The seismic cycle in subduction zones: quantification of deformation rates and strain partitioning in the 1960 Chile earthquake segment
Final Report Abstract
Subduction zones have generated the largest earthquakes on Earth; there, it has been thought that the longer the time since the last earthquake, the larger the next earthquake’s slip, and consequently magnitude will be. However, historical and paleoseismic data has shown variable recurrence times and magnitude of large subduction earthquakes, which not necessarily follow this logical predictor. Gaining insight into this poorly understood problem is of utmost importance. This project aimed at obtaining a paleoseismic record of subduction-zone earthquakes and linking it with the record of inland faulting resulting from strain partitioning in oblique convergence zones. The main aims of this project were interrupted by the occurrence of the Maule earthquake, which on 27 February 2010 ruptured adjacent to the study area reaching a moment magnitude of 8.8. This was a unique opportunity to test some of the working hypotheses of this project by surveying the effects of this large seismic event. Together with Chilean colleagues we benefited from an UNESCO grant to conduct a post-earthquake survey and describe and measure the effects associated with land-level changes, surface deformation, tsunami inundation, and splay faulting. The main results are: (1) the Arauco Peninsula apparently represents a persistent barrier to great megathrust earthquakes as it arrested the 1960 and 2010 events; (2) regions of high permanent uplift rate exceeding 1 mm/yr form broad upwarpping regions at the edges of the 2010 rupture, suggesting that deep-seated processes control segmentation of the rupture, possibly changes in the geometry of the plate interface; (3) movement of secondary faults that splay from the plate interface occurred during the 2010 event below Isla Santa Maria. In parallel, we obtained modern deformation rates from a permanent GPS station installed in the frame of this project, which shows fast rates implying strong interseismic plate coupling. In addition, we obtained a paleoseismic record of megathrust earthquake at Guafo Island in the 1960 segment. The main highlight is the identification of a major event that uplifted the island permanently dated around the year AD 800 from radiocarbon measurements of in-situ remains of juncus sp rhizomes. The results of both the 2010 and 1960 earthquake segments suggest that earthquake segments may be persistent in space but with variations in their recurrence period with supercycle behavior.
Publications
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2009. Impact of megathrust geometry on inversion of coseismic slip from geodetic data: Application to the 1960 Chile earthquake. Geophysical Research Letters 36, L16310
Moreno, M.S., Bolte, J., Klotz, J., Melnick, D.
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2011. Coastal uplift and tsunami effects associated to the 2010 M w8.8 Maule earthquake in central Chile. Andean Geology 38, 219-238
Vargas, G., Farías, M., Carretier, S., Tassara, A., Baize, S., Melnick, D.
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2011. Heterogeneous plate locking in the South- Central Chile subduction zone: Building up the next great earthquake. Earth and Planetary Science Letters 305, 413-424
Moreno, M., Melnick, D., Rosenau, M., Bolte, J., Klotz, J., Echtler, H., Baez, J., Bataille, K., Chen, J., Bevis, M., Hase, H., Oncken, O.
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2012. Darwin seismic gap closed by the 2010 Maule earthquake. Andean Geology 39, 558-563
Melnick, D., Moreno, M., Cisternas, M., Tassara, A.
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2012. Ecological implications of extreme events: Footprints of the 2010 earthquake along the Chilean coast. PLoS ONE 7, e35348
Jaramillo, E., Dugan, J.E., Hubbard, D.M., Melnick, D., Manzano, M., Duarte, C., Campos, C., Sanchez, R.
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2012. Toward understanding tectonic control on the M w 8.8 2010 Maule Chile earthquake. Earth and Planetary Science Letters 321-322, 152-165
Moreno, M., Melnick, D., Rosenau, M., Baez, J., Klotz, J., Oncken, O., Tassara, A., Chen, J., Bataille, K., Bevis, M., Socquet, A., Bolte, J., Vigny, C., Brooks, B., Ryder, I., Grund, V., Smalley, B., Carrizo, D., Bartsch, M., Hase, H.
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2014. Splay fault triggering by great subduction earthquakes inferred from finite element models. Geophysical Research Letters 41, 385-391
Li, S., Moreno, M., Rosenau, M., Melnick, D., Oncken, O.
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2015, Differential development of the BioBío canyon and its tributary, offshore Chile: Implications for the controls of canyon activity during sealevel highstand: Geosphere, 11(4), 1-30
Bernhardt, A., Melnick, D., Jara-Muñoz, J., Argandoña, B., and González, J.
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2015. Responses of dune plant communities to continental uplift from a major earthquake: sudden releases from coastal squeeze. PLoS ONE 10, e0124334
Rodil, I., Jaramillo, E., Hubbard, D.M., Dugan, J.E., Melnick, D., Velasquez, C.
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2015. Turbidite paleoseismology along the Chilean continental margin – feasible or not? Quaternary Science Reviews 120, 71-92
Bernhardt, A., Melnick, D., Hebbeln, D., Luckge, A., Strecker, M.R.
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2015. Unraveling sea-level variations and tectonic uplift in wavebuild marine terraces, Santa María Island, Chile. Quaternary Research 83, 216-228
Jara-Muñoz, J., Melnick, D.
