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TitleLearning from crustal deformation associated with the M9 2011 Tohoku-oki earthquake
AuthorWang, K; Sun, T; Brown, L; Hino, R; Tomita, F; Kido, M; Iinuma, T; Kodaira, S; Fujiwara, T
SourceSubduction top to bottom 2; by Bebout, G E (ed.); Scholl, D W (ed.); Stern, R J (ed.); Wallace, L M (ed.); Agard, P (ed.); Geosphere vol. 14, no. 2, 2018 p. 552-571, (Open Access)
Alt SeriesNatural Resources Canada, Contribution Series 20170258
PublisherGeological Society of America
Mediapaper; on-line; digital
File formatpdf; html
ProvinceOffshore region
AreaTohoku; Japan
Lat/Long WENS 140.0000 145.0000 41.0000 35.5000
Subjectsgeophysics; tectonics; structural geology; marine geology; tectonic setting; tectonic elements; plate margins; subduction zones; earthquakes; seismicity; structural features; faults; rheology; modelling; crustal studies; crustal movements; deformation; stress patterns; displacement; bathymetry; geodesy; subsidence; Japan Trench; M-9 2011 Tohoku-oki earthquake; geological hazards; rupture zone; megathrust locking pattern; coseismic slip; seafloor geometry; fault geometry; fault creep; global navigation satellite systems (GNSS)
Illustrationsgeoscientific sketch maps; time series; models; profiles; cross-sections; graphs; tables
ProgramAssessing Earthquake Geohazards, Public Safety Geoscience
Released2018 02 24
AbstractNumerous observations pertaining to the magnitude 9.0 2011 Tohoku-oki earthquake (offshore Japan) have led to new understanding of subduction zone earthquakes. By synthesizing published research results and our own findings, we explore what has been learned about fault behavior and Earth rheology from the observation and modeling of crustal deformation before, during, and after the earthquake. Before the earthquake, megathrust locking models based on land-based geodetic observations correctly outlined the along-strike location of the future rupture zone. Their incorrect definition of the locking pattern in the dip direction demonstrates the need to model the effects of interseismic viscoelastic stress relaxation and stress shadowing. The observation of decade-long accelerated slip downdip of the future rupture zone raises new questions on fault mechanics. During the earthquake, seafloor geodetic measurements revealed huge coseismic displacements (up to 31 m). Modeling of bathymetry difference before and after the earthquake suggests >60 m of coseismic slip of the most seaward 40 km of the fault in the main rupture area, with the slip peaking at the trench. Large differences in shallow slip between published rupture models are due mainly to the near absence of near-trench deformation measurements, but model simplifications in fault and seafloor geometry also bear large responsibility. After the earthquake, seafloor geodetic measurements provided unambiguous evidence for the dominance of viscoelastic relaxation in short-term postseismic deformation. There is little deep afterslip in the fault area where the decade-long pre-earthquake slip acceleration is observed. Investigating the physical processes responsible for the complementary spatial distribution of pre-slip and afterslip calls for new scientific research.
Summary(Plain Language Summary, not published)
The devastating 2011 M=9 Tohoku-oki earthquake is the best recorded great megathrust earthquake in history. Many lessons have been learned from the analyses of the various types of data. In this invited contribution to the GEOSPHERE Themed Issue (i.e., special issue) Subduction Top to Bottom 2 (or ST2B-2), we synthesize studies of crustal deformation observations and modeling before, during, and after the earthquake. Lessons learned are directly relevant to understanding megathrust earthquake processes at the Cascadia subduction zone and therefore important to the assessment of earthquake and tsunami hazards along Canada's west coast.