Preprints
https://doi.org/10.5194/se-2021-53
https://doi.org/10.5194/se-2021-53

  28 May 2021

28 May 2021

Review status: this preprint is currently under review for the journal SE.

Forearc density structure of the overriding plate in the northern area of the giant 1960 Valdivia earthquake

Andrei Maksymowicz1, Daniela Montecinos-Cuadros1, Daniel Díaz1, María José Segovia1, and Tomás Reyes2,3 Andrei Maksymowicz et al.
  • 1Departamento de Geofísica, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile
  • 2Departamento de Geología, Universidad de Chile, Santiago, Plaza Ercilla 803, Chile
  • 3Instituto de Geocronología y Geología Isotopica (INGEIS-CONICET), Universidad de Buenos Aires (UBA), Argentina

Abstract. The objective of this work is to analyse the density structure of the continental forearc in the northern segment of the 1960 Mw 9.6 Valdivia earthquake. Regional 2D and local 3D density models have been obtained from available gravity data in the area, complemented with new gravimetric stations. Models are constrained by independent geophysical/geological information and new TEM and MT soundings. The results show a segmentation of the continental wedge along and perpendicular to the margin, highlighting a high density anomaly, below the onshore forearc basin, that limits the Late Paleozoic-Early Mesozoic metamorphic basement in the region where Chaitenia terrain has been proposed. A progressive landward shift of this anomaly correlates with the high slip patch of the giant 1960 Mw 9.6 Valdivia earthquake. Based on these results, we propose that the horizontal extension of the less rigid basement units conforming the marine wedge and Coastal Cordillera domain could modify the process of stress loading during the interseismic periods, and also that changes in position and extension of the Late Paleozoic-Early Mesozoic accretionary complex could be linked with the frictional properties of the interplate boundary. This analysis provides new evidence of the role of the overriding plate structure on the seismotectonic process in subduction zones.

Andrei Maksymowicz et al.

Status: open (until 14 Jul 2021)

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Andrei Maksymowicz et al.

Andrei Maksymowicz et al.

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Short summary
This work analyses the density structure of the continental forearc in the northern segment of the 1960 Mw 9.6 Valdivia earthquake. Results show a segmentation of the continental wedge along and perpendicular to the margin. The extension of the less rigid basement units conforming the marine wedge and Coastal Cordillera domain could modify the process of stress loading during the interseismic periods. This analysis highlights the role of the overriding plate on the seismotectonic process