[1] The moment magnitude 7.8 earthquake that struck offshore the Mentawai islands in western Indonesia on 25 October 2010 created a locally large tsunami that caused more than 400 human causalities. We identify this earthquake as a rare slow-source tsunami earthquake based on: 1) disproportionately large tsunami waves; 2) excessive rupture duration near 125 s; 3) predominantly shallow, neartrench slip determined through finite-fault modeling; and 4) deficiencies in energy-to-moment and energy-to-durationcubed ratios, the latter in near-real time. We detail the real-time solutions that identified the slow-nature of this event, and evaluate how regional reductions in crustal rigidity along the shallow trench as determined by reduced rupture velocity contributed to increased slip, causing the 5-9 m local tsunami runup and observed transoceanic wave heights observed 1600 km to the southeast. Citation: Newman, A. V., G. Hayes, Y. Wei, and J. Convers (2011), The 25 October 2010 Mentawai tsunami earthquake, from real-time discriminants, finite-fault rupture, and tsunami excitation, Geophys. Res. Lett., 38, L05302,

[1] We develop an updated radiated seismic energy E catalog of global earthquakes with seismic moment M 0 ≥ 10 19 Nm (M W ≥ 6.7) from 1997 through mid-2010, recording 342 events using 17849 seismograms. Station-specific corrections and event duration-dependent total P wave group calculations allow for improved E determinations for large-and long-duration earthquakes. We find the global mean energy-to-moment ratio = log 10 (E/M 0 ) = −4.59 ± 0.36. Robust deviations are found for thrust ( T = −4.74), strike-slip ( SS = −4.44), and normal ( N = −4.51) faulting events. For two regions with recent energy deficient tsunami earthquakes (TsE), we examine all large thrust earthquakes with M 0 ≥ 5 × 10 17 Nm (M W ≥ 5.7), to identify a regional characterization in their relative radiated energy-to-moment ratio. While thrust events along Java, Indonesia, the site of two TsE events in 1994 and 2006, are comparable ( T−JV = −4.91) to the global thrust average, events along the Middle America Trench (MAT), the site of the 1992 Nicaragua TsE, are consistently deficient ( T−MAT = −5.15). Along the MAT, a trend of increased deficiency in radiated energy to the southeast occurs in the direction of more rapid plate convergence. Global thrust mechanisms become increasingly deficient in radiated seismic energy at shallow depths, with TsE events representing the shallowest and most energetically deficient end-member of the events in the study. Results suggest thrust events are highly variable but tend to increase in apparent stress from about 15 kPa near the surface to 2 MPa near 70 km depth.

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[1] We estimate the seismic rupture durations from global large earthquakes (moment magnitude ≥ 7.0) by characterizing changes in the radiated P-wave energy and by introducing the time-averaged cumulative energy rate (TACER), which approximates rupture duration based on the peak first local maximum of an earthquake's high-frequency energy measured at teleseismic broadband seismometers. TACER is particularly useful for real-time evaluations, including the identification of slow-rupturing tsunami earthquakes. In cases of long unilateral earthquake rupture and good azimuthal station distribution, the per-station behavior of TACER may identify the approximate rupture direction, rupture velocity, and length due to (2013), Rapid earthquake rupture duration estimates from teleseismic energy rates, with application to real-time warning, Geophys. Res. Lett., 40,[5844][5845][5846][5847][5848]

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