The Tohoku-Oki earthquake from Earth to Oceans and Space: a critical case-study for earthquake and tsunami anticipation – TO_EOS

The main approaches developped in the project:
_a non-linear imagery of the coseismic slip history through the joint inversion of all related data sets,
_a fine analysis of the continuous and high-rate GPS data of the japanese GEONET network through the comparison of different processing strategies,
_identify the origin of the different ionospheric signals and their relation to the earthquake and tsunami, through event comparison and modeling of the solid earth-ocean-atmosphere coupling effects.

Expected results:
Describe the slip and seismicity evolution across of the different phases of the seismic cycle,
Conclude on the potential of atmospheric and ionospheric waves to improve the existing warning systems,
Improve the processing strategies of continuous, high-rate GPS signals. Identify potential slow slip events pre-Tohoku-Oki,
Description of the evolution of slip over the 15 years pre-Tohoku-Oki

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4 articles published in international peer-reviewed journals.

A fundamental question raised by the 2011, Mw9.0, Tohoku-oki earthquake is to know whether seismic rupture of giant earthquakes can be anticipated either in time (months, days or hours before the rupture), location and/or magnitude, and how, within 10 minutes after the quake, the amplitude of a tsunami can be estimated before it reaches the coast. Over the last decades, scientists have tried to address this question through different approaches, but mainly by (1) trying to isolate potential precursory signals or (2) improving our knowledge of the seismic cycle (how stress and strain balance over several earthquakes) to understand the physical parameters that control the size and location of those large earthquakes. More recently, a third more practical approach was developed called (3) early-warning which takes advantage of the slower propagation speed of seismic or tsunami waves compared to our communication networks to provide at least a few seconds or minutes to anticipate the approaching waves and gauge the threat they represent.
Here, we propose a project which acknowledges all these different approaches to bring new, critical perspectives on earthquake anticipation based on the unique data set of the Tohoku-oki earthquake. More specifically, the project will challenge each approach via three distinct tasks:
• Detailed modeling of the whole seismic sequence of the Tohoku-oki earthquake to better understand the interplay between the different phases of the seismic cycle. The coseismic model will integrate all the available data -High-Rate GPS, sea-bottom geodesy, GPS buoys, InSAR, telesesismic, strong motion and deep ocean-pressure data- to provide a detailed and tightly constrained kinematic solution. In parallel, we will focus on the modeling of pre- and post-seismic deformation using the refined GPS solutions (Task 3), and perform a systematic analysis of the source process of all major pre- and post-mainshock seismic events using the novel SCARDEC method (Vallee et al., 2011).
• Analyze and model the ionospheric perturbations related to the earthquake and the tsunami source. Our first analysis (Rolland et al., in press) indicates that both the earthquake and tsunami signals can be identified within minutes of the earthquake initiation. Improving our understanding of those signals could turn out to be critical for the definition of a new type of early-warning system and improve our ability to estimate the tsunami amplitude at the source,
• Perform a critical analysis and modeling of the possible slow-slip events prior the Tohoku-oki earthquake as suggested by the analysis of the airglow data over Hawaii and the deep sea-bottom pressure measurements in the Pacific (Makela et al, in press). So far, clues of the existence of such signals have been provided but only on the basis of sparse measurements. The dense continuous GPS network of Japan, with more than a thousand sites, recording at high-rate frequency (1 Hz), enables us for the first time to investigate the possible presence of precursory signals in details.
Hence, the potential of this ambitious project to improve earthquake and tsunami anticipation, not only relies on an in-depth analysis of the unique data set of the Tohoku-oki earthquake and tsunami, but it also extends the spectrum of the analysis via original and multidisciplinary tasks combining land, sea and space data.