Jiang, Junle and Simons, Mark (2016) Probabilistic imaging of tsunamigenic seafloor deformation during the 2011 Tohoku-oki Earthquake. Journal of Geophysical Research. Solid Earth, 121 (12). pp. 9050-9076. ISSN 2169-9313. http://resolver.caltech.edu/CaltechAUTHORS:20170302-075008224
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Diverse observations from the 2011 M_w 9.0 Tohoku-oki earthquake pointed to large coseismic fault slip proximal to the Japan Trench. This seismic failure prompted a reevaluation of the conventional view that the outer forearc is generally aseismic. However, the nature of near-trench fault slip during this event remains debated, without consensus on whether slip peaked at the trench or at greater depths. Here we develop a probabilistic approach to image the spatiotemporal evolution of coseismic seafloor displacement from near-field tsunami observations. In a Bayesian framework, we sample ensembles of nonlinear source models parameterized to focus on near-trench features, incorporating the uncertainty in modeling dispersive tsunami waves in addition to nominal observational errors. Our models indicate that seafloor in the region of the earthquake was broadly uplifted and tilted seaward approaching the deep-ocean trench. Over length scales of ~40 km, seafloor uplift peaks at 5 ± 0.6 m near the inner-outer forearc transition and decreases to 2 m at the trench axis over a distance of 50 km, corresponding to a seafloor tilt of 0.06 ± 0.02 m/km. Over length scales of ~20 km, peak uplift reaches 7 ± 2 m at the similar location, but uplift at the trench is less constrained. Elastic modeling that reproduces the observed tilt requires a coseismic slip deficit at the trench. Such a deficit is effectively consistent with a metastable frictional model for the shallowest megathrust. While large shallow earthquakes in the region cannot be completely ruled out, aseismic deformation is the most likely mode for satisfying the long-term slip budget.
|Additional Information:||© 2016 American Geophysical Union. Received 17 NOV 2016; Accepted 27 NOV 2016; Accepted article online 6 DEC 2016; Published online 23 DEC 2016. This study was supported by a grant to M.S. from the National Aeronautics and Space Administration (NASA) (grant 1447107) and was carried out at the Jet Propulsion Laboratory and the California Institute of Technology under a contract with the National Aeronautics and Space Administration and funded through the President's and Director's Fund Program. We thank J.-P. Ampuero, J.-P. Avouac, T. Heaton, H. Kanamori, and N. Lapusta for helpful discussions and comments on an early draft of the manuscript. Ensembles of source models are available from the authors upon request.|
|Subject Keywords:||Tohoku-oki earthquake; tsunami; seafloor deformation; Bayesian inversion; uncertainty characterization; subduction zone megathrust|
|Official Citation:||Jiang, J., and M. Simons (2016), Probabilistic imaging of tsunamigenic seafloor deformation during the 2011 Tohoku-oki Earthquake, J. Geophys. Res. Solid Earth, 121, 9050–9076, doi:10.1002/2016JB013760|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||03 Mar 2017 18:29|
|Last Modified:||10 Mar 2017 15:49|
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