred in 2008 near the town of Pica, under the Central Valley of northern Chile, which was well
recorded with both strong motion and broadband instruments. This event generated maximum ground accelerations of up to 0.67 g in Pica, one of the largest recorded for this type of events. Overall, its observed ground motions are larger than expected
by prediction models, particularly at short periods. The mainshock rupture exhibits a large stress drop of 250 MPa, inferred via S-wave spectrum modeling, which is likely a contributing factor to its large ground accelerations. Its hypocenter was
located at 33 km depth in a cold and brittle region of the crust, with an inferred 9 km long by 8 km wide rupture via Bayesian inversion of waveforms. The fault plane is striking towards the NW and dipping towards the NE, as defined by the moment
tensor solution and aftershock distribution. This geometry is similar to that of crustal earthquakes occurring under the neighboring Coastal Cordillera, including the large 2020 Mw 6.3 Loa River crustal earthquake, suggesting that the Pica earthquake
is under the same stress field, and likely occurred in a buried branch of the margin-perpendicular reverse faults mapped in the Coastal Cordillera. These factors indicate the possibility of more similar events occurring in northern Chile, where our
recurrence estimates show that Mw greater than or equal to 5.7 crustal events have occurred on average, every three years. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Dans cet présentation, nous examinons l'un des tremblements de terre crustaux les plus importants (et les mieux enregistrés) dans le nord du
Chile. Nous examinons le type de rupture, l'emplacement et la profondeur, les modèles de répliques et la relation avec la géologie locale. Les mouvements du sol montrent des secousses plus importantes que prévu et ont des implications pour
l'amélioration des modèles de risques sismiques dans le nord du Chile. Les résultats de cette étude ont également des applications dans le nord de la Cascadia - qui est également une zone de subduction active avec une géométrie de subduction et des
types de tremblements de terre similaires. |
| GEOSCAN ID | 329447 |
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