Coseismic seafloor deformation in the trench region during the Mw8.8 Maule megathrust earthquake

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.

Asthenosphere Flow Modulated by Megathrust Earthquake Cycles

“…Offshore geodetic data are admittedly challenging to obtain, despite recent progress (Maksymowicz et al, 2017;Tomita et al, 2017;Wallace et al, 2016;Yokota et al, 2016), but these measurements may be most effective to constrain the rheology of the subducting slab and fault processes near the trench. Flow in the oceanic asthenosphere creates landward surface displacements above the coseismic rupture and seaward displacements away from it.…”

“…Flow in the oceanic asthenosphere creates landward surface displacements above the coseismic rupture and seaward displacements away from it. Offshore geodetic data are admittedly challenging to obtain, despite recent progress (Maksymowicz et al, 2017;Tomita et al, 2017;Wallace et al, 2016;Yokota et al, 2016), but these measurements may be most effective to constrain the rheology of the subducting slab and fault processes near the trench. The rheological properties of the mantle wedge are less well constrained, but viscoelastic flow in the backarc contributes significantly to postseismic deformation, producing displacement compatible with all other deformation mechanisms above the land.…”

Along‐Arc Heterogeneity of the Seismic Structure Around a Large Coseismic Shallow Slip Area of the 2011 Tohoku‐Oki Earthquake: 2‐D Vp Structural Estimation Through an Air Gun‐Ocean Bottom Seismometer Experiment in the Japan Trench Subduction Zone

“…According to geodetic data (Moreno et al, ) and the joint analysis of geodetic, seismological, and tsunami data (Yue et al, ), this megathrust earthquake caused large and small shallow slip at 34.5°S and 35°S, respectively. In addition, the coseismic seafloor deformation was observed, indicating the occurrence of “slip to the trench” (Maksymowicz et al, ). In this area, the accretionary prism at 34.5°N is smaller than at 35°N (Contreras‐Reyes et al, ), revealing an inverse correlation between the prism width and shallow slip amount similar to the Tohoku‐oki earthquake.…”

Subduction zone megathrust earthquakes

“…Efforts are under way to synthesize the accumulated data sets (e.g., Kanamori, 2014;Lay, 2015;Ye et al, 2016bYe et al, , 2016cDenolle and Shearer, 2016;Meier et al, 2017;Melgar and Hayes, 2017;Hayes, 2017), and we will not attempt to summarize the multitude of studies. Large shallow coseismic slip occurred in the 2015 Illapel (e.g., Li et al, 2016;Melgar et al, 2016), 2011 Tohoku (e.g., Lay et al, 2011b;Iinuma et al, 2012;Ozawa et al, 2012;Satake et al, 2013;Romano et al, 2014;Bletery et al, 2014;Melgar and Bock, 2015;Lay, 2017), 2010 Maule (e.g., Vigny et al, 2011;Yue et al, 2014b;Yoshimoto et al, 2016;Maksymowicz, et al, 2017), and 2004 Sumatra (e.g., Ammon et al, 2005;Rhie et al, 2007;Fujii and Satake, 2007) events, accompanying slip on the downdip portions of the megathrusts. In other cases, such as the 2014 Iquique, Chile (e.g., Lay et al, 2014;Hayes et al, 2014b), 2012 Nicoya, Costa Rica (e.g., Yue et al, 2013;Liu et al, 2015), 2003 Tokachi-oki, Japan (e.g., Miyazaki and Larson, 2008;Romano et al, 2010), and 2007 Pisco, Peru, ruptures (e.g., Lay et al, 2010a;Sladen et al, 2010), slip was concentrated on the central or deeper portion of the rupture zone, with no shallow coseismic slip.…”