Abstract
Strong spatial variation of rupture characteristics in the moment magnitude (M(w)) 9.0 Tohoku-Oki megathrust earthquake controlled both the strength of shaking and the size of the tsunami that followed. Finite-source imaging reveals that the rupture consisted of a small initial phase, deep rupture for up to 40 seconds, extensive shallow rupture at 60 to 70 seconds, and continuing deep rupture lasting more than 100 seconds. A combination of a shallow dipping fault and a compliant hanging wall may have enabled large shallow slip near the trench. Normal faulting aftershocks in the area of high slip suggest dynamic overshoot on the fault. Despite prodigious total slip, shallower parts of the rupture weakly radiated at high frequencies, whereas deeper parts of the rupture radiated strongly at high frequencies.
Highlights
Strong spatial variation of rupture characteristics in the moment magnitude (Mw) 9.0 Tohoku-Oki megathrust earthquake controlled both the strength of shaking and the size of the tsunami that followed
The 11 March 2011 moment magnitude (Mw) 9.0 Tohoku-Oki Earthquake occurred on the Japan Trench plate boundary off the eastern shore of northern Honshu
The empirical Green’s function (eGf) approach assumes that waveforms from a small earthquake approximate the point dislocation response from points near the source of the eGf event, once the appropriate time shift due to the location difference is taken into account
Summary
Strong spatial variation of rupture characteristics in the moment magnitude (Mw) 9.0 Tohoku-Oki megathrust earthquake controlled both the strength of shaking and the size of the tsunami that followed. The Tohoku-Oki earthquake started with relatively small amplitude arrivals during the first 3 s that are only clearly visible at seismically quiet stations The reversal of rupture propagation direction, from upward to downward, shown in Fig. 1 is a feature observed in numerical models with dynamic overshoot.
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