Abstract
The Mw 8.8 megathrust earthquake that occurred on 27 February 2010 offshore the Maule region of central Chile triggered a destructive tsunami. Whether the earthquake rupture extended to the shallow part of the plate boundary near the trench remains controversial. The up-dip limit of rupture during large subduction zone earthquakes has important implications for tsunami generation and for the rheological behavior of the sedimentary prism in accretionary margins. However, in general, the slip models derived from tsunami wave modeling and seismological data are poorly constrained by direct seafloor geodetic observations. We difference swath bathymetric data acquired across the trench in 2008, 2011 and 2012 and find ~3–5 m of uplift of the seafloor landward of the deformation front, at the eastern edge of the trench. Modeling suggests this is compatible with slip extending seaward, at least, to within ~6 km of the deformation front. After the Mw 9.0 Tohoku-oki earthquake, this result for the Maule earthquake represents only the second time that repeated bathymetric data has been used to detect the deformation following megathrust earthquakes, providing methodological guidelines for this relatively inexpensive way of obtaining seafloor geodetic data across subduction zone.
Highlights
Large slip near the Japanese trench has been reported for the 2011 Mw9.0 Tohoku earthquake by inversion of seismological data and tsunami waveforms[1,2,3]
The Maule earthquake occurred in a region of the Nazca-South America subduction zone where the trench is filled by ~1.5 s (~2 km) of sediment and the accretionary prism is 40–50 km wide[11,14]
Addition of tsunami records seaward of the trench to the data for inversion of the slip history suggests slip to deformation front[12] along the segment of the margin that we address with our study in spite of the presence of young, accretionary wedge sediments in the upper plate
Summary
Large slip near the Japanese trench has been reported for the 2011 Mw9.0 Tohoku earthquake by inversion of seismological data and tsunami waveforms[1,2,3] This large near trench slip (up to 60 m) has been confirmed by the analysis of the seafloor deformation derived from GPS-Acoustic data[4], direct submarine seafloor inspection[5], changes in seafloor depth[6] and sub-seafloor structure imaged on seismic reflection profiles acquired before and after the earthquake[7]. Rupture along the up-dip subduction interface is expected to be dissipated (e.g., refs 10 and 11), joint inversions of GPS, teleseimic and tsunami data provided evidences of large co-seismic slip near the trench during the Maule earthquake[12], and during the Mw 7.8 Mentawai earthquake[13], both located at accretionary margins. Before and after the February 27, 2010 Mw 8.8 Maule earthquake, supports this conclusion by providing direct evidence for a change in the elevation of the continental wedge near the deformation front
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